[Federal Register Volume 83, Number 146 (Monday, July 30, 2018)]
[Notices]
[Pages 36625-36627]
[FR Doc No: 2018-16214]

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DEPARTMENT OF LABOR

Occupational Safety and Health Administration

[Docket No. OSHA-2007-0042]

TUV Rheinland of North America, Inc.: Applications for Expansion
of Recognition

AGENCY: Occupational Safety and Health Administration (OSHA), Labor.

ACTION: Notice.

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SUMMARY: In this notice, OSHA announces the applications of TUV
Rheinland of North America, Inc., for expansion of its scope of
recognition as a Nationally Recognized Testing Laboratory (NRTL) and
presents the agency's preliminary finding to grant the applications.

DATES: Submit comments, information, and documents in response to this
notice, or requests for an extension of time to make a submission, on
or before August 14, 2018.

ADDRESSES: Submit comments by any of the following methods:
    Electronically: You may submit comments and attachments
electronically at: https://www.regulations.gov, which is the Federal
eRulemaking Portal. Follow the instructions online for submitting
comments.
    Facsimile: If your comments, including attachments, are not longer
than 10 pages, you may fax them to the OSHA Docket Office at (202) 693-
1648.
    Mail, hand delivery, express mail, messenger, or courier service:
When using this method, you must submit a copy of your comments and
attachments to the OSHA Docket Office, Docket No. OSHA-2007-0042,
Occupational Safety and Health Administration, U.S. Department of
Labor, Room N-3653, 200 Constitution Avenue NW, Washington, DC 20210.
Deliveries (hand, express mail, messenger, and courier service) are
accepted during the Docket Office's normal business hours, 10:00 a.m.
to 3:00 p.m., ET.
    Instructions: All submissions must include the Agency name and OSHA
docket number (OSHA-2007-0042) for the Information Collection Request
(ICR). All comments, including any personal information you provide,
are placed in the public docket without change, and may be made
available online at https://www.regulations.gov. For further
information on submitting comments, see the ``Public Participation''
heading in the section of this notice titled SUPPLEMENTARY INFORMATION.
    Docket: To read or download comments or other material in the
docket, go to https://www.regulations.gov or the OSHA Docket Office at
the above address. All documents in the docket (including this Federal
Register notice) are listed in the https://www.regulations.gov index;
however, some information (e.g., copyrighted material) is not publicly
available to read or download through the website. All submissions,
including copyrighted material, are available for

inspection at the OSHA Docket Office. You may also contact Kevin
Robinson at the contact information below to obtain a copy of the ICR.
    Extension of comment period: Submit requests for an extension of
the comment period on or before August 14, 2018 to the Office of
Technical Programs and Coordination Activities, Directorate of
Technical Support and Emergency Management, Occupational Safety and
Health Administration, U.S. Department of Labor, 200 Constitution
Avenue NW, Room N-3653, Washington, DC 20210, or by fax to (202) 693-
1644.

FOR FURTHER INFORMATION CONTACT: Information regarding this notice is
available from the following sources:
    Press inquiries: Contact Mr. Frank Meilinger, Director, OSHA Office
of Communications, U.S. Department of Labor, telephone:<PHONE_NUMBER>;
email: [email protected].
    General and technical information: Contact Mr. Kevin Robinson,
Director, Office of Technical Programs and Coordination Activities,
Directorate of Technical Support and Emergency Management, Occupational
Safety and Health Administration, U.S. Department of Labor, phone:
(202) 693-2110 or email: [email protected].

SUPPLEMENTARY INFORMATION:

I. Notice of the Applications for Expansion

    The Occupational Safety and Health Administration is providing
notice that TUV Rheinland of North America, Inc. (TUVRNA), is applying
for expansion of its current recognition as an NRTL. TUVRNA requests
the addition of four (4) recognized testing and certification sites,
and two (2) additional test standards to its NRTL scope of recognition.
    OSHA recognition of an NRTL signifies that the organization meets
the requirements specified in 29 CFR 1910.7. Recognition is an
acknowledgment that the organization can perform independent safety
testing and certification of the specific products covered within its
scope of recognition. Each NRTL's scope of recognition includes (1) the
type of products the NRTL may test, with each type specified by the
applicable test standard and (2) the recognized site(s) that has/have
the technical capability to perform the product-testing and product-
certification activities for test standards within the NRTL's scope.
Recognition is not a delegation or grant of government authority;
however, recognition enables employers to use products approved by the
NRTL to meet OSHA standards that require product testing and
certification.
    The Agency processes applications by a NRTL for initial recognition
and for an expansion or renewal of this recognition, following
requirements in Appendix A to 29 CFR 1910.7. This appendix requires
that the agency publish two notices in the Federal Register in
processing an application. In the first notice, OSHA announces the
application and provides its preliminary finding. In the second notice,
the agency provides the final decision on the application. These
notices set forth the NRTL's scope of recognition or modifications of
that scope. OSHA maintains an informational web page for each NRTL,
including TUVRNA, which details the NRTL's scope of recognition. These
pages are available from the OSHA website at http://www.osha.gov/dts/otpca/nrtl/index.html.
    TUVRNA currently has five facilities (sites) recognized by OSHA for
product testing and certification, with its headquarters located at:
TUV Rheinland of North America, Inc., 12 Commerce Road, Newtown,
Connecticut 06470. A complete list of TUVRNA sites recognized by OSHA
is available at https://www.osha.gov/dts/otpca/nrtl/tuv.html.

II. General Background on the Applications

    TUVRNA submitted two applications, one dated March 30, 2016 (OSHA-
2007-0042-0030) and another dated April 19, 2017 (OSHA-2007-0042-0031),
to expand its recognition to include the addition of four recognized
testing and certification sites located at: TUV Rheinland (Shenzhen)
Co., Ltd. 1f East & 2-4F, Cybio Technology Building No. 1, No. 16,
Keibei 2nd Road, High-Tech Industrial Park North, Nashan District,
518057 Shenzhen China; TUV Rheinland (Shanghai) Co., Ltd, TUV Rheinland
Building No. 177, Lane 777, West Guangzhong Road, Zhabei District,
Shanghai 200072, P.R. China; TUV Rheinland Taiwan Ltd., 11F., No 758,
Sec. 4, Bade Rd., Songshan Dist., Taipei City 105, Taiwan; and TUV
Rheinland Taiwan Ltd., Taichung Branch Office, No. 9, Lane 36, Minsheng
Rod., Sec. 3, Daya District, Taichung City 428, Taiwan. TUVRNA's
applications also requested the addition of two additional test
standards to its scope of recognition. In 2017 OSHA staff performed an
on-site review of TUVRNA's testing facilities on August 7-8 at TUV
Rheinland Shanghai, August 10-11at TUV Rheinland Shenzhen, August 14-15
at TUV Rheinland Taipei, and August 16, 2017 at TUV Rheinland Taichung,
in which the assessors found some nonconformances with the requirements
of 29 CFR 1910.7. TUVRNA addressed these issues sufficiently, and OSHA
staff preliminarily determined that OSHA should grant the applications
for expansion.
    Table 1 below lists the appropriate test standards found in
TUVRNA's applications for expansion for testing and certification of
products under the NRTL Program.

  Table 1--Proposed List of Appropriate Test Standards for Inclusion in
                   TUVRNA's NRTL Scope of Recognition
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           Test standard                     Test standard title
------------------------------------------------------------------------
NFPA 496..........................  Purged and Pressurized Enclosures
                                     for Electrical Equipment.
UL 698A...........................  Industrial and Classification of
                                     Mercantile and Bank Burglar-Alarm
                                     Systems.
------------------------------------------------------------------------

III. Preliminary Finding on the Applications

    TUVRNA submitted acceptable applications for expansion of its scope
of recognition. OSHA's review of the application files and detailed on-
site assessments indicate that TUVRNA can meet the requirements
prescribed by 29 CFR 1910.7 for expanding recognition to include the
addition of four sites and these two test standards for NRTL testing
and certification. This preliminary finding does not constitute an
interim or temporary approval of TUVRNA's applications.
    OSHA welcomes public comment as to whether TUVRNA meets the
requirements of 29 CFR 1910.7 for expansion of its recognition as a
NRTL. Comments should consist of pertinent written documents and
exhibits. Commenters needing more time to comment must submit a request
in writing, stating the reasons for the request by the due date for
comments. OSHA will limit any extension to 10

days unless the requester justifies a longer time period. OSHA may deny
a request for an extension if it is not adequately justified. To obtain
or review copies of the exhibits identified in this notice, as well as
comments submitted to the docket, contact the Docket Office,
Occupational Safety and Health Administration, U.S. Department of
Labor, listed in ADDRESSES. These materials also are available online
at https://www.regulations.gov under Docket No. OSHA-2007-0042.
    OSHA staff will review all comments to the docket submitted in a
timely manner. After addressing the issues raised by these comments,
staff will make a recommendation to the Assistant Secretary for
Occupational Safety and Health on whether to grant TUVRNA's
applications for expansion of its scope of recognition. The Assistant
Secretary will make the final decision on granting the applications. In
making this decision, the Assistant Secretary may undertake other
proceedings prescribed in Appendix A to 29 CFR 1910.7.
    OSHA will publish a public notice of this final decision in the
Federal Register.

Authority and Signature

    Loren Sweatt, Deputy Assistant Secretary of Labor for Occupational
Safety and Health, authorized the preparation of this notice.
Accordingly, the Agency is issuing this notice pursuant to 29 U.S.C.
657(g)(2), Secretary of Labor's Order No. 1-2012 (77 FR 3912, Jan. 25,
2012), and 29 CFR 1910.7.

    Signed at Washington, DC, on July 24, 2018.
Loren Sweatt,
Deputy Assistant Secretary of Labor for Occupational Safety and Health.
[FR Doc. 2018-16214 Filed 7-27-18; 8:45 am]
 BILLING CODE 4510-26-P


[Federal Register: October 31, 2008 (Volume 73, Number 212)]
[Notices]
[Page 65009-65010]
[DOCID:fr31oc08-136]

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DEPARTMENT OF TRANSPORTATION

Federal Motor Carrier Safety Administration

[Docket No. FMCSA-00-7165; FMCSA-04-17984; FMCSA-05-23238; FMCSA-06-
24783]

Qualification of Drivers; Exemption Renewals; Vision

AGENCY: Federal Motor Carrier Safety Administration (FMCSA), DOT.

ACTION: Notice of final disposition.

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SUMMARY: FMCSA previously announced its decision to renew the
exemptions from the vision requirement in the Federal Motor Carrier
Safety Regulations for 13 individuals. FMCSA has statutory authority to
exempt individuals from the vision requirement if the exemptions
granted will not compromise safety. The Agency has reviewed the
comments submitted in response to the previous announcement and
concluded that granting these exemptions will provide a level of safety
that will be equivalent to, or greater than, the level of safety
maintained without the exemptions for these commercial motor vehicle
(CMV) drivers.

FOR FURTHER INFORMATION CONTACT: Dr. Mary D. Gunnels, Director, Medical
Programs,<PHONE_NUMBER><EMAIL_ADDRESS>FMCSA, Department of
Transportation, 1200 New Jersey Avenue, SE., Room W64-224, Washington,
DC 20590-0001. Office hours are from 8:30 a.m. to 5 p.m. Monday through
Friday, except Federal holidays.

SUPPLEMENTARY INFORMATION:

Electronic Access

    You may see all the comments online through the Federal Document
Management System (FDMS) at http://www.regulations.gov.

Background

    Under 49 U.S.C. 31136(e) and 31315, FMCSA may grant an exemption
for a 2-year period if it finds ``such exemption would likely achieve a
level of safety that is equivalent to, or greater than, the level that
would be achieved absent such exemption.'' The statute also allows the
Agency to renew exemptions at the end of the 2-year period. The comment
period ended on October 9, 2008.

Discussion of Comments

    FMCSA received no comments in this proceeding.

Conclusion

    The Agency has not received any adverse evidence on any of these
drivers that indicates that safety is being compromised. Based upon its
evaluation of the 13 renewal applications, FMCSA renews the Federal
vision exemptions for Robert L. Aurandt, Donald Bostic, Jr., Harry R.
Brewer, Clarence N. Florey, Jr., Joseph H. Fowler, Donald R. Hiltz,
Kelly R. Konesky, Gregory T. Lingard, Hollis J. Martin, Kevin C.
Palmer, Charles O. Rhodes, Gordon G. Roth, and Daniel A. Sohn.
    In accordance with 49 U.S.C. 31136(e) and 31315, each renewal
exemption will be valid for 2 years unless revoked earlier by FMCSA.
The exemption will be revoked if: (1) The person fails to comply with
the terms and conditions of the exemption; (2) the exemption has
resulted in a lower level of safety than was maintained before it was
granted; or (3) continuation of the exemption would not be consistent
with the goals and objectives of 49 U.S.C. 31136 and 31315.

    Issued on: October 21, 2008.
Larry W. Minor,
Associate Administrator for Policy and Program Development.
[FR Doc. E8-26059 Filed 10-30-08; 8:45 am]

BILLING CODE 4910-EX-P


[Federal Register Volume 81, Number 105 (Wednesday, June 1, 2016)]
[Notices]
[Pages 35029-35031]
[FR Doc No: 2016-12829]

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DEPARTMENT OF HEALTH AND HUMAN SERVICES

Food and Drug Administration

[Docket No. FDA-2015-E-0861]

Determination of Regulatory Review Period for Purposes of Patent
Extension; OTEZLA

AGENCY: Food and Drug Administration, HHS.

ACTION: Notice.

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SUMMARY: The Food and Drug Administration (FDA) has determined the
regulatory review period for OTEZLA and is publishing this notice of
that determination as required by law. FDA has made the determination
because of the submission of an application to the Director of the U.S.
Patent and Trademark Office (USPTO), Department of Commerce, for the
extension of a patent which claims that human drug product.

DATES: Anyone with knowledge that any of the dates as published (in the
SUPPLEMENTARY INFORMATION section) are incorrect may submit either
electronic or written comments and ask for a redetermination by August
1, 2016. Furthermore, any interested person may petition FDA for a
determination regarding whether the applicant for extension acted with
due diligence during the regulatory review period by November 28, 2016.
See ``Petitions'' in the SUPPLEMENTARY INFORMATION section for more
information.

ADDRESSES: You may submit comments as follows:

Electronic Submissions

    Submit electronic comments in the following way:
     Federal eRulemaking Portal: http://www.regulations.gov.
Follow the instructions for submitting comments. Comments submitted
electronically, including attachments, to http://www.regulations.gov
will be posted to the docket unchanged. Because your comment will be
made public, you are solely responsible for ensuring that your

comment does not include any confidential information that you or a
third party may not wish to be posted, such as medical information,
your or anyone else's Social Security number, or confidential business
information, such as a manufacturing process. Please note that if you
include your name, contact information, or other information that
identifies you in the body of your comments, that information will be
posted on http://www.regulations.gov.
     If you want to submit a comment with confidential
information that you do not wish to be made available to the public,
submit the comment as a written/paper submission and in the manner
detailed (see ``Written/Paper Submissions'' and ``Instructions'').

Written/Paper Submissions

    Submit written/paper submissions as follows:
     Mail/Hand delivery/Courier (for written/paper
submissions): Division of Dockets Management (HFA-305), Food and Drug
Administration, 5630 Fishers Lane, Rm. 1061, Rockville, MD 20852.
     For written/paper comments submitted to the Division of
Dockets Management, FDA will post your comment, as well as any
attachments, except for information submitted, marked and identified,
as confidential, if submitted as detailed in ``Instructions.''
    Instructions: All submissions received must include the Docket No.
FDA-2015-E-0861 for ``Determination of Regulatory Review Period for
Purposes of Patent Extension; OTEZLA.'' Received comments will be
placed in the docket and, except for those submitted as ``Confidential
Submissions,'' publicly viewable at http://www.regulations.gov or at
the Division of Dockets Management between 9 a.m. and 4 p.m., Monday
through Friday.
     Confidential Submissions--To submit a comment with
confidential information that you do not wish to be made publicly
available, submit your comments only as a written/paper submission. You
should submit two copies total. One copy will include the information
you claim to be confidential with a heading or cover note that states
``THIS DOCUMENT CONTAINS CONFIDENTIAL INFORMATION.'' The Agency will
review this copy, including the claimed confidential information, in
its consideration of comments. The second copy, which will have the
claimed confidential information redacted/blacked out, will be
available for public viewing and posted on http://www.regulations.gov.
Submit both copies to the Division of Dockets Management. If you do not
wish your name and contact information to be made publicly available,
you can provide this information on the cover sheet and not in the body
of your comments and you must identify this information as
``confidential.'' Any information marked as ``confidential'' will not
be disclosed except in accordance with 21 CFR 10.20 and other
applicable disclosure law. For more information about FDA's posting of
comments to public dockets, see 80 FR 56469, September 18, 2015, or
access the information at: http://www.fda.gov/regulatoryinformation/dockets/default.htm.
    Docket: For access to the docket to read background documents or
the electronic and written/paper comments received, go to http://www.regulations.gov and insert the docket number, found in brackets in
the heading of this document, into the ``Search'' box and follow the
prompts and/or go to the Division of Dockets Management, 5630 Fishers
Lane, Rm. 1061, Rockville, MD 20852.

FOR FURTHER INFORMATION CONTACT: Beverly Friedman, Office of Regulatory
Policy, Food and Drug Administration, 10903 New Hampshire Ave., Bldg.
51, Rm. 6250, Silver Spring, MD 20993,<PHONE_NUMBER>.

SUPPLEMENTARY INFORMATION:

I. Background

    The Drug Price Competition and Patent Term Restoration Act of 1984
(Pub. L. 98-417) and the Generic Animal Drug and Patent Term
Restoration Act (Pub. L. 100-670) generally provide that a patent may
be extended for a period of up to 5 years so long as the patented item
(human drug product, animal drug product, medical device, food
additive, or color additive) was subject to regulatory review by FDA
before the item was marketed. Under these acts, a product's regulatory
review period forms the basis for determining the amount of extension
an applicant may receive.
    A regulatory review period consists of two periods of time: A
testing phase and an approval phase. For human drug products, the
testing phase begins when the exemption to permit the clinical
investigations of the drug becomes effective and runs until the
approval phase begins. The approval phase starts with the initial
submission of an application to market the human drug product and
continues until FDA grants permission to market the drug product.
Although only a portion of a regulatory review period may count toward
the actual amount of extension that the Director of USPTO may award
(for example, half the testing phase must be subtracted as well as any
time that may have occurred before the patent was issued), FDA's
determination of the length of a regulatory review period for a human
drug product will include all of the testing phase and approval phase
as specified in 35 U.S.C. 156(g)(1)(B).
    FDA has approved for marketing the human drug product OTEZLA
(apremilast). OTEZLA is indicated for treatment of adult patients with
active psoriatic arthritis. Subsequent to this approval, the USPTO
received a patent term restoration application for OTEZLA (U.S. Patent
No. 7,427,638) from Celgene Corporation, and the USPTO requested FDA's
assistance in determining this patent's eligibility for patent term
restoration. In a letter dated May 11, 2015, FDA advised the USPTO that
this human drug product had undergone a regulatory review period and
that the approval of OTEZLA represented the first permitted commercial
marketing or use of the product. Thereafter, the USPTO requested that
FDA determine the product's regulatory review period.

II. Determination of Regulatory Review Period

    FDA has determined that the applicable regulatory review period for
OTEZLA is 3,494 days. Of this time, 3,128 days occurred during the
testing phase of the regulatory review period, while 366 days occurred
during the approval phase. These periods of time were derived from the
following dates:
    1. The date an exemption under section 505(i) of the Federal Food,
Drug, and Cosmetic Act (the FD&C Act) (21 U.S.C. 355(i)) became
effective: August 28, 2004. FDA has verified the Celgene Corporation
claim that August 28, 2004, is the date the investigational new drug
application (IND) became effective.
    2. The date the application was initially submitted with respect to
the human drug product under section 505(b) of the FD&C Act: March 21,
2013. FDA has verified the applicant's claim that the new drug
application (NDA) for OTEZLA (NDA 205437) was initially submitted on
March 21, 2013.
    3. The date the application was approved: March 21, 2014. FDA has
verified the applicant's claim that NDA 205437 was approved on March
21, 2014.
    This determination of the regulatory review period establishes the
maximum potential length of a patent extension. However, the USPTO
applies several statutory limitations in its calculations of the actual
period for patent extension. In its application for patent extension,

this applicant seeks 1,186 days of patent term extension.

III. Petitions

    Anyone with knowledge that any of the dates as published are
incorrect may submit either electronic or written comments and ask for
a redetermination (see DATES). Furthermore, any interested person may
petition FDA for a determination regarding whether the applicant for
extension acted with due diligence during the regulatory review period.
To meet its burden, the petition must be timely (see DATES) and contain
sufficient facts to merit an FDA investigation. (See H. Rept. 857, part
1, 98th Cong., 2d sess., pp. 41-42, 1984.) Petitions should be in the
format specified in 21 CFR 10.30.
    Submit petitions electronically to http://www.regulations.gov at
Docket No. FDA-2013-S-0610. Submit written petitions (two copies are
required) to the Division of Dockets Management (HFA-305), Food and
Drug Administration, 5630 Fishers Lane, Rm. 1061, Rockville, MD 20852.

    Dated: May 25, 2016.
Leslie Kux,
Associate Commissioner for Policy.
[FR Doc. 2016-12829 Filed 5-31-16; 8:45 am]
 BILLING CODE 4161-01-P


38 Summary of Technical Literature Examining the Physiological Effects of Temperature What are the conclusions for incubation requirements?

Spawning signals the beginning of the life cycle stage ( egg deposition and initial egg incubation) that is most sensitive to warm waters. Critical spawning temperatures for a variety of salmonids are summarized in Table 5. Because the spawning period, egg fertilization, and initial incubation are sensitive life stages dependent on thermal regimes, special consideration must be given to ensure that criteria to protect incubation are applied at the proper time of year.

Table 5. Upper optimal temperature regimes based on constant or acclimation temperatures necessary to achieve full spawning protection of the nine key cold water fish species indigenous to the Pacific Northwest Fish species Critical spawn temperatures Upper optimal temperature range ° F ( ° C) Single daily maximum temperature ° F ( ° C)

Chinook 48.2 50 ( 9 10) 56.3 58.1 ( 13.5 14.5)

Pink 50 53.6 ( 10 12)

Chum 46.4 50 ( 8 10)

Char 35.6 42.8 ( 2 6) 42.8 ( 6)

Sockeye 46.4 50 ( 8 10)

Coho 44.6 50 ( 7 10)

Cutthroat 44.6 50 ( 7 10)

Rainbow 44.6 50 ( 7 10)

Steelhead 51.8 53.6 ( 11 12)

Growth For growth, what are the demands for energy and how is the balance determined by temperature?

In terms of energy budgets, fish production energy ( P) equals the sum of growth ( G), reproduction ( Rp), shed scales ( Ex), and secretions ( S), as shown in the following equation:

P = G + Rp + Ex + S.

Energy assimilated from food equals the difference between energy ingested and defecated, or A = I ! F.

Energy assimilated is distributed into production ( P), respiration ( R), and excretion ( U), as 39 Summary of Technical Literature Examining the Physiological Effects of Temperature follows:

A = P + R + U.

The symbols used above follow terminology of Ricker ( 1968) and Odum ( 1968).

Energy is needed to maintain the basic metabolic rate and is fundamental to sustain life. In addition, some energy must be diverted to activity ( swimming) to perform the functions of food capture, escape from predators, migrat ion, and so on. If the active metabolism is not sufficient ly high, energy is not available for feeding activity and, subsequently, growth and reproduction. When water temperatures rise toward lethal conditions, resting metabolism rate increases dramatically and feeding rat e declines to zero. When water temperatures are high, most of the fish's assimilated energy may be required simply to keep up with basic metabolic demand. When active metabolism ( energy expendit ure for swimming) declines so t he fish can divert available energy to basic metabolic demands, feeding declines. And, even when food is available, feeding no longer occurs if the temperature is above the feeding temperature limit. This may have an adaptive benefit, because digesting food under high temperature conditions incurs a metabolic demand ( specific dynamic action). The more overall energy the fish expends in basic metabolism and food digestion, given a declining food intake, the lower will be the assimilated energy that the fish can utilize for growth, reproduction, or resistance to environmental extremes. This latter use of energy is needed for resistance to disease and recuperation from cumulative stresses of predator avoidance, migration, high temperature stress, and so on ( Kelsch 1996).

Why is it important to be concerned with growth rate, production, and fish density?

Production is the elaboration of tissue by a population over a specified period of time, regardless of the fate of the tissue ( Warren 1971). Production energy is stored as body tissue growth, gametes, or released as secretions ( e. g., mucus). Production ( e. g., growth) for any time period in which growth rate is relatively constant can be calculated as the product of the growth rate ( e. g., mg/ g/ d) and mean biomass ( e. g., g/ m2). Production for longer time periods is calculated as the summation of production for the short time intervals in which growth rate is relatively constant. Production can also be computed graphically as the area under t he curve where number of individuals in the population at an instant in time is plotted against the mean weight of those individuals ( Warren 1971). Regardless what method is used to calculate production, production is clearly a funct ion of population size, survival, and growth rate, which in turn may be influenced by water temperature, other water quality factors, food availability, level of predation, and so on.

Temperature regime is an important influence on fish density. Control on density can occur through a combination of survival effects, behavioral avoidance, and interspecific competition. Li et al. ( 1993) reported a decline in steelhead biomass from 18 g/ m2 at a maximum summer water temperature of 60.8 ° F ( 16 ° C) in tributaries of the John Day River to 0 g/ m2 at a maximum temperature of 82.4 ° F ( 28 ° C). The sharp reduction in biomass with increasing temperature is an indication of either progressive mortality or emigration from zones exceeding temperature preferenda. Likewise, Ebersole et al. ( in press) reported for tributaries of the Grande Ronde River, Oregon, that rainbow trout density declined steadily between a mean daily maximum 40 Summary of Technical Literature Examining the Physiological Effects of Temperature temperature of 53.6 ° F ( 12 ° C) to zero at approximately 75.2 ° F ( 24 ° C). The literat ure on the effect of water temperature in controlling fish density is extensive ( McCullough 1999).

Because fish are mobile and migration to avoid high water temperatures is sometimes an option, it is not easy to extrapolate temperature fish density effects to a whole watershed to estimate total population size or population production. Nonetheless, the numerous studies showing a decline in fish density with increasing water temperature probably indicate lethal and sublethal effects and preference for habitats in which growth is optimum as much as they indicate simple avoidance behavior. Production is calculated as the product of growth rate and mean biomass ( see above). Energy stored as production is distributed primarily in somatic growth and reproduction. The ability to divert energy to reproduction is feasible when there is sufficient scope for activity and this depends on ambient temperatures and food availability. In addition, population viability is related to population abundance.

What is the optimum range o r optimum temperature for growth of various salmo nids?

Chinook. Chinook production in an experimentally modeled stream at 53.6 ° F ( 12 ° C) was 65% higher than at 60.8 ° F ( 16 ° C) ( Bisson and Davis 1976, as cited by CDWR 1988, p. 31). An optimum growth temperature of 59 ° F ( 15 ° C) was recommended by Banks et al. ( 1971 as cited by Garling and Masterson 1985). Brett et al. ( 1982) recommended 58.6 ° F ( 14.8 ° C) as the growth optimum for juvenile chinook feeding on a food ration of 60% of the maximum ( assumed to be a typical level in nature). Marine and Cech ( 1998) determined that growth rates of fall chinook under sublethal rearing temperatures ( 69.8 75.2 ° F [ 21 24 ° C]) were substantially less than growth rates at 55.4 60.8 ° F ( 13 16 ° C). Wilson et al. ( 1987) recommended 50.9 ° F ( 10.5 ° C) as the midpoint of the growth optimum for Alaskan chinook, based on studies in southeastern and southcentral Alaska. Preferred rearing temperatures for chinook were reported as high as 58.3 ° F ( 14.6 ° C) ( Reiser and Bjornn 1979). The preferred temperature range for fingerlings was 53.6 55.4 ° F ( 12 13 ° C) ( based on determination of mean of the distribution) when the fish were acclimated to temperatures ranging from 50 to 75.2 ° F ( 10 24 ° C) ( Brett 1952). If growth temperatures are maintained between 50 and 60 ° F ( 10 15.6 ° C), growth rate would be > 80% of the maximum level observed in feeding at 60% satiation ( a level considered by Brett et al. [ 1982] to correspond to naturally occurring food availability levels). Growth rate under 60% satiation feeding at 58.6 ° F ( 14.8 ° C) is expected to be approximately 1.8%/ d ( Brett et al. 1982). Lower levels of food availability would reduce the optimum growth temperature. Temperatures above 60 ° F ( 15.6 ° C) significantly increase the risk of mortality from warm water diseases. A synthesis of this evidence leads t o a recommended optimum production temperature zone of 50 60 ° F ( 10.0 15.6 ° C).

The optimal growth zone of 50 60 ° F ( 10 15.6 ° C) falls within the range for positive growth at 40.1 ° F ( 4.5 ° C) ( lower limit) and 66.4 ° F ( 19.1 ° C) ( upper limit) ( see Armour 1990). The 39.4 and 66.4 ° F ( 4.1 and 19.1 ° C) limits tabulated in Armour ( 1990) are zero net growth limits for a chinook population. Brett et al. ( 1982) reported a zero individual growth rate under 60% satiation feeding at 70.5 ° F ( 21.4 ° C) ( see Figure 2). If chinook were to have unlimited rations, the optimum growth temperature would be approximately 66.2 ° F ( 19 ° C) ( Brett et al. 1982).

Sockeye. Good growth of sockeye, with low mortality, occurred at 53 62 ° F ( 11.7 16.7 ° C) 41 Summary of Technical Literature Examining the Physiological Effects of Temperature ( Donaldson and Foster 1941). The upper limit to growth was similar to that observed by Brett et al. ( 1982) for chinook feeding at 60% of satiation. Sockeye ( 7 12 months old) feeding at satiation had a growth rate optimum at approximately 59 ° F ( 15 ° C). Growth rates declined at both higher and lower temperatures. Growth rates reached zero at approximately 75.2 ° F ( 24 ° C) under satiation feeding. When feeding rate was lowered to 1.5%/ d, the optimum growth temperature declined drastically to 41 ° F ( 5 ° C). At this feeding rate, growth rate (%/ d) was zero at approximately 59 ° F ( 15 ° C) ( Brett et al. 1969). Feeding rat es of Skaha Lake sockeye at 62 ° F ( 16.7 ° C) were 2.3% 3.2%/ d ( fresh weight; based on a sample of the 2 wk periods having mean temperatures of 62 ° F [ 16.7 ° C]). Feeding rates were approximately 2.2%/ d at 50 ° F ( 10 ° C), but the optimum growth occurred at this low temperature ( Donaldson and Foster 1941). Optimum Figure 2. Optimum growth ra tes of spring ch inook under various feeding regimes and constant temperatures.

growth temperature was 59 ° F ( 15 ° C) at a ration of 6%/ d, but this declined to an optimum growth temperature of 41 ° F ( 5 ° C) at a ration of 1.5%/ d ( Brett et al. 1969). 42 Summary of Technical Literature Examining the Physiological Effects of Temperature Steelhead. Wurtsbaugh and Davis ( 1977) studied growth of steelhead trout in laboratory streams under three fluctuating temperature regimes ( natural cycle, natural + 5.4 ° F [ 3 ° C], and natural + 10.8 ° F [ 6 ° C]) in all four seasons and found that trout growth could be enhanced by temperature increases up to 61.7 ° F ( 16.5 ° C). During the summer season the control temperature ( natural cycle) was 61.2 ° F ( 16.2 ° C) ( mean) and the elevated temperatures averaged 67.1 ° F ( 19.5 ° C) and 72.5 ° F ( 22.5 ° C). The average diel temperature range for the summer growth period was about 38.1 ° F ( 3.4 ° C) under the three treatments. Growth rates under food consumption rates of 5% 15% dry body wt/ d were higher under t he control temperature regime than at the elevated fluctuating regimes. Under the high temperature regime ( mean of 72.5 ° F [ 22.5 ° C]) growth rate was zero at a food consumption rate of 7%/ d. Gross food conversion efficiency decreased as temperatures increased from 61.2 to 72.5 ° F ( 16.2 22.5 ° C). Maintenance rations increased by a factor of three over the temperature range 44.4 72.5 ° F ( 6.9 22.5 ° C).

What more is specifically know n about g rowth rea ring requirements of rainbow trout?

Final preferred and optimal temperatures for rainbow trout have been reported at 53.6 66.2 ° F ( 12 19 ° C) ( Bell 1986, Taylor and Barton 1992), and scope of activity and growth for juvenile fish are commonly reported t o be optimal between 59 and 69.8 ° F ( 15 21 ° C) on a satiation diet ( Moyle 1976, McCauley and Pond 1971, Dickson and Kramer 1971, Kwain and McCauley 1978, and Huggins 1978 as cited in Kwain and McCauley 1978). However, some authors have suggested lower optimal temperature ranges. Piper et al. ( 1982) set the optimal at 50 62.1 ° F ( 10 16.7 ° C), although Sadler et al. ( 1986) found that growth and food conversion efficiency were greater at 60.8 ° F ( 16 ° C) compared with 50 ° F ( 10 ° C). McCauley and Huggins ( 1975) found that large ( 150 250 g) rainbow trout had a preferred mean temperature of 62.1 ° F ( 16.7 ° C), and that t he fish actively traveled at temperatures between 56.8 and 64.4 ° F ( 13.8 18 ° C) in a thermal gradient. Behnke ( 1992) suggested that the optimum temperature for growth and food assimilation in salmonids occurs between 55.2 and 60.8 ° F ( 13 16 ° C). Ferguson ( 1958) cites 56.5 ° F ( 13.6 ° C) as the final preferred temperature for rainbow trout, and Mckee and Wolf ( 1963, cited in Wedemeyer et al., no date) found 55.4 ° F ( 13 ° C) to be optimum. Kwain and McCauley ( 1978) suggest t hat fish over 1 year old may have a final preferred temperature of 55.4 ° F ( 13 ° C) ( cit ing the works of Garside and Tait 1958, Christ ie as reported in Fry 1971, and McCauley et al. 1977, as cited in Kwain and McCauley 1978) although as noted above, the work of McCauley and Huggins ( 1975) suggests that older fish sometimes demonstrate more intermediate temperature preferences.

Dockray et al. ( 1996) found that in a fluctuating temperature environment, temperature increases benefited growth up to daily maximum temperatures of 64.4 ° F ( 18 ° C), above which long term growth was inhibited. De Leeuw ( 1982) found that stream temperature increases that raised the summertime maximum temperature from 53.6 to 61.7 ° F ( 12 16.5 ° C) were associated with an increase in growth rates in three streams in British Columbia, Canada. Hokanson et al. ( 1977) found that a constant exposure to 63 ° F ( 17.2 ° C) produced the greatest growth rates in trout fed to satiation over a 40 d test period. Increased mortality was observed in temperatures above this growth optimum. They also noted that in fluctuating temperature experiments, growth was accelerated when the mean temperature was below the const ant temperature optimum ( 63 ° F [ 17.2 ° C]), and growth was retarded by mean fluctuating temperatures above this optimum. The highest growth rate in the fluctuat ing temperature environment occurred at a mean of 59.9 ° F 43 Summary of Technical Literature Examining the Physiological Effects of Temperature ( 15.5 ° C) ( range of 53 66.7 ° F [ 11.7 19.3 ° C]). A statistically nonsignificant decrease occurred at a mean of 63.1 ° F ( 17.3 ° C) ( range of 56.3 70 ° F [ 13.5 21.1 ° C]). The authors also concluded that rainbow trout acclimate to some temperature between the mean and the maximum daily temperatures. Sometimes, warmer waters may provide secondary benefits to rainbow trout. Cunjak and Green ( 1986) found that rainbow trout were able to compete better with brook trout at 66.2 ° F ( 19 ° C) than at either 46.4 or 55.4 ° F ( 8 or 13 ° C).

Bisson and Davis ( 1976, as cited in Li et al. 1994) found that streams with daily maximum temperatures of 60.8 73.4 ° F ( 16 23 ° C) had greater standing crops of trout than did streams with warmer maximum temperatures ( 78.8 87.8 ° F [ 26 31 ° C]). Frissell et al. ( 1992) studied the distribution of rainbow trout and found that although they could be found in water temperatures over 73.4 ° F ( 23 ° C), there was a general threshold response for age 1+ fish above 71.6 ° F ( 22 ° C) and for age 2+ fish above 69.8 ° F ( 21 ° C). Consistent with these results, Li et al. ( 1993, 1994, and 1991 as cited in Spence et al. 1996) noted that even though rainbow trout might not show avoidance reactions when stream temperatures were below 68 ° F ( 20 ° C), they actively avoided waters warmer than 73.4 77 ° F ( 23 25 ° C). Linton et al. ( 1997) noted that rainbow trout fed to satiation continued to feed and grow at a mean temperature of 68.9 ° F ( 20.5 ° C), a 30% reduction in food intake occurred at 71.6 ° F ( 22 ° C), and juvenile fish continued to feed near their thermal maximum. Linton et al. ( 1997) found that increasing the temperature regime by 3.6 ° F ( 2 ° C) over the natural ( base) level for Lake Ontario trout resulted in increased spring and early summer growth, which was lost later in the summer due to suppression of appetite and growth. Mortality rates increased from 6% to 13.1% in the warmer test water during the late summer in the first summer of testing when the mean monthly base temperature in August was 73.4 ° F ( 23 ° C). Mortality was almost nonexistent through the following summer, which had a mean August base temperature of 64.4 ° F ( 18 ° C) ( the test wat ers should have had a mean of 68 ° F [ 20 ° C]). The threshold temperature for cessation of feeding, and subsequently growth, differed from > 68 ° F ( 20 ° C) to < 68 ° F ( 20 ° C) over the two summers, and thus also fish size and age. Behnke ( 1992) cited work showing that trout reduce and finally cease feeding as temperatures rise to between 71.6 and 77 ° F ( 22 25 ° C), often well below the lethal temperature.

Although the works of Li et al. ( 1991, 1993, 1994) cited above were conducted on interior forms of rainbow trout, Behnke ( 1992) reported finding redband trout in the desert basins of southern Oregon and northern Nevada where temperatures regularly kill other trout. Trout in these intermittent desert streams were found actively feeding in water of 82.9 ° F ( 28.3 ° C). Behnke suggested that redband trout from an Oregon desert basin have an optimum feeding temperature at some untested temperature higher than 66.2 ° F ( 19 ° C). These desert redband might have a functional feeding temperature that is higher than that of rainbow trout, which have evolved in less harsh environments of temperature and water flow. A test was evaluated that compared an introduced population of rainbow trout in the Firehole River in Montana with two hatchery stocks. Temperatures in the Firehole River in summer at times reached as high as 85.1 ° F ( 29.5 ° C) due to thermal springs. The introduced population had been living in the river for approximately 20 generations, yet it was found that neither the functional feeding temperature nor the upper incipient lethal temperature had increased compared with the hat chery stocks. The author concluded that thousands of years of adaptation to a dry environment have enabled Oregon desert redband trout to feed at high temperatures, but 60 70 years seem too few to have allowed the introduced rainbow trout to raise their functional feeding temperature in the Firehole River. 44 Summary of Technical Literature Examining the Physiological Effects of Temperature Kaya et al. ( 1977) found that daily maximum temperatures exceeding 77 ° F ( 25 ° C) caused rainbow trout to move out of the mainstem of the Firehole River in Montana. These fish would move into tributary streams that averaged 10.8 18 ° F ( 6 10 ° C) lower in temperature.

The above research shows a wide range in the estimates of optimal temperature for rearing rainbow trout. This wide range may reflect the fact that the individual subspecies and specific stocks have evolved differently to fit the charact eristics of their home streams. Also, different ages and sizes of fish were used in the research. Equally plausible is that some of the temperatures for redband trout that were higher than noted for rainbow trout or other salmonids might have been based on an improper assumption that temperatures measured in the vicinity of the fish were actually those that the fish inhabited   that is, fish might actually inhabit microhabitat or habitat scale refugia to maintain their populations in otherwise hostile conditions ( see Ebersole et al. in press). Because criteria must protect bot h adult and juvenile forms of rainbow trout, an optimal temperat ure regime seems to most consistently occur in the range o f 55.4 60.8 ° F ( 13 16 ° C).

What is the relationship between growth temperatures and other physiological responses?

When fish demonstrate temperature preference in a thermal gradient, this is an adaptive mechanism that allows them to be positioned in an environment where they can achieve optimum physiological performance ( Coutant 1987, Hutchison and Maness 1979). Hutchison and Maness ( 1979) cited numerous physiological processes t hat achieve optimum performance near the thermal preferendum: growth rate, appetite, food conversion efficiency, digestion, egestion, metabolic scope, oxygen debt load, maximum sustained speed, maximum volitional speed, resting and active blood pressure, active cardiac work, cardiac scope, learning and memory, immune response, renal function, hormone secretion, reproductive function, elimination of anaerobically produced lactate, and enzyme act ivity.

Temperatures preferred or avoided are highly correlated with key physiological indices ( Stauffer 1980). Final temperature preference is correlated with optimal growth temperature ( Jobling 1981, Kellogg and Gift 1983, Christie and Regier 1988). Kellogg and Gift ( 1983) found for four fish species that nearly all preferred temperatures measured were in a range that provided 75% of maximum growth rate. The physiological optimum is derived by averaging the growth optimum and preferred temperature ( Brett 1971). Preferred temperature also is correlated with the temperature providing the maximum metabolic scope. This, in turn, is related to the temperature providing the maximum critical swimming speed ( Kelsch and Neill 1990). Also, fish tend to be more immunologically resistant to pathogens at their preferred temperatures ( Sniezko 1974, Cuchens and Clem 1977, Avtalion et al. 1980, O'Neil 1980, Rijkers et al. 1980, Avtalion 1981, Wishkovsky and Avtalion 1982, all cited in ODEQ 1995).

The preferred temperature range for chinook fingerlings was 53.6 55.4 ° F ( 12 13 ° C) ( based on determination of mean of the distribution) when acclimated to temperatures ranging from 50 to 75.2 ° F ( 10 24 ° C) ( Brett 1952). If growth temperatures are maintained between 50 and 60 ° F ( 10 15.6 ° C), growth rate would be > 80% of the maximum level observed in feeding at 60% satiation ( a level considered by Brett et al. [ 1982] to correspond to naturally occurring food availability 45 Summary of Technical Literature Examining the Physiological Effects of Temperature levels).

For sockeye, Brett ( 1971) found that swimming capacity, metabolic scope, growth on excess rations, and ingestion were maximized at 59 ° F ( 15 ° C). The temperature producing the growth optimum ( 59 ° F [ 15 ° C]) also was the final thermal preferendum determined by acute tests ( Brett 1952, 1971). A correlation between final preferred temperature and optimum growth has been found in numerous other fish species ( Christie and Regier 1988). In coho, it was found that swimming speed was maximum at 68 ° F ( 20 ° C), but growth reached a maximum on excess food rations at 62.6 68 ° F ( 17 20 ° C) ( Griffiths and Alderdice 1972).

What are temperature feeding limits for salmonids?

Temperature feeding limits are the upper and lower temperatures that result in inhibition of feeding. The ability to consume food does not guarantee that growth occurs. Food intake rate and conversion efficiency ( assimilation rate) at any temperature dictate the amount of energy assimilated. However, if metabolism rate exceeds energy assimilation rate, no energy is available for growth. In fact, the fish would lose weight because energy stored in tissue is used for metabolism.

Brett et al. ( 1982) o bserved feeding behavior of juvenile chinook from the Nechako River, in British Columbia, and the Big Qualicum River, on Vancouver Island. They reported good feeding response to unlimited food supply at 71.6 ° F ( 22 ° C), but feeding became more sporadic between 73.4 and 77 ° F ( 23 25 ° C), at which point it ceased.

Fingerling sockeye began losing appetite at 73.9 ° F ( 23.3 ° C) and stopped feeding at 75.2 ° F ( 24 ° C). Maximum feeding rate was measured as 8% dry body wt/ d at 68 ° F ( 20 ° C). Redband trout can be expected to set the upper limit for feeding response for all salmonids of the Pacific Northwest. No feeding was observed by Sonski ( 1982 as cited by Sonski 1984) for juvenile redband at 77.9 80.6 ° F ( 25.5 27 ° C). Comparing thermal tolerance by three rainbow trout species, Sonski ( 1984) found that no redband trout or Wytheville rainbow would feed at temperatures > 78.8 ° F ( 26 ° C). The Firehole River stock would not feed beyond 80 ° F ( 26.7 ° C).

In CTM ( critical thermal maximum) experiments in which the heating rate was 3.6 ° F ( 2 ° C)/ d, five species of juvenile salmonids were observed feeding up to temperatures that were 1.8 3.6 ° F ( 1 2 ° C) less than the LT50 ( Grande and Anderson 1991). Lake trout, brook trout, brown trout, rainbow trout, and Atlantic salmon were observed feeding at temperatures of 74.8, 78.2, 79.1, 79.9, and 82.6 ° F ( 23.8, 25.7, 26.2, 26.6, and 28.1 ° C), respect ively, reached during CTM experiments. A similar CTM experiment with Salmo apache in which temperature was increased 1.8 2.7 ° F ( 1 1.5 ° C)/ d showed that fish began refusing food at 68 ° F ( 20 ° C) and t otally stopped feeding at 70.1 ° F ( 21.2 ° C) ( Alco rn 1976). In no rthern California streams, juvenile steelhead were seen actively feeding in water temperatures as high as 75.2 ° F ( 24 ° C) ( Nielsen et al. 1994). However, once temperatures reached 71.6 ° F ( 22 ° C), rate of foraging began to decline.

How is feeding rate affected by acclimation temperature?

The highest temperature for normal feeding in brown trout varies with acclimation 46 Summary of Technical Literature Examining the Physiological Effects of Temperature temperature, as is probable for all fish species. Elliott ( 1981) determined that the highest temperature for normal feeding in brown trout that were acclimated to 59 ° F ( 15 ° C) was 19.1 ° C ± 0.27 ( SE). Similarly, Frost and Brown ( 1967) determined that feeding rate declined sharply above 66.2 ° F ( 19 ° C) in brown trout. When fish were acclimated to 68 ° F ( 20 ° C), no feeding took place. Under cold temperature regimes, when brown trout were acclimated to water at 50 ° F ( 10 ° C), normal feeding occurred when fish were subjected to 2.9 ° C ± 0.27. When acclimated to even lower temperature 41 ° F ( 5 ° C), normal feeding occurred at 0.4 ° C ± 0.21.

What are temperature growth limits for salmonids?

Temperature growth limits for salmonids are those lower and upper temperatures that result in zero growth on an individual basis or zero net growth of the population. The zero net growth temperature is the temperature at which net elaborat ion of tissue of the population is zero o r the temperature at which fish mortality balances the gain in growth.

With chinook, the bounds for positive growth occur at 40.1 ° F ( 4.5 ° C) ( lower limit) and 66.4 ° F ( 19.1 ° C) ( upper limit) ( see Armour 1990). The 39.4 ° F ( 4.1 ° C) and 66.4 ° F ( 19.1 ° C) limits tabulat ed in Armour ( 1990) are zero net growth limits for a chinook population. Bret t et al. ( 1982) reported a zero individual growth rate under 60% satiation feeding at 70.5 ° F ( 21.4 ° C).

Juvenile sockeye had a positive growth response between 39.2 and 69.8 ° F ( 4 21 ° C) in laboratory experiments with feeding to satiation once per day ( Donaldson and Foster 1941). Growth rate was negative at 73 ° F ( 22.8 ° C), and at this temperature mortality was significant. Good growth with low mortality occurred at 53 62 ° F ( 11.7 16.7 ° C) ( Donaldson and Foster 1941). The upper limit to growth was similar to that observed by Brett et al. ( 1982) for chinook feeding at 60% of satiation rations.

Brown trout growth can be high in the temperature range 44.6 66.2 ° F ( 7 19 ° C), but growth is poor above 68 ° F ( 20 ° C) ( Frost and Brown 1967).

Wurtsbaugh and Davis ( 1977) studied growth of steelhead trout in laboratory streams under three fluctuating temperature regimes ( natural cycle, natural + 5.4 ° F [ 3 ° C], and nat ural + 10.8 ° F [ 6 ° C]) in all four seasons and found that trout growth could be enhanced by temperature increases up to 61.7 ° F ( 16.5 ° C). During the summer season the control temperature ( natural cycle) was 61.1 ° F ( 16.2 ° C) ( mean) and the elevated temperatures averaged 67.1 and 72.5 ° F ( 19.5 and 22.5 ° C). The average diel temperature range for the summer growth period was about 6.1 ° F ( 3.4 ° C) under the three treatments. Growth rates under food consumption of 5% 15% dry body wt/ d were higher under the control temperature regime than at the elevated fluctuating regimes. Under the high temperature regime ( mean of 72.5 ° F [ 22.5 ° C]), growth rate was zero at a food consumption rate of 7%/ d.

How does food availability affect growth of salmonids at different temperature exposures?

In a laboratory setting, feeding rations can be controlled by the researchers. Feeding to satiation at a frequency of three to five times a day is not uncommon in growth experiments and is 47 Summary of Technical Literature Examining the Physiological Effects of Temperature considered to provide growth rates comparable to those under continuous feeding with excess food. In other studies, varying feeding regimes may be used to determine the temperature effects on growth at different levels of food availability.

In the field, stream productivity and nutrient availability to salmonids depend on many factors including light; nutrients including inputs of litter, decomposing salmon carcasses, and coarse woody debris; sediment loading; temperature; and streamflow ( Murphy 1998, Bilby et al. 1996). Other factors t hat may limit fish feeding in the wild include suitable instream cover and species or density dependent competition and predation ( Richardson 1993).

Food limitations in trout streams commonly cause reductions in summer growth ( Cada et al. 1987, Enseign and Strange 1990). If there is food limitation in the field, growth rates will be less than maximum for salmon and bull trout at temperatures that produce maximum growth under satiation feeding. Growth rates have been observed in the field that are less than those predicted in the labo ratory under excess feeding and suggest t hat food limitation could be the cause ( Preall and Ringler 1989, Cada et al. 1987). With food limitation, the upper temperature that produces zero growth would decline to a lower temperature. Under conditions where fish have reduced feeding rates due to food limitation, conversion efficiency can increase somewhat to compensate for the limitation in total energy intake. However, if the food limitation is significant, the energy demands of standard metabolism may be difficult to satisfy ( Cada et al. 1987). This may limit the scope of activity required to acquire food. Behavioral inhibition in swimming at higher temperatures and lack of competitive ability in foraging compared with fish tolerant of warm water can place salmonids at a disadvantage in deriving maintenance energy requirements.

Gut fullness may be an indicator of food availability. Gut fullness was monitored on several fish species on various dates from late July to mid October in several tributaries of the upper Yakima River as an index of food availability ( James et al. 1998). During this sampling period, temperatures were > 57.2 ° F ( 14 ° C). Species monitored included mountain whitefish, spring chinook, redside shiner, and rainbow trout. A high degree of diet overlap was found among the four fish species studied, indicating that competition for food is possible. Gut fullness and diet overlap together were assumed to indicate degree of competition. Summertime gut fullness for spring chinook averaged 14%, while mountain whitefish, rainbow trout, and redside shiner averaged 32%, 10%, and 10%, respectively. Low stomach fullness may indicate a low availability of food due t o production of food and intense competition. It is not clear from this research, however, what gut fullness level would be expected under satiation feeding. Growth rates are the bottom line. Comparison of growth rates at various feeding levels in t he laboratory with rat es in the field under comparable temperat ures appears to be the most direct means to infer food supply.

If food becomes limited, the positive growth zone can shrink dramatically ( i. e., the maximum temperature at which growth is positive declines) and the optimum growth zone shifts to lower temperatures to compensate for elevated respiration/ growth ratios ( Elliott 1981, p. 231). McMahon et al. ( 1999) found that growth curves for bull trout clearly depict a shift to maximum growth at lower temperatures ( 46 and 53 ° F [ 8 and 12 ° C]) when energy availability is low. Elliott found that for brown trout the temperature at which growth is zero drops from 66.2 to 46.4 ° F ( 19 8 ° C) when food rations are reduced from maximum to 12.5% of maximum. Because the growth optimum falls within 50 60 ° F ( 10 15.6 ° C) for chinook and because diseases become a 48 Summary of Technical Literature Examining the Physiological Effects of Temperature significant mortality risk beyond this level, water temperatures in major salmon rearing reaches must be managed on a stream network level from headwaters to mainstem so that temperatures can be maintained below 60 ° F ( 15.6 ° C) within the hist oric salmon rearing area and below 53.6 ° F ( 12 ° C) in bull trout historic rearing areas. Given that food rations under field conditions are typically less than satiation levels, a reduced growth zone expands the upper temperature zone and causes loading stresses. This argues for keeping temperatures no higher than the optimum growth range.

Is there evidence for food limitation in natural streams?

A stream's capacity to produce food greatly affects both abundance and growth of fish. Some of the highest freshwater production value have been reported for trout in New Zealand; production values reported for the Pacific Northwest are considerably lower, by at least an order of magnitude ( Bisson and Bilby 1998).

Factors influencing stream productivity include nutrient availability, input of organic matter from external sources, the channel's capacity to store and process organic matter, and light ( Cederholm et al. 2000). The river continuum concept describes the predictable differences in stream productivity with changes in stream size ( Vannote et al. 1980). Headwater streams in the Pacific Northwest are characterized by low levels of primary and secondary productivity ( Gregory et al. 1987). In a large watershed, first to third order streams may produce only 10% 20% of the annual gross primary production, despite having more than 80% of total stream length ( Murphy 1998). Coho, steelhead, cutthroat, bull trout, and spring chinook are among the salmonids that utilize these small headwater streams for spawning and rearing.

Productivity of Northwest streams has been further diminished by the recent decline of Pacific salmon. The role salmon populations play in maintaining ecosystem function by recycling energy and nutrients from the North Pacific Ocean to the inland Northwest has been acknowledged in numerous studies ( see Cederhom et al. 2000). The carcasses of spawned out salmon greatly influence the productivity of the otherwise generally oligotrophic ecosystems of the Pacific Northwest ( Cederholm et al. 2000). With declines of Pacific salmon, it is estimated that only 3% of the marine derived biomass once delivered by anadromous salmon to the rivers of Puget Sound, the Washington coast, the Columbia River, and the Oregon coast is currently reaching those streams ( Gresh et al. 2000 in Cederholm et al. 2000).

Growth rates of wild rainbow trout in the field have generally been reported as < 1%/ d ( see review by Wurtsbaugh and Davis 1977) but were higher in the laboratory in every season under the natural temperature regime ( mean seasonal temperatures in the laboratory of 50, 44.4, 48.9 and 61.1 ° F [ 10, 6.9, 9.4, and 16.2 ° C] in autumn, winter, spring, and summer, respectively) when fish were fed t o satiation. This study revealed that trout growth was improved by increasing temperatures up to a maximum of 61.7 ° F ( 16.5 ° C), but that this threshold applies to the field only under satiation feeding. Because the researchers measured field growth rates in an Oregon coast al stream that indicated food limitation, they concluded that temperatures less than 61.7 ° F ( 16.5 ° C) would be optimal.

In the field an increase in water temperature, when produced by canopy removal, can lead to 49 Summary of Technical Literature Examining the Physiological Effects of Temperature increased primary production. Greater primary and secondary production can increase food availability to fish ( Murphy and Hall 1981, Hawkins et al. 1983) provided that substrate sedimentation does not increase with canopy removal. However, as temperatures continue to increase, primary production can be in the form of algae not readily consumed or digested by benthic macroinvertebrates ( e. g., blue green algae rather than diatoms) ( McCullough 1975, McCullough et al. 1979), and macroinvertebrate production can be dominated by species not readily available to salmonids in the drift ( Li et al. 1994). Even if food quality remains high with increasing temperature, feeding rate and growth decline beyond the optimum temperature. Additionally, over the long run, increases in primary production in early seral stage may eventually be outweighed by longer lasting reductions as a result of increased shade in later seral stages ( Murphy and Hall 1981). Second growth hardwoods and young conifers produce a denser canopy and lack the gaps commonly found in old growth forests ( Murphy 1998).

Can growth rates be predicted under field conditions using thermal history identified under laboratory conditions?

Growth rates under controlled field conditions can be related to growt h rates obtained under laboratory conditions if feeding rates and temperatures are known; however, many subtle variables in the field ( recruitment to or movement out of the study area, varied caloric content of forage, inter and intraspecies interactions) can complicate these comparisons. Differences between laboratory and field growth rates can be attributable to a great number of factors.

Typically, temperatures in laboratory experiments are kept constant ( i. e., fluctuating less than ± 1.8 ° F [ 1 ° C] around the mean). First, to compare laboratory and field growth rate we must know the field water temperature regime. Growth rates should be measured over days to weeks to improve the ability to detect a change. The temperature regime must be described by an index ( e. g., daily mean, daily maximum) in order to relate it to laboratory growth rates. For example, if growth rate under a constant laboratory temperature o f 50 ° F ( 10 ° C) is 2%/ d and under field conditions a 2%/ d growth rate is experienced by fish under a 50 ° F ( 10 ° C) ± 3.6 ° F ( 2 ° C) diel temperature regime, then we might conclude that the mean diel temperature in the field adequately represents the growth conditions. However, food is generally limiting in the field. If this is the case and if the mean field temperature adequately represents the growth response, we would expect field growth rate to be lower than laboratory rates at the same constant mean temperature. The situation can be more complicated, however, because growth rate is related to acclimation temperature. In a fluctuating temperature regime, fish can acclimate to a temperature between the mean and maximum of the cycle. If this is so, the feeding rate in the field ( and consequently growth rate) might be higher than under a const ant diel temperature equal to the mean of the cycle, despite the lower food availability. That is, there may be some compensation for lower food availability due to fluctuating temperature conditions. In summary, field growth depends on the food availability and quality, the effect ive acclimation temperature, and the exposure temperature.

The ability to model brown trout growth in the laboratory and field under fluctuat ing temperatures arose from Elliott's ( 1975a, b) studies of brown trout growth under constant temperatures. This model has often been found capable of predicting growth under both constant and fluctuating temperatures ( Elliott 1994). Elliott ( 1975a) found that growth rates in the 50 Summary of Technical Literature Examining the Physiological Effects of Temperature laborat ory over 42 d periods in which temperature fluctuated as much as ± 4.1 ° F ( 2.3 ° C) around the mean for the entire period closely matched those predicted by entering the mean temperature into the growth model. Growth experiments in the field ( a small stream near Windermere, England) were also conducted. In one experiment, temperature increased from 44.2 ° F ( 6.8 ° C) in March to 53.8 ° F ( 12.1 ° C) in June; in another, temperature decreased from 55.2 ° F ( 12.9 ° C) in August to 45 ° F ( 7.2 ° C) in November. Estimates of growth in the field made by entering the mean weekly temperatures ( calculated as the mean of seven daily mean temperatures) into the growth model revealed good agreement between predicted and actual final weights in a 4 wk growth period. Edwards et al. ( 1979) modeled brown trout growth on 10 British streams and were able to show that predicted growth was 60% 90% of potential growth, assuming feeding on maximum rations. Predicted monthly growth based on mean monthly temperatures was 2% different from computations based on temperatures taken every 4 h. Likewise, Preall and Ringler ( 1989) developed a computer model of brown trout growth based on Elliott's work and predicted potential growth for populations in three central New York streams based on initial weight, condition factor, and weekly mean temperature. These authors measured actual growth under fluctuating temperatures in the field that were 60% 90% of potential, as determined from their model. Jensen ( 1990) measured growth on 12 populations in Norwegian rivers and determined that mean growth rates of anadromous brown trout parr were 76% 136% of the maximum inferred from the temperature regime.

Jensen ( 1990) concluded from his field work that growth rates exceeding laboratory derived maxima under constant temperatures and satiation feeding could be explained by interpopulation genetic differences o r the ability of fish in the field to feed at great er rates under fluctuating temperatures than under constant temperatures. It is also possible that the ability to assess temperatures actually experienced in the field is poor and not well represented by mean reach temperature. Jensen ( 1990) noted t hat in two streams growth was best predict ed by using the 75% temperature ( the median between the mean and maximum), whereas for another stream growth was best predicted using mean temperature. Assuming that Jensen could measure the actual diel cycle experienced by brown trout in these streams, the similar ability of the 75% temperature in predicting growth and in estimating equivalent acclimation temperatures in UILT tests is interesting. It appears that physiological conditioning of fish in fluctuating temperatures adjusts their growth and thermal tolerance toward levels that would be predicted under constant temperatures located between the mean and the maximum.

Another possible explanation no t given by Jensen ( 1990) for greater growth rates in the field is that food quality in the field is better than that provided in laboratory experiments. Also, fat content of macroinvertebrates in the drift could be higher than the average of prey available in the benthos and provide a high calorie diet. Food quantity, however, is often considered limiting to fish growth in the field ( Brett et al. 1982). Growth rates of wild rainbow trout in the field have generally been reported as < 1%/ d ( see review by Wurtsbaugh and Davis 1977), but were higher than this in the laboratory in every season under the natural temperature regime ( mean seasonal temperatures in the laboratory of 50, 44.4, 48.9, 48.9 and 61.1 ° F [ 10, 6.9, 9.4, and 16.2 ° C] in autumn, winter, spring, and summer, respectively) when fish were fed to satiation.

Other studies have noted that mean temperatures are useful in predicting growth rates. Growth rates of sockeye fry ( Babine Lake, BC, stock) were measured at satiation feeding ( 3 51 Summary of Technical Literature Examining the Physiological Effects of Temperature times/ d) from March to mid May under three temperature regimes: constant 50 ° F ( 10 ° C), declining 23.4 to 12.6 ° F ( 13 to 7 ° C), and increasing 12.6 23.4 ° F ( 7 to 13 ° C). Mean temperature was 50 ° F ( 10 ° C) in each treatment. Rate of temperature change in the declining or increasing treatments was 1.8 ° F ( 1 ° C)/ wk over a 56 d period. Although mean temperature can be a suitable index to growth rate under a fluctuating temperature regime, the studies above did not subject fish to either extreme temperature maxima or extreme diel fluctuations.

Has acclimation to a temperature higher than the mean of a diel cycle been demonstrated?

In addition to the research discussed above, Clarke ( 1978) measured growth rates of juvenile sockeye in the laboratory at constant and fluctuating temperatures. At constant temperatures ranging from 45.5 to 63.5 ° F ( 7.5 17.5 ° C), growth rates increased linearly. This response was defined by the equation y = 0.0660x ! 0.311, where x is mean temperature and y is growth rate (% wt/ d). At 45.5 ° F ( 7.5 ° C), growth rate was approximately 0.2%/ d and at 63.5 ° F ( 17.5 ° C) it was approximately 0.8%/ d. At a constant 50 ° F ( 10 ° C) regime, growth rate was 0.35%/ d ( estimated by regression for all constant temperature growth experiments), but under fluctuating regimes of 44.6 55.4 ° F ( 7 13 ° C) and 41 59 ° F ( 5 15 ° C) ( mean daily temperatures of 50 ° F [ 10 ° C]), growth rates were about 0.47%/ d and 0.63%/ d, respectively. This study indicated that specific growth rate ( as % wt/ d) at 44.6 55.4 ° F ( 7 13 ° C) was equivalent to that observed at a constant temperature of 52.5 ° F ( 11.4 ° C). Under the diel regime with great amplitude ( 41 59 ° F [ 5 15 ° C]), growth was equivalent to that observed at a constant temperature of 57 ° F ( 13.9 ° C). This indicates that under diel fluctuating regimes, there was an acclimation to an equivalent temperature between the mean and the maximum temperature. In terms of growth rates, t his acclimation effect was similar to that observed in survival under thermal stress with prior acclimation in cyclic diel temperature regimes.

Are there seasonal differences in growth rates not related to temperature?

Jensen ( 1990) noted that a decreasing autumn temperature trend caused growth to be less at a given temperature than at the same temperature under a generally increasing temperature trend in spring. Such a seasonal effect has been observed in brown trout and Atlantic salmon by some authors, but others have not detected any seasonal difference at comparable temperatures ( Jensen 1990). A study by Mortensen ( 1985 as cited by Jensen 1990) indicated that 0+ and 1+ brown trout gro wth rate in the field during spring was accurately predicted using Elliott's model, but growth rate was only 60% 90% of predicted rates in summer and 0% 30% in winter. Jensen attributed the realized growth rate to seasonal limitation in food availability.

What research seems to best describe the influence of fluctuating temperature on growth?

Probably the best study of the effect of fluctuating temperature on salmonids is that of Hokanson et al. ( 1977). It is especially useful as a central point for evaluating other studies because of the range of temperatures evaluated, the fact that both growth and survival were evaluated, and its consistency with the vast literature on thermal effects. 52 Summary of Technical Literature Examining the Physiological Effects of Temperature Hokanson and colleagues studied growth and survival of rainbow trout ( O. mykiss) juveniles reared on maximum rations under fluctuating temperatures ( T ° F ± 6.8 ° F [ 3.8 ° C]) versus constant temperatures. The physiological optimum ( PO) temperature of rainbow trout is 60.8 64.4 ° F ( 16 18 ° C). These authors noted that specific growth rate at mean temperatures less than PO was lower for a given mean temperature under a co nstant ( T ° F) versus a fluctuating ( T ° F ± 6.8 ° F [ 3.8 ° C]) temperature regime. This indicates a benefit of a fluctuating regime when the mean temperature is less than PO. In this temperature zone, a constant temperature of T+ 2.2 ° F ( 1.5 ° C) provided comparable specific growth rate to juveniles reared at T ° F ± 6.8 ° F ( 3.8 ° C). In other words, we would have to increase an initial constant temperature by 2.7 ° F ( 1.5 ° C) to provide growth rates equivalent to t hose exhibited under a fluctuating regime having a mean equal to the initial constant temperature. However, specific growth rates at mean temperatures greater than PO were higher at constant than fluctuating temperatures having the same mean temperature. This indicates that when water temperature under field conditions is greater than PO, it is not safe to assume that a fluctuating regime is protective on the basis of its mean, even if the mean itself is not injurious under constant temperature experiment s. The negative influence of the diel cycle appears to come from exposure to temperatures higher than the mean when the mean is greater than PO.

This pattern led Hokanson and colleagues to suggest that the growth of rainbow trout appears to be accelerated under fluctuating temperatures when the mean temperature is below the constant temperature optimum for growth and retarded by fluctuating temperatures when the mean is higher. Hokanson et al. suggested that water quality standards ( based on weekly mean values) should be set such that the average weekly temperature is below the constant test temperature producing maximum growth. They determined that rainbow trout growth rates under fluctuating regimes do not correspond to those in a constant temperature regime having a mean equal to that for the cycle. Rat her, they acclimate to some value between the mean and maximum daily temperatures and consequently their growth rates reflect this " effective" temperature. Looked at ano ther way, the optimal fluctuating regime had a mean of 59.9 ° F ( 15.5 ° C) with a range of 53 66.7 ° F ( 11.7 19.3 ° C), and the optimal constant test temperature of 63 ° F ( 17.2 ° C) fell approximately midway between the daily mean and the daily maximum of the optimal fluctuating test.

Most of the research on o ptimal growth temperatures is conducted at a const ant temperature. Water quality standards, however, must apply to naturally fluctuating thermal environments. Because temperature directly affects the metabolism of fish, a fish kept continuously in warm water will experience more metabolic enhancement than one that experiences the same temperature for only 1 or 2 hours per day. Thus, constant test results cannot be reasonably applied directly to the daily maximum temperature in a fluctuating stream environment. Although the constant temperature test results could be used to represent daily mean temperatures, it is believed that the daily maximum temperature is more influential to the biology and should be the focus of any standards developed.

Clarke ( 1978) studied individual specific growth rates of underyearling sockeye salmon after 42 d at five constant temperatures ranging from 45.5 to 63.5 ° F ( 7.5 7.5 ° C) and two diel cycles of 44.6 55.4 ° F ( 7 13 ° C) and 41 59 ° F ( 5 15 ° C). At constant temperature, there was a linear increase in growth rate over the range 45.5 63.5 ° F ( 7.5 17.5 ° C). Bot h thermocycles had a mean of 50 ° F 53 Summary of Technical Literature Examining the Physiological Effects of Temperature ( 10 ° C), but growth was greater on the 41 59 ° F ( 5 15 ° C) cycle. The author notes that the equivalent constant temperature for specific growth rate in length on the 44.6 55.4 ° F ( 7 13 ° C) cycle was increased significantly from 50 ° F ( 10 ° C) in o ne replicate ( 54.1 ° F [ 12.3 ° C]) but no t in the other ( 51.4 ° F [ 10.8 ° C]). Specific growth rate in length on the 41 59 ° F ( 5 15 ° C) cycle was equivalent to t hat on a const ant temperature of 59.5 ° F ( 15.3 ° C). Specific growth rate in weight on the 44.6 55.4 ° F ( 7 13 ° C) cycle was equivalent to that on a constant 52.5 ° F ( 11.4 ° C); on the 41 59 ° F ( 5 15 ° C) cycle it was the equivalent of a constant 57 ° F ( 13.9 ° C). This study concludes that underyearling sockeye salmon exposed to diel thermocycles are able to acclimate their growth rates to a temperature above the mean of the cycle.

Dickerson et al. ( 1999 and unpublished data, as cited in Dunham 1999) conducted experiments with hatchery reared Pyramid Lake strain Lahontan cutthroat trout. Fish were exposed to 1 wk fluctuating temperatures ( 68 78.8 ° F [ 20 26 ° C]; mean = 73.4 ° F [ 23 ° C]) and to constant temperatures of 55.4, 68, and 73.4 ° F ( 13, 20, and 23 ° C). Growth rates in the fluctuating temperature tests were lower than for fish exposed to constant temperatures of 55.4 and 68 ° F ( 13 and 20 ° C), but were similar to groups of fish held at a constant 73.4 ° F ( 23 ° C).

Hahn ( 1977) invest igated the effect s of fluctuating ( 46.4 66.2 ° F [ 8 19 ° C]) and constant ( 47.3, 56.3, 65.3 ° F [ 8.5, 13.5, 18.5 ° C]) temperatures on steelhead trout fry and yearlings. He found that as many fish remained in the fluctuating regime as in the constant 56.3 ° F ( 13.5 ° C) temperature water; twice as many remained in the fluctuating temperature regime as remained in the constant 65.3 ° F ( 18.5 ° C) temperatures; and twice as many fish remained in constant 47.3 ° F ( 8.5 ° C) water as in the fluctuating temperature regime. By inference, Hahn found the relationship among the three constant temperatures was the same as the relationship of each to the fluctuating temperature: twice as many fish in 56.3 ° F ( 13.5 ° C) as in 65.3 ° F ( 18.5 ° C), twice as many fish in 47.3 ° F ( 8.5 ° C) as in 56.3 ° F ( 13.5 ° C), and four times as many fish in 47.3 ° F ( 8.5 ° C) as in 65.3 ° F ( 18.5 ° C). We can conclude from Hahn's work that juveniles had equal preference for constant ( 56.3 ° F [ 13.5 ° C]) water and fluctuat ing ( 46.4 66.2 ° F [ 8 19 ° C]) water with a mean of 56.3 ° F ( 13.5 ° C). Although not a growth t est, the Hahn study supports t he general premise t hat daily mean temperatures are reasonable approximations of constant exposure test temperatures.

Grabowski ( 1973) conducted growth experiments with steelhead trout. Fish were fed a percentage of body weight according to feeding charts twice per day based on temperature and changes in body weight. To evaluate growth, fish were subjected to four test temperatures for 8 wk. These four regimes were a fluctuat ing test from 46.4 to 64.4 ° F ( 8 18 ° C) ( mean 55.4 ° F [ 13 ° C]) and constant tests held at 46.4, 59, and 64.4 ° F ( 8, 15, and 18 ° C). Steelhead grew better at 59 ° F ( 15 ° C) than at ot her temperatures. Fish in the fluctuating test had the second highest growth rate and actual weight gain. Growth rate in the fluctuating test was only 13% less than that at the constant test of 59 ° F ( 15 ° C), while growth rates at 46.4 and 64.4 ° F ( 8 and 18 ° C) were 47% and 21% less, respectively. Plotting the data using the midpoint in the fluctuating test as a surrogate for a constant test condition creates near linear growth from 46.4 to 59 ° F ( 8 15 ° C), with a steep drop as temperature progresses to 64.4 ° F ( 18 ° C). Thus the mean of the fluctuat ing treatment appears generally comparable to a constant test temperature of the same value.

Thomas et al. ( 1986) investigated the effects of diel temperature cycles on coho salmon. Temperature cycles ( 50 55.4, 48.2 59, 46.4 62.6, and 43.7 68 ° F [ 10 13, 9 15, 8 17, and 54 Summary of Technical Literature Examining the Physiological Effects of Temperature 6.5 20 ° C]) were used to simulate observed temperatures in clearcuts of southeastern Alaska. Different levels of feeding, including starvation, were used in each of the tests. Cyclic temperatures for 40 d, averaging 51.8 ° F ( 11 ° C) daily, did not influence growth of age 0 fish on any ration in comparison to t he controls ( kept at a constant 51.8 ° F [ 11 ° C]). Plasma cortisol and glucose concentrations were significantly greater in fish maintained for 20 d in the 43.7 68 ° F ( 6.5 20 ° C) cycle, which may be an indicator of long term stress. Thus, in the work by Thomas et al. ( 1986) the daily mean of the fluctuating test and the constant test exposures produced essentially equivalent results, but stress conditions were noted to o ccur in cycles with daily peak temperatures of 68 ° F ( 20 ° C).

Everson ( 1973) used the data of Averett ( 1969) to show that growth rates and gross efficiencies of food conversion of fish kept at moderate constant temperatures ( 59.9 ° F [ 15.5 ° C]) were somewhat greater than those of fish exposed to temperatures that fluctuated about a similar mean value ( 60 ° F [ 15.6 ° C]), whereas at higher average temperatures the fluctuation of temperature markedly benefited the growth and food conversion efficiency of the fish. Thus Everson showed support for the assumption that fluctuating temperatures can produce greater benefits to growth than can higher constant temperatures.

What is the range of laboratory growth rates under fluctuating temperature vs. constant temperature?

There appears to be considerable controversy regarding the effect o f fluctuating temperatures vs. constant temperatures on juvenile growth rate. Peterson and Martin Robichaud ( 1989) studied growth of Atlantic salmon under daily temperature cycles of 53.6 68 ° F ( 12 20 ° C) and 60.8 68 ° F ( 16 20 ° C) relative to constant temperatures of 60.8 and 68 ° F ( 16 and 20 ° C) and could find no differences.

Thomas et al. ( 1986) measured growth of juvenile coho for 40 d periods under constant 51.8 ° F ( 11 ° C) temperature vs. diel temperature cycles of 50, 55.4, 48.2, 59, 46.4, 62.6, and 43.7 68 ° F ( 10 13, 9 15, 8 17, and 6.5 20 ° C), all of which averaged 51.8 ° F ( 11 ° C). They found that the growth rates of 0+ age fish at any of the food rations were not significantly different among temperature regimes, although the growth at 4% and 8% ration ( i. e., 8% of body weight/ day) was better than at 1%.

Konstantinov et al. ( 1989) reported that under fluctuat ing thermal regimes coho salmon have a decreased respiration rate and increased growth rate relative to that at constant temperatures. This coupling o f respiration and growth causes greater efficiency in use of assimilated energy in growth. Konstantinov and Zdanovich ( 1986 as cited by Behnke 1992) measured greater growth rates in several fish species under fluctuating vs. constant temperature regimes. Konstantinov et al. ( 1989), summarizing several of their studies on effect of fluctuating thermal regimes on fish, stated that growth rate under a fluctuating regime tends to be 10% 40% greater than at constant temperatures equal to the mean of the cycle.

Biette and Geen ( 1980) reported variable response of 0+ age sockeye to cyclic temperature regimes relative to constant temperatures depending on food ration. Under zooplankton rat ions equal to 4.0% 6.9% dry body weight/ d and a fluctuating temperature similar to that experienced 55 Summary of Technical Literature Examining the Physiological Effects of Temperature in the field in diel migrations, sockeye grew as well or more rapidly than under constant temperatures of 60.6, 59.5, 52.3, or 43.1 ° F ( 15.9, 15.3, 11.3, or 6.2 ° C). This ration was estimated to be comparable to that consumed under field conditions in Babine Lake. Rearing sockeye underwent diel vertical migrations between the hypolimnion, having temperatures of 41 48.2 ° F ( 5 9 ° C), and the epilimnion, with 53.6 64.4 ° F ( 12 18 ° C) water. During periods of maximum lake temperature, sockeye inhabited the epilimnion for 2 h in early afternoon and 2 h in early evening. At higher food rations, growth at constant high or intermediate temperatures exceeded that under cyclic temperatures. At both high and low rations, food conversion efficiency and growth were greater in a constant temperature regime than under fluctuat ing conditions during daily vertical migrations in the field.

Wurtsbaugh and Davis ( 1977) studied growth of steelhead trout in laboratory streams under three fluctuating temperature regimes ( natural cycle, natural + 5.4 ° F [ 3 ° C], and nat ural + 10.8 ° F [ 6 ° C]) in all four seasons and found that trout growth could be enhanced by temperature increases up to 29.7 ° F ( 16.5 ° C). During the summer season the control temperature ( natural cycle) was 61.1 ° F ( 16.2 ° C) ( mean) and the elevated temperatures averaged 67.1 and 72.5 ° F ( 19.5 and 22.5 ° C). The average diel temperature range for the summer growth period was about 6.1 ° F ( 3.4 ° C) under the three treatments. Growth rates under food consumption rates of 5% 15% dry body wt/ d were higher under the control temperature regime than at the elevated fluctuating regimes. Under the high temperature regime ( mean of 72.5 ° F [ 22.5 ° C]) growth rate was zero at a food consumption rate of 7%/ d. Gross food conversion efficiency decreased as temperatures increased from 61.1 to 72.5 ° F ( 16.2 22.5 ° C). Maintenance rations increased by a factor of three over the temperature range 44.4 72.5 ° F ( 6.9 22.5 ° C). This study revealed that trout growth was improved by increasing temperatures up to a maximum of 61.7 ° F ( 16.5 ° C), but that this threshold applies to the field only under satiation feeding. Because researchers measured field growth rates in an Oregon coastal stream indicating food limitation, they concluded that temperatures less than 61.7 ° F ( 16.5 ° C) would be optimal for the trout. Food limitations in trout streams not uncommonly cause great reductions in summer growth ( Cada et al. 1987).

Laboratory growth experiments were run on juvenile rainbow trout reared in Lake Ontario water ( Dockray et al. 1996). Growth was measured for juveniles over a 90 d period in which " control" temperatures followed the ambient lake diel fluctuations and also varied in daily mean temperature from 55.4 to 75.2 ° F ( 13 24 ° C) over this summer period. A water treatment facility resulted in increasing control temperatures by 3.6 ° F ( 2 ° C) over background for each day of the growth study. Growth rate over this period was significantly less for the warmer regime, having mean daily temperatures of 59 78.8 ° F ( 15 26 ° C). A comparison of the day 0 30 initial growth period with the day 60 90 growth period is revealing. The initial period had daily control temperatures varying from 55.4 to 64.4 ° F ( 13 18 ° C); the final period had temperature variation from 66.2 to 75.2 ° F ( 19 24 ° C). The treatment temperature regime was equal to the daily control temperatures + 3.6 ° F ( 2 ° C). In the first 30 d period, food conversion efficiencies were 42.4% and 45.6%, respectively, for the control and treatment fish. For the final 30 d period, conversion efficiencies were 27.3% and 6.2%, respectively. The warmer temperature regimes in the final 30 d period substantially reduced conversion efficiency from the initial period. This effect was very pronounced in the 69.8 78.8 ° F ( 21 26 ° C) regime for treatment fish in the final 30 d growth period. In addition, growth was just barely positive for the last 30 d growth period for fish in the 69.8 78.8 ° F ( 21 26 ° C) regime. 56 Summary of Technical Literature Examining the Physiological Effects of Temperature Troughs stocked at high density with rainbow trout were supplied with Columbia River water in test s of growth rate and disease susceptibility ( Fujihara et al. 1971). Water in troughs was maintained at ambient conditions for July ( 63.8 71 ° F, mean 67.4 ° F [ 17.7 21.7 ° C, mean 19.7 ° C]), ambient! 4 ° F ( 2.2 ° C), and ambient+ 4 ° F ( 2.2 ° C). Growth rate under the reduced temperature was 44% greater than under the ambient condition, even though mortality rates associated with columnaris disease were comparable.

In anot her study on O. mykiss ( st eelhead parr from Dworshak National Fish Hatchery, Idaho), growth rate under a fluctuating temperature with feeding 2 times/ d to satiation was contrasted with growth at constant temperatures of 46.4, 59, and 64.4 ° F ( 8, 15, and 18 ° C) for 2 and 8 wk periods. Best steelhead growth occurred at 59 ° F ( 15 ° C). By contrast, instantaneous growth rate under t he fluctuating temperature was 11% less ( Grabowski 1973). The thermocycle was sinusoidal, so a mean temperature of 55.4 ° F ( 13 ° C) can be inferred. Growth at constant temperatures of 46.4 and 64.4 ° F ( 8 and 18 ° C) was 36% and 29% less than at 59 ° F ( 15 ° C) ( Grabowski 1973). These data allow one to hypothesize that the effective growth temperature for the 46.4 64.4 ° F ( 8 18 ° C) cycle was close to 59 ° F ( 15 ° C), but it is not possible to determine whether it was slightly above or below 59 ° F ( 15 ° C).

In summary, laboratory studies indicate that increasing food rations between 1% and 8% body weight/ d results in an increased growth rate ( Thomas et al. 1986, Elliott 1994). Growth rates have been found to be no different under fluctuating than under constant temperature equal to the mean of the cycle ( Peterson and Martin Robichaud 1989, Thomas et al. 1986). In contrast, growth rates under fluctuating regimes have been reported as greater than at constant temperatures equal to the mean of the cycle ( Konstantinov et al. 1989, Konst antinov and Zdanovich 1986, Clarke 1978, Biette and Geen 1980). The study by Biette and Geen ( 1980) indicates that a fluctuating temperature regime might confer a growth advantage on juvenile sockeye under low, rather than high, food availability as typically found in lake environments. Enhanced growth under a fluctuating temperature regime might reflect an acclimation to a temperature higher than the mean of the cycle, similar to responses exhibited in tests of lethal temperatures in survival studies.

Other studies have reported that fluctuating temperature regimes are not all equal. For example, under three fluctuating regimes in which diel temperature varied approximately 6.1 ° F ( 3.4 ° C) in each, steelhead growth rate was greatest in the fluctuating regime with the lowest mean ( 61.7 ° F [ 16.5 ° C]) as opposed to those with means of 67.1 and 72.5 ° F ( 19.5 and 22.5 ° C) ( Wurtsbaugh and Davis 1977). A very similar result was obtained with rainbow trout ( Fujihara et al. 1971), in which the highest growth rate occurred at the lowest mean temperature ( 63.5 ° F [ 17.5 ° C]) in a fluctuating regime. In another study with steelhead, highest growth rate occurred at 59 ° F ( 15 ° C) under constant temperatures ( Grabowski 1973). In this study a fluctuating regime ( 46.4 64.4 ° F [ 8 18 ° C]) with a mean of 55.4 ° F ( 13 ° C) had a growth rate less than that at 59 ° F ( 15 ° C). Studies that indicate a reduction of growth rate under fluctuating temperatures occurs when fluctuations extend above the zone of best constant temperature growth ( approx. 55.4 60.8 ° F [ 13 16 ° C]) for salmonids under satiation feeding. Fluctuating temperatures appear to provide a growth benefit to salmonids when the mean of the cycle is lower than the const ant temperature growth optimum. In this manner all the studies cited above are consistent with findings of Hokanson et al. ( 1977).