Previous PageTable Of ContentsNext Page



2. Interactions

Both capture fisheries and aquaculture may generate positive and/or negative impacts on the coastal area and these need to be taken into account in the definition of policy measures for the sector. Synergistic and complementary impacts tend to be similar within the fisheries sector and between fisheries and the other sectors (they are hence dealt with together). Negative externalities generated by the fisheries sector tend to be different in capture fisheries compared to aquaculture (the two are therefore considered separately).


Positive impacts of the fisheries sector can be considered according to the three broad categories of effects the sector may have on: economic development; coastal area management; and ecosystem monitoring and rehabilitation.

2.1.1 Regional and national economic development

The fisheries sector, as with other economic activities, may provide a focus for overall economic development (e.g. in island states, such as Iceland, and in coastal countries with extensive coastlines and rich fisheries resources, such as Mauritania or Peru). Most frequently the sector will have a strong regional impact.

The resource rents that the sector generates, especially the capture fisheries subsector, can be used to finance investments within or outside the sector, provided a mechanism exists for such rents to be collected by a resource owner (usually the state).

One specific contribution of the sector is the employment opportunities it generates, especially in remote and marginal areas (see Section 1.1.1).

The fisheries sector contributes to domestic food security and self-sufficiency, although this objective may conflict with the desire to earn foreign exchange. In the Philippines, the shift in the utilization of coastal ponds from the production of milkfish largely for domestic consumption to the production of the more lucrative shrimp for export has had negative consequences on domestic supplies of milkfish. Valuable rice land may also have been lost as a result of conversion into, or salinization by, shrimp ponds (Primavera, 1994).

2.1.2 Coastal area management

The fishing industry can make a positive contribution to the wider objectives of coastal area management. Fishing activities (e.g. ports, fishing boats, landing sites and fish markets) contribute to shaping the landscape, giving it attributes that are attractive to many people, both those living permanently in the area and tourists. In addition, the relative dispersion of the activity, in particular artisanal fishing, may contribute to maintaining viable rural communities and balancing the trend towards growing coastal urbanization.

2.1.3 Ecosystem monitoring and rehabilitation

The fisheries sector is also an observer of the coastal environment capable of alerting the relevant authorities in case of some major hazard such as pollution. In addition, major changes in ecosystems are often first witnessed by fishers and fish farmers.

Aquaculture can provide relief to overexploited species. Overexploitation, both biological and economical, is generally a result of the higher prices obtainable for such species, which in turn is what provides investors with good profitability from related aquaculture operations. By contributing to satisfying the demand for such species, aquaculture can have a positive impact on the state of wild species; higher supplies will tend to bring down prices, making capture fishing efforts less attractive. This effect has been noted in the case of salmon, for example.

For some species, aquaculture may also contribute effectively to conservation. Tisdell (1989) gives the example of giant clams, a species that has been overexploited to the point of being listed in the Convention on International Trade in Endangered Species. However, not all countries are signatories to the Convention and even when they are, loopholes can be found. All species of giant clam have now been successfully bred in captivity and mariculture may therefore be used as an effective means of conservation.


There are a number of complementary interactions pertaining to the fisheries sector. These include market and non-market linkages and the use of collective goods and services.

2.2.1 Market linkages

Market linkages include intrasectoral interactions (e.g. between capture fisheries and ancillary activities such as net-making, or between capture fisheries and aquaculture through the supply of fishmeal), and cross-sectoral interactions (e.g. between forestry and fisheries through the supply of timber for boat-building, or between agriculture and aquaculture through the supply of feed).

2.2.2 Non-market linkages

The activity of fishing or fish farming is often included as an element of a household's wider production function. Inputs used (e.g. upstream production such as boats or gear) and outputs provided (e.g. fish caught) are exchanged within such households, outside the market. Such complementarities may in some cases determine part of the fisheries sector dynamics; for example, the supply of capital and labour of the fishing activity may evolve in close relation to agricultural activities undertaken by the household.

2.2.3 Use of collective goods and services

This includes for example, harbour facilities or road networks. Various sectors such as aquaculture, agriculture and tourism may also derive benefits from the existence of a natural (e.g. mangrove) or artificial (e.g. dyke) protection from erosion and storm surge.


Most of the negative externalities generated by the fisheries sector are intrasectoral, i.e. they affect mainly the sector itself.

2.3.1 Negative externalities generated by capture fisheries

Negative externalities generated by capture fisheries include an excessive decrease in biomass, modification of the coastal environment, space congestion problems, subsectoral conflicts and impacts on other sectors.

Excessive decrease in biomass. In the absence of fishing, a fish stock will tend to some average size that reflects the carrying capacity of the environment and interactions with other species (predators, etc.). Changes in environmental conditions (e.g. exceptional conditions for larval survival or the increase in a predator stock) will alter the biomass of the stock. Fishing adds another predator to the system.

The reduction in biomass is not a problem in itself, provided management measures lead to the regeneration of the resource. However, it is an issue if the reduction is so great that the fish stock faces biological (and thus commercial) extinction. It is also an economic issue if, as a result of reduced biomass, high effort levels are required to produce a given catch where lower effort levels would be needed for the same catch if the fish stock were allowed to recover.

Modification of the coastal environment. Although all fishing methods involve some perturbation of the marine environment, some have an environmental impact that extends far beyond the target species, for example the use of poisons and explosives, trawling and the use of other moving gears that tend to plough the sea bed, thereby significantly perturbing the benthos. In addition, habitat might be affected when infrastructures such as harbours are built, involving the conversion of wetlands or the disappearance of some microhabitats or critical nursery space.6

Efforts aimed at a target species may affect other fish and non-fish species. This kind of problem affects particularly trawling and net-based fishing generally. The optimal mesh size required for one species may be smaller than for a second species found in the same area with the result that significant by-catches are taken of the second species. Where a trawl fishery exploits many species simultaneously, as in tropical waters, this problem may prove intractable. Stocks of larger species may be consistently biologically overexploited to the point of extinction. Introducing devices aimed at avoiding such wastage can entail prohibitive costs and the alternative to the by-catch may be not to fish at all.

Space congestion problems. The development of capture fisheries also generates space congestion problems that may prove to be particularly stringent in the coastal area, especially near densely populated areas. This concerns the activity of fishing itself, but also fish landings, and shelter and maintenance of the fleet and gear, including associated infrastructure.

Subsectoral conflicts (industrial, artisanal, recreational). There are various sources of conflict within the fisheries sector. These include conflict for a particular fishing area or for the fish stock, or between artisanal and industrial fishers. For example, large-scale fishing vessels often operate closer to shore than the law allows. Conflicts also occur between commercial and recreational fisheries (see Box D.2).

Fisheries and ecotourism

The coastal fisheries resources available to many countries constitute not only a source of food and income but also an important tourist attraction. The concept of ecotourism centres around the use of the resources of the coastal area for water sports such as swimming and diving, and the touristic interest of fish, coral reefs and other underwater resources. Sport fishing and diving are also gaining increasing importance for tourism. Touristic uses can be beneficial, for instance, game fishing generates substantial revenues and is selective, while for many reef-dependent species, localized fishing sanctuaries can help to reduce conflict between user groups.

However, with few exceptions, exploitation of sea and fisheries resources for tourism will usually lead to conflicts with more traditional fishing activities since fishers rarely reap the benefit from this alternative use of the resource they draw their livelihoods from. Simultaneously increasing tourism and fishing will thus always lead to allocation problems. Coordination of traditional fisheries, marine reserves and various forms of tourism is the best way to avoid conflicts among different users of coastal areas. Short- and long-term resource allocation strategies will have to be established in accordance with countries' economic and social needs.

Impacts on other sectors. Impacts on other sectors in the coastal area relate essentially to the status of marine populations, pollution and the availability of space.

Decreased biomass or modification of species assemblages brought about by fishing may have cross-sectoral consequences where other users such as local diving operators or environmental conservation associations place a value on the affected species or species assemblages. The resulting conflicts may be particularly strong if the impacts concern non-fish species, such as marine mammals, sea birds or sea turtles. Insofar as conservationist activities are in the longer-term interests of fishers themselves, dialogue is required to overcome the dispute.7

In addition, the fishing industry affects other sectors through pollution, e.g. water pollution from fishing vessels, air pollution from fish smoking, fishing vessels and processing plants, or noise pollution from traffic generated by fishing activity, especially relating to the movement of fish from the market to the consumer. Waste generated by fish landing sites and tar balls on beaches creates substantial pollution and discourages tourism and bathing uses of the coast.

2.3.2 Negative externalities generated by aquaculture

The long-term trend in aquaculture appears to be towards intensification and increased control over the site and species characteristics (World Bank, 1992). The characteristics of coastal resources used by aquaculture, especially the fluid nature of water resources (and hence water quality) and lack of clearly defined resource-use rights8 explain most of the negative externalities generated by the sector.

Overexploitation. Aquaculture may contribute to various kinds of overexploitation. For example by affecting populations of wild seed (when aquaculture depends on wild stocks) and fishmeal species in cases of cultured species (such as salmon or shrimp which require high-protein feeds).

In large-scale oyster culture (for example in France), where sharing the resource base implies sharing the overall trophic capacity of the coastal embayment (i.e. available primary production and other sources of nutrients), many growers assumed that by increasing individual stocks a greater share of the resource could be reaped. In fact, such competitive overstocking by growers can result in stagnation of total output (caused by excessive total biomass), decreased productivity, longer growing cycles, higher natural mortality and a greater risk of disease epidemics (Heral, Bacher and Deslous-Paoli, 1989). The main reason for this is that, while access is limited on the basis of area, productivity depends on the overall trophic capacity of the entire bay which is shared by all the sites in the area.

This example demonstrates that limiting access is not always sufficient unless the correct variable is identified. A better approach in this case would be to limit overall production according to estimated carrying capacity, and share it among growers, taking measures to ensure that quotas are not exceeded.

Pollution and habitat degradation. Aquaculture itself can generate pollution through release of organic waste, chemicals and inorganic nutrients. For example:

Other negative impacts of aquaculture can arise from the clearing of mangroves, which are seen as an unproductive resource, their total goods and services being unrecognized,9 to build fish ponds (destruction of wetland habitats). It has been estimated that in the Philippines, severe mangrove loss occurred over the period 1967 to 1977 (WRI, 1986; Primavera, 1994). Moreover, in Thailand and Taiwan, Province of China, for example, intensive shrimp culture in coastal ponds has been observed to cause saltwater intrusion, leading to degradation of agricultural land, as well as to land subsidence (Insull, Barg and Martosubroto, 1995).

Impacts on ecosystem structure. Farmed fish may escape and pose a risk to wild species inhabiting open waters in the same area through competition for habitat and food. They may also spread disease. Also associated with the problem of escape is the effect that aquaculture might have on genetic diversity.

Subsectoral conflicts. Another source of negative impacts is linked to the economic and social effects that aquaculture development may have; large-scale aquaculture may result in the displacement of fishers, or other small-scale resource users, especially where common property resources are not regulated. Conflicts can be particularly severe between traditional aquaculturists producing for local needs, and commercial fish farming enterprises producing for export markets.

Impacts on other sectors. As with capture fisheries, the negative externalities generated by aquaculture activities are mainly intrasectoral although cross-sectoral impacts also exist. Aquaculture may limit public use of water space (e.g. physical obstructions to fisheries and navigation) or be seen as affecting landscape aesthetics in areas of natural scenic beauty, and this could lead to a decline in tourism. In this respect, it should be noted that the site requirements of aquaculture (sheltered, unpolluted waters) are often those valued by other users, primarily tourists.


Coastal waters are the ultimate recipient for pollutants coming from land, rivers, air and the sea. Coastal lagoons, estuaries, semi-enclosed seas and shallow littoral waters of the open coast seem to be the areas where most damage is concentrated. This will need to be considered in the definition of management strategies for the coastal area.

Fisheries institutions and the other sectors

Few coastal area management schemes neglect fisheries. However, the emphasis is often on the management of fishery habitats rather than the regulation of fishing effort or the establishment of quota schemes. The reasons for this are quite clear; fisheries are often an important economic sector in the coastal area and fishing communities reside therein. More importantly, fishing communities are often the segment of the coastal population most seriously affected by detrimental environmental effects and spatial competition with other sectors. However, there is the paradox that, as other economic sectors expand in the coastal area, the relative economic importance of fisheries declines, weakening the influence that fisheries sector institutions can exert on policy decisions.

In Trinidad, for example, the role of fisheries in terms of their contribution to national income and employment is minimal compared to that of other sectors, so it was not possible for a coastal management process to be headed by the Fisheries Department even though the latter had initiated such a process. In Sri Lanka, on the other hand, where fisheries play a relatively more important role in the coastal area, the management programme was initially located within the ministry responsible for fisheries even through the main concern was coastal erosion which threatened wider interests than fisheries. In the Maldives, integrated reef resource management has also been initiated by the ministry responsible for fisheries, but tourism interests clearly also weigh heavily.

In the United States, which promulgated coastal zone management legislation in the 1970s, fisheries management measures such as effort regulations and quotas are normally not dealt with in the coastal zone management programmes of the various states, but are handled through regional fisheries management councils. However, fisheries benefit from measures to maintain sensitive coastal ecosystems and measures to limit and reduce water pollution.

In the Philippines, fisheries sector institutions and fishing communities play a major role in coastal zone management programmes while coordination is done largely through intersectoral agencies such as the National Economic and Development Authority and the Department of Environment. Broad government responsibilities have been decentralized and delegated to local municipalities and, where fishing communities make up a large percentage of the local population, they can exert significant influence. However, the interests of small- and large-scale fishers are often in conflict, and local-level interests can be overruled through forces from the centre. Nevertheless, the degree of decentralization and delegation of management authority need to be important considerations of any demand that fisheries sector participants (such as fishers' organizations) may make on the institutional structure of coastal management programmes.

An important lesson from the above examples is that it is in the interests of the fisheries sector institutions to take the initiative of a process of coastal area management; this will usually allow them to exert more influence on future developments. In this regard, an important principle stated in the coastal zone management legislation (or policy) of some countries is to give priority to coast-dependent development. The application of this principle provides a first rationale for allocating scarce coastal resources by giving added weight to uses (or sectors) that by their very nature are dependent on inherent attributes of the coastal area. Fisheries and fishing communities clearly fall within this category whereas many activities of other sectors may not.

When complex intersectoral management problems arise in the coastal area, and the role of fisheries declines, the influence of fisheries sector institutions may depend on the kind of alliances they can create with other sectors or segments of the population on issues of common interest.

Fisheries agencies also need to change their orientation, developing more interest in what other sectors are planning to undertake in the coastal area. Furthermore, they need to develop or acquire expertise to be able to evaluate the consequences of these undertakings on the fisheries and fishing communities.

Source: Willmann, 1996.

2.4.1 Pollution

Most aquatic pollution in coastal areas originates from land-based sources, the rest coming from shipping, waste dumping, oil production and offshore mining.10 Land-based pollution can be transported in a variety of ways (e.g. rivers, freshwater runoff, the atmosphere). Pollution may significantly decrease marine environmental quality. Population growth in coastal areas, which leads to urban development and changes in land and other resource uses, also induces various forms of pollution. A major factor is increased waste water discharge into the sea leading to nutrient and organic enrichment and ecosystem disruption, including adverse consequences of eutrophication and reduction of freshwater inflow caused by irrigation and urban uses.

Another common source of pollution is agricultural waste such as toxic compounds from pesticides. Many such compounds have long half-lives and consequently tend to have long-term effects. Industrial waste also comprises many toxic substances including heavy metals, radioactive elements, acids and industrial chemicals. Oil spills are another common source of acute pollution.

Aquatic pollution, even at low levels, may influence fish production in numerous ways: reduction of stocks by mass mortality (particularly of larval and juvenile fish); gradual decline or changes in species composition of fish populations or entire ecosystems; increased occurrence of diseases; slower growth rates; and deterioration of the food quality of fish. Long-term effects of aquatic pollution on fish should not be underestimated. Species may be disadvantaged through chronic effects such as tissue damage, impaired reproduction or abnormal larval development.

Pollution can have especially severe effects on shellfish. In Canada, for example, over 200 000 ha of near-shore waters are closed for shellfish harvesting because of pollution; in the United States, one-third of shellfish beds have been closed. On a larger scale, the crash of the entire fisheries economy of the Black Sea area as a result of pollution, overfishing and the introduction of exotic species that feed on fish larvae is estimated to cost some US$1 billion per year (Barg and Wijkstrom, 1994).

Both capture fisheries and aquaculture are affected by land-based pollution. The problem is at once `worldwide yet highly specific to different geographic, ecological, social and economic situations' (Dahl, 1993). As a result, there can be no unique solution although some general principles may perhaps be enunciated.

Many of these problems may be aggravated, if not actually caused by, coastal tourism. Tourism leads to increased sewage, much of which is left untreated, resource depletion and conflict (e.g. between recreational and commercial fishers). Such problems are likely to be especially severe in the case of islands (Bass, 1993). Because the principal gains from tourism are clearly priced and easily observable, whereas the environmental costs generally affect unpriced resources, there is a tendency to overestimate the net social benefits of tourism and, consequently, to favour this sector over competing ones such as fisheries. Rational resource use requires that all benefits and costs associated with an activity be identified.11

2.4.2 Perturbation of critical habitats

Civil engineering works (e.g. road construction, dams, ports) may place further stress on coastal ecosystems as a result of soil runoff and degradation of critical habitats. Similarly, agriculture and forestry activities, through their impact on soil stability, may affect coastal sedimentation.12 Because of their importance for the productivity of marine communities and because of their particular location in the coastal area, a number of critical habitats must be considered specifically, as growing pressures on them may have significant consequences for the fisheries sector. These include mangroves, sea grass, lagoons and estuaries (see Box D.1).

The common feature of these habitats is that they provide valuable services that are difficult to observe and are unpriced. Because they are difficult to observe, there is a tendency to ignore them, for example fishers themselves may trawl through sea grass meadows despite the impact that this may have on their own future welfare. In many cases the value of such resources is grossly underestimated, pointing to an urgent need for studies and research to demonstrate their value. Given the widespread impact on the fisheries sector, the fisheries authorities should take the lead in organizing such work. More importantly, since the resources are unpriced, there is no mechanism for their value to be reflected. As a result, overexploitation of such habitat resources follows in the same way that it does in open-access fisheries.

6 See also Section 2.4.2.

7 See Part A, Section 2.3.4, Figure A.8 and Box A.20.

8 See Part A, Section 2.2.2.

9 See Part A, Section 1.6.1 and Part C, Box C.1 and Figures C.1 and C.2.

10 See also Part A, Section 1.3 for more on inland sources of pollution.

11 See Part A, Section 1.6.3.

12 See Part A, Sections 1.1, 1.3 and 1.7.

Previous PageTop Of PageNext Page