The ecology and social systems of Red Sea butterflyfish were
studied along the Sinai coast. Distribution, population density
and sociography indicate a preponderance of monogamy in all
species, independent of reef zonation and seasonal or long-term
changes of the reef environment. The social and mating systems
are mutual monogamy; partners remain together for up to 6 years.
Links between the monogamy and benthic habits of these fish are
indicated by their feeding ecology and by a comparison with
Indopacific plankton-feeding species, which usually occur in
groups. Territories are defended pairwise. Pair partners nearly
always remain within visual contact, but a species-typical
distance apart. Pair swimming is independent of season or time
of day. Experimental partner removals led to speedy replacement
of mates. Possible causes of high partner permanency with little
partner fidelity are discussed. In good habitats, single
territorial adults do not occur. They would be unable to defend
and maintain a territory o