ABSTRACT
Blennioid fish display a range of feeding modes, trophic niches and ecological roles that belie their small body size. Some species feed on algae and detritus, providing a vital link between primary consumers and higher trophic levels, whilst at the other end of the spectrum, some species are piscivores, feeding on smaller fish, or the scales, mucus and fins of larger fish. Blennioids are often abundant relative to other larger bodied fish and represent a significant portion of fish communities on coral reefs (Townsend and Tibbetts, 2000; Wilson, 2001a), rocky shores (Muñoz and Ojeda, 1997; Prochazka, 1998) and sandy sediments (Prochazka and Griffiths, 1992). Small body size (most species have total lengths < 100 mm) incurs high metabolic costs for many species, which are
satisfied by a combination of selective and intensive feeding. These feeding strategies, combined with high abundances, can have a profound impact on the environment in which the blennies live. For example, on rocky shores, selective feeding by the herbivore, Scartichthys viridis, alters the composition of the algal community (Ojeda and Muñoz, 1999). Conversely, carnivorous blennies with generalist diets can reduce the abundance of herbivorous invertebrates, inducing a trophic cascade where biomass and diversity of algae increases (Bruno and O’Connor, 2005). On coral reefs, top down control of algal biomass by intensive feeding of herbivores is considered particularly important, as this maintains a benthic environment suitable for settlement and growth of corals. Blennioid feeding on algal assemblages can be intense on some reefs (Hatcher, 1981). However, many of the blennies on coral reefs ingest relatively small amounts of algae and comparatively large amounts of detritus (Wilson, 2000), implying that their role as algal-removing herbivores is negligible and emphasising the importance of correctly assessing diet before making implications about their ecological role.
