Trophic status and feeding selectivity of blennies (Blenniidae: Salariini)

Abstract

An evaluation of the dietary resources available to, and selected by, blennies of the tribe Salariini was used to assess their trophic status on the Great Barrier Reef. Gut-content analysis of nine species of blennies found detrital aggregates to be the dominant item ingested. Samples of the dietary resources available to one of these species, Salarias patzneri, were compared biochemically. Of the two main dietary categories (detrital aggregates and filamentous algae), detrital aggregates were the major resource available, accounting for 53 ± 4.6% (SE) of the organic matter present. The mean C:N values for detrital aggregates (17.2 ± 0.8) and filamentous algae (20.0 ± 1.8) were very similar, as were protein concentrations (1.8 ± 0.1 and 2.1 ± 0.1 μg mg⁻¹, respectively). However, mean carbohydrate concentrations were much lower in the aggregates than the filamentous algae (19 ± 2 and 76 ± 13 μg mg⁻¹, respectively). Comparison of the inorganic particles ingested to those available indicated that S. patzneri selectively fed on particles <125 μm, (predominantly detrital aggregates) and avoided particles >250 μm, (predominantly algal filaments). The patterns of resource availability, nutritional quality and selectivity suggest that salariin blennies utilise detrital aggregates as their primary dietary resource.