Influence of selected factors on the dietary compositions of three targeted and co‐occurring temperate species of reef fishes: implications for food partitioning

Abstract

The dietary compositions of three medium to large targeted fish species, which co-occur over reefs in temperate waters of south-western Australia, were determined. These data were then used to ascertain statistically the extent to which body size, season and habitat influence the diets of these species and the degree to which food resources were partitioned among and within those species, and thus reduced the potential of interspecific and intraspecific competition. On the west coast, Bodianus frenchii (Labridae) and Epinephelides armatus (Serranidae) spent their whole life over prominent limestone reefs, as did Glaucosoma hebraicum (Glaucosomatidae) in all but juvenile life, when it lived over low-relief, limestone substrata. The dietary composition of each species changed with increasing body size, which, in G. hebraicum, was particularly pronounced at c. 300 mm total length (L(T)) and therefore at the size when this species shifts habitat. When the three species co-occurred over the same reefs, their dietary compositions were significantly different, with that of B. frenchii being by far the most discrete, reflecting a far greater contribution by sedentary taxa. Thus, the diet of B. frenchii was distinguished from those of the other two species in containing substantial volumes of bivalve and gastropod molluscs and echinoid echinoderms and essentially no teleosts. Although the diets of G. hebraicum and particularly E. armatus were dominated by teleosts, and especially for larger individuals, the former species ingested greater volumes of cephalopods and small crustaceans. The pointed jaws of B. frenchii, with their forwardly directed and interlocking anterior incisors, are ideally adapted for biting and retaining their invertebrate prey, which are attached to or reside within reef crevices. In contrast, the mouths of G. hebraicum and E. armatus are broader and rounder and contain numerous small, slender and inward-pointing teeth. These teeth, in conjunction with prominent backward-curved canines in E. armatus, facilitate the capture and retention of fish prey. Observations in situ indicate that G. hebraicum is a suction feeder, while E. armatus is predominantly a ram feeder. Although reef environments on the west and south coasts differ, the diet of B. frenchii on these coasts differed only slightly. Interspecific differences in diet, combined with size-related changes in dietary compositions and the occupation of different habitats by juvenile and adult G. hebraicum, reduce the potential for competition for food resources among and within B. frenchii, G. hebraicum and E. armatus and thus helps facilitate the coexistence of these species which historically have been abundant over reefs in south-western Australia.

Ontogenetic diet shifts in snapper (Pagrus auratus: Sparidae) within a New Zealand estuary

“…The clear ontogenetic diet shift seen in this study from small prey such as copepods and mysids to larger prey like crabs, bivalves and fish is similar to many other opportunistic species of fishes (Grossman 1980;Gillanders 1995;Cocheret de la Moriniere et al 2003;Xue et al 2005;Platell et al 2010). These shifts may be caused by a number of factors.…”

“…Understanding the diet of fishes is required for a variety of ecological and management purposes (Platell et al 2010). The growth, survival and reproduction of fish depend on the quality and quantity of food taken in and the nutrients generated by feeding (Wootton 1990).…”

An innovative statistical approach to constructing a readily comprehensible food web for a demersal fish community

“…While it should be recognised that the overall compositions of the diets of these species did change with increasing body size when using a finer taxonomic scale (Platell et al, 2010;Sommerville et al, 2011;French et al, 2012), the use of those finer taxonomic scales for the dietary categories in the present study would have produced a prohibitively large number of predator guilds for the analyses employed in the current study and thus mitigated against the construction of a readily comprehensible food web.…”

“…The dietary compositions of many fish species change as those species increase in body size (Werner and Gilliam, 1984;Blaber and Bulman, 1987;Platell et al, 1998aPlatell et al, , 2010Shepherd and Clarkson, 2001; Cocheret de la Morinière et al, 2003;French et al, 2012) and also sometimes change with time of year (Jaworski and Ragnarsson, 2006;Lek et al, 2011;Schückel et al, 2011).…”

Similar cryptic behaviour during the early juvenile phase of two unrelated reef fishes:Epinephelides armatusandBodianus frenchii

“…frenchii appears to provide access to food resources essential to the growth of this early 180 life stage and ensures intra-specific partitioning of these resources for both species. However, 181 the dissimilarity of the diets of the juveniles of those two species, owing to their different 182 mouth morphology, would also permit their successful co-occurrence in that microhabitat 183 (Platell et al 2010). This is because small E. armatus tend to consume teleosts and decapod 184 crustaceans, while small B. frenchii consume mostly gastropods and, to a lesser extent, other 185 invertebrates, such as polychaetes, bivalves, small crustaceans and decapods (Platell et …”