Differences in feeding ecology among three co-occurring species of wrasse (Teleostei : Labridae) on rocky reefs of temperate Australia

The foraging behaviours and dietary compositions of three co-occurring labrids (Ophthalmolepis lineolatus, Notolabrus gymnogenis and Pictilabrus laticlavius), which are conspicuous on rocky reefs in temperate south-eastern Australia, were investigated between 2003 and 2005. SCUBA observations at two locations showed that the feeding intensity, and hence the associated effects of these fishes on rocky reef invertebrate prey, was temporally consistent. Relative differences in the contributions of ingested prey and use of different feeding microhabitats demonstrated that the feeding ecology differed significantly among the three species. Thus, O. lineolatus fed on proportionately higher volumes of polychaetes, polyplacophorans, marginellid gastropods (especially Austroginella sp.), bivalves and echinoids, which were sighted opportunistically in a wide selection of microhabitats, but particularly in sand/rubble. Ambush hunting was used regularly by smaller N. gymnogenis and all sizes of P. laticlavius to forage on amphipods, small decapods and small gastropods at algal bases or fronds and Diopatra dentata tubes. Amphipods were similarly important in the diet of smaller O. lineolatus. Larger N. gymnogenis foraged opportunistically over an increased reef area and made greater use of microhabitats that offered minimal prey refuge (e.g. sand/rubble, bare rock/steel) from which common prey, in particular decapods, were obtained. The significant intra- and inter-specific differences in dietary compositions, allied with differences in the use of feeding microhabitats, would facilitate co-occurrence of these three conspicuous species and contribute to maintaining high richness of labrid species in reef systems. Echinoids were regularly consumed by each species but they made a moderate contribution to the diet of only O. lineolatus, which suggests that only one of the three labrids is likely to play a significant role in regulation of echinoid densities in these rocky reef habitats. However, the broad diets and diverse forging strategies employed by these labrid species imply that they have a system-wide influence on invertebrate prey on rocky reefs

Importance of saltmarsh to fish species of a large south-eastern Australian estuary during a spring tide cycle

The dietary compositions of fish species over saltmarsh in a large south-eastern Australian estuary (Brisbane Water) were explored to ascertain the importance of this habitat type to the fish community of that estuary. Following tidal inundation, 12 fish species (<120 mm total length) were obtained using fyke nets, with Ambassis jacksoniensis being particularly abundant. The stomachs of all fish contained undigested prey, implying that they fed while on the saltmarsh. Three species (A. jacksoniensis, Atherinosoma microstoma and Redigobius macrostoma) fed nearly exclusively on the crab zoeae that were released in high numbers by saltmarsh crabs. The diets of these three species significantly differed from those of the other species, which comprised mainly foraminiferans, copepods, crabs, polychaetes, terrestrial insects and/or detritus. Substantial partitioning of food resources also occurred between the other nine species. With increasing body size, A. jacksoniensis fed more on benthic prey (polychaetes and copepods) and less on crab zoeae. This study highlights the importance of saltmarsh as providing both protection and food resources for fish species during even short periods of tidal inundation by its provision of a superabundant food source (crab zoeae) and other prey, and underscores the need for recognition of saltmarsh in management plans for fish

Diets and Resource Partitioning among Three Sympatric Gurnards in Northeastern Tasmanian Waters, Australia

<p>Dietary niches can support the coexistence of closely related sympatric species in marine systems, which can lead to the presence of greater abundances of those species that can potentially support their fisheries or greater abundances for other fish species that prey upon those species. Dietary relationships for three species of gurnard (Family Triglidae) that occur together in the benthic coastal environment of northeastern Tasmania, Australia (Red Gurnard <i>Chelidonichthys kumu</i>, Grooved Gurnard <i>Lepidotrigla modesta</i>, and Roundsnout Gurnard <i>Lepidotrigla mulhalli</i>), were examined for the presence of such dietary niches. The species are either fishery-important (Red Gurnard) or provide prey (Grooved Gurnard and Roundsnout Gurnard) for fishery-important species (e.g., Platycephalidae and Zeidae). Based on stomach content analyses, all three gurnards were shown to be bottom-feeding carnivores that consumed mainly benthic crustaceans, particularly decapods and amphipods, with teleosts also being important in the diets of only the larger Red Gurnard. Nonmetric multidimensional scaling ordination and multivariate analyses based on volumetric contributions of different prey taxa to the stomach contents revealed significant differences in dietary composition among all three species, implying a partitioning of food resources. Size-related and temporal changes in dietary composition were each significant among the three gurnards, but there were no interactions between body size and time. Principal components analysis of head and mouth morphology demonstrated that mouth protrusiveness was the dominant morphological difference among species, which may in part account for the niche partitioning observed from the stomach content analysis. Given the important role of gurnards in benthic food webs, these relationships will improve the specification of ecosystem-based fisheries models and their ability to predict the effects of environmental and anthropogenic perturbations.</p> <p>Received June 29, 2016; accepted April 9, 2017</p