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Analysis of diet and feeding strategies within an assemblage of estuarine larval fish and an objective assessment of dietary niche overlap

Gaughan, D.J. and Potter, I.C. (1997) Analysis of diet and feeding strategies within an assemblage of estuarine larval fish and an objective assessment of dietary niche overlap. Fishery Bulletin, 95 (4). pp. 722-731.

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Fish larvae and zooplankton were sampled during seven consecutive months from four regions of Wilson Inlet, an estuary in south-western Australia. Mouth size, prey size, and dietary composition of larvae of the gobiids Afurcagobius suppositus, Pseudogobius olorum, and Favonigobius lateralis, the blenniid Parablennius tasmanianus, and the syngnathid Urocampus carinirostris were determined. Dietary niche overlap (DNO) was calculated for co-occurring species pairs, both with and without incorporating a measure of relative prey (zooplankton) abundance. Significance of DNO was assessed 1) objectively, with boot-strapping of the dietary data and 2) subjectively, by assigning significance to values >0.6. The diet of A. suppositus was dominated by harpacticoids, polychaete larvae, and the calanoid Gladioferens imparipes, whereas diets of the other species were dominated by copepod nauplii and postnaupliar stages of the cyclopoid Oithona simplex, the proportions of the latter increasing with growth of the larvae. Small numbers of large and small prey items were found in the stomachs of A. suppositus (mean=2.5), which had the largest mouth, whereas large numbers (mean= 28.7) of small prey and no large items were found in the stomachs of P. tasmanianus, which had the second largest mouth. Between these extremes, P. olorum, U. carinirostris, and F. lateralis each ate mostly small and intermediate-size prey, supplemented by a few large prey. The data did not support the hypothesis that an increase in the difference in gape size between species would decrease the prevalence of significant DNO. The lack of a consistent relation between mouth size and DNO among the five species is evidence that interspecific dietary differences reflect differences in feeding behavior. With bootstrapping, the prevalence of significant (P<0.05) DNO between species pairs was 32.6% when prey data were included in the analyses and 46.5% when prey data were not included. By subjectively assigning significance to DNO values >0.6, we obtained substantially less conservative estimates that indicated the prevalence of significant DNO was >53%.

Publication Type: Journal Article
Murdoch Affiliation: School of Biological and Environmental Sciences
Publisher: US National Marine Fisheries Services
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