Seasonality, dietary overlap and the role of taxonomic resolution in the study of the diet of three congeneric fishes from a tropical bay.

Maíra Pombo,Márcia Regina Denadai,Alexander Turra

doi:10.1371/journal.pone.0056107

Maíra Pombo, Márcia Regina Denadai + Show 1 more

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https://doi.org/10.1371/journal.pone.0056107

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Abstract

Not only seasonality but also taxonomic resolution of prey categories has been shown to affect diet studies. We analyzed the stomach contents of three sympatric species, Stellifer rastrifer, S. brasiliensis and S. stellifer, sampled monthly from August 2003 to October 2004 in Caraguatatuba Bay, southeastern Brazil. General characteristics and similarities among their diets were evaluated by considering high taxonomic ranks of all prey groups, and also the lower taxonomic ranks of the main prey groups. Dietary similarity was relatively high among species and low between seasons, and both evaluation criteria gave the equivalent results. The rare items, however, provided information about resource partition, and the species compositions of the most important groups were apparently good indicators of food availability.

Highlights

In view of the profound effect of competition on population and community dynamics [1], the co-existence of two or more exploiters of quite similar resources is a focus of many ecological studies
That both seasonal variations and taxonomic resolution influence studies on the diet of fishes, and to investigate how different dietary groups, including those that are accidentally ingested, and different levels of taxonomic resolution can relate to community studies, the aim of this study was (i) to observe general characteristics and similarities of the diets of three sympatric species; to assess whether seasonality influences the species’ diet and dietary similarities, considering (ii) high taxonomic ranks of all prey groups, including rare items, and (iii) lower taxonomic ranks of the main prey groups, i.e., as refined as possible, so that information provided by both evaluation criteria could be compared
The range, mean and standard deviation of total lengths were similar among S. rastrifer (5.00 to 14.05; 8.23 6 2.07), S. brasiliensis (4.90 to 12.00; 7.91 6 1.68 cm) and S. stellifer (3.85 to 12.6; 8.21 6 1.68 cm)

Summary

Introduction

In view of the profound effect of competition on population and community dynamics [1], the co-existence of two or more exploiters of quite similar resources is a focus of many ecological studies This topic is especially interesting in situations of limited resources, which nearly always intensify competition, leading competitors to develop a wide range of strategies to avoid direct competition, including high levels of dietary specialization [2,3]. Most studies on the diet of S. rastrifer, S. brasiliensis and/or S. stellifer deal with demersal fish communities as a whole, using small samples or broad prey categories, or do not include gravimetric measurements [13,14,15,16,17] All these reports indicated that the diets of sympatric species tend to be similar and based on crustaceans, which offered an opportunity to investigate how they share the available resources. The factors that may bias dietary studies in these ecosystems include temporal variations, which have an important role in fish feeding behavior and in affecting interactions among competitors [18] and the degree of taxonomic resolution, which may bias the observation of seasonal oscillations [19,20]

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