Longitudinal use of feeding resources and distribution of fish trophic guilds in a coastal Atlantic stream, southern Brazil

Abstract

This study described the use of food resources and the distribution of fish trophic guilds along the longitudinal gradient of a coastal Atlantic stream, southern Brazil. Allochthonous resources (terrestrial insects) predominated in the headwaters, whereas autochthonous food items (algae, fish) and detritus predominated in the mouth section. Detritivorous, aquaticinvertivorous, and terrestrial-and aquatic-insectivorous species occurred throughout the gradient, while omnivorous and piscivorous in the headwaters and middle stretches, respectively, and herbivorous in the middle and mouth. Detritivores and aquatic-insectivores were significantly more specialized than the other guilds, however, there was no evidence of a longitudinal increase in trophic specialization. Density and biomass of aquatic-invertivores and aquatic-insectivores decreased, whereas that of detritivores increased longitudinally. The distribution of trophic guilds was significantly associated with the stream section, where aquatic and terrestrial insectivorous were more frequent in rocky and flowed stretches from the headwater and detritivores in deeper environments with finer particles of substrate from the mouth. This suggests that fish assemblages in coastal streams with a steep longitudinal gradient may follow patterns in the use of food resources according with the food availability along the river, as predicted by the River Continuum Concept.Este estudo descreve o uso dos recursos alimentares e a distribuição das guildas tróficas de peixes ao longo do gradiente longitudinal de um riacho da encosta Atlântica, Sul do Brasil. Recursos alóctones (insetos terrestres) foram consumidos com maior frequência na cabeceira, entretanto, recursos de origem autóctone (algas, peixes) e detritos foram mais frequentemente registrados na foz. Espécies detritívoras, invertívoras aquáticas, insetívoras terrestres e aquáticas ocorreram ao longo de todo gradiente, enquanto que as onívoras e piscívoras na cabeceira e meio, respectivamente, e herbívoras no meio e foz. Detritívoras e insetívoras aquáticas foram significativamente mais especializadas em relação às demais guildas; entretanto, não houve nenhuma evidência de aumento longitudinal da especialização trófica. A densidade e a biomassa de invertívoras e insetívoras aquáticas diminuíram, enquanto que das detritívoras aumentaram no sentido cabeceira-foz. A distribuição das guildas tróficas foi significativamente associada com a secção do riacho, onde insetívoras aquáticas e terrestres foram mais frequentes em trechos rochosos e de elevado fluxo da cabeceira, enquanto que detritívoras em ambientes mais profundos com partículas finas de substrato da foz. Tais resultados sugerem que assembleias de peixes de riachos tropicais de encosta, os quais apresentam acentuado gradiente longitudinal, podem seguir padrões de uso dos recursos alimentares de acordo com a disponibilidade alimentar ao longo do rio, como previstos no Conceito de Continuidade de Rios.

Diet and ecomorphological relationships of an endemic, species-poor fish assemblage in a stream in the Iguaçu National Park

“…had low values for diet breadth (below 0.2), which shows that although the species used resources from different trophic levels, their diets tended to be restricted to a small number of abundant items. For streams with higher species richness, the diet breadth has also been found to be low (Wolff et al, 2013;Winemiller et al, 2008). These patterns and the results found here suggest that dietary specialization may not necessarily be linked only to interspecific competition or to the availability of resources (Esteves & Lobón-Cerviá, 2001;Mazzoni et al, 2012;Vitule et al, 2013).…”

Fish assemblages in Atlantic Forest streams: the relative influence of local and catchment environments on taxonomic and functional species

“…; Wolff et al. ). Because non‐native species can seriously undermine the ecological integrity of freshwater ecosystems (Hermoso & Clavero ), we investigated the pattern in native and non‐native distribution from a functional perspective.…”

Use of food resources by small fish species in Neotropical rivers: responses to spatial and temporal variations

“…The influence of spatial and seasonal changes in trophic relationships has been recognized for a long time (ARGERMEIER 1982, SCHOENER 1989, POLIS et al 1996, HAHN et al 1997, WINEMILLER & JEPSEN 1998, HOLT 2002 and has gained importance recently in the ecological context (GIMENES et al 2010, CORRÊA et al 2011, PETTIT et al 2011, POMBO et al 2013, WOLFF et al 2013. However, some aspects that influence the availability of resources along spatial gradients and aspects related to seasonality need to be further clarified.…”