Feeding ecology of the beach silverside Atherinella blackburni (Atherinopsidae) in a tropical sandy beach, Southeastern Brazil

Abstract

Gonzalez and Vaske Junior: Feeding of Atherinella blackburni in Brazil 346Feeding ecology of the beach silverside Atherinella blackburni (Atherinopsidae) in a tropical sandy beach, Southeastern Brazil A ecologia alimentar do peixe-rei (Atherinella blackburni) na zona de arrebentação de uma praia arenosa tropical, localizada no sudeste do Brasil, foi acessada a partir da análise do conteúdo alimentar de 198 peixes. Fatores como o tamanho, a estação do ano e o período do dia foram analisados para compreender como estes influenciam a dieta da espécie. Os resultados mostram que A. blackburni é um peixe nerítico costeiro com amplo nicho alimentar. As presas mais recorrentes foram os crustáceos zooplanctônicos, insetos e moluscos bentônicos, sendo os crustáceos da subclasse Copepoda o item dominante na dieta em ocorrência e abundância. A. blackburni aparenta possuir uma leve mudança ontogênica em sua dieta, variando de moluscos bentônicos para crustáceos e em seguida para insetos ao longo do seu ciclo de vida. A atividade diária também demonstrou ser um fator importante para a ecologia alimentar de A. blackburni. O predomínio de peixes pequenos durante o período da manhã, juntamente com as principais presas para esta classe de tamanho, sugere que indivíduos pequenos utilizem as áreas mais rasas para alimentação durante o período da manhã e, durante a noite, movem-se para águas mais profundas em busca de proteção contra predadores. A. blackburni appears to have a slight ontogenetic shift in its diet, changing from benthic molluscs to crustaceans and insects along its life cycle. The diel activity also reveals to be an important factor to the A. blackburni feeding ecology. The predominant occurrence of small fish during the morning, along with the main preys for this size class, suggests that small individuals use shallower waters as feeding grounds during the morning and, during the night, they move to deeper waters for protection against predators. Resumo AbstRActDescriptors: Diel activity, Diet, Ontogenetic shift, Resources partitioning, Surf zone, Zooplanktivorous.

Seasonal Evaluation of the Condition Factor in a Surf-Zone Assemblage From Southeastern Brazil

“…In this study only A. blackburni was subject to reproductive cycles, so it was the only species in which this variable could influence K. But, similarly to the other species in this study, mainly juvenile individuals without reproductive cycle influence, A. blackburni showed no variation of K value between seasons. Atherinella blackburni is found only on the shores of the Atlantic Ocean, always occurring in the surf zone (Schultz, 1949;Gilbert and Caldwell, 1967;Gonzales and Vaske-Júnior, 2017). This is the only species among others in our study that presents a complete life cycle in this environment.…”

“…We might suggest that temperature does not affect abundance or K in A. blackburni on Praia Grande beach. Gonzales and Vaske-Júnior (2017) showed that the availability of food in the surf zone varies according to physicochemical conditions and season, but despite that, they confirm that A. blackbuni has a generalist strategy and feeds on any available organisms along the year. Considering the relative low temperature variation (betewn 18 oC and 22oC, see: Roling et al, 2007), the constantly available food at the study area (Lasiak, 1981;Carter, 1988;Brown and Mclachlan, 1990), and based on stable allometric condition factor we might suggest A. blackburni does not have a well-defined reproductive seasonality in the Brazilian southeastern coast.…”