Diet and feeding strategy of the dusky grouper Mycteroperca marginata (Actinopterygii: Epinephelidae) in a man-made rocky habitat in southern Brazil

Abstract

The dusky grouper (Mycteroperca marginata) is a marine species usually associated with rocky bottoms and reefs. The present work investigated the diet and feeding strategy of a dusky grouper population inhabiting a 4.5 km long pair of rocky jetties located in the mouth of Patos Lagoon estuary. No prior research has been conducted in such man-made habitat and the current study provides a basis for comparative studies on the diet of the dusky grouper populations inhabiting natural vs. manmade rocky habitats. Similarly with previous studies on natural substrates, crabs and fishes were the main food categories consumed (%IRI = 85.1 and %IRI = 12.6, respectively), whereas shrimps and mollusks had lower importance in the diet (%IRI = 1.9 and 0.4, respectively). As previously reported for dusky grouper populations inhabiting reefs and rocky bottoms, the present work revealed conspicuous size related dietary shifts. Blue crabs and fishes become increasingly important food items in the diet of larger individuals (> 500 mm, TL). Finally, it was found that the studied dusky population has a generalist feeding strategy with a high between-individual variation in prey consumption. Such strategy remained similar across the size increment of the species. Our findings suggest that man-made rocky substrates provide suitable feeding grounds for the dusky grouper in southern Brazil and could be used as an additional tool in the conservation efforts of this endangered species.A garoupa-verdadeira (Mycteroperca marginata) é uma espécie marinha geralmente associada a fundos rochosos e recifes. O presente trabalho investiga a dieta e estratégia alimentar de uma população da garoupa-verdadeira que habita um longo (4,5 km) par de molhes de pedra na desembocadura do estuário da laguna dos Patos, sul do Brasil. Não há trabalhos anteriores realizados nesse tipo de habitat construído pelo homem e este trabalho fornece uma base de comparação com estudos de dieta de outras populações da garoupa-verdadeira ocorrendo em habitats naturais. De modo similar ao encontrado em estudos prévios realizados em substratos naturais, caranguejos e peixes foram as principais categorias de alimento consumidas (%IRI = 85,1 e %IRI = 12,6, respectivamente), enquanto camarões e moluscos tiveram menor importância na dieta (%IRI = 1,9 e %IRI = 0,4, respectivamente). Como reportado anteriormente para populações de garoupa-verdadeira que habitam recifes e fundos rochosos, o presente trabalho revelou marcadas mudanças na dieta em função do tamanho da espécie. Siri-azul e peixes tornam-se gradativamente mais importantes na dieta de indivíduos maiores (> 500 mm de comprimento total, CT). Finalmente, foi observado que a população de garoupa-verdadeira teve uma estratégia alimentar generalista com uma elevada variação entre indivíduos no consumo de presas. Essa estratégia permaneceu similar ao longo do aumento em tamanho da espécie. Os resultados do presente trabalho sugerem que substratos rochosos estabelecidos pelo homem propiciam locais de alimentação adequados para a ...

Feeding ecology of two sympatric species of large-sized groupers (Perciformes: Epinephelidae) on Southwestern Atlantic coralline reefs

“…Despite the fact that some fish species regurgitated their prey(s) after capture, as already stated for some large-fish species (Randall, 1967), including groupers (Randall, Brock, 1960;Nakai et al, 2001;Dierking, Meyer, 2009), we suspect that epinephelids regularly experience long periods of empty stomachs (e.g. Condini et al, 2011;López, Orvay, 2005;Reñones et al, 2002), as a combined result of resource availability, digestion rates and energy balance (Arrington et al, 2002). Both species are opportunistic (Smith, 1971;Randall, 1967;Sierra et al, 2001), "sit and wait" ambush predators (Bullock, Smith, 1991;Brulé et al, 2005), and the regular occurrence of empty stomachs provides support to the idea that they are intermittent rather than continuous feeders.…”

Age, growth, and reproductive aspects of the dusky grouper Mycteroperca marginata (Actinopterygii: Epinephelidae) in a man-made rocky habitat in southern Brazil

“…In both cases, individuals were caught using hook and line following the procedures described in Condini et al (2011). There were no individuals captured during austral winter and early spring (June to November), probably due to the harsh conditions that usual prevail during these months.…”

The feeding habits of the endemic Remo flounder, Oncopterus darwinii (Actinopterygii: Pleuronectidae), in an exposed sandy beach’s surf zone in southern Brazil

“…However, a huge variation in prey number and volume found in the stomachs was observed in smaller Remo flounders, with less prey in number and volume than larger flounders. This pattern is common in different species in studies addressing diet composition and variations in ontogeny (Teixeira et al 2010, Condini et al 2011 and can be attributed to a combination of factors, for instance a larger mouth, improved ability to handle prey, and faster swim capability.…”