Feeding habits of a small demersal fish: Longfinned dwarf sea bass, Dules auriga (Teleostei: Serranidae), from the Southwest Atlantic

Abstract

Dules auriga is a small, endemic and demersal species that occurs in the Southwest Atlantic Ocean (SWA). Knowledge of the trophic ecology of this species will be essential to understanding its role as predator in this marine region. The aim of this study was to determine the diet composition, feeding strategy, and trophic level of D. auriga in the coastal waters off Uruguay and northern Argentina (34° – 41°S). A total of 309 individuals ranging from 81 to 174 mm total length (TL) were analyzed. Dules auriga fed mainly on polychaetes (50.04 % prey-specific index of relative importance, %PSIRI), followed by amphipods (16.32 % PSIRI), brachyuran crabs (10.76 % PSIRI), and echinoderms (10.36 % PSIRI). Relationships between the number of prey and maturity stage, TL, region, and season were evaluated using a multiple hypothesis modeling approach. Echinoderms consumption was higher in the south region, whereas amphipods and polychaetes were higher in the north region. Brachyuran crabs were more consumed in the cold season. The consumption of echinoderms increased with increasing body size of D. auriga. On the other hand, the consumption of amphipods decreased with body size. Polychaetes were more preyed by mature individuals than immature individuals. The size of the brachyuran crabs consumed not increased with increasing body size of D. auriga, but it was registered a continued inclusion of narrow range size of this prey in the diet. The analysis of the feeding strategy indicates a specialization on polychaetes. The specific trophic level was 3.24, indicating that D. auriga is a secondary consumer. This comprehensive investigation enhances understanding of trophic dynamics of D. auriga, providing a foundation for future ecological investigations in the SWA.