Feeding Habits of Dwarf Goatfish (Upeneus parvus: Mullidae) on the Continental Shelf in the Gulf of Mexico

Feeding habits of dwarf goatfish on the continental shelf off Alvarado, Veracruz, Mexico, were analyzed to determine seasonal variation and size-class changes in diet composition and trophic overlap between size classes. Food was found in 63% of the 1,437 dwarf goatfish guts analyzed. The 52 dietary items identified consisted mainly of crustaceans, with Solenocera vioscai being the most important prey. Dwarf goatfish exhibited seasonal and size-class changes in prey consumption. Despite the high number of prey items, low values of diversity and diet breadth were found in the trophic spectrum. A high trophic overlap between size classes was observed in the north-winds season between length classes (92-111 vs 112-130 mm) (λ = 0.81) and (92-111 vs 131-150 mm) (λ = 0.80), and (112-131 vs 131-150 mm) (λ = 0.67). In the rainy season high overlaps were obtained between (92-111 vs 112-131 min) (λ = 0.73) and (112-131 vs 131-150 mm) (λ = 0.84) length classes. Dwarf goatfish appear to be opportunistic carnivorous predators that impact benthic and epibenthic invertebrates

Observaciones tróficas de tres especies de peces de importancia comercial de Bahía Concepción, Baja California Sur, México

Se revisaron los contenidos estomacales de tres especies de peces de importanciacomercial: Balistes polilepis (Steindachner), Calamus brachysomus (Lockington) y Hoplopagrus guentheri Gill. Las muestras analizadas corresponden a 102 peces provenientes de 5 colectas realizadas durante 1987. Se aplicó el método combinado del Indice de Importancia Relativa para obtener información sobre las preferenciastróficas de los peces. Se encontró que estas especies depredan principalmente a invertebrados bentónicos, aunque en algunas ocasiones incorporan en su dieta a pecespequeños y algas

Diet of the yellowfin snook, Centropomus robalito (Actinopterygii: Perciformes: Centropomidae), in the southwestern Gulf of California

Background. The yellowfin snook, Centropomus robalito Jordan et Gilbert, 1881, is one of the most important species in southwestern Gulf of California fisheries. It is caught in estuarine systems by coastal fishermen and as bycatch on the continental platform, by the industrial shrimp fishery. Dietary analysis are important to understanding the trophic interactions and the position of species within a foodweb and to understand the dynamics of marine communities. In this study, we describe the diet of the yellowfin snook in the southwestern Gulf of California and quantify the effects of sex and size on the species’ diet. Materials and methods. Stomachs of C. robalito were obtained from the shrimp fishery that operates off the southwestern Gulf of California. Percentages by number, weight, and frequency of each food category were determined, and the index of relative importance (%IRI) was calculated to define the main food categories. Diet breadth and diet similarity between sexes and among sizes were also calculated. Results. A total of 401 stomachs were inspected, of which practically all (n = 385; 96%) contained food. According to %IRI, the main prey consumed comprised the shrimp Trachypenaeus pacificus (73%), Xiphopenaeus riveti (10%), and Penaeus spp. (7%). Secondary items included: the stomatopod Squilla mantoidea (4%), Unidentified organic matter (UOM, 3%), and the fish Porichthys sp. (2%). Centropomus robalito is a specialist predator with a low diet Breadth value (Bi = 0.14). While there were no significant differences in diet between the sexes (Analysis of similarities [ANOSIM]; R = 0.014; P = 0.50), there were differences among sizes (ANOSIM, R = 0.361; P = 0.01). Conclusion. Centropomus robalito is a second-order predator that feeds mainly on shrimp, which are abundant throughout its distribution area. The feeding strategy of C. robalito fits the optimal foraging theory. This fish feeds on the most abundant species, obtaining a higher energetic benefit than it would obtain from less available prey, or from more mobile and larger prey that would imply expending more energy in the search, attack, and manipulation of these prey

Feeding habits of the leopard grouper, Mycteroperca rosacea (Actinopterygii: Perciformes: Epinephelidae), in the central Gulf of California, BCS, Mexico

Background. The leopard grouper, Mycteroperca rosacea (Streets, 1877), is endemic to north-western Mexico and has high commercial value. Although facts of its basic biology are known, information on its trophic ecology, in particular, is scarce. The objective of the presently reported study was to characterize the feeding habits of M. rosacea through the analysis of stomach contents, and to determine possible variations linked to sex (male or female), size (small, medium, or large), or season (spring, summer, autumn, or winter), in order to understand the trophic role that this species plays in the ecosystem where it is found. Materials and methods. Fish were captured monthly, from March 2014 to May 2015 by spearfishing in Santa Rosalía, BCS, Mexico. Percentages by the number, by weight, and frequency of appearance of each food category, the index of relative importance (%IRI), and prey-specific index of relative importance (%PSIRI) were used to determine the importance of each prey item in the leopard grouper diet. Diet breadth was calculated using Levin’s index. Possible differences in the diet by sex, size, or season were identified through a multivariate PERMANOVA analysis. Results. A total of 341 leopard grouper specimens were collected, 309 of which had stomachs containing food. A total of 28 prey species were identified. According to the %IRI, the contribution to the diet of the coastal pelagic prey Nyctiphanes simplex and Sardinops sagax (Jenyns, 1842) was 87%, whereas according to the %PSIRI the contribution to the diet of those two prey species was 57%, in addition to several demersal prey species. A PERMANOVA analysis indicated that there were significant differences in the diet of leopard grouper by sex, size, and season, but the interactions sex–size, sex–season, size–season, and sex–size–season, were not significant. Conclusion. Mycteroperca rosacea was identified as a carnivorous predator with narrow trophic width, with significant differences in diet according to the sex, size, season, and size–sex interactions, which could be the result of different energetic requirements, hunting abilities, and food availability. The %PSIRI turned out to be the most adequate index to determine the feeding habits of fish, as it provides a better mean value to determine the most important prey