Feeding biology of the flatfish Citharichthys spilopterus (Bothidae) in a tropical estuary of Mexico

The flatfish Citharichthys spilopterus Gunther 1862 is the most common both id in the coastal lagoons of the Gulf of Mexico. The objective of the prese nt study was to describe the trophic biology of this species in the tropica l coastal lagoon of Tampamachoco, Mexico. For the diet analysis, we used mu ltivariate discriminant analysis and trophic niche breadth. The morphologic al analysis showed that the features of the bucco-pharyngeal cavity, the la rge stomach and the short intestine of this flatfish relate to a carnivorou s habit. The overall diet showed that this species is a third-order consume r, feeding mainly on fish (52%, mainly gobies) and crustaceans (36%, mostly decapods). Diet and trophic niche breadth showed no significant difference s between sexes (P > 0.1). By contrast, there were significant ontogenetic differences in the diet and trophic niche breadth, where larger C. spilopte rus were almost entirely piscivorous and showed the narrowest trophic niche . As the flatfish grew in size there was a trend toward the consumption of larger prey. The importance of copepods and peracarids correlated inversely with flatfish size (P < 0.001), but fish prey correlated directly to flatf ish size (P < 0.001). Likewise, there was an inverse significant correlatio n between niche trophic breadth and flatfish size (P < 0.005). There were a lso significant seasonal differences in the diet (P < 0.02), related to the availability and vulnerability of prey in the lagoon during the dry and ra iny seasons. However, the trophic niche showed no significant differences b etween seasons. Finally, we discuss the advantages of discriminant analysis applied to evaluate differences among diets of fish groups when compared w ith other bivariate and multivariate techniques.