Feeding habits of red drum (Sciaenops ocellatus) in Galveston Bay, Texas: Seasonal diet variation and predator-prey size relationships

Feeding habits, seasonal diet variation, and predator size-prey size relati onships of red drum (Sciaenops ocellatus) were investigated in Galveston Ba y, Texas through stomach contents analysis. A total of 598 red drum ranging from 291-763 mm total length were collected and their stomach contents ana lyzed during fah 1997 and spring 1998. The diet of red drum showed signific ant seasonal patterns, and was dominated by white shrimp (Penaeus setiferus ) during fall. and gulf menhaden (Brevoortia patronus) during spring. Blue crab (Callinectes sapidus) was an important component of red drum diets dur ing both seasons. Significant differences existed between prey types consum ed during fall and spring as red drum diet reflected seasonal variation in prey availability. Predictive regression equations were generated to estima te original carapace width of blue crabs from several measurements taken fr om carapace fragments recovered in red drum stomachs. Regressions were high ly significant (r(2) > 0.97) and increased the number of blue crabs Kith si ze information nearly three fold. Predator size-prey size relationships wer e determined for red drum feeding on white shrimp, gulf menhaden, and blue crab. Although regression slopes were statistically significant, prey sizes increased only slightly with increasing red drum size. Comparisons of prey sizes consumed by red drum with sizes occurring in the field indicate that red drum feed in nearshore shallow water habitats, which serve as nursery areas for many juvenile fishes and crustaceans. Our findings demonstrate th at red drum feed on several prey species of commercial and recreational val ue and may hare important effects on estuarine community structure.