THE USE OF INFAUNA BY JUVENILE PENAEUS-AZTECUS IVES AND PENAEUS-SETIFERUS (LINNAEUS)

Penaeus aztecus Ives, the brown shrimp, and Ponaeus setiferus (Linnaeu s), the white shrimp, co-occur in Texas salt marshes as juveniles. Alt hough their life cycles are similar, evidence indicates that the speci es utilize different resources for the primary faunal element of their diets. Prey selection and growth studies have shown that brown shrimp successfully remove infauna from natural sediment Further, a diet of polychaetes, whether alone or in combination with algae, produced grow th in the species. Brown shrimp appear to be trophically linked to inf aunal populations, thus the structure and dynamics of the benthic comm unity may directly affect local brown shrimp productivity. Areas domin ated by surface-dwelling polychaetes as opposed to deep burrowers may provide more accessible foraging opportunities for juvenile brown shri mp. By contrast, white shrimp neither removed infauna nor grew to a si gnificant degree when provided polychaetes or amphipods as food. White shrimp are omnivorous but do not rely on infaunal material to the sam e extent as brown shrimp. The primary faunal element in the diet of wh ite shrimp has not yet been identified. The dietary differences betwee n the two species may play a role in determining which species dominat es in regions with varying marsh accessibility. Although not the only factors influencing penaeid survival and growth, prey choice and avail ability may greatly affect production and Local success of penaeid pop ulations.