| Abstract: | Penaeus aztecus Ives, the brown shrimp, and Penaeus setiferus (Linnaeus), the white shrimp, co-occur in Texas salt marshes as juveniles. While their basic life cycles are similar, evidence indicates that the species utilize different resources for the primary faunal element of their diets. Through prey selection and growth studies, brown shrimp were shown to successfully remove infauna from natural sediment. Further, a diet of polychaetes, whether alone or in combination with algae, produced growth in the species. By contrast, white shrimp neither removed infauna nor grew to a significant degree when provided polychaetes or amphipods as food. A predator-exclusion caging study suggested that brown shrimp may significantly affect polychaete populations in marsh areas, but their impact on amphipods or any taxon living in open bay bottom is not clear and may be much less. Pressures defining infaunal populations may vary with habitat and group of animal considered. Brown shrimp appear to be trophically linked to infaunal populations. The structure and dynamics of the benthic community may to directly affect local penaeid productivity. Areas dominated by surface dwelling polychaetes as opposed to deep burrowers may provide more accessible foraging for juvenile brown shrimp. White shrimp are omnivorous as well, but do not rely on infaunal material to the same extent as the brown shrimp. The primary faunal element in the diet of white shrimp has not yet been identified. The dietary differences between the two species may play a role in defining which species dominates in regions with varying marsh accessibility. While prey choice and availability are not the only factors influencing penaeids, they may greatly affect production and local success of populations. |
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