Utilization of estuarine organic matter during growth and migration by juvenile brown shrimp Penaeus aztecus in a South Texas estuary

The trophic dynamic Links of migratory juvenile brown shrimp Penaeus aztecu s were investigated along the South Texas coast from the Aransas Pass to Co rpus Christi and Nueces Bay and to the nursery ground in the Nueces Delta. Shrimps and their potential food sources were measured for delta(13)C and d elta(15)N ratios between December 1995 and July 1996. During this period, s hrimp length increased from 10 to 11 mm, when the animals entered Corpus Ch risti Bay as larvae, to 80-90 mm, when they returned to Mexico Gulf as sub- adults. Brown shrimp exhibited spatial and temporal delta(13)C variation (f rom -25.2 to 12.5 parts per thousand), indicating a high diversity of food sources throughout their migration. From delta(13)C values, the main source s used as food sources by juvenile brown shrimp in the Rincon Bayou marsh w ere Spartina alterniflora and S. spartinae detritus and benthic diatoms. de lta(13)C and delta(15)N values showed that organic matter inputs carried by the river inflow can also contribute significantly to the feeding of migra tory brown shrimp. In these marsh habitats, shrimp isotopic ratios changed rapidly, suggesting high tissue turnover rates. The study showed that coast al marshes after restoration through the introduction of freshwater inflow may provide feeding habitats favorable for growth and development of juveni le brown shrimp.