Brown shrimp (Penaeus aztecus) were marked with injections of biological stains and fluorescent pigments and released in the Swan Quarter Bay tributary of Pamlico Sound, North Carolina, to obtain population dynamics information including movement, migration, growth, and mortality. From July to September, 1967,6,163 shrimp were marked and released. Of these, 1,030 (16.7%) were returned. The average interval between release and recapture was 12 days, and the average distance traveled during this time was 3 miles. Only one shrimp was recaptured in the Atlantic Ocean. These data do not clearly indicate the most probable route or routes of movement from the study area to the ocean. Modes of size distribution curves were at 115 mm total length during the eight-week mark-release phase of the study, indicating an apparent "level of equilibrium" condition. This level was maintained by movement of larger individuals from the area, immigration of small ones from upstream reaches, and growth within the area. The mean growth curve indicates brown shrimp reach a count of 70-per-pound (headless) in 12 weeks, 50-per-pound in 14 to 15 weeks, and attain an average maximum size of 15-per-pound. Total mortality estimates for two separate experiments indicate 71% and 63% per week were removed by the combined effects of fishing and natural causes.
