Ecological aspects of selected crustacea of two marsh embayments on the Texas Coast

Abstract

Crustacea from two marsh embayments, Oyster and Alligator Lakes, were collected twice a month for two years, identified, and their seasonal abundance determined with respects to temperature and salinity. Collection included commercial penaeid shrimp, grass shrimp (Palaemonetes), sergestid shrimp, and mysid shrimp. During the summer of 1969, three tests were conducted on the effects of aerial application of malathion, in concentrations used in mosquito control, on the juvenile commercial shrimp Penaeus aztecus Ives and Penaeus setiferus (Linn.). Dead and live shrimp samples, and water samples taken before and during the test were analyzed by means of gas-chromatography and thin-layer chromatography. In all three tests the commercial shrimp suffered mortalities ranging from 14 to 80 percent while the control shrimp suffered no deaths attributable to the pesticide. Water analysis demonstrated a high concentration of malathion immediately after application and a progressive reduction 24, 33, and 48 hours after application. Malathion values in live shrimp taken from boxes during the test were consistently greater than the values obtained from dead shrimp removed during the same period. It was hypothesized that shrimp demonstrating tolerance to malathion, could continue to accumulate the pesticide, whereas a dead shrimp could no longer actively accumulate the pesticide or even may lose pesticide through leaching to the surrounding medium. Field tests indicated that P. aztecus possesses a faster and, in most cases, a greater sensitivity to malathion than P. setiferus. Tidal activity shown to alter the exposure of the shrimp to malathion by moving target water into or out of the area, or by concentrating the affected water on the shrimp. ...