White shrimp, Penaeus setiferus (Linnaeus), spawning in the Gulf of Mexico 1973-1975

Abstract

White shrimp (Penaeus setiferus) were sampled in gulf waters of the Texas coast to determine their spawning grounds, the percentage of gravid females in the population and whether discrete spawning populations exist. Data were also obtained on the seasonal abundance of shrimp, shrimp size, and the effect of temperature on spawning and movement. Samples were obtained with 13.7 m (45 ft) otter trawls at 7, 11, 15 and 22 m (4, 6, 8 and 12 fm) near the major passes. Most spawning occurred between April and August with a spawning peak in June. Evidence of spawning was found at all depths sampled but was most prevalent at 7-15 m (4-8 fm), the principal spawning depth being 11 m (6 fm). In samples in which gravid females were found, they constituted 4-25% (but usually less than 10%) of the catch. No discrete spawning populations were found. The advent of spawning coincided with an increase in water temperature; the emigration of small shrimp from the bays coincided with a temperature increase. The temperature range during the major spawning period (June) was 26.6-27.2 C. The largest shrimp and the lowest catches per hour were obtained in July-August, indicating mortality after spawning.