Seasonal and spatial variations reproductive activity and biochemical composition of Penaeus setiferus and Penaeus aztecus in the Gulf of Mexico.

Penaeus setiferus and P. aztecus compose the bulk of the Texas catch of shrimp, the most valuable fishery product in the state. This study compares the maturation and reproduction of P. setiferus and P. aztecus near an offshore brine diffuser (at a depth of 21m) to that at two control locations. The parameters used in this evaluation included frequency of capture of ripe mated females, number of eggs and percent hatch from onboard spawns, stage of ovarian development of females and relative size and biochemical composition (total carbohydrate, total lipid and total protein) of the gonad and hepato-pancreas of males and females. Seven 10-day collecting cruises were conducted between October 1979 and September 1980, and approximately 3,00 shrimp were dissected and analyzed. Descriptions and photographs of characteristic size and color of each stage of ovarian maturation are presented for each species. Fecundity and hatching rate averaged 257,000 and 55 percent, respectively, for P. setiferus, and 167, 800 and 77.6 percent, respectively, for P. aztecus. Reproductive activity of P. setiferus was observed from May through September with a peak in June while P. aztecus was reproductively active from July through October with a peak in September. Size at first maturity was estimated as 160-170 mm total length for females of P. setiferus and P. aztecus, 150-160 mm for P. setiferus males, and 110-120 mm for P. aztecus males. Gonad size in males reached as asymptote of maximum size at 170-180 mm total length in P. setiferus and 150-160 mm in P. aztecus.