Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Eight species of Prionotus, collected from 5-100 m in the Gulf of Mexico along a cross-shelf transect off Freeport, Tx during October 1977-August 1981, were studied to determine life history patterns and how they partition resources. Only four species were abundant: P. tribulus, P. paralatus, P. longispinosus, and P. stearnsi. Prionotus spp. mature at 80 mm (P. stearnsi and P. rubio), 85 mm (P. tribulus and P. paralatus), 100 mm (P. ophryas), 105 mm (P. roseus), and 120 mm (P. longispinosus). Sizes at Age 1 were 99-140 mm (P. tribulus), 99-138 mm (P. longispinosus), 98-122 mm (P. paralatus), 75-125 mm (P. stearnsi), and 95-129 mm (P. ophryas). Most fish were less than 200 mm. Typical maximum sizes were 155-175 mm (P. tribulus), 145-160 mm (P. longispinosus), 160-165 mm (P. paralatus), 180-195 mm (P. rubio), 125 mm (P. stearnsi), and 155-160 mm (P. ophryas). Fish were typically 1-3 years old at these typical maximum sizes, and most were Age 1 and less. Apparent total annual mortality rates were 80-100%. The eight species fit into three categories based on their bathymetric distributions and community memberships: (1) members of the inshore white shrimp community which occurs from 5 m to about 16 m (P. tribulus); (2) members of the offshore brown shrimp community which occurs from about 36 to at least 100 m (P. paralatus, P. stearnsi, and P. roseus); and (3) members of a transition fauna which occurs between the outer edge of the white shrimp community and the inshore edge of the brown shrimp community from about 18-27 m (P. longispinosus, P. rubio, P. ophryas, and P. scitulus). Comparisons among species indicate a common pattern of population dynamics that favors r-strategy (short life spans, high mortality rates, and rapid turnover of biomass), but with temporally segregated spawning and spatially segregated distributions. Spawning grounds seem to lie toward the northcentral Gulf with current transport mechanisms carrying young toward the northwestern Gulf. Prionotus spp. from the northwestern Gulf show quite different life history attributes than their congeners from mid Atlantic and New England regions.



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