Table 4. — Comparison of postlarval and 

 juvenile pink shrimp abundance between 

 interior Florida Bay, Atlantic Florida Bay, 

 and Biscayne Bay, March to May 1965 



[ Numbers within parentheses indicate number 

 of samples] 



Table 5. --Average fish catch per unit effort 

 over the Continental Shelf, northwestern 

 Gulf of Mexico in 1964 



^ See figure 10 for locations. 



ECOLOGICALLY ASSOCIATED ORGANISMS 



We are studying some of the many organisms, 

 mostly fishes and crustaceans, that are closely 

 associated with, and often innpede, the harvest 

 of Gulf coast shrinnp. Little is currently known 

 of how these forms affect commercial shrimp 

 populations through predation, crowding, or 

 connpetition for food. 



Bottomfish samples collected monthly 

 through December 1964 at 36 sannpling sta- 

 tions on the connmercial offshore shrimp 

 grounds in the northwestern Gulf of Mexico 

 were examined, and the resulting data were 

 prepared for analysis. We collected samples 

 with a 45-ft. 2-in. stretched-mesh, flat shrimp 

 trawl equipped with rollers. At each station, 

 after we weighed the total finfish catch, we 

 sav^ed a subsample weighing about 7 1/2 lb., 

 which was brought to the laboratory for deter- 

 mination of species composition. We are now 

 analyzing these data and also 2 1/2 yr. of 

 data compiled by the Industrial Fishery Pro- 

 gram to detern-iine seasonal, depth, and spatial 

 relative abundance of finfish species that live 

 on the shrimp grounds. Upon completion of 

 this survey we will study the life histories 

 of certain species of fishes so we can under- 

 stand better their relations to the shrimp 

 populations. 



The average catch per unit of effort in 

 1964 of all fish species combined was about 

 2 to 4 times greater off Louisiana than off 

 Texas. These catch-effort averages, which 



West of Mississippi River. 



are reported as pounds per hour, were very 

 similar to those calculated from samples 

 taken at the same depths in 1963 (table 5). 



In a preliminary analysis of the data col- 

 lected off the Texas coast in 1963, the catches 

 per unit effort of 10 finfish species, which 

 constituted over two-thirds of the total poundage 

 of fish caught, were compared seasonally at 

 three depth ranges to the corresponding 

 catches per effort of the two major com- 

 mercial shrimp species. 



White shrimp were more abundant by weight 

 in the inshore waters (4 and 7.5 fath,), 

 whereas brown shrinnp were more abundant 

 in nniddepths (12 and 15 fath.) and offshore 

 (25 and 40 fath.). The peak seasonal abundance 

 of white shrimp was during fall and that of 

 brown shrimp was in summer at nniddepths 

 and in fall offshore (fig. 13). 



Seacatfish, Galeichthys felis , and southern 

 kingfish, Menticirrhus annericanus, were most 

 abundant in inshore waters (4 and 7.5 fath.) in 

 sunimer--the time of offshore moven-ients of 

 juvenile brown shrimp fronn estuarine nursery 

 areas along the Texas coast. These fish were 

 not taken on the offshore brown shrimp 

 grounds. 



Shoal flounder, Syaciunn gunteri (see fig. 13), 

 as well as Atlantic croaker, Micropogon 

 undulatus ; spot, Leiostomus xanthurus ; and 

 silver and sand seatrout, Cynoscion nothus 

 and Cj, arenarius , were taken fronn all three 

 depth ranges. In the middepth range the 

 greatest catches of the latter four species 

 coincided seasonally with the largest brown 

 shrimp catches. 



Rock seabass, Centropristis philadelphicus 

 (see fig. 13), and longspine porgy, Stenotomus 

 caprinus , occurred nnostly in the catches 

 from the offshore brown shrimp grounds. 

 None was taken on the white shrimp grounds. 

 Inshore lizardfish, Synodus foetens , had a 

 similar seasonal catch distribution; it occa- 

 sionally occurred, however, in the catches 

 from the inshore white shrinnp grounds. 



Donald Moore, Project Leader 



18 



