FISHERY BULLETIN: VOL. 79. NO. 2 



METHODS 



Shrimp samples were collected at 22 bay and 3 

 offshore stations along the Texas coast (Figure 1). 

 Most bay sampling was done by the Texas Parks 

 and Wildlife Department, Coastal Fisheries Divi- 

 sion, as part of their 1978 spring shrimp survey. 

 Depths at bay stations were 1-2 m; offshore trawl- 

 ing areas were located in 27-29 m depths. Open 

 bay stations had unvegetated mud bottoms and 

 were not within 0.25 km of a major swamp, sea 

 grass meadow, or marsh. Sea grass stations were 

 all in or on the edge of large sea grass meadows 

 measuring at least 5 ha. 



Four open bay stations deserve individual men- 

 tion. Clear Lake (station 100) and the old Arroyo 

 Colorado (station 13) receive substantial amounts 

 of domestic sewage. Station 94, at the mouth of the 

 Tres Palacios River, had the lowest salinities of 

 any station. Station 92 in Turtle Bay was in the 



open bay, but well-developed Spartina sp. marshes 

 were present on the shore. 



Shrimp were collected either with bar seines or 

 trawls and then frozen in seawater for later iden- 

 tification and S^^C analysis. Surface temperature 

 and salinity were measured at the time of collec- 

 tion. Spring samples were mostly collected during 

 a 6-wk period from mid-April to 1 June 1978. 

 Offshore samples were collected 26 July 1978. 



White muscle tissue was dissected from shrimp 

 abdomens for S^^C analysis. Both composite and 

 individual samples were prepared. Composite 

 samples contained equal-weight tissues from in- 

 dividual shrimp. Preliminary analysis of the 

 number of pooled brown shrimp required for an 

 accurate estimate of mean shrimp S^^C showed 

 that combining five or six individuals is generally 

 sufficient (Figure 2); accordingly, composite sam- 

 ple sizes were ^rlO for all shrimp, and averaged 34 

 individuals/sample. For individual shrimp, mus- 



FlGURE L — Shrimp collection stations 

 in the northwestern Gulf of Mexico. 



GALVESTON BAY 



TEXAS 



MATAGORDA BAY 



SAN 95 



ANTONIO 



ARANSAS 7 

 &COPANQ 

 BAYS./^^ 



LOWER 

 LAGUNA, , 

 MADRE >• \^-^ 



GULF OF MEXICO 



50 



km 



MEX. 



338 



