98° W 



93' 



30° 

 N 



TEXAS 



26^ 



73 M- 

 91 ivf 



GULF OF 

 MEXICO 



FIGURE 1. — RV Oregon II shrimp survey sites off the Texas coast, June-July 1981. 



In the laboratory, each sample was thawed and the 

 fishes were sorted and measured to the nearest milli- 

 meter (standard length for most genera; disc width or 

 total length for others). In most cases, fishes <150 

 mm in length or width were discarded, since they 

 were unlikely shrimp predators. However, in samples 

 consisting of at least 75% potentially carnivorous 

 fishes of < 150 mm, a minimum of 50% of these fishes 

 was examined. All discards were recorded. 



Each fish was examined by opening the abdomen 

 and removing the stomach. Empty stomachs were 

 recorded. Stomach contents were identified visually, 

 in some cases with a dissecting microscope, to 10 

 broad taxonomic categories: polychaetes, molluscs, 

 holothurians, mysids, stomatopods, shrimps, crabs, 

 squids, fishes, and octopi. Detritus was also recorded 

 as a discrete category. Penaeid shrimps and fishes 

 were further identified to genus and species when 

 possible. Tail lengths ofTrachypenaeus and Sicyonia 

 were recorded as falling into one of a series of 5 mm 

 size classes, while those of Penaeus aztecus were 

 measured to the nearest millimeter. Fishes were sub- 



sequently grouped into about 25, 50, or 100 mm size 

 classes to examine size- and depth-related differ- 

 ences in diet. However, many species were represent- 

 ed by too few individuals to justify comparison or 

 showed no size-related diet changes; thus, data from 

 only a few species are presented with size-class infor- 

 mation. Results are presented as frequency of occur- 

 rence of the various food items in stomachs contain- 

 ing food. Food categories having a 30% or greater 

 frequency of occurrence are referred to as "major," 

 while those having <30% frequencies are referred to 

 as "minor." 



Results and Discussion 



We examined the stomachs of 7,374 fishes of 81 

 species (11% of the total individuals collected). The 

 frequency of occurrence of food items in stomachs is 

 summarized in Appendix Table 1. A total of 61,385 

 fishes, including 17 more species, were discarded 

 without examination for reasons presented in the 

 previous section (Appendix Table 2). Shoal flounder, 



397 



