100' w. 



lOO'w. 



60* w. 



Figure l. — Crosshatching shows localities in areas 1, 2, and 3 where stomachs of skipjack and yellowfin 



tunas were collected. 



tuna and 40 to 155 cm. for yellowfin tuna. (Not 

 all tunas were measured.) Most of the tunas 

 were caught in areas 2 and 3 (table 1). 



The interval between capture of fish and 

 removal of stomachs varied considerably, from 

 a few minutes for fish captured by live bait to 

 several hours for some of the fish caught by 

 longline and purse seine. In most collections', 

 each stomach was pierced in several places and 

 then placed in an individual polyethylene bag 

 that contained 10 percent Formalin.' 



Samples from West African waters were pre- 

 served in Formalin and shipped to TABL in 

 sealed metal drums ; samples from BCF labora- 

 tories or from commercial tuna vessels arrived 

 at TABL either frozen or preserved in For- 

 malin. 



At the laboratory, frozen stomachs were 

 thawed and the contents were removed, pre- 

 served in 10 percent Formalin, and later sorted. 

 Before forage organisms were sorted and identi- 

 fied, the stomach contents were leached in fresh 

 water for 12 to 24 hours to remove the For- 

 malin. After the food items had been sorted 

 into major groups, they were identified as com- 

 pletely as possible and the number of each taxo- 

 nomic entity (species or higher taxonomic 

 group) was recorded on data sheets for each 

 stomach. Each taxon was measured volumet- 

 rically by the displacement of water in a gradu- 

 ate cylinder of appropriate size. Bait found in 

 the stomachs was not included as food. 



- Trade names referred to in this paper do not imply endorsement 

 of commercial products by the Bureau of Commercial Fisheries. 



446 



U.S. FISH AND WILDLIFE SERVICE 



