Ocean are scarce. The only reference to a 

 relation between areas of primary productivity 

 and abundance of tunas was found in recent 

 Soviet scientific publications. Soviet investi- 

 gators who linked the distribution of tuna with 

 areas of high biological productivity were: 

 Zharov et al., 1964; Zharov, 1965, 1966, 1967; 

 Bogdanov et al., 1967; and Sokolov, 1967a, 

 1967b. 



Alverson's (1960, 1963b) studies have shown 

 that although the presence of an adequate stock 

 of tuna food in the eastern tropical Pacific 

 did not necessarily ensure the presence of 

 tunas, chances of finding the fish were far 

 greater in areas with abundant food than in 

 food-impoverished waters. Furthermore, ac- 

 cording to Blackburn (in press), the correlation 

 between occurrence of tunas and their prey in 

 the eastern tropical Pacific was closer than 

 that between tunas and the organisms (phyto- 

 plankton and zooplankton) on which tunas do 

 not prey. 



The papers reviewed emphasize the need 

 for additional studies of tuna food and feeding 

 in the Atlantic. I believe this need for broader 

 study must be met through an accumulation of 

 data collected under contemporaneous long- 

 term programs that seek to measure zoo- 

 plankton, micronekton (tuna prey primarily), 

 large carnivores, and oceanographic condi- 

 tions . 



Tunas as "Collectors" of Marine Organisms 



Tunas are often excellent collectors of 

 marine species. Numerous organisms de- 

 scribed in the literature for the first time 

 were taken from tuna stomachs. Collections 

 from the stomach contents of Germo alalunga 

 ( = T_. alalunga ) provided the basis for descrip- 

 tions of the fauna of the Gulf of Gas cony by 

 Bouxin and Legendre (1936) and Legendre 

 (1934, 1940). These authors examined 24,293 

 prey organisms and identified 106 taxa from 

 stomachs of T. alalunga caught in June, July, 

 August, and September over 4years (1929-32). 

 Totals were: invertebrates 68 taxa, 70 per- 

 cent of the total number of food organisms; 

 crustaceans 33 taxa, 61 percent; and cephalo- 

 pods 24 taxa, 9 percent. Of the crustaceans, 

 57 percent were amphipods. Brachyscellus 

 crusculum contributed 48 percent of the total 

 number of crustaceans, and Nematoscelis 

 megalops 24 percent. The 38 taxa of identified 

 fish made up 29 percent of the total organisms; 

 57 percent of the fish were Maurolicus muel- 

 leri . 



Until Penrith's (1963) survey, Oreosoma 

 atlanticum and Tetragonurus cuvieri were 

 rare in museum collections; his Lestidium sp. 

 and Taractes sp. represented the first records 

 of these genera from South African water s; and 

 C entr opholoides falcatus was known from the 

 type species only. The presence of these spe- 

 cies in tuna stomachs suggested to Penrith 



that the fish might not be as rare as they were 

 thought to be, but that their apparent rarity 

 might be linked to existing inadequate methods 

 for catching midwater organisms. 



Russell (I960), used stomach contents of 

 T. albacares to construct a taxonomic key to 

 North Atlantic heteropods. 



Chevreux (1893) described certain hyperiid 

 amphipods on the basis of stomach contents of 

 albacore caught between France and the Azores. 



Collections of juvenile tunas are valuable 

 aids in determining the location of the nursery 

 areas of different species. Klawe (1961) re- 

 ported juvenile T. atlanticus and Euthynnus 

 alletteratus , Scomberomorus sp. and Katsu- 

 wonus pelamis in stomachs of K. pelamis and 

 E. alletteratus in his studies of young scom- 

 brids from the waters between Cape Hatteras 

 and the Bahama Islands. 



Feeding Habits 



Most of the publications reviewed indicated 

 that tunas are indiscriminate pelagic feeders; 

 some of the authors surmised that the fish 

 also feed near the bottom. Beebe (1936) stated 

 that yellowfin and blackfin tunas feed near the 

 bottom at all times. Bane (1965) found that 

 goatfishes, squirrelfishes, triggerfishes, sur- 

 geonfishes, and jacks were the most numer- 

 ous fishes in the stomachs of blackfin tunas 

 collected near Puerto Rico; most of the food 

 fish were small (5-7 cm. long) and were com- 

 mon in nearby reefs and rocky areas. Bane 

 also found invertebrates in tuna stomachs, 

 among which were shrimp, squid, larval sto- 

 matopods, small octopi, lobster and crab 

 larvae, and gastropod shells. The presence of 

 benthic crustaceans and cephalopods in the 

 stomachs of bluefin tuna collectednear islands 

 in the Adriatic also suggests that tuna some- 

 times feed near the bottom (Morovic, 1961). 

 Da Cruz (1965) noted large numbers of small 

 Balistidae in the stomachs of blackfin tunas 

 and stated that blackfin tunas often must feed 

 near the bottom because small Balistidae are 

 usually found on coral bottoms. 



Marchal (1959), who studied the food of 

 Neothunnus albacora (=T. albacares ) in the 

 Gulf of Guinea, divided the forage organisms 

 into pelagic, bathypelagic, and coastal species. 



Food in Relation to Species and Size of Tunas 



In one of the more comprehensive studies of 

 food of several species of tuna, Penrith (1963) 

 showed important interspecific differences in 

 feeding habits of tunas off the Cape of Good 

 Hope, although he did not discuss food in rela- 

 tion to area or season of capture, or size of 

 tuna. He found that T. alalunga , T. albacares , 

 and T_. obesus fed mainly on fish, cephalopods, 

 and shrimp. T. alalunga consumed a wide 

 variety of fishes and large quantities of macro- 

 plankton. X- albacares fed mainly on large 

 surface organisms, but took macroplankton 



