Review of Studies of Tuna Food in the Atlantic Ocean 



By 



ALEXANDER DRAGOVICH, Fishery Biologist 



Tropical Atlantic Biological Laboratory 



Bureau of Commercial Fisheries 



Miami, Florida 33149 



ABSTRACT 



Published and unpublished reports are reviewed and methods used to evaluate 

 the data are discussed. A description is presented of the food of seven Atlantic 

 tunas of commercial importance: little tuna ( Euthynnus alletteratus ), skipjack tuna 

 ( Katsuwonus pelamis ), yellowfin tuna ( Thunnus albacares ), blackfin tuna (T_. atlanti- 

 cus ), the bluefin tuna complex (T. thynnus thynnus and T. maccoyii ), bigeye tuna 

 (T. obesus ), and albacore (T. alalunga ). Their food consists mainly of pelagic fish 

 (mostly juveniles, some larvae and adults), crustaceans (mostly macrozooplankton), 

 and mollusks (chiefly cephalopods). The greatest number of food items are fish taxa 

 (331), followed by crustaceans (111) and mollusks (74). Prey organisms are listed 

 alphabetically, according to the tuna species. The food consumed by the species of 

 tuna was generally similar. Differences in food between the juvenile and adult blue- 

 fin tuna were pronounced; juveniles fed largely on crustaceans whereas adults fed 

 primarily on fishes. Seasonal differences were noted in the composition of the food 

 of skipjack and yellowfin tunas in African waters. 



INTRODUCTION 



A thorough knowledge of food and feeding of 

 tunas is important to an understanding of re- 

 gional and local aggregations of tunas and their 

 behavior (Reintjes and King, 1953; King and 

 Ikehara, 1956; Alverson, 1963b). 



Interest in the food of Atlantic tunas was 

 evidenced as early as the second half of the 

 19th century (De Monaco, 1888). French re- 

 searchers have continued their interest in tuna 

 food studies to the present time. Publications 

 in English began in the 1920's and are con- 

 tinuing. Contributions by Soviet, Spanish, Por- 

 tuguese, and Yugoslavian authors were pub- 

 lished in the 1960's. 



The present paper reviews published and 

 unpublished reports on the food of tunas in the 

 Atlantic Ocean. Some of the papers consider 

 feeding and food in detail; others mention them 

 only incidentally. I do not summarize each 

 paper individually in this review but discuss 

 points of interest to a fishery biologist. 



I divided the reports that were reviewed into 

 six categories (number of reports in paren- 

 theses): descriptive publications (9), notes (9), 

 reports on data (9), reviews (1), incidental 

 papers (28), and taxonomic works (2). The cate- 

 gories are so designated in the bibliography. 

 Descriptive papers in general contain detailed 



presentations and interpretations of results; 

 notes are largely brief reports based on lim- 

 ited observations; reports on data refer to 

 untreated data in tabular form; reviews contain 

 information mostly from other papers, which 

 is summarized and sometimes accompanied 

 by interpretation and comment; incidental 

 papers give information on food or feeding 

 habits in only a casual fashion (titles may be 

 completely unrelated to the food of tunas); and 

 taxonomic papers treat taxonomic aspects of 

 tuna forage in some detail. 



The most important commercial species of 

 tunas dealt with in the papers reviewed were: 

 little tuna (Euthynnus alletteratus ), skipjack 

 tuna ( Katsuwonus pelamis ), yellowfin tuna 

 ( Thunnus albacares ), blackfin tuna (T. atlanti- 

 cus ). the bluefin tuna complex ( T. thynnus thyn- 

 nus and T, maccoyii) , bigeye tuna (T_. obesus ), 

 and albacore (T. alalunga ). (The synonymy of 

 each species includes many more names than 

 those mentioned above.) Albacore received the 

 most attention in the papers. 



The number of stomachs on which different 

 reports were based varied widely--from one 

 to several thousand. 



Fishing gear used to capture tuna consisted 

 of trolling lines (with artificial lures), pole 

 and line, purse seine, longline, spears, rod 

 and reel, and harpoons. 



