Comparative food studies of yellowfin in tuna, Thunnus albacares, and blackfin tuna, Thunnus atlanticus, (Pisces: Scombridae) from the Southeastern and Gulf Coast of the United States

Abstract

[Automated (and shortened) translation of the Polish Summary—No original English Abstract available.] The data are from 206 yellowfin (Thunnus albacares) and 96 blackfin (Thunnus atlanticus), obtained in sports fishing off the coast of the southern United States and the Gulf of Mexico between April 1980 and July 1982. Stomach contents were tested for the frequency of individual food item components, their quantity and volume. Invertebrates and fish were present in the diet of yellowfin and blackfin tuna almost equally (85% and 77%). The majority of invertebrates in terms of incidence are cephalopods (62%) and crustaceans (52%). Fish were represented mainly by representatives of the families: Scombridae – 12%, Balistidae – 11.2%, and Syngnathidae – 8.2%. Moreover, especially the yellowfin tuna ate various floating materials, such as plastic, feathers, floating algae, and lumps of mazut. Invertebrates occurring in 82% of the blackfin tuna (Th. atlanticus) accounted for 77% of the number of diatery items and 31% of the volume of the food mass. Fish were present in 67% of the specimens and constituted 26% of the number of food items and 68% of the volume. Of the invertebrates, crustaceans were the most common (67.4% and cephalopods 36.0%). Fish were represented mainly by the following families: Balistidae – 10.1%, Trichiuridae – 5.6%, and Carangidae – 4.5%. Blackfin tuna also ate randomly floating materials, such as plastics, sea algae. A statistical comparison of the diets of both species did not show a significant correlation. In general, the diet of yellowfin and blackfin tuna is that of strong aggressive predators, and such as fish food, which is strained through a filter apparatus, will gill tiny objects near the water's surface. The fish, occurring in 77% of yellowfin and 67% of blackfin tuna, were mainly younger or older larvae found among the floating Sargassum clumps. In general, they represented 23 families. Adult Exocoetidae, Scombridae, and Syngnathidae have occasionally occurred in yellowfin tuna, as have Serranidae, Sciaenidae, and Stromateidae in blackfin tuna. Among yellowfin tuna of various ages, the most common were: Scombridae (12.2%), Balistidae (11.2%), Syngnathidae (8.2%), and Diodontidae (5.1%). 53 stomachs contained fish that were difficult to identify. The most common fish of blackfin tuna were: Balistidae (10.1%), Trichiuridae (5.6%), Carangidae (4.5%), and Syngnathidae (4.5%). 44.9% of stomachs contained remains difficult to identify. Of the mollusks, they were found almost exclusively in both species of cephalopods. Two of their groups were represented, Teuthidida and Octopodida. Squids were more common, quantitatively like by volume, 50.5% and 40.0% in yellowfin and 31.5% and 21.5% in blackfin (quantitative and volumetric)._x000D_[...] […][...] […][...] _x000D_In summary, yellowfin and blackfin tuna are predators capable of capturing fast, relatively large prey, but on the other hand, they use their straining gill apparatus to take up much less food from the surface. The main food is fish, cephalopods, and crustaceans. In general, it can be assumed that their diet does not show high selectivity, which probably also affects their wide range of occurrence.