Two studies recently published by researchers from the Spanish Institute of Oceanography (IEO) and the University of Bergen, have shown that the coexistence of tuna larvae of different species and sizes in the spawning areas is essential for the survival of such early life stages, since cannibalism can constitute a significant fraction of natural mortality during this period.

Researchers at the Oceanographic Centre of the Balearic Islands of the Spanish Institute of Oceanography (IEO) in collaboration with the Department of Biology of the University of Bergen (Norway) have recently published two studies related to ecology and survival of larvae of different species of tuna.

The first one indicates that one of the mechanisms that can influence the survival rates of tuna larvae is cannibalism, as well as predation among larvae of different species of tuna. Both processes play a major role in determining larval abundance of these species during their first days of life, and so it would condition the level of recruitment to the juvenile stages.

"These large predators measure at hatching about 3 millimeters and grow rapidly, being able in less than a month to feed on smaller larvae of other species of tuna or even the same species," says Patricia Reglero, lead author of the work. "In environments with little wealth of invertebrate prey, as in almost all tuna spawning areas in the world, the survival of various species of tuna may depend on the coexistence of larvae of different sizes and the predator-prey relationships established bamong them," she adds.

The second study shows that in one of the most important spawning areas of tuna in the world, the Balearic Islands, in the summer zooplankton community coexist relatively high densities of larvae of three species of tuna: bluefin, albacore and bullet tuna. Therefore the relationships of predation and competition for food between them could be important.

The results of both studies were obtained within the framework of the project "Ecology and larval recruitment processes of decapod crustaceans, cephalopods and teleost fish in the Balearic Sea" funded by the National R+D+I Plan of the Ministry of Science and Innovation, ending in December 2012.