Annual migrations, diving behavior, and thermal biology of Atlantic bluefin tuna, Thunnus thynnus, on their Gulf of Mexico breeding grounds

Authors: S. Teo, et. mucho al, 2006.

This paper is an empirical analysis of data collected via pop-up and archival tags implanted in breeding tuna. The tags record internal and external temperature of the tuna, as well as their depth, every 120 seconds. (Not all tags do this, but this is the gist of the data.) The authors compile this data for a sample of 28 mature tuna, and use the data to draw striking conclusions about tuna breeding behavior, and how it relates to their thermal biology. Tuna are normally cold water fish, and as a consequence normally have a relatively low thermal exchange coefficient $K$ (i.e. they retain heat well.) Since their breeding ground in the Gulf of Mexico are quite warm, however, and they need to spend a lot of time near the surface, the thermal exchange coefficient rises as they begin to breed, and the regulate their temperature by diving. This partially exchanges the high mortality rate of bluefin tuna caught in the GOM on pelagic long-lines: unable to dive, they become thermally stressed, which when added to the stress of capture does them in.