Bluefin Tuna

Blue Fin TunaIntroduction

The blue fin tuna exhibits the ability to transverse across drastically temperature diverse waters due to its endothermic abilities. Bluefin tuna (Thunnus thynnus) exhibits the ability to transverse across drastically different ambient waters. Bluefin tuna migrate between cold water feeding grounds and warm water spawning grounds and also make vertical dives so deep that the ambient temperatures can easily vary from 3C to 30C. In order to survive such drastic temperature changes that are necessary for their transoceanic migration and foraging behaviors, bluefin tuna possess endothermic abilities that allows them to maintain stable body temperatures.

The Bluefin Tuna

These fish have been known to traverse large migratory distances, such as across the Atlantic and Pacific Oceans (up to 8000 km). Bluefin tuna can reach lengths over 3 meters long and can weigh up to 900 kg. Due to their incredible size they have been long hunted by fishermen for their meat, which has placed bluefin tuna on the endangered species list (Premium tuna fetches $100,000 at auction). Because of the bluefin tuna’s dwindling population world wide, it is crucial to being to understand their foraging and spawning behaviors in order to preserve the existing bluefins.

Migration and Endothermy

Bluefin tuna migrate vast expanses of ocean in efforts to find warmer spawning waters. In the transoceanic journey alone they subject themselves to a wide range of ambient temperatures. In order to make this journey safely and avoid hypothermia, bluefin tuna possess the ability to regulate their body temperature by use of endothermy. Endotherms are often given the quantifier as “warm-blooded” due to bluefin’s ability to raise their body temperature above ambient temperatures. The tuna, like other endothermic fishes, actively produces heat through swimming and digestion and then is able to conserve it through visceral counter current heat exchangers (Dickson and Graham) (more in Mechanism).In order to maintain stable body temperatures, the warmest muscle mass of the bluefins only fluxes over 5C over a 20C ambient temperature change. This ability has allowed tuna to adapt the ability to migrate across vast oceanic spans and has therefore expanded their foraging and spawning niche (Carey and Teal 1967). Due to its endothermic abilities, the Atlantic tuna can go from its cold feeding grounds along the North American coast to warm spawning grounds (29.8 degrees C) in the Gulf of Mexico and Mediterranean (Teo et al., Annual migrations, 2007, Ravier and Frometin). Endothermy also allows the fish deep (deepest dive recorded at 672m- Wilson et al.), giving it the advantage to hunt plentiful areas and avoid ocean currents (Teo et al. Annual Migrations 2007).

This website will analyze migration and endothermy in the blue fin tuna based on Niko Tinbergen’s four questions: Phylogeny, Ontogeny, Adaptive Value and Phylogeny.

Four Questions