Southern Bluefin

In a small high-end sushi countered restaurant, the cut of tuna is dependant on domestically caught tuna. Typically from Ōma, the Maguro there is considered the finest in the winter months. You can see the cuts are very similar, (photoed below), cut from the same piece, the cuts differ in colour slightly, as the tuna has varying colours of red throughout the section.

These sashimi cuts are from “true tuna”, bluefin tuna a member of Scombridae family a subgenus species. The bluefin is world-famous for the price it fetches, prized in sushi counters across Japan. The Scombridae are famously fast, swimming to stay alive, and mostly delicious in taste.

The southern bluefin tuna does not require a separate pump mechanism to pump water over the gills, the water passes as they are always under constant movement. The faster it swims, the increasing the oxygen uptake it gets. This overall high oxygen uptake works in close coordination with a well-adapted circulatory system to meet the high metabolic needs of the southern bluefin tuna.

Their major arteries and veins run longitudinally to and from the red swimming muscles, which are found close to the spinal column, just underneath the skin.  Southern bluefin tuna have a high blood hemoglobin content and the meat can be super red. This species of tuna inhabits ocean areas that are relatively high in salinity compared to the rest of the world’s oceans.

Southern bluefin tunas are thermo-conserving and can function over a wide range of temperature conditions, which allows them to dive from the surface of the water to depths of 1000m, in only a few minutes.

The southern bluefin tuna experience a wide range of ambient water temperatures, from a minimum of 2.6 °C to a maximum of 30.4 °C. These tunas often migrate vertically through the water column in search of their preferential temperature, as well as spend time in cooler waters searching for prey.

In fact on National Geographic they have a regular show on Tuna fishing, it makes me shiver when I watched it. These fishermen are “yahoos”, and have no idea what they are doing, a tragedy for the tuna.