southern bluefin tuna
Southern Bluefin Tuna are an important apex predator in the Great Southern Reef ecosystem. These waters provide a summer home for young southern bluefin tuna (one to four years), with large numbers migrating into the warm, shelf waters each year to feed on abundant prey. As the largest of the tuna species, these fish are one of the top predators in the marine food chain.
Speedy swimmers
These fish are made for speed. They have hydro-dynamic bodies shaped like torpedoes with retractable fins and the sharpest eyesight of any bony fish. Traveling up to 70 km/h, these attributes are perfect for the long distances they travel during their migrations. Swimming continuously, and at high speeds, they have a high demand for oxygen but are specially adapted with highly advanced respiratory and circulatory systems.
Unfussy eaters
Because of their advanced circulatory system, the southern bluefin tuna, an endotherm, is able to maintain a body temperature that is warmer than the water around them like mammals, an ability found rarely in other fish. This trait is what allows them to dive from the surface down deep in merely minutes and maintain their large migratory patterns. As a pelagic species, they can be found as deep at 500 meters within the southern hemisphere waters of all the world’s oceans preying on a variety of different fish, crustaceans, cephalopods, and salps.
A massive migration
Southern bluefin tuna reach maturity at 11 to 12 years, and are known to spawn in the warmer tropical waters of the north-eastern Indian Ocean between Indonesia and Australia in what is called the Java Sea. Females have been estimated to produce up to 15 million eggs per season. Juveniles, as young as one year, will travel south along the western Australia coastline and turn into the Leeuwin Current and move along the Great Southern Reef while others turn the opposite direction and go to the Indian Ocean. The entire population of juveniles will then congregate in The Bight during the summer months to feed, and will keep migrating in this pattern for the first 4-5 years of their lives.
“Southern Bluefin Tuna gain about 80-90% of their annual growth as they feed for four months along the Great Southern Reef. This reefy system is vital to the nourishment and success of the species.”
Healthy harvesting
Southern Bluefin Tuna are world renowned as one of the most sought after by fisheries for their delicate meat. An invaluable resource to Australia's economy, the fishery is a multimillion dollar industry. Back in the 1960s and 70s, the southern bluefin tuna was highly overfished and were a high volume low value fishery. In this video, tuna researcher Kirsten Rough explains how extensive research and strict regulations have helped develop the fishery which is now sustainable and maintains a low volume yet high value output.
Fast Facts:
Species: Thunnus maccoyii
Family: Scombridae (mackerel, tuna, bonito)
Order: Scombriformes (bony fish)
Feeding: Other fish, crustaceans, cephalopods and other marine animals
Habitat: Open water in the pelagic zone
Distribution: Worldwide in the southern hemisphere
Special Power: Super speed
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