Species in Peril:
Bluefin tuna
Bluefin tuna
Bluefin, the largest tuna
Biological features of bluefin tuna:
Bluefin tuna is a multiple spawning fish that spawn every year during the spawning season which is from mid-April to June. It spawns by eggs and the number of the eggs depends of the size and the age of the female. A 5 years old female produces about 5 million eggs compared to a 15–20 years female that can carry up to 45 million eggs. Fertilization of the eggs happens in the water and after two days of incubation without parental care, hatching happens.
The bluefin tuna larvae feeds on small zooplankton, but juvenile and adults feeds on a wide variety of prey and is able to adapt to whatever food becomes available. Bluefin tuna juveniles grow about 30cm per year which is slower than other tuna species. Then growth in length become less in adults than in juveniles, while growth in weight increases.
Bluefin tuna is a long-lived fish which means its natural mortality is low, and its higher during juvenile stages. Predation of bluefin tuna is from large pelagic sharks and killer whales. Bluefin tuna males are higher in fish nets than females and this causes lower growth for females.
Threats to bluefin tuna
Bluefin tuna fishing is very ancient, but it increased dramatically after the use of traps in commercial fisheries. Fishing was mainly targeting juvenile bluefin tuna until late 90s when large fish starts to be in demand especially by Japan. The development of bluefin tuna market affected the fishing equipment and techniques to be more powerful. This development also caused an expansion in fishery areas which yields catches of 40,000-50,000 tons a year. As a result, bluefin tuna population decreased and is labeled endangered. One of the solutions to protect bluefin tuna is putting a quota for catches of only 2,500 tons and a size limit of 6.4 kg. other solutions that the International Commission for the Conservation of Atlantic Tunas (ICCAT) has used to protect bluefin tuna are increase the minimum size andensure transfer of fish to cages from nets.
Other threats on bluefin tuna are oil spills that restrict the habitat of the fish and cause harm on the health of species. Climate change can also have an effect on the habitat of bluefish tuna. The change in the temperature of the water that gets warmer would affect migration and spawning of the Atlantic bluefin tuna.
7-10 INTERESTING FACTS
- Bluefin tuna have the widest geographical distribution among species of tuna.
- Bluefin tuna can live in a range of temperatures from 3 °C to 30 °C because it has stable body temperature.
- Bluefin tuna adults do not feed during the spawning season.
- The largest bluefin tuna is 678.58kg and it was caught in 1979.
- Bluefin tuna is easily affected by fishing because of its slower growth, later maturity, shorter spawning season, larger size and longer life span.
- The International Commission for the Conservation of Atlantic Tunas (ICCAT) were founded in 1966.
- The eyes of Atlantic bluefin tuna are the smallest among other tuna species.
Species Name
Rhinocerotidea
Estimated Population
26,000 globally
Conservation Status
Critically endangered
Range
limited parts of sub-Saharan Africa
Reasons for Population Decline
Poaching and illegal trafficking of their horns
Trophy Hunting
Habitat loss
