19 January 2012
Global Source: Fiji Times, by Seini Tawakelevu-WWF South Pacific
By-catch entangled in the net of a tuna purse seiner in the Atlantic Ocean.
This week we will be introducing to you the fourth valuable species of commercial significance in our region - the skipjack tuna. Also known as the Yatusewa or Yatuvuai, the skipjack is the dominant tuna species harvested worldwide with 70 percent caught in the Pacific Ocean alone.
Two stocks of skipjack can be found in this region. One in the eastern Pacific Ocean (EPO) and the other in the western and central Pacific Ocean (WCPO), with a large proportion of the global tuna catch derived from the latter.
Behavior
Skipjacks cover a wide range of the open ocean, occur all year-round and have been sighted moving in schools around floating objects or large marine mammals. This makes them easier to catch. In most cases, they live up to about five years although reports have established their maximum age at eight to 12 years.
However bleak the implications may seem, it is interesting to note that what they lack in life span, they make up for in high fertility. Skipjacks mature early, estimated at nine months for their female counterparts in the WCPO with one adult producing 80,000 to two million eggs a year. This uniqueness of the skipjack tuna, as a rapid breeder, makes it resilient to fishing pressure.
Reel and Afterlife
Skipjack tuna in the WCPO is commonly caught using large purse seine nets (inspired by drawstring purses) by distant water fishing nation fleets from Japan, Korea, Taiwan and the US.
The Philippines and Indonesia also account for a fair portion of the total skipjack catch and of late, domestic fleets from PNG. The skipjack is also harvested, to a lesser extent, by pole-and-line, longline, gillnets, troll and handlines.
As a commodity, skipjack is most often sold as canned light tuna. For sushi or sashimi, it is sold as katsuo, which is smoked and dried to make katsuobushi, the main ingredient in making dashi (fish stock). The use of katsuobushi in Japanese cuisine is deeply embedded in tradition and its origins can be traced back to the Muromachi period (1336 - 1573). The major canned tuna markets include Europe and the US. In 2004, canned tuna imported to the US amounted to US$365 million ($F656.711m).
Conservation Concern and Way Forward
Adult skipjack often mix with juvenile bigeye and yellowfin at the surface. This places the young tunas at risk of being captured by methods (usually purse seine) utilizing fish attractants or fish aggregating devices (FADs) that target skipjack.
Measures such as: the annual FAD closure; 100 percent catch retention; introduction of minimum mesh size; and closure of the high seas pockets are already having a positive impact on the tuna industry. These developments were promoted by eight nations who control one of the richest fishing grounds in the WCPO. They are the Parties to the Nauru Agreement (PNA) comprising Federated States of Micronesia, Kiribati, Marshall Islands, Nauru, Palau, PNG, Solomon Islands and Tuvalu.
The skipjack fishery that the PNA manage was last week certified as sustainable to the Marine Stewardship Council (MSC) standard. It is a milestone achievement for Pacific Islands and by far the largest tuna fishery globally to have attained the MSC certification.
To put the size of the PNA fishery into perspective, their combined exclusive economic zones form what is nearly twice the size of Australia.
The annual “free-school†skipjack catch from the PNA area totals 275,000 metric tons which is equivalent to the weight of 490 fully-fuelled Airbus A380s at a retail value of approximately USD 1.3 billion with minimal by-catch of other species and juvenile tuna.
Quick Facts:
- Common name - Skipjack Tuna
- Scientific Name - Katsuwonus pelamis (italicized)
- Habitat - Open Ocean
- Location - Pacific, Atlantic and Indian Oceans between 45 degrees North and 40 degrees South
- Conservation Status - All five stocks are healthy.
