Tuna: Skipjack

Aku, Aku jerky, Canned light tuna

Skipjack range throughout the world’s tropical and subtropical oceans. Their breeding grounds are located in the warmest waters of the central Atlantic, central and west-central Pacific, and central Indian Ocean. While they wander significant distances, they are not considered truly migratory. The skipjack’s preferred habitat is the upper mixed layer of oceanic waters, in lattitudes between 45° N and 40° S. Skipjack do not have site-specific spawning grounds; instead, they spawn year round opportunistically over large areas of the tropical and subtropical oceans. Large schools of skipjack are sometimes caught together with juvenile yellowfin and bigeye. The largest skipjack on record weighed 18 kg, although the average weight of individuals caught is approximately 3 kg and 35 cm in length. Skipjack attain sexual maturity at about 1-2 years of age. Some fishing industry sources report that skipjack have a maximum life span of about 3 years.

Skipjack tuna have an enormous range, being distributed throughout all the world’s tropical and subtropical oceans. They attain sexual maturity at 1-2 years of age; for females. Some fishing industry sources report that skipjack have a maximum life span of about 3 years. Skipjack do not have site-specific spawning grounds; instead, they spawn opportunistically over large areas of the tropical and subtropical oceans. They are broadcast spawners and prolific reproducers. Their wide distribution, very rapid sexual maturity, relatively long life, widely-dispersed spawning grounds, and broadcast spawning system make skipjack tuna inherently resistant to fishing pressure.

ATLANTIC: The National Marine Fisheries Service (NMFS) considers western Atlantic skipjack fully exploited. While catches remain high Atlantic-wide, there is cause for concern because no stock assessment has been completed. Currently, NMFS has no working estimate for maximum sustainable yield, minimum spawning biomass, or overfishing threshold for Atlantic skipjack. Thus, NMFS lists the outlook for this stock as “unknown”.
PACIFIC:About 67% of the world’s skipjack comes from the Pacific ocean. IATTC reports that skipjack are “almost certainly underfished in the Eastern Pacific Ocean.” This species continues to support enormous fisheries year after year. IATTC’s 2001 summary finding is that both eastern and western Pacific skipjack stocks appear quite healthy. Because stocks are considered extremely abundant, or even underfished, Pacific skipjack earn a stock status rating of “Healthy”.

Concern has been raised regarding all pelagic longlining for tuna in the North Pacific. High numbers of endangered sea turtles and seabirds are caught as bycatch. Some measures have been taken in U.S. waters (Hawaii)including the prohibition of shallower (swordfish-style)longlining and area/seasonsal closures of fishing grounds with high incidences of bycatch. Overall, bycatch in U.S. longline fleets is a high conservation concern.

Pelagic longlining has no contact with benthic habitats and therefore is a low conservation concern.

ATLANTIC: The International Convention for the Conservation of Atlantic Tunas (ICCAT)currently manages Atlantic skipjack tuna. For 2000, ICCAT had no management measures in effect for Atlantic skipjack. There are no estimates for maximum sustainable yield, replacement yield, relative biomass or relative fishing mortality.
PACIFIC: In the eastern and central-western Pacific, skipjack tuna are managed under an international treaty administered by the Inter-American Tropical Tuna Commission (IATTC). Portions of the western Pacific are still without a central management authority.
General monitoring provisions used by ICCAT and IATTC nations include reporting of boat positions and catches; inspections when the ships are in port; requirements that fishing gear be stowed when the boat is outside its authorized fishing grounds; requirements that the boats carry position-fixing equipment, and requirements that they accept onboard observers working for management agencies. NMFS’ National Observer Program hires independent observers to cover various percentages of boats in various U.S-based fisheries. Enforcing international tuna fishing law is a challenge, given that boats operate on the high seas far from easy observation. Overall, the management of skipjack tuna is a moderate conservation concern.

How was it caught?

Consumption advisory due to mercury.