SKIPJACK TUNAQUICK FACTS | Sustainability | Production | Supply Chains | Environment, Climate |
| Biology | Selected Countries, Areas | Link, Refs | Contributors, Revs |
WILD HARVEST FISHERIES
All skipjack production is from wild harvest fisheries. Skipjack is heavily fished yet is abundant and very resilient because it is fast-growing, short-lived, and very fecund.
IUCN Red List Status
State of the Stock(s) and Impacts of Fishing
The skipjack resources of the Western and Central Pacific and Indian oceans are not overfished. The International Seafood Sustainability Foundation’s (ISSF Status of the Stocks Technical Report) assessment of the resource for each ocean states:Stock abundance
Certificates for sustainability of wild harvest fisheryMarine Stewardship Council: http://www.msc.org/
[SKJ-014] Several conservation and sustainable/fair food organizations also promote sustainable tuna campaigns.
Skipjack is a difficult species to assess, due to its high and variable productivity and its continuous and variable recruitment that make growth estimates difficult.
Western and Central Pacific Ocean
For the WCPO skipjack stock, status assessment and data management services are provided by the Oceanic Fisheries Programme of the Secretariat of the Pacific Community (SPC) and reviewed by the Scientific Committee of the Western and Central Pacific Fisheries Council. Skipjack assessment is based on catch, effort, fish size and tagging data. Japanese pole-and-line catch-per-unit-effort (CPUE) time series is used to estimate biomass trends, assumptions are made about growth (Hoyle et al, 2011) and adjustments made for estimated misreporting of species composition of skipjack, yellowfin-bigeye (Hampton & Williams, 2011). The International Sustainable Seafood Foundation takes the Western and Central Pacific Fisheries Commission stock assessments, plus other reliable information, in making their sustainability assessments of stock abundance, fishing mortality and environment.
[Image SKJ-017] Fishing mortality on skipjack has increased since 1972, particularly in the western region. The depletion is estimated to be approximately 35% (Hoyle et al, 2011). Even so, skipjack is being exploited at a moderate level relative to its biological potential. Assuming recent skipjack recruitment levels in the equatorial zone of the Western and Central Pacific Ocean, Lehoday et al (2011a) estimated that annual harvests could be 1.8–2.0 million tonnes (which is above current levels), but they warn that recent recruitment has been above normal and future recruitment will be affected by climate and fishing.
In the Indian Ocean, poorer data and the rapid development of artisanal and semi-industrial fleets have made assessment of the Indian Ocean skipjack resource less certain than in the case of the Western and Central Pacific (Kolody et al, 2011; de Bruyn & Murua, 2011, IOTC, 2011b). Skipjack assessment is based on total catch, average weight and catch rates from the French and Spanish purse seine fleets, plus, when available, the Maldivies pole-and-line fishery (IOTC, 2011a).
The aggregate Indian Ocean skipjack population is assessed as moderately depleted but not overfished (Kolody et al, 2011). However, a major factor negatively affecting stock assessment is the poor reporting of data and statistics for some fisheries – notably the gillnet fishery, which catch approximately 41% of the total skipjack catch in the Indian Ocean (ISSF, 2012). The suggested discrete western Indian Ocean sub-population appears to be in less depleted than the aggregate Indian Ocean population.
The first Indian Ocean skipjack assessment was conducted in 2011. Average catches of 2005–2010 (500,000 t) were lower than the median value of MSY – 564,000 t (IOTC, 2011b), indicating that the stock is not overfished.
The skipjack resource is managed by regional tuna fisheries management organizations (RFMOs) and by national governments.
Industrial tuna fisheries are managed by the Indian Ocean Tuna Commission (IOTC – www.iotc.org) and the Western and Central Pacific Fisheries Commission (WCPFC – www.wcpfc.int). The Inter-American Tropical Tuna Commission (IATTC – www.iattc.org)) management area encompasses the Eastern Pacific, with some overlap with the WCPFC Convention Area. The RFMOs meet annually to consider and endorse recommended management actions. [Image (maps) SKJ-021][See Slide Show for convention area maps]
Regional associations, such as the Parties to the Nauru Agreement (PNA) are increasingly influential in tuna fisheries management. Individual island countries also manage their tuna resources, through national tuna management plans.
Each of the tuna RFMOs has a scientific committee that advises the RFMO management on stock status, monitoring and management advice and implications using their own and additional scientific advice provided by specialist organizations and individual national experts (Aranda et al, 2010). The scientific committees also maintain databases for the catch, effort, size frequency, tagging, biological data, observer, sampling and other data (Banks et al, 2011).
On the ‘receiver’ end, the EU regulations against illegal, unreported and unregulated (IUU) fishing vessels (Council Regulation (EC) No. 1005/2008 and Commission Regulation (EU) No 468/2010) and the bans imposed by some marketing chains (in UK, USA) on canned tuna harvested around fixed FADs are, in effect, management measures. International environment campaigns by organizations such as Greenpeace, the Pew Environment Group and WWF increasingly target skipjack management decisions, especially on FAD fishing and bycatch.
Western and Central Pacific Ocean
Western and Central Pacific Convention Area management measures include port inspections, at-sea inspections, an observer program, regional programs, positive vessel list (vessels authorised to fish in flag States of RFMO member countries), IUU vessel lists, release tool for sea turtles (Miyake et al, 2010), fishery closures, total allowable catch and effort, ‘freezing’ vessel capacity, reducing excess fleet capacity, reducing ‘trading’ of fishing effort, and obligatory carrying of satellite-linked tracking devices. The first management action limiting fishing in the WCPFC Convention Area was adopted in December 2008. It incorporated an annual three-month closure for purse-seine fishing on FADs, other floating objects and whale sharks. It required that all caught tuna be retained on board (WCPFC, 2008: CMM2008-01).Regional inter-governmental and industry organizations concerned with tuna in the Western and Central Pacific are:
IOTC management measures (IOTC, 2010, IOTC 2012a) include port inspections, an observer program, transshipment controls, use of VMS (for vessels greater than 15 m and fishing on the high seas: ISSF, 2011c), limitations on fishing capacity (Resolution 12/07), gear (Resolution 12/12) and area closures (Resolution 12/13), electronic logbooks for purse-seiners (ISSF, 2011), a vessel registry, positive vessel list, IUU vessel list, required use of a release tool for sea turtles, and other conservation measures (for sea birds and sharks) not relevant to the skipjack fisheries. The Indian Ocean Tuna Commission (IOTC) is developing criteria for a quota allocation system.
Skipjack are not produced in aquaculture.
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