SKIPJACK TUNAQUICK FACTS | Sustainability | Production | Supply Chains | Environment, Climate |
Globally, skipjack is among the top 10 aquatic species, by quantity, produced. Skipjack caught in the Western and Central Pacific and the Indian oceans comprises nearly half of total world tuna production (all species) and about 80% of world skipjack catch. Skipjack comprise about 70% of the total tuna catch of the Western and Central Pacific Ocean (FFA, 2011) and about 49% of the total tuna catch of the Indian Ocean (IOTC, 2011c).
Currently, about 2 million t of skipjack are harvested from the Asia-Pacific: about 1.5 million tonnes (t) from the Western and Central Pacific Ocean (WCPFC, 2012a) and 0.5 million t from the Indian Ocean. This quantity comprises almost one half of total global tuna catches.
Skipjack is caught by local fishers and/or foreign licensed vessels using many different fishing gears, from traditional to industrial and recreational, including purse-seine, pole-and-line, ring nets, hand lines, troll and gillnets. (Lehodey et al, 2011; Hoyle et al, 2011). Most skipjack fishing targets surface schools that occur naturally, e.g., around floating objects, or that are aggregated by human actions, e.g., by drifting and fixed fish aggregating devices (FAD) and chumming with bait.
Developing countries’ fleets are very diverse (Miyake et al, 2010) and range from coastal and artisanal, through semi-industrial to fully industrial vessels; developed country fleets are industrial scale and much less diverse.
Small Scale Fisheries and Large and Industrial Scale Fisheries
Purse seining is the major fishing method for skipjack. Purse seine fleets usually operate in equatorial waters from 10°N to 10°S. The sizes of national fishing fleets has fluctuated widely in the last 10 years, in response to markets, costs (e.g. fuel), size of the resource, and access to fishing areas. Over the past four to five years, the U.S. and China purse seine fleets have expanded, the additions to the fleets being large boats with increased fish hold capacity. Purse-seining is a highly technological fishing operation and is capital intensive; new industrial scale vessels costing at least US$25 million (Barclay & Cartwright, 2007); smaller nationally registered vessels costing less.
[SKJ-009 & SKJ-010] Floating fish aggregation devices (FADs) aid the harvest of tunas in the purse seine fishery and have led to the expansion of fishing grounds and seasons. The type of association of tunas and floating or anchored devices has become a prime issue in tuna management, most notably for yellowfin and bigeye tuna.
Purse seine vessels primarily target surface-swimming skipjack, and also catch small yellowfin and bigeye tuna. Catches associated with floating objects (e.g., natural logs and FADs) are largely of skipjack; the yellowfin component being much less than that of skipjack and bigeye catches (in weight) (Miyake et al, 2010). In free (unassociated) sets, yellowfin dominate the catch in the Indian Ocean (IOTC, 2011a; Pianet et al, 2011), but skipjack dominate in Western and Central Pacific Ocean sets.
Western and Central Pacific Ocean
[Image SKJ-019] Many Western and Central Pacific Ocean domestic fleets operate around anchored FADs (Babaran, 2006). Small-scale artisanal fisheries, including in the Philippines and Indonesia, include boats that use trolling gear, and various fishing gear such as hand lines/hook and line, ring nets, pole-and-line, trolling, and traditional methods (Lehodey et al, 2011, Hoyle et al, 2011). Trolling is a particularly common fishing method in nearshore waters of the Pacific, and enhanced where anchored FADs are available.
Operating on the high seas and, under agreements, in EEZs, fishing fleets from Korea, Taiwan Province of China, Japan, and the USA account for just over 50% of the Western and Central Pacific Ocean purse seine catch. Most of the remaining purse seine catch is taken by vessels based in Pacific Islands countries fishing under the Federated States of Micronesia (FSM) Arrangement that permits domestic vessels of PNA members to access the fisheries of other PNA members on terms similar to those of the distant water fleets, and Philippines vessels. Catches by fleets flagged to or chartered by Pacific Island countries (part of their domestic fleets) have much increased in recent years (Oceanic Fisheries Programme, 2012, Lehodey et al, 2011).
In addition to purse seine vessels, the skipjack fisheries include the Japan distant-water (temperate north Pacific) and offshore pole-and-line fleets, and Japan domestic pole-and-line fleets based in island countries (Hoyle et al, 2011). Artisanal and ‘other’ gears contribute only minor amounts to the total catch (Williams & Terawasi, 2011).
The majority of the Indian Ocean skipjack catch is taken in the Western Indian Ocean (Pianet et al, 2011) and, increasingly, south of India and Sri Lanka (IOTC 2011a). About half the total skipjack catch is by ‘non-industrial’ fishing gears (IOTC, 2011c), many of which are mechanized, large-scale driftnet (Iran and Pakistan) and multi-day gillnet vessels (Sri Lanka) classified as ‘semi-industrial’ (MRAG, 2012; IOTC 2012b).
In the Indian Ocean, four main fishery types target skipjack (Kolody et al, 2011): pole & line (specifically, the Maldivian Pole-and-Line fleet but also Minicoy in India); log-associated purse seine sets from the European Union (EU)/Seychelles fleets; unassociated (or free) purse seine sets from the EU/Seychelles fleets; and ‘other’ – that includes purse seine from other nations and all other fleets (primarily gillnet fleets from Sri Lanka, Iran, Oman (Adam, 2010), Pakistan and Indonesia).
Most of the recent catch increases are from the gillnet fisheries of Sri Lanka, Indonesia, Iran and Pakistan. Historically, these fleets mostly operated in coastal waters but in recent years long distance trips to international waters have become more common (Kolody et al., 2011). Vessels from Iran and Sri Lanka have been using drifting gillnets even on the high seas in recent years, reaching as far as the Mozambique Channel. The activities of these fleets are poorly understood and limited fishing data are provided (IOTC, 2011c).
Small-scale artisanal fisheries in the Indian Ocean include boats that use trolling gear, and various other fishing equipment such as hand lines/hook and line, ring nets, pole-and-line, trolling, and traditional methods (Lehodey et al, 2011, Hoyle et al, 2011), especially in coastal or gulf parts of the Indian Ocean.
Skipjack is an important game fish usually taken by trolling on light tackle using plugs, spoons, feathers, or strip bait (Collette, 2001).
Skipjack are not produced in aquaculture.