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Fisheries in the Pacific

 | 
Simonne Pauwels
, 
Elodie Fache

Overview of tuna fisheries, stock status and management framework in the Western and Central Pacific Ocean

Valérie Allain, Graham Michael Pilling, Peter Gregory Williams, Shelton Harley, Simon Nicol et John Hampton

Texte intégral

Introduction

  • 1 The longitude 150° W delimits two geographic entities: the WCPO to the west and the Eastern Pacific (...)

1The tuna fisheries in the Western and Central Pacific Ocean (WCPO), encompassed by the Convention Area of the Western and Central Pacific Fisheries Commission (WCP-CA)1 (fig. 1), are diverse. They range from small-scale, artisanal operations in the coastal waters of Pacific states to large-scale, industrial purse seine, pole-and-line and longline operations in the exclusive economic zones (EEZs) of Pacific states and in international waters (high seas). The main species targeted by these fisheries are skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus) and albacore tuna (Thunnus alalunga). Tuna are highly migratory species travelling across the region. The catch supplies fresh and frozen tuna markets for local consumption and for export as well as canning industries based in the Pacific Islands and abroad.

2The tuna fishery in the WCPO is the largest in the world with 2,627,696 tonnes (t) of tuna caught in 2013. This tonnage represented 82% of the total 2013 Pacific Ocean catch of 3,213,733 t and 58% of the global tuna catch (the provisional estimate for 2013 is 4,517,435 t) (Williams and Terawasi 2014).

3The exploitation of tuna delivers important economic benefits to Pacific Island Countries and Territories (PICTs) through the sale of fishing access rights and the profits and employment generated by the fishing and fish processing industries (Bell et al. 2015; Gillett et al. 2001). The value of the tuna catch in the WCPO was estimated at U.S.$6.2 billion in 2013 (Williams and Terawasi 2014). In 2012, fishing access revenues represented between 11 and 63% of total government revenue in six PICTs (Kiribati, Tuvalu, Federated States of Micronesia, Nauru, Marshall Islands and Palau) (Bell et al. 2015), and given the increases in access fees since 2012 this share is likely to have increased. Tuna fishing and processing also provide employment for thousands of people mainly in Papua New Guinea, Solomon Islands, Fiji and American Samoa (Gillett 2009). Total direct and indirect tuna-related employment is estimated to be between 5 and 8% of all wage employment in the region, and tuna canneries employ 5% of all formally employed women in the region (Gillett et al. 2001).

4Given the importance of the tuna fisheries, their sustainability needs to be monitored through the collection of a broad range of biological, economic and fisheries information. This information is used in stock assessments to evaluate the status of the tuna stocks. However, uncertainties in this information have implications for stock assessment outputs, the evaluation of management options, and hence the advice provided to managers. Access to reliable historical data is not always guaranteed, and fishing companies and countries can be slow in providing data, which limits the data available. Illegal, unreported and unregulated fishing (IUU) is moreover difficult to estimate (Agnew et al. 2009). In addition, knowledge of the basic biology of the species is incomplete. In stock assessments, some uncertainties in information and their potential impact on assessment results are tested; however these uncertainties in information increase the uncertainty in stock status advice and hence management decisions may be more precautionary than would otherwise be necessary.

Figure 1: The Western and Central Pacific Ocean (WCPO), the Eastern Pacific Ocean (EPO) and the Western and Central Pacific Fisheries Commission (WCPFC) Convention Area (WCP–CA) in dashed lines

Figure 1: The Western and Central Pacific Ocean (WCPO), the Eastern Pacific Ocean (EPO) and the Western and Central Pacific Fisheries Commission (WCPFC) Convention Area (WCP–CA) in dashed lines

This map is indicative only of agreed and potential maritime jurisdictional limits within the Pacific Islands.
This map does not necessarily reflect coastal state claims and is without prejudice to negotiations that countries may enter into. Data related to EEZ areas were mostly extracted from Claus
et al. 2014.
© Pacific Community, 2015.

5The present review provides a broad description of the tuna fishing techniques, the tuna and other species exploited and the data collected for monitoring in the WCPO. It draws on the 2013 catch estimates compiled for the WCPO and the status of tuna stocks. It also includes sections covering the tuna resource management framework in the Western and Central Pacific Fisheries Commission (WCPFC). Lastly, the review presents issues and new developments concerning monitoring, which provides information to scientists and managing agencies for the development of conservation and management measures aiming to ensure the sustainability of tuna stocks, ecosystems and fisheries.

The pelagic fisheries2 of the Western and Central Pacific Ocean

  • 2 Pelagic fisheries are the fisheries occurring in the water column of the ocean away from the seaflo (...)

6In the present paper a fishery is defined by one or several of the following elements: people involved, species caught, area of water, method of fishing and class of boats. A fishery can be composed of several fleets defined in terms of vessel nationality, fishing location, species caught, class of boats, duration of fishing trips, fish preservation method, and base port. Vessels of the same nationality are classified into a domestic fleet if they are fishing in their home waters, into a foreign fleet if they are based in a country different from their flag nationality, or into the distant-water fleet if they undertake voyages of several months over large areas of the region.

Purse seine fishery

7Purse seine fishing consists of encircling tuna schools with a large net (1,500-2,000 m long and 150-250 m depth), which is closed at the bottom before being hauled on board (fig. 2a). The fishing operation, meaning the surrounding of the fish school, is called a set. The fish are scooped on board from the net and frozen in brine. This fishing technique targets free schools (visually spotted feeding at the surface of the water from the boat or using helicopters), and schools aggregated around floating objects, which can be large animals such as marine mammals or whale sharks, but which are primarily in the WCPO man-made drifting or anchored fish aggregating devices (FADs) (fig. 2d), or natural drifting logs. There is no purse seine fishing around dolphins in the Western and Central Pacific. The fishing technique can result in catches of small and large fish; larger fish are generally caught when setting on free schools, and smaller fish when setting on schools associated around floating objects under which small fish aggregate. The resulting catch mainly supplies canneries.

Figure 2: The main tuna fishing gears: purse seine (a), longline (b), pole-and-line (c), and fish aggregating device (d)

Figure 2: The main tuna fishing gears: purse seine (a), longline (b), pole-and-line (c), and fish aggregating device (d)

© Pacific Community (William Sokimi for pictures a, b and d; Malo Hosken for picture c).

  • 3 http://www.wcpfc.int/doc/cmm-2012-04/conservation-and-management-measure-protectionwhale-sharks-pur (...)

8In the WCPO region, the purse seine fishery is primarily a skipjack fishery, unlike in other ocean areas where purse seine fishing targets yellowfin and skipjack. Skipjack generally account for 65-77% of the purse seine catch within the WCPO, with yellowfin accounting for 20-30% and bigeye accounting for only a small proportion (Williams and Terawasi 2014). Small amounts of albacore tuna and Pacific bluefin tuna are also taken in temperate water purse seine fisheries in the North Pacific. Overall, tuna species represents 99% of the catch. The main bycatch species caught are rainbow runner (Elagatis bipinnulata), silky sharks (Carcharinus falciformis), dolphinfish (Coryphaena hippurus), frigate (Auxis thazard) and bullet tuna (Auxis rochei), kawakawa (Euthynnus affinis), oceanic triggerfish (Balistidae), wahoo (Acanthocybium solandri) and marlins (Xiphioidei). There is limited interaction with protected species, such as whale sharks and manta rays. Historically, some vessels deliberately set around whale sharks associated with tuna schools, but this practice was banned by a WCPFC conservation and management measure that entered into force on 1 January 2014.3

  • 4 There are a large number of ring net (see footnote 6) and small purse seine vessels in the Indonesi (...)

9The total number of purse seine vessels was relatively stable over the period 1990-2006 (in the range of 180-220 vessels), but over the last seven years, the number of vessels has gradually increased, attaining a record level of 297 vessels4 in 2013 (fig. 3) (Williams and Terawasi 2014).

Figure 3: Number of purse seine vessels operating in WCPO (Harley et al. 2015)

Figure 3: Number of purse seine vessels operating in WCPO (Harley et al. 2015)

This does not include the Japanese Coastal purse seine fleet and the Indonesian, Philippine and Vietnamese domestic purse seine/ring net fleets which account for over 1,000 vessels (Williams and Terawasi 2014).

  • 5 In 2013, there were an additional 40 vessels in the category less than 200 gross register tonnage ( (...)

10The majority of the historic WCPO purse seine catch has come from the industrial fleets of the four main distant-water fishing nations (DWFNs) — Japan (41 vessels), Korea (27), Chinese Taipei (34) and USA (40) — which accounted for a total of 142 vessels in 20135 (Williams and Terawasi 2014). The industrial purse seine fleets of Pacific Island countries has gradually increased in number over the past two decades to 95 vessels in 2013 (fig. 3). This fleet covers vessels fishing under multilateral and bilateral agreements and domestically-based vessels, and comprises vessels from the Federated States of Micronesia (FSM; 10 vessels), Kiribati (12 vessels), Marshall Islands (10 vessels), Papua New Guinea (PNG; 51 vessels including their chartered vessels), Solomon Islands (5 vessels), Tuvalu (1 vessel) and Vanuatu (6 vessels). The remainder of the industrial purse seine fishery includes several fleets which entered the WCPO tropical fishery in the 2000s (e.g., China, Ecuador, El Salvador, New Zealand and Spain) (Williams and Terawasi 2014).

  • 6 Ring net vessels are smaller than purse seine vessels and have a manual winch to haul the net on bo (...)
  • 7 In 2010, conservation and management measures were adopted by the WCPFC to limit the catch of tropi (...)
  • 8 The westernmost high seas pocket was reopened to Philippine traditional fresh/ice chilled fishing v (...)

11In addition to the industrial purse seine fleets, a large number of smaller domestic Philippine purse seine and ring net6 vessels operate in the Philippines and northern Indonesian waters. Prior to 2010, they also operated in the high seas pocket between Palau, Indonesia, FSM and PNG. These fleets accounted for 190,000-250,000 t annually in the period 2004-2009. The closure of the high seas pocket7 (2010-2012) resulted in a considerable decline in the domestic Philippine purse seine catch, but also in increased activity by Philippine-flagged vessels fishing in PNG waters under bilateral arrangements. Following an exemption under recent tropical tuna conservation and management measures,8 the domestic-based Philippine fleet recommenced activities in the high seas pocket between Palau, Indonesia, FSM and PNG during 2013. Prior to 2013, the domestic Indonesian purse seine fleet accounted for a catch level similar to the Philippine domestic fishery but generally did not fish in high seas areas. During 2013, the Indonesian fleet catch estimate increased substantially (215,582 t) because of increased onshore processing facilities and more vessels entering the domestic fleet. The domestic fleets of Indonesia and the Philippines have usually accounted for about 13-20% of the total WCPO purse seine catch (Williams and Terawasi 2014).

  • 9 Fish do not form dense schools in the subtropical and temperate areas.
  • 10 ENSO refers to a climatic phenomenon occurring across the whole Pacific Ocean and characterised by (...)

12The geographical distribution of the purse seine fishery is concentrated in the equatorial band where fish form dense schools,9 with the highest catches in the latitudinal zone 5°N - 10°S (fig. 4). The purse seine catch/effort distribution in tropical areas of the WCPO is strongly influenced by El Nino–Southern Oscillation Index (ENSO)10 events, with fishing effort typically expanding further to the east during El Niño years and contracting to western areas during La Niña periods (Williams and Terawasi 2014).

Figure 4: Spatial distribution of the purse seine catch by species in 2004-2013 (Harley et al. 2015)

Figure 4: Spatial distribution of the purse seine catch by species in 2004-2013 (Harley et al. 2015)

The size of the largest pie corresponds to the maximum value of 1,344,000 t.

13Sets on free-swimming (unassociated) schools of tuna have dominated over recent years and represented 68% of all sets for all purse seine fleets in the WCPO in 2013 (fig. 5). The proportion of sets on drifting FADs in 2013 (22%) is consistent with recent years and remains amongst the highest over the past decade, but the number and proportion (5%) of sets on floating logs is now at the lowest level ever (Williams and Terawasi 2014).

Figure 5: Time series showing the percentage of total sets by school type for the major purse seine fleets operating in the WCPO

Figure 5: Time series showing the percentage of total sets by school type for the major purse seine fleets operating in the WCPO

Longline fishery

14Longline fishing consists of horizontally deploying a mainline, maintained on the surface with floats, and attaching to this mainline vertical branchlines ending with baited hooks. The mainline can be as long as 100 km and hold as many as 3,000 hooks located between the subsurface and 100 to 400 m depth. After letting the line sit in the water (‘soak’) for several hours, it is slowly hauled on board and both empty hooks and fish caught are recovered one by one (fig. 2b), with the fish usually then stored fresh on ice, in brine, or frozen. Because of the size of the hooks used and the depth of fishing, this technique typically catches larger tuna. In contrast to purse seining, longline fishing does not require spotting fish schools. This technique supplies fresh and frozen markets (including sashimi) and canneries.

15The composition of the longline catch has varied since the beginning of the fishery. While yellowfin tuna catches used to be dominant in the past, the catch composition has changed since 2005 and in recent years albacore has been the main target, accounting for 44% of catch, while yellowfin and bigeye each accounted for 28% (Williams and Terawasi 2014). Overall, tuna species account for 50% to 75% of the total catch (in weight) in the longline fisheries. Non-tuna species in the longline catch are principally shark and billfish species, dolphinfish, opah (moonfish – Lampris guttatus), wahoo, escolar (Lepidocybium flavobrunneum) and barracudas (Sphyraenidae). Interactions with seabirds and marine mammals are very low in the tropical WCPO; interactions with seabirds take place mainly in temperate areas. Catches of marine turtles (five different species) have been observed at a low encounter rate in the equatorial longline fisheries.

16The total number of vessels involved in the longline fishery has generally fluctuated between 3,000 and 6,000 over the past 30 years (fig. 6), making longline vessels around 10 to 20 times more numerous than purse seiners.

17The fishery involves two main types of operations (Williams and Terawasi 2014):

  • large (typically > 250 gross register tonnage – GRT) distant-water freezer vessels which undertake long voyages (many months) and operate over large areas of the region. These vessels may target yellowfin and bigeye tuna for the frozen sashimi market, albacore tuna for canneries, or recently swordfish. This fleet comprises vessels from Japan, Korea, Chinese Taipei, mainland China, Vanuatu, Portugal and Spain. Distant-water longline fleet dynamics have continued to evolve in recent years, with the number of vessels dropping from 687 in 2004 to 349 vessels in 2013 for the Japanese, Chinese Taipei and Korean distant-water longline fleets and the Japanese foreign longline fleet.

  • smaller (typically < 100 GRT) vessels which are usually domestically-based, undertaking trips of less than one month, with ice or chill capacity, serving fresh local or air-freight sashimi markets or albacore canneries. This category comprises Pacific Island domestic vessels from American Samoa, Cook Islands, Fiji, French Polynesia, Kiribati, New Caledonia, Samoa, Solomon Islands, Tonga, Micronesian countries, PNG and Vanuatu. The domestic fleets of Australia, Japan, New Zealand and Hawaii target different species depending on the market, season and/or area involved. There are also domestic fleets in Indonesia, the Philippines and Vietnam. Finally there are several foreign fleets based in Pacific Island countries, such as Chinese Taipei sashimi longliners based in Micronesia, Guam, and the Philippines. Mainland China also has vessels based in Micronesia.

Figure 6: Longline vessels operating in the WCPO (Harley et al. 2015)

Figure 6: Longline vessels operating in the WCPO (Harley et al. 2015)

Available data does not make the distinction between foreign “distant-water” and “offshore” fleets.

18A significant change in the WCPO longline fisheries over the past 10 years (2003-2013) has been the growth of the Pacific Island domestic albacore fleets (involving American Samoa, Cook Islands, Fiji, French Polynesia, Kiribati, New Caledonia, Samoa, Solomon Islands, Tonga and Vanuatu). Taking just 33% of the total south Pacific albacore longline catch in 1998, these fleets accounted for around 50-60% of the catch in recent years (Williams and Terawasi 2014). The number of vessels in the national fleets (including chartered vessels) active in this fishery has risen to over 450 (mainly small vessels) and catches are now at a level similar to that of distant-water longline vessels active in the WCPO (Williams and Terawasi 2014).

  • 11 These types of vessels are not included in fig. 6.

19Small vessels in Indonesia, the Philippines and Vietnam also use handline and small vertical longline gears, usually fishing around the numerous arrays of anchored FADs in their home waters.11

20Large-vessel, distant-water fleets from Japan, Korea and Chinese Taipei account for most of the longline effort in the WCPO, which is spatially widespread (fig. 7). The activity of foreign fleets from Japan, mainland China and Chinese Taipei is restricted to tropical waters. The substantial effort in the west of the region is primarily carried out by Indonesian, Chinese Taipei and Vietnamese domestic fleets. The growth in domestic longline fleets in the South Pacific (5°S-25°S) over the past decade is notable; the most prominent fleets in this category are the Cook Islands, Samoan, Fijian, French Polynesian and Vanuatu fleets (Williams and Terawasi 2014).

Figure 7: Spatial distribution of WCPO longline catch by species in 2004-2013 (Harley et al. 2015)

Figure 7: Spatial distribution of WCPO longline catch by species in 2004-2013 (Harley et al. 2015)

Note that the data on the distant-water efforts of Chinese Taipei and other fleets targeting albacore in the North Pacific is poor. The size of the largest pie corresponds to the maximum value of 67,000 t.

Pole-and-line fishery

21Pole-and-line fishing consists of baiting schools of tuna visually spotted at the surface of the water from the boat, and catching them at the surface, one by one, with poles (fig. 2c). The boat is equipped with tanks to maintain live bait (i.e., small fish caught in coastal areas). Each boat has a crew of 20-30 fishermen distributed at the bow and stern of the boat on special platforms, catching fish with 2-3 m long poles with a short line, at the extremity of which hangs a feathered jig mounted on a barbless hook. Due to the size of the hooks used, the fishing at the surface and the manual hauling, this technique catches small to medium-size fish. Fish are frozen in brine to supply the cannery industry.

22Skipjack tends to account for the majority of the catch (~70-83% in recent years, but typically more than 85% of the total catch in tropical areas), and albacore (8-20% in recent years) is taken by Japanese coastal and oceanic fleets in the temperate waters of the North Pacific (Williams and Terawasi 2014). The remainder of the catch consists of yellowfin tuna (5-16%) and a small component of rarer bigeye tuna (1-4%). Overall, tuna species represent 96% of the catch. The main bycatch species caught are rainbow runner, dolphinfish and small silky sharks.

23The WCPO pole-and-line fishery has several components (Williams and Terawasi 2014):

  • the year-round tropical skipjack fishery, mainly involving the domestic fleets of Indonesia, Solomon Islands and French Polynesia, and the distant-water fleet of Japan,

  • seasonal subtropical skipjack fisheries in the domestic (home) waters of Japan, Australia, Hawaii and Fiji,

  • a seasonal albacore/skipjack fishery east of the Japanese EEZ conducted by Japanese vessels.

24Japanese distant-water and oceanic fleets and Indonesian fleets account for nearly all of the WCPO pole-and-line catch (99% in 2013) (Williams and Terawasi 2014).

  • 12 Bonitiers are 10 to 12 m long boats targeting skipjack using mainly pole-and-line and operating clo (...)

25Economic factors and technological advances in the purse seine fishery (primarily targeting the same species, skipjack) have prompted a gradual decline in the number of pole-and-line fishery vessels in all of the fleets (fig. 8) (Williams and Terawasi 2014). Pacific Island pole-and-line domestic fleets in particular have declined in recent years with fisheries formerly operating in Fiji, Palau and Papua New Guinea no longer active; only one vessel is now operating (occasionally) in Kiribati; and there has been a substantial reduction in the Solomon Islands pole-and-line fishery during the 2000s. Several vessels continue to fish in Hawaii, and the French Polynesian bonitier fleet12 remains active (45 vessels in 2013), but an increasing number of vessels have turned to longline fishing. Provisional statistics suggest that the Indonesian pole-and-line fleet has also declined over recent years (Williams and Terawasi 2014).

  • 13 https://www.msc.org/(Accessed on December 7, 2015).

26Increased market demand for ecolabelled tuna is driving, on a global scale, audits of tuna fisheries against standards such as that of the Marine Stewardship Council.13 There has been increased interest in undertaking ecolabelling audits for pole-and-line tuna, as the fishing approach is seen as a relatively ‘clean’ method of fishing, with minimal bycatch of non-target species. This provides an advantage for ecolabelling schemes where low bycatch levels are seen as an important asset, and there is at least one initiative underway, in Papua New Guinea, to revitalize the domestic pole-and-line fisheries in the Pacific Islands as a result. In regard to the eco-friendliness of the pole-and-line fishery, it is important to note that this fishery is dependent on live bait which is only available in limited areas and seasons; moreover this nearshore/lagoon bait fishery is complex both ecologically and socioeconomically (Gillett 2011).

27Effort and catch in tropical areas (fig. 9) is usually year round. The pole-and-line effort in the vicinity of Japan by both oceanic and distant-water fleets is seasonal (Williams and Terawasi 2014). There also was some seasonal effort by pole-and-line vessels in Fiji and Australia during the 1995-2013 period. The effort in French Polynesian waters is essentially represented by the bonitier fleet.

Figure 8: Pole-and-line vessels operating in the WCPO (Harley et al. 2015)

Figure 8: Pole-and-line vessels operating in the WCPO (Harley et al. 2015)

Pole-and-line vessels from the Japanese coastal and Indonesian domestic fisheries are not included in the figure.

Figure 9: Average distribution of WCPO pole-and-line catch (2003–2012) (Harley et al. 2015).

Figure 9: Average distribution of WCPO pole-and-line catch (2003–2012) (Harley et al. 2015).

Catches by the pole-and-line fleet based in Hawaii and the bonitier fleet in French Polynesia are not shown in this figure. The size of the largest pie corresponds to the maximum value of 263,000 t.

Tuna and other species caught in the pelagic fisheries

  • 14 Omitting stocks such as bluefin tuna caught in the northern Pacific.

28The four main tuna species in the tropical and subtropical waters of the WCPO14 are skipjack, yellowfin, bigeye and albacore tunas (fig. 10).

29Skipjack tuna are found across the region, but the centre of abundance lies in the equatorial waters where they form large surface schools. Skipjack are relatively small, their typical capture size is between 40 and 70 cm, corresponding to fish between one and three years of age, with very few captured fish exceeding 80 cm. Skipjack tuna are fast growing (reaching 42-45 cm within their first year), relatively short-lived (few live longer than 3-4 years) and mature early (~1 year of age). Skipjack are highly fecund and can spawn year round over a wide area of the tropical and subtropical Pacific. These biological characteristics promote rapid turnover in skipjack populations.

30Yellowfin and bigeye tunas are also widespread over the region, with a centre of abundance for juveniles in the tropical waters. Adult yellowfin tuna are usually found within the upper 250 m, while adult bigeye tuna are found at deeper depths (300-500 m).

31Yellowfin are a relatively large tuna species; their capture size in the WCPO varies depending on the fishing techniques used (see section “he pelagic fisheries of the Western and Central Pacific Ocean”). Specimens measuring 20 to 70 cm in length are fish between 3 months and 1.5 years of age caught by purse seine and pole-and-line; those 90 to 160 cm are fish between 1.5 and 6-7 years of age caught by purse seine and longline. Very few captured fish exceed 180 cm. Yellowfin tuna are fast growing (reaching > 45 cm within their first year), have a life span of up to ~ 7 years of age and mature around 2-3 years of age. Yellowfin are highly fecund and can spawn year round over a wide area of the tropical and subtropical Pacific, providing environmental conditions (such as water temperature) are suitable. These biological characteristics promote moderate turnover in yellowfin populations.

Figure 10: The four main tuna species in the tropical and subtropical waters of the WCPO: yellowfin (Thunnus albacares), bigeye (Thunnus obesus), albacore (Thunnus alalunga), and skipjack (Katsuwonus pelamis) tunas

Figure 10: The four main tuna species in the tropical and subtropical waters of the WCPO: yellowfin (Thunnus albacares), bigeye (Thunnus obesus), albacore (Thunnus alalunga), and skipjack (Katsuwonus pelamis) tunas

© Pacific Community (illustrations by Les Hata).

32Bigeye tuna are among the largest tuna species. Like yellowfin tuna, their capture size in the WCPO shows two distinct modes related to differences in fishing techniques (see section “The pelagic fisheries of the Western and Central Pacific Ocean”). Specimens measuring 20 to 75 cm in length are fish between 3 months and 1.7 years of age caught by mainly purse seine and pole-and-line; those measuring 100 to 180 cm are fish between 2 and 10 years of age caught by longline. Very few captured fish exceed 200 cm. Bigeye tuna grow more slowly than either yellowfin or skipjack, reaching around 40 cm after one year, have a longer lifespan (at least 12 years) and mature later (around 3-4 years of age). They are highly fecund and can spawn year round over a wide area of the tropical and subtropical Pacific, providing environmental conditions (such as water temperature) are suitable. These biological characteristics promote only moderate turnover in bigeye populations. This feature, combined with their susceptibility to multiple gear types throughout their lifespan, render bigeye tuna less resilient to exploitation than more productive species like skipjack.

  • 15 The North Pacific albacore tuna stock is not fished by the PICTs; it is mainly exploited by Japan, (...)

33Albacore tuna is a subtropical/temperate species. There are two separate stocks of Pacific albacore tuna located respectively in the northern and southern hemispheres. In the present document, the North Pacific albacore stock is not considered.15 The centre of abundance for adult South Pacific albacore tuna is located at latitudes 10°-30°S, where they are caught by longline, the only fishing gear capable of targeting depths of 100-400 m. Albacore tuna of all age classes are rarely caught in equatorial waters or in the Central Pacific. In these areas, the level of dissolved oxygen absorbed by the fish through their gills is too low for their survival (Bard et al. 1999). Subadult albacore tuna (50-90 cm) are found in temperate surface waters (30-40° S). Albacore tuna are relatively large tuna. Again, their capture size in the WCPO shows two distinct modes related to differences in fishing techniques (see section “The pelagic fisheries of the Western and Central Pacific Ocean”). Specimens measuring 50 to 70 cm in length are fish approximately 1.5 and 2.5 years of age caught by trolling, those measuring 80 to 110 cm are fish mostly between 3 and 10 years of age caught by longline. Very few captured fish exceed 130 cm. Albacore are relatively slow growing (reaching > 45 cm within their first year), have a life span of up to ~10 years of age and mature around 4-5 years of age. Mature albacore spawn in tropical and subtropical waters between latitudes 10 and 25° S, with individual fish becoming available to surface fishing at about latitude 40° S approximately one to two years later, at a size of 45-50 cm. From this area, albacore appear to gradually disperse towards the tropics, but may make seasonal migrations between tropical and subtropical waters. These biological characteristics promote moderate turnover in albacore populations.

34Different fishing fleets may target different species but the species targeted is mainly determined by the fishing location in relation to the abundance of the species (e.g., albacore tuna is targeted in temperate waters while skipjack is targeted in equatorial waters) and by the fishing technique.

35The fisheries targeting tuna also catch a range of other associated species, and more than 200 bycatch species have been observed in catches. Some of the associated species are of commercial value (by-products), while many others are discarded (tab. 1). There are also incidents of the capture of species of ecological and/or social significance (‘protected species’), including marine mammals, sea turtles and some species of shark (e.g., whale sharks). Information concerning the catch composition of the main tuna fisheries in the WCPO comes largely from the various observer programmes operating in the region.

Table 1: List of the main bycatch species caught by tuna fisheries

Common name

Scientific name

Fisheries

Status

Billfishes

Black marlin

Istiompax indica

LL, PS

Commercial

Blue marlin

Makaira nigricans

LL, PS

Commercial

Sailfish

Istiophorus platypterus

LL, PS

Commercial

Striped marlin

Kajikia audax

LL, PS

Commercial

Swordfish

Xiphias gladius

LL

Commercial

sharks and rays

Blue shark

Prionace glauca

LL

Discard

Mako sharks

Isurus sp.

LL

Commercial

Oceanic whitetip shark

Carcharhinus longimanus

LL, PS

Discard

Silky shark

Carcharhinus falciformis

LL, PS, PL

Discard

Thresher sharks

Alopias sp.

LL

Discard

Hammerhead sharks

Sphyrna sp.

LL

Discard

Manta rays

Manta sp. and Mobula sp.

PS

Discard

Pelagic stingray

Dasyatis violacea

LL

Discard

other species

Barracudas

Sphyraena spp.

LL, PS

Commercial

Dolphinfish

Coryphaena hippurus

LL, PS, PL

Commercial

Rainbow runner

Elagatis bipinnulata

LL, PS, PL

Commercial

Wahoo

Acanthocybium solandri

LL, PS

Commercial

Opah (moonfish)

Lampris guttatus

LL

Commercial

Lancetfish

Alepisaurus sp.

LL

Discard

Pomfrets

Bramidae

LL

Commercial

Snake mackerel

Gempylus serpens

LL

Discard

Escolar

Lepidocybium flavobrunneum

LL

Discard

Oilfish

Ruvettus pretiosus

LL

Discard

LL = longline, PS = purse seine, PL = pole-and-line

Fisheries data and monitoring

36Data on fisheries are crucial to monitor the status of tuna stocks and for countries to take informed management decisions. Countries that have ratified the WCPFC Convention have obligations in terms of the provision of data to the Commission. They have to provide annual catch estimates by species and fishing gear, catch and fishing effort data by geographic area and time period, and fish size composition. To comply with these obligations, the countries have access to several sources of information that are submitted to the WCPFC:

  • logsheets recording catch of the main species and fishing effort are provided by fishing vessels to the national fisheries authorities of the PICTs in whose waters they were fishing and to their flag state. For example, a Japanese vessel fishing in the Marshall Islands and Kiribati will provide the logsheets of the fishing operations conducted in each EEZ to the national fisheries authorities of the Marshall Islands and Kiribati, and to Japanese fisheries authorities. Detailed information on vessels is also provided, including vessel nationality. In general only tuna and the main commercial species are recorded on logsheets; however with management measures implemented on sharks, it is required that specific shark catches are recorded. Exact locations are not always provided. Provision of logsheets is compulsory for all industrial fleets.

  • in-port information on unloaded catch, catch composition and size-frequency of the catch are recorded by port samplers of the national fisheries authorities of the PICTs where fish are unloaded. Only commercial species are seen at port. The exact location of the catch is not always known as the catch from different sets and areas are mixed in vessel wells.

  • on-board vessel observers from the national fisheries authorities of the PICTs record catch, effort, catch composition and size-frequency of all the species caught. On-board observers can record very detailed information; this is notably the only way to obtain information on fish discarded at sea and better catch species composition. With a target to achieve 100% observer coverage on purse seiners, and provisional coverage of ~80% in tuna catches in 2013-2014, activities of those vessels are much better covered than longliners, for which the coverage was ~2% in tuna catches in 2014 with a 5% target (Williams 2015).

  • satellite Vessel Monitoring Systems (VMS) on purse seine and longline vessels, which provide information on location at regular intervals. A WCPFC conservation and management measure has made these systems mandatory on all vessels fishing for highly migratory fish stocks on the high seas, and national regulations require these systems on vessels fishing within EEZs. While primarily a monitoring, control and surveillance tool, VMS data also provide opportunities for scientific data and research. It provides vessel position information at hourly intervals, allowing an analysis of fleet behaviour and dynamics which could not be easily performed using daily logsheet information.

  • 16 The PTTP, endorsed by the WCPFC, was designed and implemented by the Pacific Community (SPC) in col (...)
  • 17 Tags are implanted on fish caught during tagging cruises and the fish are released immediately. Eac (...)

37Another critical source of information for monitoring fisheries impact and the status of stocks are tagging programmes, which provides information on the growth, movement, natural mortality and fishing mortality of tuna. In the WCPFC, tagging programmes have been implemented for the last 30 years (Leroy et al. 2015). The most recent one, the Pacific Tuna Tagging Programme (PTTP),16 started in 2006 and is still active in 2016. The PTTP concentrates its activities over the entire equatorial WCPO. It tags skipjack, yellowfin and bigeye tuna with both conventional and electronic tags.17 This is the largest tagging programme ever undertaken to monitor tuna stocks. As of May 2015, more than 400,000 tuna had been tagged by scientists on chartered pole-and-line and trolling fishing vessels since the beginning of the PTTP and 73,000 tags had been recaptured (return rate = 18%) by fishing vessels, at unloading ports, and in canneries.

38Scientific research conducted by research institutions in the Pacific also focuses on obtaining information on reproduction pattern and fecundity, age and growth, trophic structure and ecosystem functioning. Such information contributes to determine the status of the tuna stocks and associated ecosystems.

39Economic data is becoming increasingly important for fishery management; however there are no major agreements concerning their provision and management.

Catch estimates

40Annual total catches of the four main tuna species (skipjack, yellowfin, bigeye and albacore) in the WCPO increased steadily during the 1980s as the purse seine fleet expanded, and remained relatively stable during most of the 1990s until a sharp increase in catch in 1998. The 1998 increase in catch is due to a combination of increased use of FADs and a shifting of the fleets towards the east on better fishing grounds during the strong 1997-1998 El Niño event (see section “Purse seine fishery”). Over the past seven years (2007-2013) there has been an upward trend in total tuna catch (fig. 11). The total WCPO tuna catch for 2013 was estimated at 2,627,696 t, the second-highest catch on record after 2012. This tonnage represented 82% of the total 2013 Pacific Ocean catch of 3,213,733 t and 58% of the global tuna catch (the provisional estimate for 2013 is 4,517,435 t) (Williams and Terawasi 2014).

41In 2013, purse seine fishery accounted for an estimated 1,899,015 t (72% of the total catch in the WCPO, and the highest-ever catch for this fishery) (fig. 11) for an estimated delivered value of US$3,947 million. During the 1980s the purse seine catch increased steadily, and during the 1990s it fluctuated between 800,000 and 1,200,000 t. Since 2002, when a significant increase in catch was observed in relation to increased fishing effort, the purse seine catch and effort have been continuously increasing.

42In 2013, longline fishery accounted for an estimated 230,137 t (9% of the total catch in the WCPO). Although this was the lowest catch since 1999, with an estimated value of US$1,276 million, it rivals the much larger purse seine catch in terms of landed value. This is due to the high value of longline fish sold on the sashimi market in comparison to the low value of purse seine fish sold to canneries. The WCPO longline tuna catch steadily increased from the early years of the fishery (i.e., the early 1950s) to 1980 (226,229 t), but declined to 155,402 t in 1984. Catches steadily increased between 1984 and the late 1990s, when catch levels were again similar to those observed in 1980. Annual catches in the longline fishery since 2000 have been maintained at a high level (> 200,000 t) despite a decrease in the number of fishing vessels. This high catch is due to a change in the dynamic of the longline fleets. While longline vessels mainly targeted tropical yellowfin tuna in the 1970s and 1980s, in recent decades the fleets have been targeting subtropical albacore tuna, which have been more exploited and show higher catch rates than in the past. In 2013, the pole-and-line catch was estimated at 221,715 t (8% of the total catch in the WCPO — the lowest since the late 1960s), for an estimated delivered value of US$506 million. Pole-and-line catches have continuously declined for three decades.

43The remainder of the 2013 catch (~ 260,000 t — 10%) was taken by troll gear and a variety of artisanal gear, mostly in eastern Indonesia, the Philippines, and Vietnam.

  • 18 Drifnets are nets that can reach up to 50 km long and are set vertically in the water, maintained b (...)

44The 2013 WCPO skipjack catch (1,810,166 t — 69% of the total catch) was the highest recorded catch (fig. 11). Skipjack catches have increased steadily since 1970, more than doubling during the 1980s due to growth in the international purse seine fleet combined with increased catches by domestic fleets from the Philippines and Indonesia, and the catches continued to increase in subsequent years. The 2013 WCPO yellowfin catch (524,022 t — 20%) was slightly below the average of the past 10 years. Yellowfin catch had been slowly increasing over time but since 1998, it jumped to a new level with annual catches regularly exceeding 500,000 t, mainly due to increased catches in the purse seine fishery. The 2013 WCPO bigeye catch (150,281 t — 6%) is around the average of the preceding nine years, with a 7% decrease from the 2012 catch, driven by a reduction in longline catches. The 2013 WCPO albacore catch (143,227 t — 5%) was the second highest on record. Prior to 2001, south Pacific albacore catches were generally in the range of 25,000-50,000 t, with a significant peak in 1989 (49,076 t) when driftnet18 fishing was still in existence. Since 2001, catches have greatly exceeded this range, primarily as a result of the growth in several Pacific Island domestic longline fisheries.

Figure 11: Catch (in tonnes) by gear (top) and species (bottom) for the Western and Central Pacific region, 1960-2013 (Harley et al. 2015)

Figure 11: Catch (in tonnes) by gear (top) and species (bottom) for the Western and Central Pacific region, 1960-2013 (Harley et al. 2015)

Note that data for 2013 are preliminary.

Status of stocks

  • 19 Five to nine regions defined in the WCPO area according to the tuna species.
  • 20 The assessment model is fitted to the data to best mimic the patterns and values observed in terms (...)

45In the WCPFC, the status of tuna stocks is based on single-species stock assessments, which are performed separately for each of the tuna stocks discussed in the section “Tuna and other species caught in the pelagic fisheries”. The main assessment approach is MULTIFAN-CL, a computer program that implements a statistical, length-based, age and spatially-structured19 model for fisheries stock assessment (Hampton and Fournier 2001). The main data sets to which the model is fitted are time series of catch and effort data (i.e., the level of removals from the stock, and the amount of fishing effort required to achieve these removals), tuna length frequencies (which supplies information on, for example, the way different fishing gears impact the stock, e. g., catching larger or smaller individuals), and tagging information (which provides an idea of movement between areas of the WCPO). Biological information such as estimates of the rate at which tuna grow, the age at which individuals become sexually mature, the rate at which young are produced, and the rate at which tuna die from natural causes (natural mortality, by age), are also used. The model estimates tuna abundance per age class, quarter and area.20

  • 21 There are two key reference point types. Limit reference points (LRPs) represent stock or fishing l (...)

46The assessments are reviewed by the WCPFC Scientific Committee (and occasionally by independent experts) and are used to provide advice on the status of tuna stocks to regional organisations and national fisheries authorities in charge of the management of these stocks. This advice is based upon outputs from the assessment model, including estimates of the quantity of fish of each species in the WCPO and the level of fishing mortality (the rate at which fish are removed from the stock through fishing). These are compared to ‘reference points’21which indicate specific levels of these values that are of interest to managers. Related to reference points, the concept of maximum sustainable yield (MSY) is central to fisheries management. MSY is the largest average catch (yield) that can — in theory — continuously be taken from a stock under average environmental conditions without affecting stock health. Related indices frequently used as reference points within the WCPFC are:

    • 22 When F is greater than FMSY or F/FMSY is greater than 1, it is considered that overfishing of the s (...)

    F/FMSY, the level of current fishing mortality (F) compared to the fishing mortality which will support the maximum sustainable yield (FMSY);22

    • 23 Within the WCPFC, a limit reference point of 20% SBF = 0 has been adopted for key tuna stocks as it (...)

    SB/SBF = 0, the current amount of spawning biomass (or adult tuna quantity) (SB) compared to the estimated amount of adult fish that would be present within the stock if it had not been fished (SBF = 0).23

47These indices are used to draw a plot which provides a visual display of the estimated status of the four tuna stocks relative to reference points (fig. 12).

Figure 12: The modified Kobe plot (“Majuro plot”) identifying the status of the stocks according to reference points on fishing mortality (F/Fmsy) and spawning biomass (SB/SBF0)

Figure 12: The modified Kobe plot (“Majuro plot”) identifying the status of the stocks according to reference points on fishing mortality (F/Fmsy) and spawning biomass (SB/SBF0)

The plot describes the 2012 stock status for skipjack (Rice et al. 2014), bigeye (Harley et al. 2014) and yellowfin (Davies et al. 2014) and the 2010 stock status for South Pacific albacore (SP Albacore) (Hoyle et al. 2012). Stocks located in the white area are estimated healthy, overfishing is occurring for stocks in the orange area (catches are too high for sustainability) and stocks in the red area are overfished (the level of the spawning biomass is too low to sustain the stock). Many stock assessment runs are performed for each stock, using different combinations of input parameters (e. g., different estimates of growth rate, rates at which fish die due to natural causes, etc.). These lead to slightly different estimates of current stock status. Hence the stock assessment run selected as the ‘reference case’ for management advice is shown as the main ‘point’ (plain circle), and the range of estimated status from key uncertainty runs with these different input parameters are shown as lines radiating out from that point.

Skipjack tuna

  • 24 While estimates of fishing mortality for skipjack have increased over time, 2012 fishing mortality (...)

48The 2014 stock assessment results suggested that the skipjack stock is not overfished.24 Despite recent catches slightly above the estimated MSY of 1,532,000 t, the assessment continues to show that the stock is currently only moderately exploited and fishing mortality levels are sustainable. However, there is concern that high catches in the equatorial region could result in a reduction in the latitudinal range of the stock toward the tropical area (‘range contraction’), thus reducing skipjack availability to high latitude fisheries (Harley et al. 2015).

Yellowfin tuna

  • 25 2012 fishing mortality rates for yellowfin tuna were estimated to be about 0.72 times the level of (...)

49The 2014 stock assessment found highly likely that the yellowfin tuna stock is not experiencing overfishing and is not in an overfished state.25 Despite increases in recent years, fishing mortality appears to be below the level of fishing mortality associated with maximum sustainable yield (F MSY). However, recent catches were close to or exceeded the MSY of 586,400 t by up to 13%, indicating that this level of catch will not be sustainable in the long term. It is considered that yellowfin tuna is at least fully exploited. It was noted that levels of fishing mortality differed between regions, and that fishery impact was highest in the tropical region (Harley et al. 2015).

Bigeye tuna

  • 26 Fishing mortality is estimated to have increased over time, particularly in recent years, and 2014 (...)

50It is considered that overfishing is occurring on an overfished bigeye tuna stock,26 and urgent measures are necessary to rebuild the stock and decrease the fishing mortality, particularly of juveniles. Like for yellowfin tuna, the 2014 stock assessment noted that levels of fishing mortality differed between regions, and that fishery impact was highest in the tropical region (Harley et al. 2015).

South Pacific albacore tuna27

  • 27 The North Pacific albacore tuna stock is not exploited by PICTs and is not considered in the presen (...)
  • 28 The last assessment at the time of writing (May 2015)(performed in 2012 by SPC) indicated that fish (...)

51The 2012 stock assessment found that the South Pacific albacore tuna stock is not experiencing overfishing and is not in an overfished state.28 Nevertheless, it is estimated that the current level of longline catch is having a considerably higher impact than in previous years on this stock, which is vulnerable to longline fishery. Despite the apparent biological health of the stock, it is estimated that fisheries in many PICTs could see declines in individual vessel’s daily catches and fishery profitability (Harley et al. 2015).

Management framework

52As tuna are considered highly migratory, management interventions are more effective at the regional scale. Yet management interventions are discussed and implemented at three different levels within the WCPO.

  • 29 Four subsidiary bodies support the work of the WCPFC. The Scientific Committee (SC) provides the be (...)
  • 30 Mitigation methods are fishing techniques or practices implemented to avoid the capture, minimise t (...)

53At the regional level, the annual Commission meeting of the WCPFC develops ‘Conservation and Management Measures’ (CMMs) for fisheries and stocks on the basis of advice from its Committees,29 including the Scientific Committee advice on stock status (see section “Status of stocks”). These CMMs are often specific to fishing gear types, primarily because, as noted earlier, different gear types target different species. For example, recent CMMs aiming to limit fishing impacts on tropical tuna, in particular bigeye, focus on reducing longline catches and limiting fishing effort by purse seiners on FADs, because these fishing approaches have a strong negative impact on that stock. CMMs have also been developed for non-target species, such as mitigation methods30 to reduce shark and bird bycatch.

54At the subregional level, two key organisations develop management measures:

    • 31 Australia, Cook Islands, Federated States of Micronesia, Fiji, Kiribati, Marshall Islands, Nauru, N (...)

    The Pacific Islands Forum Fisheries Agency (FFA) is an organization composed of 17 PICT members31 with a common fisheries interest in the Pacific Ocean region. FFA strengthens national capacity and regional solidarity through technical assistance and other support to its members. The member countries make sovereign decisions about their tuna resources and participate in regional decision making on tuna management through agencies such as the WCPFC, the Parties to the Nauru Agreement (PNA) and the new Tokelau Arrangement. FFA not only helps its members implement WCPFC and subregional management measures, it also helps them draft management measures for wider adoption within that Commission, including requiring action compatible with national measures to be taken on the high seas. FFA provides advice on options for fisheries development, including facilitating investment in onshore facilities such as processing plants. FFA also facilitates bilateral and multilateral negotiations between its members and foreign fleets, particularly regarding the US purse seine fleet.

    • 32 In 2015, the PNA total allowable effort was 44,623 days for purse seine fishing within their EEZs. (...)

    The PNA is comprised of eight tropical countries, a subset of the FFA membership: the Federated States of Micronesia, Kiribati, the Marshall Islands, Nauru, Palau, Papua New Guinea, Solomon Islands and Tuvalu. The territory of Tokelau is also an active member of the PNA Vessel Day Scheme (VDS), and conforms with the implementing arrangements of the Nauru Agreement. Around 75% of the WCPO skipjack catch is caught in the waters of these countries. As a group, the PNA aims to sustainably manage the purse seine fishery, primarily using the VDS. The VDS sets the total number of purse seine fishing days32 per year within PNA waters, covering the PNA members’ combined EEZs. The total number of days is determined based on scientific advice from the Scientific Committee of the WCPFC about the status of the tuna stocks and management objectives. The number of days is allocated amongst the Parties for 12-month periods based on the proportion of tuna and the number of vessel days fished in the waters of each of the Parties. Each country can then sell these days to fishing companies/nations at a minimum benchmark price or higher. In this way, Pacific Islanders gain direct economic benefits and contribute to the sustainable management of the tuna resource. Examples of management measures taken by the PNA, and subsequently incorporated into WCPFC CMMs, include bans on FAD sets by purse seiners during specific months of the year, and full tuna catch retention. The PNA has also led work on developing a target reference point for WCPO skipjack tuna. A PNA vessel day scheme for longline vessels has recently been agreed and is in the process of being implemented.

55Other subregional organisations involved in the tuna fisheries and their management are:

    • 33 Northern Mariana Islands, Guam, Palau, Federated States of Micronesia, Marshall Islands, Papua New (...)
    • 34 SPC is composed of seven divisions: geoscience, economic development, social development, fisheries (...)

    the Pacific Community (SPC) which provides technical assistance, training and scientific support to 22 member countries and territories33 and to other subregional and regional organisations, including the WCPFC. The SPC’s main activities on oceanic fisheries34 are training, support for oceanic fishery monitoring (observers and port samplers), fisheries catch and effort data management, scientific information on biology and ecology of tuna and large pelagic fish, ecosystem modelling, information on impacts of climate change, stock assessments of tuna, billfish and key shark species, and the provision of scientific advice to inform management decisions.

  • the Te Vaka Moana (TVM), established in 2010, is a group of six fisheries administrations of countries located in the southern part of the region: Cook Islands, New Zealand, Niue, Samoa, Tokelau and Tonga. The TVM’s goal is to secure and enhance long-term economic benefits derived from fisheries and protect the important contribution fisheries make to the food security of Pacific communities. It has interest in the implementation of fisheries management frameworks, including through monitoring, control, surveillance and enforcement systems, processes and activities.

  • the Melanesian Spearhead Group (MSG), established in 2007, is a group of four independent countries — Papua New Guinea, Solomon Islands, Vanuatu and Fiji — and the Kanak socialist national liberation front (FLNKS) advocating for political independence in New Caledonia. The MSG’s goal is to facilitate cooperation, promote stability and implement policies to achieve sustained improvements in livelihoods in Melanesian countries.

56Finally, CMMs and subregional decisions are implemented in national fisheries legislation within EEZs and by the nations of vessels fishing in high seas. Individual countries do not rely on decisions taken within the Commission or other groups to drive national management, and make decisions for their own EEZs. Examples are the Palau ‘shark haven’, declared in 2009, and the New Caledonia shark sanctuary, declared in 2013, which banned commercial fishing for sharks within the two countries’ respective EEZs. Most Pacific Island states, particularly those which are members of the FFA, have national tuna management plans that detail the national objectives and management mechanisms for the fishery defined by governments, and contain rules applying to tuna fishing within their EEZs, consistent with wider management decisions.

57Representatives of these national, subregional and regional organisations meet throughout the year, and annually during the Commission meeting of the WCPFC.

Some issues and developments to provide reliable scientific information to managers

  • 35 EAFM is an approach ensuring that benefits from living resources are high while the direct and indi (...)

58In addition to tuna single-species stock status assessments, the ecosystem approach to fisheries management (EAFM)35 (promoted by several international initiatives since 1995, see Garcia and Cochrane 2005) needs information on bycatch species and on the ecosystem. Despite the scarcity of data, the development of observer programmes in the WCPO (see section “Fisheries data and monitoring”) has enabled the recent development of single-species assessments for billfish and shark species (swordfish, blue marlin, oceanic whitetip shark, silky shark and blue shark), as well as detailed studies on bycatch. Moreover, ecosystem single-species and multispecies models are under development to provide managers with ecosystem indicators and detailed information on the impact of fisheries and climate variation on the whole ecosystem.

59Uncertainties in the information used within stock assessments highlight the need to continue to improve fisheries monitoring to obtain the data required to produce more reliable estimates and management decisions. The increased coverage rate of observation on-board fishing vessels is a valuable source of detailed information on both the target species and bycatches. Moreover, new techniques are being developed to speed up the processing and receipt of fisheries data using electronic reporting and monitoring (e-reporting and e-monitoring). E-reporting is the electronic recording of catch and effort data by vessel officers. These data in electronic format are directly sent to national fisheries authorities and information is immediately accessible for analysis without having to await the return of paper logsheets. E-monitoring is the use of electronic equipment such as video cameras as an alternative or adjunct to on-board observers to record information on fishing activities. These new approaches have the potential to improve data collection and data quality, enhance assessments, and support alternative management approaches to improve the management of WCPO tuna stocks.

Bibliographie

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Hoyle, Simon, John Hampton and Nick Davies
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th Meeting of the Scientific Committee of the Western and Central Pacific Fisheries Commission, Busan, Republic of Korea, 7-15 August 2012 (WCPFC-SC8-2012, SA-WP-04, Rev. 1).

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Notes

1 The longitude 150° W delimits two geographic entities: the WCPO to the west and the Eastern Pacific Ocean (EPO) to the east. The WCP-CA has been defined for fisheries management; it includes the WCPO, but extends north and south of the WCPO and partially overlaps the EPO in the southern hemisphere. For simplification WCPO will be used as an approximation of the WCP-CA in the text.

2 Pelagic fisheries are the fisheries occurring in the water column of the ocean away from the seafloor as opposed to benthic fisheries, which occur in contact with the seafloor such as bottom trawling.

3 http://www.wcpfc.int/doc/cmm-2012-04/conservation-and-management-measure-protectionwhale-sharks-purse-seine-operations (accessed on December 7, 2015).

4 There are a large number of ring net (see footnote 6) and small purse seine vessels in the Indonesian, Japanese coastal and Philippine domestic fisheries which are not included in this total.

5 In 2013, there were an additional 40 vessels in the category less than 200 gross register tonnage (GRT) which are a part of the Japanese purse seine fleet, but these are not included here.

6 Ring net vessels are smaller than purse seine vessels and have a manual winch to haul the net on board while purse seiners are equipped with an electrical winch.

7 In 2010, conservation and management measures were adopted by the WCPFC to limit the catch of tropical tuna. One of the measures consisted in a closure of the high seas pockets, i.e., international waters wholly enclosed by EEZs, located between 10°N-10°S and 130°E-180°
(http://www.wcpfc.int/system/files/CMM%202008-01%20%5BBigeye%20and%20yellowfin%5D.pdf). Accessed on December 7, 2015.

8 The westernmost high seas pocket was reopened to Philippine traditional fresh/ice chilled fishing vessels in 2012 (http://www.wcpfc.int/system/files/CMM-2012-01-Conservation-and-Management-Measure-BET-YFT-and-SKJ.pdf). Accessed on December 7, 2015.

9 Fish do not form dense schools in the subtropical and temperate areas.

10 ENSO refers to a climatic phenomenon occurring across the whole Pacific Ocean and characterised by two phases: a warming phase, El Niño, and a cooling phase, La Niña. During El Niño, a band of warm ocean water develops in the central and east-central equatorial Pacific, while during La Niña, the sea surface temperature is 3-5° C lower than normal. The atmosphere (temperature, rainfall and winds) and ocean (surface and vertical temperature and currents) are both impacted, and these impacts in turn affect living organisms, resulting, for example, in the displacement of tuna and tuna fisheries. The ENSO cycle has a global impact reaching beyond the Pacific Ocean.

11 These types of vessels are not included in fig. 6.

12 Bonitiers are 10 to 12 m long boats targeting skipjack using mainly pole-and-line and operating close to the shore in territorial waters.

13 https://www.msc.org/(Accessed on December 7, 2015).

14 Omitting stocks such as bluefin tuna caught in the northern Pacific.

15 The North Pacific albacore tuna stock is not fished by the PICTs; it is mainly exploited by Japan, USA, Canada and Chinese Taipei. Fisheries statistics for this stock are managed and analysed by the International Scientific Committee for Tuna and Tuna-like Species that reports to the Northern Committee of the WCPFC.

16 The PTTP, endorsed by the WCPFC, was designed and implemented by the Pacific Community (SPC) in collaboration with Papua New Guinea, Solomon Islands, University of Hawaii and the Inter-American Tropical Tuna Commission (IATTC). http://www.spc.int/tagging/webtagging (Accessed on December 8, 2015).

17 Tags are implanted on fish caught during tagging cruises and the fish are released immediately. Each tag carries a unique number that identifies the fish tagged. Conventional tags are 10 cm long and 2 mm wide plastic tubes equipped with a barbed head placed in the flesh on the back of the fish. The tag protrudes externally and is easily spotted when the fish is recaptured. Electronic tags, in contrast, are miniature computerised data recorders measuring a range of parameters (depth, temperature, light intensity). Measuring 2 to 12 cm long, these small devices can be implanted surgically in the body cavity, while larger devices can be attached to the back of the fish. Fish implanted with an internal electronic tag also carry a visible external conventional tag. External electronic tags or satellite tags will detach automatically from the fish and will transmit their data via satellite once at the surface. Conventional and electronic internal tags need to be recovered by fishermen after they catch the released fish.

18 Drifnets are nets that can reach up to 50 km long and are set vertically in the water, maintained by floats at the surface or near the surface. They drift with the current, and fish striking the net become entangled in the mesh. Driftnet fishing ceased in 1991.

19 Five to nine regions defined in the WCPO area according to the tuna species.

20 The assessment model is fitted to the data to best mimic the patterns and values observed in terms of relative abundance indices (catch per unit of effort), tagging information, and tuna size frequencies.

21 There are two key reference point types. Limit reference points (LRPs) represent stock or fishing levels that are to be avoided as they result in a biological danger to stock sustainability. Target reference points (TRPs) represent stock or fishing levels that would achieve the objectives of fishery managers (e.g., sustainability, good fishery catch rates, profitability). For example, if the stock assessment indicates that the stock is beyond the limit reference point, or the fishing mortality is too high, management action would be needed to reduce fishing levels to allow the stock to recover.

22 When F is greater than FMSY or F/FMSY is greater than 1, it is considered that overfishing of the stock is occurring, meaning that the rate at which fish are being caught is not sustainable in the long term.

23 Within the WCPFC, a limit reference point of 20% SBF = 0 has been adopted for key tuna stocks as it is considered a level below which the health of tuna stocks will be affected. It means that when the current adult biomass represents less than 20% of the amount that would theoretically have been present if no fishing had occurred, the stock is considered overfished, meaning that the level of the stock is too low. At present, the Commission has not adopted target reference points. However, at the time of writing (May 2015), discussions on options for SB/SBF = 0 target reference points for skipjack within the range of 40-60% of unfished spawning biomass were ongoing.

24 While estimates of fishing mortality for skipjack have increased over time, 2012 fishing mortality rates for skipjack tuna were estimated to be about 0.62 times the level of fishing mortality associated with maximum sustainable yield (FMSY). Therefore, overfishing was not occurring (i.e., F was less than FMSY). Estimated recruitment shows an upward trend over time, but estimated biomass declined over time to 52% of the level predicted in the absence of fishing, so still above the limit reference point of 20%, and within the region of the target reference point levels being discussed (40-60%).

25 2012 fishing mortality rates for yellowfin tuna were estimated to be about 0.72 times the level of fishing mortality associated with maximum sustainable yield (FMSY), which indicated that overfishing was not occurring (i.e., F was less than FMSY). Both biomass and recruitment had declined gradually over the duration of the fishery, with current spawning biomass estimated to be about 38% of the level predicted in the absence of fishing, so still above the limit reference point of 20%.

26 Fishing mortality is estimated to have increased over time, particularly in recent years, and 2014 fishing mortality levels were 1.57 times the FMSY level (F was greater than FMSY). The biomass of spawners was estimated to have declined over the duration of the fishery, with current spawning biomass estimated to be about 16% of the level predicted in the absence of fishing, so below the limit reference point of 20%.

27 The North Pacific albacore tuna stock is not exploited by PICTs and is not considered in the present document.

28 The last assessment at the time of writing (May 2015)(performed in 2012 by SPC) indicated that fishing mortality on adult fish had increased considerably over the past decade, but that overall estimates of 2011 fishing mortality were well below FMSY. Spawning biomass levels remained well above SBMSY.

29 Four subsidiary bodies support the work of the WCPFC. The Scientific Committee (SC) provides the best available scientific advice. The Technical and Compliance Committee (TCC) is in charge of evaluating the enforcement of WCPFC decisions. The Northern Committee (NC) makes recommendations on species mostly found north of 20°N. The Finance and Administration Committee (FAC) deliberates on the WCPFC’s budget. All WCPFC members are part of the SC, the TCC and the FAC. Participation in the NC is limited to those members located north of 20°N or fishing for “northern stocks” (stocks which occur mainly north of 20°N).

30 Mitigation methods are fishing techniques or practices implemented to avoid the capture, minimise the mortality, and reduce the catch of unwanted species.

31 Australia, Cook Islands, Federated States of Micronesia, Fiji, Kiribati, Marshall Islands, Nauru, New Zealand, Niue, Palau, Papua New Guinea, Samoa, Solomon Islands, Tokelau, Tonga, Tuvalu, Vanuatu.

32 In 2015, the PNA total allowable effort was 44,623 days for purse seine fishing within their EEZs. One purse vessel fishing during a day represents one day and two vessels fishing during the same day represent two days.

33 Northern Mariana Islands, Guam, Palau, Federated States of Micronesia, Marshall Islands, Papua New Guinea, Nauru, Kiribati, Solomon Islands, Tuvalu, Tokelau, Cook Islands, French Polynesia, Vanuatu, Fiji, Wallis and Futuna, Samoa, American Samoa, New Caledonia, Tonga, Niue, Pitcairn Islands.

34 SPC is composed of seven divisions: geoscience, economic development, social development, fisheries including oceanic and coastal, land resources, public health, and statistics for development.

35 EAFM is an approach ensuring that benefits from living resources are high while the direct and indirect impacts of fishing on marine ecosystems are low and not detrimental to the future functioning, diversity and integrity of those ecosystems.

Table des illustrations

Titre Figure 1: The Western and Central Pacific Ocean (WCPO), the Eastern Pacific Ocean (EPO) and the Western and Central Pacific Fisheries Commission (WCPFC) Convention Area (WCP–CA) in dashed lines
Légende This map is indicative only of agreed and potential maritime jurisdictional limits within the Pacific Islands.This map does not necessarily reflect coastal state claims and is without prejudice to negotiations that countries may enter into. Data related to EEZ areas were mostly extracted from Claus et al. 2014.© Pacific Community, 2015.
URL http://books.openedition.org/pacific/docannexe/image/423/img-1.jpg
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Titre Figure 2: The main tuna fishing gears: purse seine (a), longline (b), pole-and-line (c), and fish aggregating device (d)
Légende © Pacific Community (William Sokimi for pictures a, b and d; Malo Hosken for picture c).
URL http://books.openedition.org/pacific/docannexe/image/423/img-2.jpg
Fichier image/, 680k
Titre Figure 3: Number of purse seine vessels operating in WCPO (Harley et al. 2015)
Légende This does not include the Japanese Coastal purse seine fleet and the Indonesian, Philippine and Vietnamese domestic purse seine/ring net fleets which account for over 1,000 vessels (Williams and Terawasi 2014).
URL http://books.openedition.org/pacific/docannexe/image/423/img-3.jpg
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Titre Figure 4: Spatial distribution of the purse seine catch by species in 2004-2013 (Harley et al. 2015)
Légende The size of the largest pie corresponds to the maximum value of 1,344,000 t.
URL http://books.openedition.org/pacific/docannexe/image/423/img-4.jpg
Fichier image/, 236k
Titre Figure 5: Time series showing the percentage of total sets by school type for the major purse seine fleets operating in the WCPO
URL http://books.openedition.org/pacific/docannexe/image/423/img-5.jpg
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Titre Figure 6: Longline vessels operating in the WCPO (Harley et al. 2015)
Légende Available data does not make the distinction between foreign “distant-water” and “offshore” fleets.
URL http://books.openedition.org/pacific/docannexe/image/423/img-6.jpg
Fichier image/, 184k
Titre Figure 7: Spatial distribution of WCPO longline catch by species in 2004-2013 (Harley et al. 2015)
Légende Note that the data on the distant-water efforts of Chinese Taipei and other fleets targeting albacore in the North Pacific is poor. The size of the largest pie corresponds to the maximum value of 67,000 t.
URL http://books.openedition.org/pacific/docannexe/image/423/img-7.jpg
Fichier image/, 96k
Titre Figure 8: Pole-and-line vessels operating in the WCPO (Harley et al. 2015)
Légende Pole-and-line vessels from the Japanese coastal and Indonesian domestic fisheries are not included in the figure.
URL http://books.openedition.org/pacific/docannexe/image/423/img-8.jpg
Fichier image/, 160k
Titre Figure 9: Average distribution of WCPO pole-and-line catch (2003–2012) (Harley et al. 2015).
Légende Catches by the pole-and-line fleet based in Hawaii and the bonitier fleet in French Polynesia are not shown in this figure. The size of the largest pie corresponds to the maximum value of 263,000 t.
URL http://books.openedition.org/pacific/docannexe/image/423/img-9.jpg
Fichier image/, 220k
Titre Figure 10: The four main tuna species in the tropical and subtropical waters of the WCPO: yellowfin (Thunnus albacares), bigeye (Thunnus obesus), albacore (Thunnus alalunga), and skipjack (Katsuwonus pelamis) tunas
Légende © Pacific Community (illustrations by Les Hata).
URL http://books.openedition.org/pacific/docannexe/image/423/img-10.jpg
Fichier image/, 204k
Titre Figure 11: Catch (in tonnes) by gear (top) and species (bottom) for the Western and Central Pacific region, 1960-2013 (Harley et al. 2015)
Légende Note that data for 2013 are preliminary.
URL http://books.openedition.org/pacific/docannexe/image/423/img-11.jpg
Fichier image/, 192k
Titre Figure 12: The modified Kobe plot (“Majuro plot”) identifying the status of the stocks according to reference points on fishing mortality (F/Fmsy) and spawning biomass (SB/SBF0)
Légende The plot describes the 2012 stock status for skipjack (Rice et al. 2014), bigeye (Harley et al. 2014) and yellowfin (Davies et al. 2014) and the 2010 stock status for South Pacific albacore (SP Albacore) (Hoyle et al. 2012). Stocks located in the white area are estimated healthy, overfishing is occurring for stocks in the orange area (catches are too high for sustainability) and stocks in the red area are overfished (the level of the spawning biomass is too low to sustain the stock). Many stock assessment runs are performed for each stock, using different combinations of input parameters (e. g., different estimates of growth rate, rates at which fish die due to natural causes, etc.). These lead to slightly different estimates of current stock status. Hence the stock assessment run selected as the ‘reference case’ for management advice is shown as the main ‘point’ (plain circle), and the range of estimated status from key uncertainty runs with these different input parameters are shown as lines radiating out from that point.
URL http://books.openedition.org/pacific/docannexe/image/423/img-12.jpg
Fichier image/, 91k

Auteurs

Fisheries research scientist at the Pacific Community (SPC). Her domains of expertise include fish biology and ecology, ecosystem functioning, fisheries, and climate change impact. After studying the deep sea fish populations exploited by trawl fisheries in the north-east Atlantic, she moved to the Pacific where she has spent the last 15 years working on the tuna fisheries of the Western and Central Pacific Ocean. Her work has particularly focused on understanding the tuna ecosystem through studies of the trophic interactions between fish species as well as an analysis of the various compartments of this ecosystem, from primary producers to top predators. She has also studied the impact of seamounts on tuna catches, tuna fisheries by catches, and tuna movement and ecosystem organization through biological markers such as mercury and stable isotopes. Her recent publications include several co-authored articles in specialised journals, such as Deep Sea Research Part II: Topical Studies in Oceanography (Volume 113, 2015), and in multidisciplinary scientific journals, such as PLoS ONE (Volume 7(5), 2012) and Proceedings of the National Academy of Science US (Volume 107(21), 2010). They also include contributions to SPC’s publications on various topics, for instance the vulnerability of open ocean food webs to climate change in the tropical Pacific (Chapter 4 in Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change, edited by J.D. Bell, J.E. Johnson and A.J. Hobday, 2011, http://www.spc.int/climate-change/fisheries/assessment/main-book.html).

Currently a senior fisheries scientist at SPC. With over 20 years of experience in analyzing, assessing and providing scientific advice on tropical, temperate and polar marine and freshwater ecosystems and fisheries, he currently performs scientific assessments of tuna stocks and fisheries within the Western and Central Pacific Ocean. He also provides scientific advice to underpin the decisions of regional and subregional tuna management bodies in the region, including the Pacific Islands Forum Fisheries Agency (FFA), Parties to the Nauru Agreement (PNA) and Western and Central Pacific Fisheries Commission (WCPFC). His areas of work include the development of biological and economic reference points for tuna stocks, the examination of effort creep in tuna fisheries, and food security for Pacific Islands. His recent references include articles in scientific journals such as Food Security (Volume 7(1), 2015) and working papers for WCPFC (see the “Management issues theme” tab at https://www.wcpfc.int/meetings/11th-regular-session-scientific-committee).

BSc in marine biology from Sydney University in 1978. After further professional education in computer programming, he pursued a career in corporate information technology (IT) in Australia from 1979 through 1987. During this time he completed post-graduate studies in IT at Macquarie University, Sydney. In 1999, he also obtained an MBA (Technology Management) from Deakin University, Melbourne. Peter joined the Oceanic Fisheries Programme (OFP) at SPC in 1987 to take a lead role in establishing the databases which have been fundamental for the stock assessment work conducted by OFP over the past two decades. He is currently the Principal Fisheries Scientist in charge of the Data Management section within OFP. Other than database-related work and interacting with colleagues from Pacific Island countries, he has a keen interest in various tunafishery areas, particularly bycatch issues and the Western and Central Pacific Fisheries Commission (WCPFC)’s work on improving fisheries monitoring and data management in the diverse domestic tuna fisheries of Indonesia, Philippines and Vietnam.

Currently the Principal Fisheries Scientist and team leader of the Stock Assessment and Modelling section within the Oceanic Fisheries Programme (OFP) at SPC. His team is responsible for undertaking stock assessments for the major tuna stocks in the Western and Central Pacific Ocean. Shelton has 14 years of experience in Pacific tuna fisheries science. In addition to his time at SPC, he was New Zealand’s scientific representative for the Western and Central Pacific Fisheries Commission (WCPFC) and the Commission for the Conservation of the Southern Bluefin Tuna (CCSBT) from 2004 to 2008. He also worked as a scientist at the Inter-American Tropical Tuna Commission.

Currently the Principal Fisheries Scientist and team leader of the Ecosystem Monitoring and Analyses section within the Oceanic Fisheries Programme (OFP) at SPC. He undertakes primary research and analyses on tuna species and the ecosystem they are dependent upon in the Western and Central Pacific Ocean. This works encompasses life-history studies, tagging to estimate exploitation and movement rates, trophic ecology, and the modelling of ecosystem dynamics and climate impacts. He has over 25 years of experience in the field of ecology and has worked closely with senior resource managers, scientists and industry representatives on matters ranging from the implementation and interpretation of applied research to the modelling of ecosystems and applications of adaptive management. His key references include articles in scientific journals such as Climatic Change (Volume 119 (1), 2013), Deep Sea Research Part II: Topical Studies in Oceanography (Volume 113, 2015), and Fish and Fisheries (doi: 10.1111/faf. 12126, 2015).

Worked for more than 30 years in the area of tuna biology and ecology, stock assessment and fisheries management. He joined SPC in 1987 after having worked for seven years at the Commonwealth Scientific and Industrial Research Organisation (CSIRO, Australia) on the stock assessment of southern bluefin tuna. He has been instrumental in the implementation of formal assessments for tuna stocks in the western and central Pacific Ocean. Since 2002, he has been the Chief Scientist of the Oceanic Fisheries Programme (OFP) at SPC, one of the world’s most respected pelagic fisheries research programmes and the key provider of scientific services and advice regarding tuna fisheries to the island states and territories of the Pacific, the Forum Fisheries Agency (FFA) and the Western and Central Pacific Fisheries Commission (WCPFC). His key references include articles in Nature (Volumes 389, 1997 and 434, 2005), the Canadian Journal of Fisheries and Aquatic Sciences (Volumes 55(9), 1998 and 57(5), 2000), and Science (Volume 314(5806), 2006).

© pacific-credo Publications, 2016

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