Tuna Fisheries Management Research Articles

Habitat suitability of the Atlantic bluefin tuna by size class: An ecological niche approach

An ecological niche modelling (ENM) approach was used to predict the potential feeding and spawning habitats of small (5–25kg, only feeding) and large (>25kg) Atlantic bluefin tuna (ABFT), Thunnus thynnus, in the Mediterranean Sea, the North Atlantic and the Gulf of Mexico. The ENM was built bridging knowledge on ecological traits of ABFT (e.g. temperature tolerance, mobility, feeding and spawning strategy) with patterns of selected environmental variables (chlorophyll-a fronts and concentration, sea surface current and temperature, sea surface height anomaly) that were identified using an extensive set of precisely geo-located presence data. The results highlight a wider temperature tolerance for larger fish allowing them to feed in the northern – high chlorophyll levels – latitudes up to the Norwegian Sea in the eastern Atlantic and to the Gulf of Saint Lawrence in the western basin. Permanent suitable feeding habitat for small ABFT was predicted to be mostly located in temperate latitudes in the North Atlantic and in the Mediterranean Sea, as well as in subtropical waters off north-west Africa, while summer potential habitat in the Gulf of Mexico was found to be unsuitable for both small and large ABFTs. Potential spawning grounds were found to occur in the Gulf of Mexico from March–April in the south-east to April–May in the north, while favourable conditions evolve in the Mediterranean Sea from mid-May in the eastern to mid-July in the western basin. Other secondary potential spawning grounds not supported by observations were predicted in the Azores area and off Morocco to Senegal during July and August when extrapolating the model settings from the Gulf of Mexico into the North Atlantic. The presence of large ABFT off Florida and the Bahamas in spring was not explained by the model as is, however the environmental variables other than the sea surface height anomaly appeared to be favourable for spawning in part of this area. Defining key spatial and temporal habitats should further help in building spatially-explicit stock assessment models, thus improving the spatial management of bluefin tuna fisheries.

Fewer Fish for Higher Profits? Price Response and Economic Incentives in Global Tuna Fisheries Management

This paper evaluates industry-wide economic incentives arising from changes in product prices in an industry exploiting a common renewable resource (tropical tunas) that is regulated via output limits. Changes in prices alter economic incentives by affecting revenues, profits, conservation, and nonmarket public benefits. Economic incentives in industries exploiting common resources have been examined from multiple angles. However, industry level variation in market prices arising from changes in public regulation has not been explored. We analyse the impact on economic incentives due to changes in output limits and market prices through estimation of ex-vessel price and scale flexibilities for imported skipjack and yellowfin in Thailand’s cannery market. The unitary scale flexibility, estimated from the General Synthetic Inverse Demand Systems, indicates no loss in revenue and even potential profit increases resulting from lower harvest levels that could arise from lower catch limits. However, for a revenue neutral or positive outcome to be achieved, the three inter-governmental tuna Regional Fisheries Management Organizations, which manage the majority of the yellowfin and skipjack tuna in the Pacific and Indian Oceans, would have to coordinate multilaterally to set the catch limits for both species.

Modelling the spatial behaviour of a tropical tuna purse seine fleet.

Industrial tuna fisheries operate in the Indian, Atlantic and Pacific Oceans, but concerns over sustainability and environmental impacts of these fisheries have resulted in increased scrutiny of how they are managed. An important but often overlooked factor in the success or failure of tuna fisheries management is the behaviour of fishers and fishing fleets. Uncertainty in how a fishing fleet will respond to management or other influences can be reduced by anticipating fleet behaviour, although to date there has been little research directed at understanding and anticipating the human dimension of tuna fisheries. The aim of this study was to address gaps in knowledge of the behaviour of tuna fleets, using the Indian Ocean tropical tuna purse seine fishery as a case study. We use statistical modelling to examine the factors that influence the spatial behaviour of the purse seine fleet at broad spatiotemporal scales. This analysis reveals very high consistency between years in the use of seasonal fishing grounds by the fleet, as well as a forcing influence of biophysical ocean conditions on the distribution of fishing effort. These findings suggest strong inertia in the spatial behaviour of the fleet, which has important implications for predicting the response of the fleet to natural events or management measures (e.g., spatial closures).

Sub-regionalisation of fisheries governance: the case of the Western and Central Pacific Ocean tuna fisheries

Shifting political alliances and new environmental challenges are prompting debate over processes of sub-regionalisation and whether the interplay between multiple scales of governance leads to positive synergistic outcomes or negative institutional disruption. Regional management of tuna fisheries in the Western and Central Pacific Ocean is an example where a web of treaties, conventions and institutional frameworks underlie international cooperation. Through examining the interplay between the regional Western and Central Pacific Fisheries Commission and sub-regional Parties to the Nauru Agreement, this paper explores the extent to which the PNA and WCPFC interact in the management of regional tuna fisheries. The results demonstrate that for contested marine resources such as fisheries, international sub-regions can go beyond functional units to also present wider opportunities to shift power relations in favour of small island states. Additionally, the presence of sub-regional groups like the PNA has served to challenge the performance of the WCPFC, stimulating greater debate and progress within the regional body. The paper concludes that the combined work of the PNA and the WCPFC puts them ahead on many issues and may represent a testing ground for a functional multilateralism utilising both regional and sub-regional governance platforms for the management of shared resources.

LENGTH-WEIGHT RELATIONSHIP, SIZE DISTRIBUTION AND ANNUAL CPUE’s OF ALBACORE IN EASTERN INDIAN OCEAN

Albacore (Thunnus alalunga, Bonnaterre, 1788) is one of the tropical tuna species in the Eastern Indian Ocean incidentally caught by the Indonesian tuna longliner. Scientific observer series data during the period of 2005 – 2012 showed that the catches were geographically distributed within the area bordered by 5 – 350 S and 75 – 1300 E. High CPUE mainly occurred in sub area between 250 and 350 S. Some biological observations indicated that immature albacore specimens were mainly recorded in areas of south of 250 S while mature albacore were concentrated in the area between 100 S and 250 S. Length – weight measurements for pooled male and female was W= 0.00008FL2.7271. The hook-rates from onboard observation showed that increasing rates occurred during 2009 to 2012. The annual landing showed that that highest occurred in 2008 and the lowest in 2011 with overall tend to decrease until 2011 and increased slightly in 2012. Series number of length frequency measurements (2005 - 2012) showed that the albacore were caught within the range of 40 – 135 cm FL and there was a tendency that the average size decreased gradually from 103 cmFL (2005) to 84 cmFL (2012). As a preliminary finding these estimates contribute as important element for consideration in the national and regional tuna fisheries management in the area.

Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives

Abstract Effective use of spatial management in the pelagic realm presents special challenges due to high fish and fisher mobility, limited knowledge and significant governance challenges. The tropical Indian Ocean provides an ideal case study for testing our ability to apply existing data sources to assessing impacts of spatial management on tuna fisheries because of several recent controversial spatial closures. We review the scientific underpinnings of pelagic MPA effects, spatio-temporal patterns of Indian Ocean tuna catch, bycatch and fish movements, and the consequences of these for the efficacy of spatial management for Indian Ocean tropical tuna fisheries. The tropical Indian Ocean is characterized by strong environmental fluctuations, regular seasonal variability in catch, large observed tuna displacement distances, relatively uniform catch-per-unit-effort and bycatch rates over space, and high fisher mobility, all of which suggest significant variability and movement in tropical tuna fisheries that are simply not well adapted to static spatial closures. One possible exception to this overall conclusion would be a large time/area closure east of Somalia. If closed for a significant fraction of the year it could reduce purse-seine bycatch and juvenile tuna catch. Dynamic closures following fish migratory patterns are possible, but more focused information on fish movements will be needed for effective implementation. Fortunately, several recent improvements in conventional fishery management and reporting will likely enhance our ability to evaluate spatial and non-spatial management options in the near future, particularly as pertaining to bycatch species.

Conservation and Management of Tuna Fisheries in the Indian Ocean and Indian Exclusive Economic Zones (EEZs)

The focus of the study is to explore the recent trend and stock status of Indian Ocean and Indian EEZ, and its conservation and sustainable management of tuna fishereis. In the Indian Ocean, tuna catches increased rapidly from about 179 959 t in 1980 to about 832 246 t in 1995. They have continued to increase up to 2005; the catch was 1 318 648 t, forming about 26% of the world catch. However, since 2006 onwards there was a decline in tuna catch and in 2010 the catch was only 1 257 908 t. Tuna production in India which was continued to increase with fluctuations from 63 633 t during 2001-2005, average 78 400 t during 2006-2010, and in 2010 the catch was only 65 863 t. Tuna is an important but not a well managed fishery in the Indian Ocean and Indian EEZ. The Indian Ocean stock is currently overfished and has no proper management regulations aimed at with sustaining the stock. In the present study, sustainable management system is evaluated with information on tuna landings, stock status and major issues on tuna fishery. To address these major issues, appropriate tuna fishing policies are proposed to help sustainable development and management of tuna fishery resource in the Indian Ocean.

Commentary: BESTTuna: Benefiting from equitable and sustainable trans-boundary tuna fisheries in the Western Pacific

In this commentary we introduce the BESTTuna research programme which addresses the challenges of governing sustainable and equitable tuna fisheries in the Western Pacific. The research in this programme attempts to build an inter-disciplinary understanding of the complex social-ecological interactions in tuna fisheries in order to contribute to the design of effective and equitable governance arrangements that can steer public and private interests in the fishery to more desirable outcomes. In addition, the programme aims to develop an effective long-term science-governance network for sustainable tuna fisheries in the Western Pacific, which generates, disseminates and uses knowledge on tuna ecology, tuna fisher behaviours, and tuna fisheries management and governance.

An ocean observation system for monitoring the affects of climate change on the ecology and sustainability of pelagic fisheries in the Pacific Ocean

Climate change presents an emerging challenge to the sustainable management of tuna fisheries, and robust information is essential to ensure future sustainability. Climate and harvest affect tuna stocks, populations of non-target, dependent species and the ecosystem. To provide relevant advice we need an improved understanding of oceanic ecosystems and better data to parameterise the models that forecast the impacts of climate change. Currently ocean-wide data collection in the Pacific Ocean is primarily restricted to oceanographic data. However, the fisheries observer programs that operate in the region offer an opportunity to collect the additional information on the mid and upper trophic levels of the ecosystem that is necessary to complement this physical data, including time-series of distribution, abundance, size, composition and biological information on target and non-target species and mid trophic level organisms. These observer programs are in their infancy, with limited temporal and spatial distribution but recent international and national policy decisions have been made to expand their coverage. We identify a number of actions to initiate this monitoring including: consolidating collaborations to ensure the use of best quality data; developing consistency between sub-regional observer programmes to ensure that they meet the objectives of ecosystem monitoring; interrogating of existing time series to determine the most appropriate spatial template for monitoring; and exploring existing ecosystem models to identify suitable indicators of ecosystem status and change. The information obtained should improve capacity to develop fisheries management policies that are resilient and can be adapted to climate change.

Towards better management of Coral Triangle tuna

Indonesia, the Philippines, and Papua New Guinea, all part of a regional sub-group known as the Coral Triangle, have sizeable skipjack, yellowfin and bigeye tuna fisheries. Recent figures suggest that as much as a third of tuna catch from the western and central Pacific Ocean can be attributed to the fleets of these countries. Historically, however, little attention has been paid to their fisheries and their regulations. Management of tuna fisheries in Indonesia and the Philippines faces many challenges, including bycatch of juveniles, lack of effective gear restrictions, subsidized fleets, and unreported catches. Papua New Guinea has countered the challenges of tuna management with several effective measures, including implementing the vessel day scheme, a type of effort quota system, and limiting the use of fish aggregating devices (FADs). This paper compares and contrasts tuna fisheries in the three countries, as well as their management regimes and current management challenges. By highlighting some of the successes that Papua New Guinea has had, we hope that Indonesia and the Philippines may be able to more effectively manage their fleets and their fish. And this in turn may lead to better regional management of a valuable transboundary resource.

Japan–Taiwan Relations in the Twenty-First Century from the Perspective of Tuna Disputes in the Atlantic Ocean

AbstractOver the last decade bilateral relations between Japan and Taiwan have been strained over the issue of tuna fishery management. In 2005, when Taiwan was still under the Democratic Progressive Party (DPP) administration, Japan proposed punitive measures against Taiwan's tuna industries in an international fisheries management body for the Atlantic Ocean. The DPP government took a pragmatic approach, solving the tuna crisis without harming Japan–Taiwan relations, as evidenced by the fact that during the tuna disputes visa-free privilege was granted to Taiwan nationals and the Japanese government openly stated that Taiwan has been a main security objective for Japan and the US. In this paper the Japan-led tuna sanction in 2005 is used as a case study to gauge overall bilateral relations thus far in the twenty-first century.

Spatio-temporal distributions of tuna species and potential habitats in the Western and Central Pacific Ocean derived from multi-satellite data

In this study, potential tuna habitats in the Western and Central Pacific Ocean (WCPO) area from 1998 to 2005 were identified using a combination of multi-satellite oceanographic data related to sea-surface temperature (SST), chlorophyll-a concentration (Chl-a) and sea-surface height anomaly (SSHA). Histogram analyses of tuna catch per unit effort (CPUE) by the Taiwanese purse seine fishery in relation to the satellite oceanographic data were used to determine tuna's preferred ranges of the three satellite-derived oceanographic parameters. The highest CPUE corresponded to areas where SST ranged from 29.0–29.5°C, Chl-a ranged from 0.0–0.1 mg m−3 and SSHA ranged from 0.0–5.0 cm. Local areas within the WCPO with similar satellite-derived oceanographic parameters were assumed to be potential tuna habitat, and a spatially explicit model was developed to determine their locations. It was found that the potential tuna habitats were distributed in warm pools, in the vicinity of the western cold tongue in the equatorial Pacific. Consequently, by using these potential habitats, tuna-fishery management and protection of habitats of tuna species can be improved, and these can possibly form the basis of fishing-ground forecasting in the future.

Influence of mesoscale eddies on spatial structuring of top predators’ communities in the Mozambique Channel

Mesoscale physical features as fronts and eddies appear to play a key role in the dynamics of marine communities. In the Indian Ocean, the Mozambique Channel (MC) is a natural laboratory to investigate mesoscale eddies (100–300 km in diameter); indeed, four to seven eddies per year are know to transit through the Channel, from North to South. We studied the structuring role of the mesoscale eddies on spatial dynamics and foraging strategy of top predators using seabirds and tuna as examples. Emphasis was on the central part of the MC (16–24°S) where eddy activity is most developed. We integrated three main categories of information: (i) satellite altimetry for sea-level anomaly (SLA) and geostrophic current, remotely-sensed surface temperature (SST) and SeaWiFS data for chlorophyll concentration (CC); (ii) individual tracking of Great Frigatebirds ( Fregata minor) to characterize foraging areas; and (iii) detailed catch statistics from purse-seine fisheries to describe distribution of tuna schools. Generalized Additive Models were applied to quantify the relative influence of mesoscale descriptors, SST and CC on foraging behaviour of Great Frigatebirds and location of purse-seine sets. Our results show that seabirds are more closely tied to mesoscale eddies compared to tuna. We underline the role of eddy boundaries on the response of frigatebirds and tuna. Good foraging conditions are promoted along the edge of eddies as a result of the interplay of the maturation process from cyclonic eddies and the concentration process by eddy interactions. A decrease in the number or intensity of eddies in the MC, as observed during strong El Niño events, could potentially affect the eddy-related ecosystem with putative negative repercussions on central-place foragers such as Great Frigatebirds. We discuss the importance of a better understanding of the “eddy system”, in marine conservation and tuna fisheries management in the Mozambique Channel.

Modelling retention and dispersion mechanisms of bluefin tuna eggs and larvae in the northwest Mediterranean Sea

Knowledge of early life history of most fish species in the Mediterranean Sea is sparse and processes affecting their recruitment are poorly understood. This is particularly true for bluefin tuna, Thunnus thynnus, even though this species is one of the world’s most valued fish species. Here we develop, apply and validate an individually based coupled biological–physical oceanographic model of fish early life history in the Mediterranean Sea. We first validate the general structure of the coupled model with a 12-day Lagrangian drift study of anchovy ( Engraulis encrasicolus) larvae in the Catalan Sea. The model reproduced the drift and growth of anchovy larvae as they drifted along the Catalan coast and yielded similar patterns as those observed in the field. We then applied the model to investigate transport and retention processes affecting the spatial distribution of bluefin tuna eggs and larvae during 1999–2003, and we compared modelled distributions with available field data collected in 2001 and 2003. Modelled and field distributions generally coincided and were patchy at mesoscales (10s–100s km); larvae were most abundant in eddies and along frontal zones. We also identified probable locations of spawning bluefin tuna using hydrographic backtracking procedures; these locations were situated in a major salinity frontal zone and coincided with distributions of an electronically tagged bluefin tuna and commercial bluefin tuna fishing vessels. Moreover, we hypothesized that mesoscale processes are responsible for the aggregation and dispersion mechanisms in the area and showed that these processes were significantly correlated to atmospheric forcing processes over the NW Mediterranean Sea. Interannual variations in average summer air temperature can reduce the intensity of ocean mesoscale processes in the Balearic area and thus potentially affect bluefin tuna larvae. These modelling approaches can increase understanding of bluefin tuna recruitment processes and eventually contribute to management of bluefin tuna fisheries.

Sovereignty and cooperation in regional Pacific tuna fisheries management: Politics, economics, conservation and the vessel day scheme

The Pacific islands region has developed a collaborative approach to fisheries management that has set global precedents in regional fisheries co-operation and significantly boosted Islanders’ capacity to manage the region’s tuna fisheries in a manner consistent with their individual national interests. Through this cooperation, the Pacific islands states have developed a collective influence in fisheries negotiations that is arguably far greater and more effective than what they could achieve individually. During 2007–2009, the Pacific islands region further developed its collective approach by establishing new initiatives in regional fisheries cooperation that are of global interest. Chief among these is the Vessel Day Scheme, which introduces a flexible and potentially tradeable permit scheme into regional management, and a supporting set of zonal based management measures. This paper examines the evolution and development of these recent management initiatives and provides a tentative evaluation of these against the conservation and management agreements entered into by the Pacific islands.

A collective approach to Pacific islands fisheries management: Moving beyond regional agreements

The sustainable management and profitable development of the Pacific island tuna fisheries is the key ocean governance challenge for the Pacific islands region in the short and medium term. Resolving these challenges is fundamental to the long term future of the region and its ability to implement oceans governance across all resource and conservation concerns. This paper identifies some key implementation challenges facing Pacific island States at the domestic level and discusses further developments in sub-regional approaches to collective management that could significantly boost the national capacity of Pacific islands States to effectively implement their coastal State obligations and sustainably manage their oceanic resources.

Associations between seabirds and subsurface predators around Oahu, Hawaii

Many species of tropical seabirds rely on subsurface predators such as tuna and dol- phins to drive prey close to the ocean's surface. We observed seabird foraging events from fishing vessels around the island of Oahu, Hawaii, to determine the prevalence and relative importance of different subsurface predators to seabird foraging. Sixty-nine seabird foraging events were observed, in 62 of which the presence and/or identity of subsurface predators could be determined. Of those 62, all but two involved subsurface predators and accounted for 99.8% of all foraging birds. Skipjack tuna Katsuwonus pelamis were the predominant (81%) subsurface predator involved in seabird feed- ing events, with odontocetes Stenella attenuata and Pseudorca crassidens (8%), mahimahi Coryphaena hippurus (6%), and yellowfin tuna Thunnus albacares (2%) being less common. Wedge- tailed shearwaters Puffinus pacificus and brown noddies Anous stolidus foraged in association with tuna schools more often than would be expected by chance alone. Red-footed boobies Sula sula, in contrast, did not associate with any subsurface predator in greater proportion than what would be expected by chance. Nine additional seabird species were observed foraging in association with sub- surface predators, but not in numbers large enough for statistical analysis. This study highlights the value of regional investigations able to uncover the variable nature of seabird-subsurface-predator associations. The finding that, in Hawaii, at least 2 species of seabirds showed tight dependence on tuna underlines the need for tuna fishery management to address the potential indirect ecological effects of fishing.

Using multi-sensor satellite remote sensing and catch data to detect ocean hot spots for albacore (Thunnus alalunga) in the northwestern North Pacific

Abstract To understand better and describe oceanic hot spots for albacore ( Thunnus alalunga ), we linked remotely sensed data from multi-sensor satellite images of TRMM/TMI sea-surface temperature (SST), SeaWiFS chlorophyll- a concentration and photosynthetically active radiation (PAR), and AVISO mean sea-level anomaly (MSLA) with fisheries catch data from 1998 to 2003. A probability map was generated based on biophysical environmental variables (SST and chlorophyll- a ) in relation to the catch data. The probability of environmental variables was combined with an eddy kinetic energy (EKE) map to describe the oceanographic features around fishing locations. Primary production was examined to assess the productivity of the fishing grounds and was calculated from chlorophyll- a , SST and PAR using the vertically generalized production model (VGPM). Results indicate that the greatest catches occurred mainly in November, and the catches were highest at warm SSTs (19.78±1.69°C) and relatively high chlorophyll- a concentrations (0.31±0.13 mg m −3 ). Highest catches occurred in areas where primary production rates ranged from 15.65 to 20.61 g C m −2 month −1 (18.12±4.98 g C m −2 month −1 ). Our analysis found that catch per unit efforts (CPUEs) tended to increase significantly in areas of increasing probability of environmental variables ( P Regions of high tuna abundance occurred in relatively high EKE and geostrophic currents, reflecting that tuna aggregations were associated with anticyclonic eddies. These eddies may trap and then concentrate albacore prey transported by the Kuroshio Extension and the Oyashio intrusion near the Shatsky Rise area, hence producing productive tuna fishing grounds. The eddy fields were areas of high catch probability. These findings suggest that the ocean hot spots for albacore are linked to hydrographic features, frontal zones and eddy fields, which influence distribution pattern and formation of tuna abundance. Our analysis provide an illustration on how multi-sensor satellite remote sensing can aid in detecting and visualizing pelagic hot spots. These results can lead to improved habitat protection and tuna fishery management.

Cultural Consensus Analysis and Environmental Anthropology: Yellowfin Tuna Fishery Management in Hawaii

Natural resource policies in the United States are implemented with a social technology of objectivity. Accordingly, resource managers rely on scientific and quantitative analyses to satisfy constituencies distrustful of regulatory authorities. Cultural consensus analysis is a powerful method for determining whether knowledge domains are structured in ways that support a conclusion that cultural members recognize certain cultural truths not known before-hand to the investigator. The authors compare hand-line fishermen and fishery scientists in Hawaii regarding their knowledge about stock structure, fish movements, resource abundance, stock condition, and fishery interactions. Yellow fin tuna fishery results show that fishermen and scientists exhibit an overall consensus about ecological knowledge, although they disagree in some areas. Some practical advantages of consensus analysis are discussed along with the possibilities for growth in the fishery social science sector, cross-cultural applied research, and the practice of environmental anthropology.

Tuna Fisheries Management in the Western and Central Pacific Ocean: A Critical Analysis of the Convention for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean and Its Implications for the Pacific Island States plus Appendix

Tuna Fisheries Management in the Western and Central Pacific Ocean: A Critical Analysis of the Convention for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean and Its Implications for the Pacific Island States plus Appendix