Last updated on 14 January 2016

SUMMARY

SUMMARY

IDENTIFICATION

SCIENTIFIC NAME(s)

Thunnus obesus

SPECIES NAME(s)

Bigeye tuna

Bigeye tuna of the Indian Ocean constitutes a single panmictic population (Chiang et a., 2008) and the stock is assessed by the Indian Ocean Tuna Commission (IOTC) considering this unit (IOTC, 2014).


ANALYSIS

Strengths

The population of bigeye tuna in the Indian Ocean is considered healthy and fishing mortality rates are sustainable. Assessments are conducted by the Indian Ocean Tuna Commission. Discarding of tropical (bigeye, skipjack, yellowfin) tunas is prohibited in purse seine fisheries. Fishing pressure (longline and purse seine) has been lowered since 2007. There are interim target and limit reference points in place and the IOTC is working towards a harvest control rule.

Weaknesses

The fishery is not regulated by TAC or catch limits. Illegal, Unreported, and Unregulated (IUU) fishing has been a major issue. Observer coverage rates are very low. Interactions with protected, endangered and threatened species along with sharks occur. There are issues with data reporting. Specifically, industrial longline fisheries from India, pole and line artisanal fisheries from the Maldives, gillnet fisheries from Iran (before 2012) and Pakistan, from gillnet and longline fisheries from Sri Lanka and artisanal fisheries from Indonesia, Comoros (before 2011) and Madagascar.

FISHSOURCE SCORES

Management Quality:

Management Strategy:

≥ 6

Managers Compliance:

≥ 6

Fishers Compliance:

≥ 6

Stock Health:

Current
Health:

9.2

Future Health:

9


RECOMMENDATIONS

RETAILERS & SUPPLY CHAIN
  • Work with IOTC Members and Cooperating Non-Contracting Parties to:
    • Develop and implement comprehensive, precautionary harvest strategies with specific timelines for all tuna stocks, including the adoption and implementation of limit and target reference points, harvest control rules, monitoring strategies, operational objectives, performance indicators, and management strategy evaluation.
    • Strengthen compliance processes and make information on non-compliance public and continue to provide evidence of compliance with all IOTC Conservation and Management Measures in a timely manner.
    • Implement a 100% observer coverage requirement for at-sea transshipment activities, as well as other measures that ensure transshipment activity is transparent and well-managed, and that all required data are collected and transmitted to the appropriate bodies in a timely manner.
    • Increase compliance with the mandatory minimum 5% longline observer coverage rates by identifying and correcting non-compliance.
    • Implement a 100% observer coverage requirement – human and/or electronic – within five years for longline fisheries.  Adopt a 100% observer coverage requirement for purse seine vessels where it is not already required and require the use of the best-available observer safety equipment, communications and procedures.
    • Adopt effective measures for the use of non-entangling FAD designs as a precautionary measure to minimize the entanglement of sharks and other non-target species, and support research on biodegradable materials and transition to their use to mitigate marine debris.
    • More effectively implement, and ensure compliance with, existing RFMO bycatch requirements and take additional mitigation action, such as improving monitoring at sea, collecting and sharing operational-level, species-specific data, and adopting stronger compliance measures, including consequences for non-compliance for all gear types.
  • Ensure all products are traceable back to legal sources. Verify source information and full chain traceability through traceability desk audits or third party traceability certification. For fisheries without robust traceability systems in place, invest in meaningful improvements to bring the fisheries and supply chain in compliance with best practices.

FIPS

  • Indian Ocean tuna - purse seine (SIOTI):

    Stage 3, Progress Rating C

CERTIFICATIONS

No related MSC fisheries

Fisheries

Within FishSource, the term "fishery" is used to indicate each unique combination of a flag country with a fishing gear, operating within a particular management unit, upon a resource. That resource may have a known biological stock structure and/or may be assessed at another level for practical or jurisdictional reasons. A fishery is the finest scale of resolution captured in FishSource profiles, as it is generally the scale at which sustainability can most fairly and practically be evaluated.

ASSESSMENT UNIT MANAGEMENT UNIT FLAG COUNTRY FISHING GEAR
Indian Ocean IOTC China Longlines
France Associated purse seining
Unassociated purse seining
Indonesia Longlines
Purse seines
Unassociated purse seining
Italy Associated purse seining
Unassociated purse seining
Maldives Longlines
Pole-lines hand operated
Mauritius Purse seines
Unassociated purse seining
Seychelles Associated purse seining
Unassociated purse seining
South Africa Longlines
Spain Purse seines
Unassociated purse seining
Sri Lanka Drifting longlines
Gillnets and entangling nets
Thailand Mechanized lines

Analysis

OVERVIEW

Last updated on 20 November 2014

Strengths

The population of bigeye tuna in the Indian Ocean is considered healthy and fishing mortality rates are sustainable. Assessments are conducted by the Indian Ocean Tuna Commission. Discarding of tropical (bigeye, skipjack, yellowfin) tunas is prohibited in purse seine fisheries. Fishing pressure (longline and purse seine) has been lowered since 2007. There are interim target and limit reference points in place and the IOTC is working towards a harvest control rule.

Weaknesses

The fishery is not regulated by TAC or catch limits. Illegal, Unreported, and Unregulated (IUU) fishing has been a major issue. Observer coverage rates are very low. Interactions with protected, endangered and threatened species along with sharks occur. There are issues with data reporting. Specifically, industrial longline fisheries from India, pole and line artisanal fisheries from the Maldives, gillnet fisheries from Iran (before 2012) and Pakistan, from gillnet and longline fisheries from Sri Lanka and artisanal fisheries from Indonesia, Comoros (before 2011) and Madagascar.

RECOMMENDATIONS

Last updated on 7 August 2018

Recommendations to Retailers & Supply Chain
  • Work with IOTC Members and Cooperating Non-Contracting Parties to:
    • Develop and implement comprehensive, precautionary harvest strategies with specific timelines for all tuna stocks, including the adoption and implementation of limit and target reference points, harvest control rules, monitoring strategies, operational objectives, performance indicators, and management strategy evaluation.
    • Strengthen compliance processes and make information on non-compliance public and continue to provide evidence of compliance with all IOTC Conservation and Management Measures in a timely manner.
    • Implement a 100% observer coverage requirement for at-sea transshipment activities, as well as other measures that ensure transshipment activity is transparent and well-managed, and that all required data are collected and transmitted to the appropriate bodies in a timely manner.
    • Increase compliance with the mandatory minimum 5% longline observer coverage rates by identifying and correcting non-compliance.
    • Implement a 100% observer coverage requirement – human and/or electronic – within five years for longline fisheries.  Adopt a 100% observer coverage requirement for purse seine vessels where it is not already required and require the use of the best-available observer safety equipment, communications and procedures.
    • Adopt effective measures for the use of non-entangling FAD designs as a precautionary measure to minimize the entanglement of sharks and other non-target species, and support research on biodegradable materials and transition to their use to mitigate marine debris.
    • More effectively implement, and ensure compliance with, existing RFMO bycatch requirements and take additional mitigation action, such as improving monitoring at sea, collecting and sharing operational-level, species-specific data, and adopting stronger compliance measures, including consequences for non-compliance for all gear types.
  • Ensure all products are traceable back to legal sources. Verify source information and full chain traceability through traceability desk audits or third party traceability certification. For fisheries without robust traceability systems in place, invest in meaningful improvements to bring the fisheries and supply chain in compliance with best practices.

1.STOCK STATUS

STOCK ASSESSMENT

Last updated on 16 January 2018

Bigeye tuna in the Indian Ocean were last assessed in 2016. Six different models were used at that time to determine the status of bigeye tuna. These included age structured and surplus production models, ASAP, BDM, ASPIC, SCAA, BSPM and SS3). The results of the SS3 model were used to determine the status of the stock and management advice. Catch data from 1974 onward were used in this assessment (IOTC 2016). 

SCIENTIFIC ADVICE

Last updated on 16 January 2018

The Indian Ocean Tuna Commission’s Scientific Committee suggested, based on the results of the 2016 assessment, that if catches of bigeye tuna are maintained below maximum sustainable yield (MSY) levels, immediate management measures are not needed (IOTC 2016).

Reference Points

Last updated on 16 Jan 2018

ParameterValue
F2015/FMSY0.76 (0.49-1.03)
SB2015/SBMSY1.29 (1.07-1.51)
SB2015/SB19500.38
MSY104,000 t (87,000-121,000 t)

**Target reference points are provisional (IOTC 2016)

CURRENT STATUS

Last updated on 16 January 2018

The 2016 stock assessment of bigeye tuna in the Indian Ocean indicates the population is not overfished or undergoing overfishing (IOTC 2016).

Trends

Last updated on 16 Jan 2018

The location of the fishery has changed little since 1990, bigeye tuna is fished throughout the Indian Ocean, with the majority of the catch being taken in western equatorial waters. However, during the last two years, the fishery has been moving far off the coast of Somalia due to active piracy in the area (IOTC 2009a).

Total catch of bigeye by longliners in the Indian Ocean increased steadily from the 1950’s to reaching 100,000 t in 1993 and around 140,000–150,000 t for a short period from 1997-1999. Longline effort has been declining since 2007. The average annual catch by longliners for the period from 2009-2013 was 105,924 t and total catches in 2013 were 109,343 t. Currently the top fleets catching bigeye tuna in the Indian Ocean are Indonesia followed by Taiwa and the Seychelles.

Abundance indices are available from Japan, Taiwan and Spain. A general decreasing trend in abundance is apparent from the mid to late 1990’s through 2008. This trend increased through 2012 but decreased again in 2013 (IOTC 2014).

2.MANAGEMENT QUALITY

MANAGEMENT

Last updated on 17 September 2018

The Indian Ocean Tuna Commission (IOTC) is an intergovernmental organization mandated to manage tuna and tuna-like species in the Indian Ocean and adjacent seas. Its objective is to promote cooperation among its Members with a view to ensuring, through appropriate management, the conservation and optimum utilization of stocks and encouraging sustainable development of fisheries based on such stocks. Members of IOTC include Australia, Belize, China, Comoros, Eritrea, European Community, France, Guinea, India, Indonesia, Republic Islamic of Iran, Japan, Kenya, Republic of Korea, Madagascar, Malaysia, Mauritius, Sultanate of Oman, Pakistan, Philippines, Seychelles, Sierra Leone, Sri Lanka, Sudan, Tanzania, Thailand, United Kingdom, and Vanuatu. The Cooperating Non-Contracting Parties are Senegal, South Africa and Uruguay.

Management measures in place include: required reporting and recording of catches and effort, and providing a record of active fishing vessels. There are interim limit and target reference point s in place and work is being made towards a decision framework tool (IOTC 2015). Discarding of tunas is prohibited by purse seine vessels (IOTC 2017).

Recovery Plans

Bigeye tuna populations are healthy in the Indian Ocean and sustainably fished, so no recovery plan is needed.

COMPLIANCE

Last updated on 16 January 2015

There is no TAC or catch limit set for this fishery in Indian Ocean. Therefore, the compliance cannot be measured. Catches have been decreasing in recent years and catches are below maximum sustainable yield (MSY) levels (IOTC 2014).

However, IUU fishing in the Indian Ocean has been a major issue, which includes a range of illicit activities: fishing without permission or out of season; harvesting prohibited species; using outlawed types of fishing gear; disregarding catch quotas; or non-reporting or under-reporting catch weights. Of particular concern are the western Indian Ocean and the maritime areas along the coast of eastern Africa. There, fishing vessels of various flags have taken advantage of the absence in coastal countries of strong enforcement mechanisms (FAO 2007). The Commission has regularly been also establishing a list of vessels presumed to have carried out illegal, unregulated and unreported fishing in the IOTC area.

There have been compliance issues with some countries regarding accurate reporting of catch and effort data. Notably, there is uncertainty surrounding catches from the pole and line fishery in the Maldives, the Iranian and Pakistan gillnet fisheries, gillnet and longline combination fisheries of Sri Lanka and from Indonesian, Comoros and Madagascar artisinal fisheries. In terms of catch and effort data, data is not available from fresh-tuna longline fisheries of Indonesia or from the Taiwanese longline fishery (since 2006). Catch and effort data is also uncertain from the Iranian purse seine fleet, and Indian, Indonesian, Malaysian, Oman and Philippines longline fleets (IOTC 2014).

3.ENVIRONMENT AND BIODIVERSITY

BYCATCH
ETP Species

Last updated on 16 January 2015

Longlines incidentally capture vulnerable species including sea birds and sea turtles. Bycatch of seabirds, sea turtles, marine mammals and sharks in pelagic longline tuna fisheries threatens some populations with extinction. Purse seines can also incidentally capture sea turtles. The Indian Ocean Tuna Commission (IOTC) has implemented several management measures addressing these incidental captures.

Regarding sea birds, a 2010 resolution, superseding previous measures, requires, when south of 25oS, use of at least two seabird mitigation methods selected from two lists of nine alternatives (IOTC, 2010b).

A 2009 resolution requires member countries to report data on sea turtle interactions and for vessels to follow sea turtles handling and release guidelines and posses and use specified turtle release equipment (IOTC, 2009c). Purse seine vessels are not allowed to encircle sea turtles while setting their nets (IOTC 2013).

There are extremely low bycatch levels in pole-and-line fisheries, where bycatch that does occur generally consists of juvenile kawakawa tuna (Euthynnus affinis_), frigate mackerel (Auxis rochei_), mahimahi (Coryphaena hippurus), and rainbow runner (Elagatis bupinnulata).Discards are believed to have high post release survival rates due to the use of barbless hooks and flick-off practices (FAO, 1997).However, concern over bycatch of reef fish and juvenile classes of target species in baitfish fisheries that supply live bait to pole-and-line fisheries has been raised, as have other ecological issues (ecosystem effects of removal of baitfish species, overexploitation of target baitfish species, habitat degradation) and socioeconomic issues (food security impacts with coastal communities) (FAO, 2008; Gillett, 2010).

Other Species

Last updated on 16 January 2015

Large bigeye tuna (averaging just above 40 kg) are primarily caught by longlines, and in particular deep longliners. Since the mid 1980’s, bigeye tuna has been caught by purse seine vessels fishing on tunas aggregated on floating objects. Purse seiners mainly take small juvenile bigeye (averaging around 5 kg) whereas longliners catch much larger and heavier fish; and while purse seiners take much lower tonnages of bigeye compared to longliners, they take larger numbers of individual fish (IOTC 2009a).

Retained catches in bigeye tuna fishery are well known for the major fleets ; but are less certain for non-reporting industrial purse seiners and longliners (NEI) and for other industrial fisheries. Discard levels are believed to be low although they are unknown for most industrial fisheries. Discard levels were estimated for the purse-seine fishery for the period 2003-2008(IOTC 2009b).

Preliminary quantitative estimates of the main bycatch species and species groups (billfishes, sharks, rays and fin fishes) were made for the whole purse seine fishery since 2003. Data are from the French and Spanish observer programs from 2003 to 2007, representing a total of 1958 observed sets (4% of the total number of sets during this period). Annual raising factors by fishing mode based on tuna production (tons per 1000 tons of tuna landed) were estimated for each species group from logbooks and observer information stratified by quarter, fishing area and fishing mode. According to these estimations, total bycatch was estimated at 9,585 t, corresponding to 35.5 t bycatch per 1000t of tuna landed. Tuna discards represents 54% of the total amount, followed by other fin fish (34%), sharks (10%), billfishes (1.5%) and rays (0.7%) (IOTC 2009d).

These mean ratios were applied to the whole purse seine fishery annual catches from 2003 to 2008 to compute total bycatches by species groups, and then distributed within the groups according to the proportion in weight of the main species or families. The bulk of the bycatch consisted of tuna discards (average annual catch 6,700t; range 5,100-8,300t). The annual bycatch of all other groups averaged some 4,000t (range 2,750-4,400t). Of this the majority was made up of “fin fishes”, with an annual mean catch close to 2,500t (range 1550-2,800t). The main species was rainbow runner (Elagatis bipinnulatus , 37% of the total), followed by triggerfishes (Balistidae, 24%), dolphinfishes (Coryphaena spp. , 11%) and carangids (Carangidae, 7%), with the balance (21%) being made up of some 50 other species. Most were caught under FADs (95%). Fin fish species composition between FAD and log schools was rather similar, although there were more dolphinfishes on FADs, and the greatest diversity was from free schools. The next most important bycatch group was “sharks”, with a total average annual catch close to 1,300t (range 1,000-1,650t). Shark bycatch was dominated by carcharhinids, the most important being the silky shark (Carcharhinus falciformis , 79%) followed by the oceanic whitetip shark (C. longimanus, 11%). 97% of sharks were caught on FADs. Shark species composition was quite similar between FAD and free schools sets.“Billfish” bycatch was relatively low, with an average annual catch of 180t (range 140-210t). The most important species were marlins (70%, mainly M. indica and T. audax ) and sailfishes (27%). Most billfishes (72%) were caught on FADs. Billfish species composition was quite similar between FAD and log sets. “Rays” were caught in smaller quantities, with an average annual catch of 50t (range 40-70t). 65% of rays were caught on FADs. The most important species group was the Mobulidae (42%), followed by the giant manta (Manta birostris , 37%) and other and unidentified rays (20%). Ray species composition is rather similar between FAD and free schools, but with a larger diversity on free schools. Overall, discards by the purse seine fishery (excluding tuna discards) remains relatively low when compared to many other fisheries, with the large majority coming from FAD sets (IOTC 2009d).

The Indian Ocean Tuna Commission (IOTC) has adopted several regulations to address the incidental capture of sharks. A 2005 resolution requires: (i) annual reporting of data on shark catches; (ii) keep all parts of retained sharks, excluding head, guts and skins, to the point of first landing; (iii) have onboard fins that total < 5% of the weight of sharks onboard, up to the first point of landing, or otherwise ensure compliance with the 5% rule through certification, observer monitoring or other method (IOTC, 2005).IOTC (2010c) prohibits the retention, transshipment or landing of all species of thresher sharks, intended to address concerns over the status of the bigeye thresher shark (Aliopias superciliosus_), but applicable to all thresher species due to the difficulty in differentiating between bigeye and other thresher species.A prohibition on the retention of oceanic whitetip sharks (_Carcharhinus longimanus) has also been implemented by the IOTC. In addition, countries are to develop a National Plan of Action for Sharks, although few have done so to date {IOTC 2013}.

HABITAT

Last updated on 5 February 2010

The research has not found any study on the impact of habitat caused by bigeye tuna fishery in Indian Ocean yet. However, study by Chuenpagdeel, et al (2003) suggested that purse seine, longline – pelagic and gillnet – mid water have low impact to the habitat.

Marine Reserves

Last updated on 05 Feb 2010

Given the highly migratory nature of tuna that is particularly highlighted in the Indian Ocean by the results of the IOTC tagging project, MPAs, to be an effective tool for management, have to cover large areas. Some authors consider this would require closing half of the area of distribution of the species.Alternatively, targeted MPAs can be designed with the aim of protecting spawning aggregations, known concentration of protected, endangered or threatened (PET) species or diversity hotspots. In the case of tunas, closure of feeding area or spawning and nursery area might be useful but they would need to be extensive (IOTC 2009b).

The SC recommended that IOTC should actively engaged with research initiatives on MPAs. This issue is now common at a global scale amongst various management bodies and research institutions. Furthermore, the SC noted that the context for pelagic MPAs is very different than that of coastal MPAs and requires further research. The SC was also informed that several research projects dealing with MPA are underway through European or French funding in the Indian Ocean and outcomes of those projects will contribute to a better understanding of the dynamics of PET or tuna species with respect to area closures(IOTC 2009b).

FishSource Scores

Last updated on 17 September 2018

MANAGEMENT QUALITY

As calculated for 2015 data.

The score is ≥ 6.

There are interim target and limit reference points and the IOTC is working on developing a harvest control rule.

As calculated for 2015 data.

The score is ≥ 6.

Managers do not limit catches through TACs and there are no other management measures specific to bigeye tuna. However, their populations are healthy.

As calculated for 2015 data.

The score is ≥ 6.

There is no TAC in place.

STOCK HEALTH:

As calculated for 2015 data.

The score is 9.2.

This measures the Ratio SSB/SSBmsy as a percentage of the SSB=SSBmsy.

The Ratio SSB/SSBmsy is 1.29 . The SSB=SSBmsy is 1.00 .

The underlying Ratio SSB/SSBmsy/SSB=SSBmsy for this index is 129%.

As calculated for 2015 data.

The score is 9.0.

This measures the Ratio F/Fmsy as a percentage of the F management target.

The Ratio F/Fmsy is 0.760 . The F management target is 1.00 .

The underlying Ratio F/Fmsy/F management target for this index is 76.0%.

To see data for biomass, please view this site on a desktop.
To see data for catch and tac, please view this site on a desktop.
To see data for fishing mortality, please view this site on a desktop.
No data available for recruitment
No data available for recruitment
To see data for management quality, please view this site on a desktop.
To see data for stock status, please view this site on a desktop.
DATA NOTES
The F and SSB series shown are actually F/Fmsy and SSB/SSBmsy. We are aware of no advised or set quotas/TAC thus qualitative scores have been assigned for 1, 2 and 3. The advised TAC is the current catch level {IOTC 2014}.

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Fishery Improvement Projects (FIPs)

SELECT FIP

Access FIP Public Report

Progress Rating: C
Evaluation Start Date: 6 Mar 2017
Type: Comprehensive

Comments:

FIP has stage 3 achievements within 12 months. FIP rating remains C

1.
FIP Development
Aug 16
2.
FIP Launch
Oct 16
Mar 17
3.
FIP Implementation
Apr 18
4.
Improvements in Fishing Practices and Fishery Management
Verifiable improvement in policy/management and fishing practices
5.
Improvements on the Water
Verifiable improvement on the water
6.
MSC certification (optional)
MSC certificate made public

Certifications

Marine Stewardship Council (MSC)

No related MSC certifications

Sources

Credits

Chiang, H., Hsu, C., Wu, G. C., Chang, S., Yang, H. 2008. Short communication Population structure of bigeye tuna (Thunnus obesus) in the Indian Ocean inferred from mitochondrial DNA, Fisheries Research 90: 305–312 http://www.researchgate.net/profile/Shui-Kai_Chang/publication/222829241_Population_structure_of_bigeye_tuna_(Thunnus_obesus)_in_the_Indian_Ocean_inferred_from_mitochondrial_DNA/links/0c9605255086a397ea000000.pdf

IOTC. 2005. Resolution 05/05 Concerning the Conservation of Sharks Caught in Association with Fisheries Managed by IOTC. Indian Ocean Tuna Commission, Mahé, Seychelles.

IOTC. 2009c. Resolution 09/06 on Marine Turtles. Indian Ocean Tuna Commission, Mahé, Seychelles

IOTC. 2010b. Resolution 10/06 on Reducing the Incidental Bycatch of Seabirds in Longline Fisheries. Indian Ocean Tuna Commission, Mahé, Seychelles.

IOTC. 2010c. Resolution 10/12 on the Conservation of Thresher Sharks (Family Alopiidae) Caught in Association with Fisheries in the IOTC Area of Competence. Indian Ocean Tuna Commission, Mahé, Seychelles.

IOTC. 2010d. Recommendation 10/13 on the Implementation of a Ban on Discards of Skipjack Tuna, Yellow Fin Tuna, Bigeye Tuna and Non Targeted Species Caught by Purse Seiners. Indian Ocean Tuna Commission, Mahé, Seychelles.

IOTC. 2011. Report of the Thirteenth Session of the IOTC Working Party on Tropical Tunas, Indian Ocean Tuna Commission, Maldives, 16-23 October, 2011, 94 pp.

IOTC. 2013. Compendium of active [and pending] conservation and management measures for the Indian Ocean Tuna Commission. Indian Ocean Tuna Commission.

IOTC, 2014. Status of the Indian Ocean bigeye (BET: Thunnus obesus) resource. IOTC-2014-SC17-ES02.

IOTC, 2016. Status of the Indian Ocean bigeye (BET: Thunnus obesus) resource. IOTC-2016-SC19-ES02.

References

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