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The IOTC Secretariat is pleased to have published the annual STOCK STATUS DASHBOARD for tuna and tuna-like species under the IOTC mandate, as well as other species impacted by IOTC fisheries. The dashboard provides a semi-interactive means of accessing key pieces of information which the IOTC Scientific Committee and its Working Parties, have used to determine the status of the 16 IOTC species, as well as a number of shark and other species which are known to be caught or otherwise interact with fleets fishing for IOTC species.
The dashboard, which is accessible via the weblink below, provides an initial interface with a colour coded stock status in relation to the Commission’s default target reference points, as well as links to the complete Executive Summary for each species or species group.
Of the 16 IOTC species (excluding southern bluefin tuna which is managed by CCSBT: see www.ccsbt.org), the following four stocks are currently considered to be overfished, subject to overfishing, or both:
The following key points will be considered by the Commission in 2015 for each species/stock, with the aim of determining if management action needs to be undertaken and in what form:
Black marlin: This is the second time that the IOTC Working Party on Billfish (WPB) has applied a Stock Reduction Analysis technique to black marlin and further testing of how sensitive this technique is to model assumptions and available time series of catches needs to be undertaken. However, the WPB considered that the assessment is the best information currently available and as such, should be used to determine stock status, with the intention that alternative techniques be applied in 2015 to validate the results. The following key points should be noted:
• Maximum Sustainable Yield (MSY): estimate for the whole Indian Ocean is between 7,600 and 13,800 t.
• Provisional reference points: Although the Commission adopted interim reference points for swordfish in Resolution 13/10 on interim target and limit reference points and a decision framework, no such interim reference points have yet been established for black marlin.
• Main fishing gear (2010–13): gillnet catches are currently estimated to comprise approximately 62% of the total estimated black marlin catch in the Indian Ocean.
• Main fleets (2010–13): Sri Lanka: 26 %; I.R. Iran: 20%; India: 18%.
Blue marlin: No new assessment was undertaken in 2014. Thus, stock status is based on the previous assessment undertaken in 2013, as well as indicators available in 2014. In 2013, a Surplus Production Model (ASPIC) stock assessment confirmed the preliminary assessment results from 2012 that indicated the stock is currently being exploited near maximum levels and that the stock is at the optimal biomass level. Two other approaches examined in 2013 came to similar conclusions, namely a Bayesian State Space model, and a data poor stock assessment method: Stock Reduction Analysis using only catch data. Total reported landings increased substantially in 2012 to 17,252 t, well above the MSY estimate of 11,690 t. In 2013 reported catches declined slightly to 13,843 t, still above the MSY level. Given the sharp increase in reported catches over the last two years, that are well above the MSY level, the stock is likely to have moved to a state of being subject to overfishing. The following key points should be noted:
• Maximum Sustainable Yield (MSY): estimate for the whole Indian Ocean is between 8,023–12,400 t, and catches should not exceed the upper estimate.
• Provisional reference points: Although the Commission adopted interim reference points for swordfish in Resolution 13/10 on interim target and limit reference points and a decision framework, no such interim points have yet been established for blue marlin.
• Main fishing gear (2010–13): Longline and gillnet catches are currently estimated to comprise approximately 69% and 29% of the total estimated blue marlin catch in the Indian Ocean, respectively.
• Main fleets (2010–13): Taiwan,China: 35%; Indonesia: 24%; Pakistan: 15%.
Striped marlin: No new assessment was undertaken in 2014. Thus, stock status is based on the previous assessment undertaken in 2013, as well as indicators available in 2014. In 2013 a Surplus Production Model (ASPIC) stock assessment confirmed the preliminary assessment results from 2012 that indicated the stock is currently subject to overfishing and that biomass is below the level which would produce MSY. Two other approaches examined in 2013 came to similar conclusions, namely a Bayesian State Space model, and a Stock Reduction Analysis using only catch data. The ASPIC model indicated that the stock has been subject to overfishing for some years, and that as a result, the stock biomass is well below the BMSY level and shows little signs of rebuilding despite the declining effort trend. In 2013 reported catches declined to 4,429 t, still above the MSY level. The following key points should be noted:
• Maximum Sustainable Yield (MSY): estimate for the whole Indian Ocean is 4,408 t (3,539–4,578). However, the biomass is well below the BMSY reference point and fishing mortality is in excess of FMSY at recent catch levels, of around 2,500 t. Catches should be reduced to below 2,500 t.
• Provisional reference points: Although the Commission adopted interim reference points for swordfish in Resolution 13/10 on interim target and limit reference points and a decision framework, no such interim points have yet been established for striped marlin.
• Main fishing gear (2013): Longline and gillnet catches are currently estimated to comprise approximately 73% and 19% of the total estimated striped marlin catch in the Indian Ocean, respectively.
• Main fleets: Taiwan,China: 32%; Indonesia: 26%; Pakistan: 9%; I.R. Iran: 8%.
Longtail tuna: Stock Reduction Analysis techniques indicate that the stock is being exploited at a rate that exceed FMSY in recent years. Whether a four quadrant stock structure of catches in the Indian Ocean or a one stock assumption is used in the analysis, the conclusions remain the same. Another analysis conducted on the northwest Indian Ocean with a Surplus Production Model (ASPIC) also indicates that the stock is subject to overfishing. More traditional methods of stock assessment need to be conducted by developing indices of abundance using catch and effort series from I.R. Iran and Indonesia. The following should be noted:
• Maximum Sustainable Yield (MSY): estimate of 120,000 t is likely being exceeded in recent years.
• Provisional reference points: The Commission has not adopted limit reference points for any of the neritic tunas under its mandate.
• Main fishing gear (2012): Gillnet catches are currently estimated to comprise approximately 69% of the total estimated longtail tuna catch in the Indian Ocean, with purse seine and other line gears taking 13.6% and 12.6% respectively.
• Main fleets (2010–12): I.R. Iran: 47%; Indonesia: 15%; Malaysia: 9%; Pakistan: 9%; Oman: 7%; India: 7%.
For further information please contact the IOTC Secretariat: [email protected] or [email protected]