One of the key actions in the implementation of the RPOA-Neritic Tunas is to improve the regional cooperation in which it aims to develop/improve sub-regional action plans for neritic tuna fisheries, the assessment of the status and trends of neritic tuna at sub - regional level. The meeting reviewed the update status and trends of Neritic tuna fisheries in the Southeast Asian region, in particular the status of the longtail tuna, the establishment of the term of reference (TOR) for the long-term establishment of the working group in which the member states agreed to support its implementation after the end of the project. The Assembly also discussed the work plan for data improvement, requirement of the capacity building.
The 2nd meeting of the Scientific Working Group on Stock Assessment of Neritic Tunas in Southeast Asian Waters (SWG-Neritic Tunas) was convened in cooperation with the Vietnam Directorate of Fisheries (D-Fish) at the Marine Fisheries Research Institute ( RIMF), Hai Phong, Vietnam from 15 to 17 June 2015. The meeting also discussed the prioritization of capacity building programmes, particularly on Stock Assessment to support effective future management of the neritic tuna fishery, which is consistent with the implementation of the approved RPOA-Neritic Tunat. In addition, the Secretariat in collaboration with MFRDMD also conducted Special Training/Workshop on LOT-KAW Stock Evaluation using specific software such as CPUE standardization, A Stock-Production Model incorporating Covariates (ASPIC)-ver.5, Kobe I ( Kobe plot) and Kobe II (Risk Assessment) and other related software.
The training/workshop could provide some recommendations that would be useful for further assessment of LOT and KAW stocks in the Southeast Asian region. In this document we report the results of our work, including CPUE standardization, stock assessments by ASPIC and Kobe plots, which also demonstrates our training and workshop progress.
Results
KAWAKAWA STOCK ASSESSMENT IN THE SOUTHEAST ASIAN WATERS (INDIAN OCEAN SIDE)
IOTC(FAO) IOTC(FAO) IOTC(FAO) FAO+data coordinator. 2) Nominal CPUE and connection to capture. Although the Kawakawa stock on the Indian Ocean side is in a safe state, it is recommended that fishing pressure and catch should not exceed the 2014 level because 53% of the uncertainty around the 2014 point is 53% (red, orange and yellow area in the Kobe Plot), while 47% is in the safe zone (green).
KAWAKAWA STOCK ASSESSMENT IN THE SOUTHEAST ASIAN WATERS (PACIFIC OCEAN SIDE)
This is because there has been a significant decline in catch after 2002 (the peak level) and the current catch level is low. In addition, the Kobe plot shows that there is no probability that the uncertainties in the 2013 estimates fall into the uncertain zone (the red, orange, and yellow areas in the Kobe plot). Thus, there are no problems to maintain current levels of catch and F (fishing pressure), but both catch and F (fishing pressure) must be kept below their MSY levels (185,000 tonnes and 0.43 respectively).
LONGTAIL TUNA STOCK ASSESSMENT IN THE SOUTHEAST ASIAN WATERS (INDIAN OCEAN STOCK)
In the first attempt with the standardized CPUE, we could not obtain the convergence even if we adjusted some parameters. However, the chance of uncertainties in the unsafe zone (red, orange and yellow) of the 2014 point is very high: 78%.
LONGTAIL TUNA STOCK ASSESSMENT IN THE SOUTHEAST ASIAN WATERS (PACIFIC OCEAN STOCK)
27 Relationship between Longtail tuna catch and nominal CPUE (Southeast Asian Pacific Waters). This is the reason why the stock status is very safe and the probability of uncertainties in the unsafe zone (red, orange and yellow) around the 2013 point none (0%). So both catch and F (Fingal pressure) can be increased more but should be less than their MSY and Fmsy levels i.e. 200,000 tonnes and 1.07 respectively.
32 Enlarged Kobe plot on the LOT stock assessment results (Pacific side). continued from the previous page).
DISCUSSION AND FUTURE WORKS
Although there are some caveats, there is some positive evidence that the results are likely to be reliable (realistic) as stated in Box 6. We may be able to find some reliable CPUEs as the data is so detailed, so some statistical treatments may produce feasible CPUE. But all stock estimates are over by then, so we can't use these CPUEs.
We may have to use it in the next chance in the future. l Conduct age/size-based stock assessments using biological data (for example, Statistics-Catch-At-Age/Size) to compare results according to ASPIC. Both catches in the entire Indian Ocean and SE Asia increased, but catches in SE Asia began to decline in 2011 (see Box 9, next page). Box 9 Comparison of catches between Southeast Asian Waters (Indian Ocean side) and the entire Indian Ocean.
Both results are very similar (red area), but the one in the entire Indian Ocean is more pessimistic, because the big catches are mainly from the Middle East (especially Iran), whose fishing has increased significantly, but is starting to decrease. fall in recent years. The same situation is observed in LOT in Southeast Asia (see Box 11, next page).
NERITIC TUNA STOCK AND RISK ASSESSMENT Part II
RISK ASSESSMENT OF KAWAKAWA (Euthynnus affinis) AND LONGTAIL TUNA (Thunnus tonggol) RESOURCES IN
THE SOUTHEAST ASIAN WATERS
Supported by
NERITIC TUNA STOCK AND RISK ASSESSMENT PART II
INTRODUCTION
Stock assessments of longtail tuna and kawakawa in Southeast Asian waters for both the Indian and Pacific sides have been completed during the 3rd meeting of the Scientific Working Group on Assessment of Neritic Tuna Stocks in SE Asian Waters (27-29 June 2016, Cholburi, Thailand) (Nishida, et al., 2016). The basic methods for the risk assessments are those used in the RFMO for tuna, i.e. Kobe II Strategy Management Matrix (Kobe II). This means that if 10 different catch levels (scenarios) are continued for the next 10 years, Kobe II gives probabilities of exceeding (not maintaining) TBmsy and Fmsy in the 3rd and 10th year.
In this paper, the author produced graphical presentations of the Kobe II matrix using the Kobe plot software (Nishida et al, 2015). In general, tuna OPPs use catch levels as TAC, which can support TBmsy and Fmsy in 10 years later by about 50% (threshold value), which is close to MSY catch levels. For example, if WS requires a more conservative measure, then 40% may be more appropriate, while for a more optimistic measure (good for anglers, but less conservative approach), 60% may be the value to choose.
RESULTS
- Kawakawa (Indian Ocean side of the Southeast Asian Waters)
- Kawakawa (Pacific Ocean side of the Southeast Asian Waters)
- Longtail tuna (Indian Ocean side in the Southeast Asian Waters)
- Longtail tuna (Pacific Ocean side of the Southeast Asian Waters)
It is therefore recommended that the total catch of Kawakawa in the Indian Ocean (Southeast Asian waters) should be less than the MSY level (55,380 tonnes). The results suggest that if the MSY level of catch (185,400 tonnes) is continued, the risk probabilities of violating TBmsy and Fmsy will be less than 56%. Therefore, it is recommended that the total catch of kawakawa in the Pacific Ocean (Southeast Asian waters) should be less than the MSY level (185,400 tonnes).
5 Risk rate (probable) (%) of TBmsy violations in 10 years with different catch rates (Kawakawa, Pacific side of Southeast Asian waters) Catch rate Risk rate. 6 Rate of risk (probable) (%) of Fmsy violations in 10 years due to different catch rates (Kawakawa, Pacific side waters of Southeast Asia). The results show that if fishing continues at the level of MSY (37 580 t), the probability of the risk of violation of TBmsy and Fmsy will be less than 53% in 10 years.
It is therefore recommended that the total catch of longtail tuna in the Indian Ocean (South East Asian waters) is less than the MSY level (37,580 t). 8 Level of risk (likely) (%) to violate TBmsy in the next 10 years of different catch levels (Longtail tuna, Indian Ocean side of Southeast Asian waters). 9 Level of risk (likely) (%) to violate Fmsy in 10 years at different catch levels (Longtail tuna, Indian Ocean side of Southeast Asian waters).
The new results suggest that even if the current catch is increased to the level of MSY (196,700 t) (123%), the risk probability of violating TBmsy and Fmsy will be around 50. Thus it is recommended that the total catch of longtail tuna in The Pacific Ocean (Southeast Asian waters) could increase to the level of MSY (196,700 t) (123%). 11 Level of risk (probably) (%) breaching TBmsy in the next 10 years from different catch levels (longtail tuna, Pacific side of Southeast Asian waters).
12 Risk level (probable) (%) at which the Fmsy will be breached over the next 10 years by different catch levels (longtail tuna, Pacific side of Southeast Asian waters). Longtail tuna, Pacific side of Southeast Asian waters). Alternative catch forecasts (relative to the 2011-2013 average catch level) and the probability (%) of violating MSY-based target reference points. Longtail tuna, Pacific side of Southeast Asian waters).
