Southern Bluefin Research Articles

Age and Growth of Southern Bluefin Tuna, Thunnus maccoyii, Based on Otolith Microstructure

Age and growth of southern bluefin tuna (SBT, Thunnus maccoyii) were estimated based on otoliths collected by Korean tuna longline vessels in the Atlantic and Indian Oceans from 2015 to 2019. A total of 739 specimens were used to estimate age and growth of SBT, with sizes ranging from 66 to 181 cm in fork length. It was confirmed that the otolith is a suitable aging characteristic for determining SBT age, and otolith annuli can be used as an annual ring. The relationship between fork length (FL) and total weight (W) was W = 7.7e − 05FL2.722 (R2 = 0.874). The von Bertalanffy’s growth parameters estimated from the non-linear method using length-at-age data were L∞ = 170.0 cm, K = 0.200/year, t0 = − 1.615 years, with 95% confidence intervals between 166 and 175 cm for L∞, 0.17–0.23/year for K, and − 2.27 to − 1.09 years for t0 from bootstrapping. The Kimura’s likelihood ratio test results of the models under assumptions of common and different parameters between female and male concluded that the growth of SBT has no difference between genders.

Analisis Filogenetik Ikan Tuna (Thunnus spp.) yang didaratkan di Pelabuhan Benoa, Bali


 
 
 
 Tuna is one of the largest fisheries commodities in Indonesia after shrimp and demersal fish. The genus Thunnus is a type of tuna that dominates the international market. The genus Thunnus consisted of seven species of tuna. In some cases, the same morphological character has caused misidentification and data collection on tuna species. Therefore, this study aimed to identify tuna species that are landed at Benoa Harbor and analyzed their phylogenetic relationships. Species identification and phylogenetic analysed in this study used the mtDNA control region locus. The results of this study indicated that there are five tuna species landed at Benoa Harbor, namely yellowfin tuna (T. albacares), longtail tuna (T. tonggol), bigeye tuna (T. obesus), southern bluefin tuna (T. maccoyii), and albacore tuna (T. alalunga). Based on phylogenetic tree reconstruction, all samples were divided into five according to the number of tuna species resulted from molecular identification. Reconstruction of phylogenetic trees is supported by genetic distance between clades has a value of 0.075 - 0.212, with the closest kinship found in yellowfin tuna (T. albacares) with bigeye tuna (T. obesus) and the farthest found in yelowfin tuna (T. albacares) with albacore tuna (T. alalunga).
 
 
 

Shallow population structure of southern bluefin tuna, Thunnus maccoyii (Castelnau, 1872) between Indian and Atlantic Oceans inferred from mitochondrial DNA sequences

Southern bluefin tuna (Thunnus maccoyii Castelnau, 1872) is distributed across most of the southern temperate ocean and migrates extensively between 30°S and 50°S. Since T. maccoyii has been continually and heavily exploited, it is necessary to investigate the genetic diversity, population structure and demographic history of T. maccoyii for effective management and conservation. Thirty-seven gonad tissues of T. maccoyii were sampled from two locations, which were in the eastern Indian Ocean and the eastern Atlantic Ocean, by scientific observers onboard Korean T. maccoyii longline vessels in 2015. We compared 1240-bp sequences of combined mitochondrial DNA (mtDNA) from the cytochrome c oxidase subunit I (COI, 504-bp) and control region (CR, 736-bp) sequences. The pairwise fixation index (F ST) and maximum-likelihood tree showed that two clades (A and B) were formed regardless of locations. Clade A occurred more commonly than clade B in both localities: the occurrence ratio of clade A was 69% in the Indian Ocean, and 79% in the Atlantic Ocean, respectively. Our findings suggest that a historic differentiation event may have occurred in T. maccoyii, but recently the connectivity between the two oceans may be possible in T. maccoyii populations.

Measurement Errors and Imperfect Detection Rates on the Transect Line in Independent Observer Line Transect Surveys

This paper proposes a parametric method for estimating animal abundance using data from independent observer line transect surveys. This method allows measurement errors in distance and size, and less than 100% detection rates on the transect line. Based on data from southern bluefin tuna surveys and data from a mike whale survey, simulation studies were conducted and the results show that 1) the proposed estimates agree well with the true values, 2) the effect of small measurement errors in distance could still be large if measurements on size are biased, and 3) incorrectly as suming 100% detection rates on the transect line will greatly underestimate the animal abundance.

Fishing Quota and International Obligation: Why Has Indonesia been Indicated as a Non-Compliant State

Indonesia committed to conserving the tuna resources by participating in some RFMOs. From all regional organizations where Indonesia has been joined, the CCSBT is the unique one, due to it governs a single tuna species, which is called Southern Bluefin Tuna. This kind of tuna is essential for Indonesia because it is the world’s most expensive tuna and SBT migrates through Indonesian fisheries management zones and goes even further within the territorial waters, where the SBT spawning area is located. This natural characteristic distinguishes Indonesia from other Parties to CCSBT. Nevertheless, the Country has been dealing with its obligation to comply with national quota allocation. For some fishing season periods, the CCSBT indicated Indonesia as a non-compliant. By applying the qualitative approach, this study considers how Indonesia’s non-compliance has been addressed in fishing for shared fish stocks. The data collection was conducted through semi-structured interviews and legal analysis of law and policy instruments. This method leads the elaboration to reveal domestic factors affecting non-compliance by Indonesia. This study argues, the fisheries legislation should consider the provision concerning fishing for resources under quota system, hence, it will provide sufficient legal base to take enforcement measures towards non-compliance with fishing quota.

The Scope of Compulsory Jurisdiction and Exceptions Thereto under the United Nations Convention on the Law of the Sea

AbstractThe establishment of a compulsory dispute settlement mechanism in the United Nations Convention on the Law of the Sea (UNCLOS) is intended to be the guarantor of the proper application of the convention. Yet the decisions of courts and tribunals seized pursuant to the procedures under Section 2 of Part XV of UNCLOS are in many regards difficult to reconcile and in some regards unable to form the basis for a jurisprudence constante. This article examines on an empirical basis the scope and limits of the compulsory dispute settlement mechanism under UNCLOS, as applied by international courts and tribunals during a period of twenty years since the first decision in the Southern Bluefin Tuna case until the recent decision on preliminary objections in the Dispute Concerning Delimitation of the Maritime Boundary between Mauritius and Maldives in the Indian Ocean.

Climate Change Impacts on Atlantic Oceanic Island Tuna Fisheries

Climate change is already affecting the distributions of marine fish, and future change is expected to have a particularly large impact on small islands that are reliant on the sea for much of their income. This study aims to develop an understanding of how climate change may affect the distribution of commercially important tuna in the waters around the United Kingdom’s Overseas Territories in the South Atlantic. The future suitable habitat of southern bluefin, albacore, bigeye, yellowfin and skipjack tunas were modelled under two future climate change scenarios. Of all the tunas, the waters of Tristan da Cunha are the most suitable for southern bluefin, and overall, the environmental conditions will remain so in the future. Tristan da Cunha is not projected to become more suitable for any of the other tuna species in the future. For the other tuna species, Ascension Island and Saint Helena will become more suitable in the future, particularly so for skipjack tuna around Ascension Island, as the temperature and salinity conditions change in these areas. Large marine protected areas have been designated around the territories, with those in Ascension and Tristan da Cunha closed to tuna fishing. Although these areas are small relative to the whole Atlantic, these model projections could be useful in understanding whether this protection will benefit tuna populations into the future, particularly where there is high site fidelity.

The shared fish stocks conservation: revisiting the unconnected enforcement

“There is plenty of other fish in the sea," goes the old cliché as many stocks have been overfished by industrial fisheries, that the over-activity made some fish species in danger. The scope of this paper covers the enforcement issue of Southern Bluefin Tuna (SBT) as endangered fish species. Taking Indonesia, New Zealand, and Australia as member States who catch SBT, this paper is a conceptual study using content analysis aiming to review how these three-member States officially treat SBT stocks. Based on the discussion, it found that since the shared characteristic of SBT, in areas beyond national jurisdiction it might create regulatory gaps. While international provisions have been entered into force in respect of endangered fish stocks in high seas areas, however, a lacuna remained in which the law cannot reach the national fishing area. This situation may lead to a discrepancy framework at the national level. Therefore, this paper argues that connectivity is crucial to link enforcement among relevant States with the real interest. In this context, the enforcement must consider the movement path of SBT from a coastal State (the spawning ground), the flag State (the fishing vessel), and the Port State (the place to land SBT).

Fishing ground and tuna productivity by tuna longline based on Benoa Bay, Bali, Indonesia

Abstract. Imron M, Tawaqal MI, Yusfiandayani R. 2021. Fishing ground and tuna productivity by tuna longline based on Benoa Bay, Bali, Indonesia. Biodiversitas 22: 961-968. The success of a longline fishing operation depends on several things such as the skill of the crew, bait used, fishing season, fishing operation, the total of fish caught, the price of the fish, productivity, and fishing grounds. Information about productivity and fishing ground becomes important to increase effectiveness and optimal profit. The methodology is carried out by conducting a survey to collect data to be processed and analyzed using productivity analysis based on Landing per Unit Effort (LPUE) and fishing activity analysis from the Vessel Monitoring System (VMS) to determine the Fishing Ground. We calculate tuna productivity from catch production (landing) per effort, meanwhile fishing ground use VMS data. Production tuna was landed at Benoa Bali from 2016-2018 fluctuated. In 2016 production of tuna albacore took a portion of 34.60%, yellowfin tuna 43.56%, bigeye tuna 15.44%, and southern bluefin tuna 6.26%. Production of tuna albacore took a portion of 35.61%, yellowfin tuna 42.64%, bigeye tuna 12.49%, and southern bluefin tuna 9.26% in 2017. Production albacore took a portion of 36.41%, yellowfin tuna 41.56%, bigeye tuna 11.79%, and southern bluefin tuna 10.24% in 2018. The highest productivity of albacore was in August 2018 with LPUE value 1.0099, yellowfin tuna was in July 2018 with LPUE value 1.2431, big eye tuna was in November 2018 with LPUE value 0.5538, and bluefin was at December 2017 with LPUE value 0.3864. The result of VMS data processing showed that tuna longline vessel based at Benoa has several locations of fishing grounds based on fishing activity for example Hindia High Seas, WPP NRI 714 (Telo gulf and Banda Sea), WPP NRI 718 (Aru Sea, Arafura Sea, and Timor Sea), ZEEI WPP NRI 718.

Changes in the Splenic Melanomacrophage Centre Surface Area in Southern Bluefin Tuna (Thunnus maccoyii) Are Associated with Blood Fluke Infections.

Melanomacrophage centres (MMCs) are aggregates of macrophages accumulating various pigments. They have been proposed as an indicator of fish immune response. Blood flukes are common parasites in farmed fish. Two cohorts of wild Southern Bluefin Tuna (Thunnus maccoyi) were examined at transfer, before treatment against blood flukes (pre-treatment) and at harvest. MMCs were assessed in histological sections using image analysis, while Cardicola forsteri and Cardicola orientalis infection severity was determined using qPCR, count of adult flukes in heart flushes and count of eggs in gill filaments. Fish from both cohorts showed the same pattern in the changes in the surface area of MMCs. The surface area of splenic MMCs increased over the ranching duration and was positively correlated to the PCR determined copy numbers of Cardicola forsteri ITS2 rDNA in the gills of those fish. However, the infection with blood fluke was more variable, both between cohorts and individuals within the same cohort. Eggs of blood fluke were detected in renal MMCs using histology. Cardicola forsteri had a higher prevalence than Cardicola orientalis. This study contributes to our understanding of blood fluke infections in Southern Bluefin Tuna and their interactions with MMCs.

Effectiveness and potential application of sex-identification DNA markers in tunas

Sex-identification DNA markers are useful tools for sexing organisms that lack externally visible sexual dimorphism, and thus, they provide biological information for ecological and evolutionary studies. Tunas of the genus Thunnus (Scombridae), which comprises 8 species, lack sexual dimorphism of external morphology or coloration. In this study, we applied recently developed genotypic sex-identification markers for Pacific bluefin tuna to other tuna species to evaluate their effectiveness in sex identification. A sex-identification marker named ‘primer pair II’ demonstrated relatively high effectiveness in all tuna species, except southern bluefin tuna. Primer pair II was further tested in 209 albacore individuals collected during the scientific observer program onboard Japanese commercial long-line vessels, and it demonstrated robust performance for genotypic sex identification. The sex ratio of this albacore sample (1:1.4) significantly deviated from the expected 1:1 with the dominance of males, and the mean body size of males was higher than that of females. As all cross-species amplifications of the male-specific markers, except those for the southern bluefin tuna, were male-heterozygous polymorphisms, it is likely that a male-heterozygous sex-associated region exists in the Thunnus genome. The evolution of sex-determination systems in tunas was analyzed by ancestral state reconstruction, which showed that a common ancestor, before the evolution of the genus, possessed the male-heterozygous sex-associated genome region.

The Exclusion of Compulsory Proceedings Entailing Binding Decisions in Light of the Southern Bluefin Tuna and South China Sea Arbitrations

For international disputes covering the same ground under a constellation of complementary and conflicting agreements, mapping the relationship between treaties is critical, especially if each contains compulsory jurisdiction clauses. Their interrelatedness or independence will affect a finding of jurisdiction. This paper considers the procedural effects of treaty parallelism on the exclusion of Part XV compulsory proceedings entailing binding decisions under the UN Convention on the Law of the Sea (UNCLOS), using as examples the Southern Bluefin Tuna and South China Sea arbitrations. The jurisprudence splits on whether an explicit exclusion is necessary in an alternative agreement to remove a dispute from Part XV’s reach. The adoption of either approach depends on how a Tribunal views the Convention. Oxman divides predominant attitudes into separate “substantive and procedural models” which form the bases of diverging lines of authority. This taxonomic exercise is pertinent not only in theory, but in practice, as Klein recognizes “a core tension existing around the operation of Part XV” is whether it is “intended to be as comprehensive and inclusive as possible” or serving “a more limited, albeit still important, purpose.” The “obvious tension between sustaining an integrated global regime and allowing further development on a regional basis” finds specific expression in divided interpretations of Articles 281 and 282, the jurisdictional prerequisites of the UNCLOS Part XV dispute settlement regime. In resolving jurisdictional problems related to treaty parallelism, invocations of lex posterior, lex specialis, and the like, may be misplaced given UNCLOS’ unique dispute settlement provisions and “something more than, or different from, specific affirmation of the effect of certain generally applicable rules of the law of treaties” may be required. Equally important is understanding the limitations in “expansive” approaches to treaty exegesis. This has broader consequences for other long-term agreements in international law’s universe of treaties, including “the ICAO Convention, or those of the GATT and WTO Agreements, or the optional clause of the ICJ Statute.” Caught in the waves of “an international legal system in transition” crashing against volatile political realities increasingly commonplace in recent sea disputes like South China Sea, this paper concludes that the unique dispute settlement regime of the Montego Bay Agreement is best buoyed by a process of harmonization. This is only feasible if fundamental attitudes towards UNCLOS, procedural and substantive model views or otherwise, “suffer a sea change.”

Seafood mislabeling in Honolulu, Hawai’i

Seafood mislabeling misleads consumers about the abundance of commercially harvested and cultured species, hinders consumer choice, and allows overfished and threatened species to reach the marketplace. Despite the importance of seafood in local culture and in the tourist-driven economy of Hawai’i, no studies of seafood label accuracy have been conducted in the state. Here, we use mitochondrial DNA barcoding to investigate patterns of seafood mislabeling in restaurants, groceries, and sushi bars in the greater Honolulu area. Our results revealed an overall mislabeling rate of 21 % (+9.3%). Sushi bars had the highest rate (27 %), followed by restaurants (23 %) and groceries (17 %). The most common mislabeled fish was Swai (Pangasianodon hypophthalmus), sold as more expensive fish under a variety of names. The overall mislabeling rate in Honolulu was lower than the national rate (33 %) found in the largest study from the U.S. mainland by Oceana, but similar to a more recent, but smaller national Oceana survey (21 %). However, comparisons of overall rates across studies can be misleading because much of the geographic variation in mislabeling is confounded by varying proportions of samples obtained from different kinds of retailers. Finally, the widespread use of acceptable – but generic – market names in Hawai’i concealed the true diversity of species for sale, including endangered species. Two species in our study (Anguilla anguilla and Thunnus maccoyii) labeled with generic but acceptable market names are considered “Critically Endangered” by the International Union for Conservation of Nature.

The Legal Impacts of The Convention for The Conservation of Southern Bluefin Tuna on The Optimum Utilization and Sustainability of Highly Migratory Fish

The sustainability of southern Bluefin tuna (SBT) is very important, since the SBT as one of the highly migratory fish which is very valuable. Because of that, the SBT are exploited tremendously and it caused serious decline of the population. Due to the reasons, the aim of the paper is to examine comprehensively the legal impacts of the Convention for The Conservation of Southern Bluefin Tuna (CCSBT) on the optimum utilization and sustainability of the SBT as one of highly migratory fish, There are two problems questions that are proposed, namely, first, how is the role of the Commission of CCSBT in the optimum utilization and sustainable conservation of the SBT. Second, how is the legal impacts of the CCSBT to the conduct of the Member States to obey the obligations of the CCSBT in order to utilize and to maintain the sustainability of the SBT in sustainable manner. The result of the paper finds that there is positive legal impacts of the CCSBT to the Member States’ conduct in order to materialize the optimum utilization and sustainability of the SBT, though, there are still some challenges. Keywords: conservation, highly migratory fish, optimum utilization, southern tuna Bluefin, sustainable manner.Southern Bluefin Tuna (SBT), as one of the highly migratory fish, is very valuable due to the high demand inthe international market. Hence, the SBT is exploited tremendously and it caused a severe decline in thepopulation. To maintain the sustainability utilization of SBT, the role of the Commission on the CCSBT isimperative. The objective of the research is to examine conceptually the legal impacts of the Convention forthe Conservation of Southern Bluefin Tuna (CCSBT) on the optimum utilization and sustainability of the SBT.It is a normative juridical research by applying conceptual and statutory approaches. The results of theresearch indicates that: first, the role of the Commission of CCSBT in the optimum utilization and thesustainability of the SBT is very significant: second, there are positive legal impacts of the CCSBT to theconduct of the Member States to comply with provisions of the CCSBT; third, the legal impacts of CCSBT areable to oblige the Member States to perform their obligations, however, there are still some challenges tomaterialize the objective of the CCSBT.Keywords: conservation; highly migratory fish; optimum utilization; southern tuna bluefin; sustainability.

Relationship between Southern Bluefin Tuna, Thunnus maccoyii, melanomacrophage centres and Cardicola spp. (Trematoda: Aporocotylidae) infection

Southern Bluefin Tuna (SBT), Thunnus maccoyii, is ranched off Port Lincoln, South Australia and is Australia's second largest economic finfish aquaculture industry. The biggest threats to SBT health identified by the industry are the blood flukes Cardicola forsteri and C. orientalis (Trematoda: Aporocotylidae). Melanomacrophage centres (MMCs) are aggregations of pigmented macrophage like cells present in spleen, kidney and liver of teleost fish. The aim of this study was to quantify MMCs in SBT anterior kidney, liver and spleen to investigate changes in relation to Cardicola spp. Infection. Samples were collected at the end of ranching from pontoons where SBT were treated with PZQ and pontoons with untreated SBT. SBT MMC percentage of surface area cover was highest in SBT spleen and lowest in the liver. Significant positive correlations were identified between SBT MMC area and SBT size in all three organs (p < 0.05). MMC area and parasite infection showed significant positive correlations in the kidney and spleen for Cardicola spp. gill egg counts, and in the kidney for C. forsteri DNA from SBT hearts and gills (p < 0.05). MMCs area increased with increased intensity of Cardicola spp. Infection and MMCs have the potential to be used as an indicator to assess health effects that Cardicola spp. have on SBT.

The Southern Bluefin Tuna Mucosal Microbiome Is Influenced by Husbandry Method, Net Pen Location, and Anti-parasite Treatment.

Aquaculture is the fastest growing primary industry worldwide. Marine finfish culture in open ocean net pens, or pontoons, is one of the largest growth areas and is currently the only way to rear high value fish such as bluefin tuna. Ranching involves catching wild juveniles, stocking in floating net pens and fattening for 4 to 8 months. Tuna experience several parasite-induced disease challenges in culture that can be mitigated by application of praziquantel (PZQ) as a therapeutic. In this study, we characterized the microbiome of ranched southern Bluefin Tuna, Thunnus maccoyii, across four anatomic sites (gill, skin, digesta, and anterior kidney) and evaluated environmental and pathological factors that influence microbiome composition, including the impact of PZQ treatment on microbiome stability. Southern bluefin tuna gill, skin, and digesta microbiome communities are unique and potentially influenced by husbandry practices, location of pontoon growout pens, and treatment with the antiparasitic PZQ. There was no significant relationship between the fish mucosal microbiome and incidence or abundance of adult blood fluke in the heart or fluke egg density in the gill. An enhanced understanding of microbiome diversity and function in high-value farmed fish species such as bluefin tuna is needed to optimize fish health and improve aquaculture yield. Comparison of the bluefin tuna microbiome to other fish species, including Seriola lalandi (yellowtail kingfish), a common farmed species from Australia, and Scomber japonicus (Pacific mackerel), a wild caught Scombrid relative of tuna, showed the two Scombrids had more similar microbial communities compared to other families. The finding that mucosal microbial communities are more similar in phylogenetically related fish species exposes an opportunity to develop mackerel as a model for tuna microbiome and parasite research.

Methodology and application of PCR-RFLP for species identification in tuna sashimi.

The Thunnini, or tuna, comprise many species with very different commercial values. The principal raw tuna product on the market is sashimi, for which the species used is difficult to identify through conventional morphological analysis. The present study amplified the cytochrome b gene (Cytb) of 4 major tuna species used for preparing sashimi—yellowfin tuna (Thunnus albacares), southern bluefin tuna (Thunnus maccoyii), bigeye tuna (Thunnus obesus), and Atlantic bluefin tuna (Thunnus thynnus)—and 4 species commonly mislabeled as components of tuna sashimi—albacore tuna (Thunnus alalunga), skipjack tuna (Katsuwonus pelamis), striped marlin (Tetrapturus audax), and swordfish (Xiphias gladius). Polymerase chain reaction (PCR) amplicons were digested with 5 restriction enzymes—Eco147 I, Hinf I, Mbo I, Xag I, and Hind II—to obtain characteristic restriction maps of the above‐mentioned raw tuna species and the commonly mislabeled species. An identification method using PCR restriction fragment length polymorphism (PCR‐RFLP) was established and validated using 39 commercial tuna sashimi samples, which verified that this method provides results consistent with those obtained by classical sequencing. PCR‐RFLP has several advantages over classical sequencing, such as simplicity, speed and accuracy. This technique could support species identification for raw tuna and sashimi.

Distinguishing discard mortality from natural mortality in field experiments based on electronic tagging

Improvements in electronic tag technology have enhanced the ability to monitor the post-release fate of fish and estimate discard mortality rates (DM) under real-world conditions. However, correctly estimating DM requires disentangling the influence of capture-related mortality from natural (background) mortality (M), particularly when M rates are elevated. To accomplish this, many published studies have used an ad hoc and largely arbitrary approach, assuming that all mortality occurring during a finite, non-standard, pre-defined period following release is strictly DM, and all mortality occurring after this period is M. This approach may lead to biased estimates of DM, which we illustrate using a simulation. Here we extend an existing parametric survival model to independently estimate DM and M from electronic tagging data generated by two DM experiments conducted on southern bluefin (Thunnus maccoyii) and yellowfin (Thunnus albacares) tuna, species experiencing contrasting levels of M. In both cases, predation following release was an important cause of mortality that may have been facilitated by capture and discarding, and therefore part of DM or the DM experiment, or may have been natural. Using a multi-model approach based on model fit and biological plausibility, we consider different assumptions for these mortality processes and attempt to account for experimental (tag-induced) mortality. Despite the modest sample sizes of the case studies, we show how our approach can be used to provide bounds on the plausible magnitude of DM in support of possible subsequent fishery management actions such as the imposition of size limits or catch retention policies.

Implementation of the UNCLOS 1982 in Utilization of Highly Migratory Species By Indonesia

Indonesia is one of the producers of tuna and tuna species (tuna, skipjack, and mackerel tuna), which are increasing every year. Its geographical location and area of its many Exclusive Economic Zones (EEZs) bordering many neighboring countries, requires Indonesia to implement the CLS 1982 provisions on far-migratory fish. In this connection, Indonesia implements two forms. Firstly, in the form of legislation, which Indonesia has issued about 17 regulations, starting from the level of the Law to the Ministerial Regulation. Secondly, Indonesia has been active as a member of regional fisheries organizations whose territory borders on the Indonesian EEZ. Consequently, from the issuance of this Ministerial Regulation, Indonesia must carry out fisheries monitoring on board, to meet the higher quality data needs. So that Indonesia is faced with carrying out monitoring on fishing vessels operating in the convention area of the RFMOs, namely the Indian Ocean Tuna Commission, the Commission for Southern Blue Fin Tuna Conservation, and the Central and Western Pacific Fisheries Commission. In order to optimize this implementation, Indonesia needs to prepare officials, facilities, and infrastructure that can support the compliance and enforcement of legislation that has been issued. Indonesia should immediately formulate fisheries policies in the high seas outside the Indonesian EEZ, which involve and benefit Indonesian fishermen.

Total Allowable Catch of Indonesian Southern Bluefin Tuna Thunnus maccoyii and Its Potential Resources in The Indian Ocean

Southern Bluefin Tuna (SBT) is a high value species fished by many countries including Indonesia, and its fishing activities has been regulated by CCSBT. This study aimed to determine the potential resource of Indonesian SBT, utilization, and review of the Total Allowable Catch (TAC) of Indonesian SBT. This research was conducted from January 2017 to April 2018. The primary data used in this study were the otolith samples and the enumeration data of SBT landed in Benoa port from 2012-2017. Virtual Population Analysis (VPA) used in this research was based on a direct aging method using otolith. This research showed that the catch at age structure was distributed from 5-22 years with mean and mode of age were 9.63 and 9 years. The average of the exploitation rate measured was 0.191 per year meaning that the level of exploitation was categorized as underfished. The optimal assumption of the exploitation rate estimated in the range of 1,577 to 2,630 tons per year which is higher than the TAC provided by CCSBT. It was concluded that from 2015 onwards, the catch efforts were more effective and efficient with the increasing level of the exploitation and the decreasing number of efforts.