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The neritic tuna catch in Sri Lankan waters is mainly composed of Auxis thazard (frigate tuna), Auxis rochei (bullet tuna), Euthynnus affinis (kawakawa) and Scomberomorus commerson (narrow-barred Spanish mackerel). Among them, frigate tuna is the dominant species presently contributing over 40% to the total neritic tuna production. Though several s...
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With the aim of obtaining the financial efficiency of the system as a whole and of its Port Authorities, a DEA-Bootstrapping model study has been performed to determine the overall performance, a methodology used mainly to obtain terminal efficiencies and applied to the port system in this article. Economic inputs have been selected, such as total...
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... The neritic tuna fishery of Sri Lanka includes frigate tuna (Auxis thazard), bullet tuna (Auxis rochei) and kawakawa (Euthynnus affinis) and the tuna-like species narrow-barred Spanish mackerel, (Scomberomorus commerson) and Indo-Pacific king mackerel (Scomberomorus guttatus). In the neritic tuna fishery, frigate tuna (Auxis thazard) dominates the catch by constituting almost 40% of the catch (Dalpathadu et al., 2019). ...
Understanding the origin of different populations is useful when managing the stocks of a species. Kawakawa (Euthynnus affinis), frigate tuna (Auxis thazard) and bullet tuna (Auxis rochei) are very important neritic tuna species found in Sri Lankan waters. Stock identification studies for these 3 species were carried out by using morphometrics as well as by using molecular techniques. The use of two or more methods for the identification of stocks makes a stock identification study more accurate and reliable. Samples were collected from the commercial fishers that operated in the Southern, Southwestern, Western, Northwestern and the Eastern coastal areas of Sri Lanka from August 2015 to July 2018. The morphometric analysis involved recording 22 morphometric measurements for each fish. The length-length relationships determined using the total length, fork length and the standard length revealed that the 3 species are showing healthy growth patterns. The Principal Component Analysis performed with all 22 morphometric measurements to determine the origin of the stocks, showed for all 3 species that different clusters contained individuals from all provinces indicating that the populations of different coastal areas have originated from one common ancestor and that they have evolved as one stock. The stock structure IOTC-2024-WPNT14-20_Rev2 analysis of the 3 species involving phylogenetic trees constructed with the sequences of the mitochondrial COI gene and the mitochondrial D-loop region support the finding of the morphometric analysis by showing that the populations of these species across different coastal areas of Sri Lanka form a single stock. This means that the populations are genetically similar and likely belong to the same genetic pool, corroborating the morphometric analysis results. Therefore, when management plans need to be implemented for these species, a unified strategy could be implemented throughout the studied coastal areas for each species. Moreover, it is recommended to conduct similar studies that combine samples from different nations. This approach would provide a comprehensive understanding of the status of fish populations across the region.
... Utilization of BLT resources in Indian waters has been reported to reach an overexploited status (E = 80.0%) (Jasmine et al., 2013;Rohit et al., 2014). Sri Lanka faces a similar problem, namely limited data relating to distribution and migration of BLT fish (Dalpathadu et al., 2019). Currently, there is no information regarding the status of BLT resource stocks in Southeast Asian waters (Kaewnuratchadasorn et al., 2020). ...
Highlight Research:The bullet tuna (Auxis rochei) was identified and analysed.The length at first maturity (Lm) of bullet tuna (Auxis rochei) was analyzedThe eligibility status of bullet tuna (Auxis rochei) has been analyzed and estimatedThe LWR curve can be used to estimate age groups of fish compared to the sigmoid curveThe CF cannot be automatically used to estimate fish worth selling AbstractThe bullet tuna (Auxis rochei), BLT or tongkol lisong (Indonesian) is a species of neritic tuna which is one of the target fish for small scale fishers. The problem of bullet tuna fisheries was that it has reached overexploitation and the immature bullet tuna are still caught. This study aimed to assess the population dynamics of the BLT and its size composition caught by small scale fishers in the Indian Ocean, West Nusa Tenggara area was carried out in Bangko-Bangko (West Lombok), Cemplung Beach (South Sumbawa) and Tanjung Luar Fishing Port (East Lombok) between July 2019 and June 2020. The data was derived from the measurement and weighing results of 1,217 BLT collected from the respective collector traders at each sampling location. The growth pattern of BLT was isometric () which meant the ideal body shape (mesomorph) and length at first maturity (FLm) was 31.11 cm. The length-weight relationship curve showed that BLT was in an immature age group (adolescent fish). Meanwhile, the composition of BLT is worth selling (Condition Factor > 1.00), fit for catch (FLc / FLm > 1.00) and worthy of maturity (FLc > FLm), respectively 99.92%, 0.82% and 0.00%. The BLT fish composition indicates that the stocks of resources and populations do not support current sustainable fisheries management.
