Stock Assessment of Kawakawa (Euthynnus affinis Cantor, 1849) in the Persian Gulf and Oman Sea (Iranian Southern Waters), Using Data Limited Approach
Stock Assessment of Kawakawa (Euthynnus affinis Cantor, 1849) in the Persian Gulf and Oman Sea (Iranian Southern Waters), Using Data Limited Approach
Seyed Ahmadreza Hashemi1, Mastooreh Doustdar2, Asadullah Ali Muhammad3* and Reza Abbaspour Naderi4
ABSTRACT
To develop a framework for investigating the catch tendency and valuation of the optimized catch limit of the Euthynnus affinis (Kawakawa) stock by gathering catch records in the Iranian southern waters. In this study, two methods were used to determine the biological reference points (BRPs) of Kawakawa in Iranian southern waters (the Persian Gulf and Oman Sea). Catch data were gathered for 26 years (1997–2022), and R software and the limited data technique were used to determine the optimal catch limit. During this time, the average catch (Ct) was 22439 tonnes (95% confidence interval 18299 -26638 tonnes), and it has climbed considerably over the previous 20 years (R = 0.88, P <0.05). By using the catch-maximum sustainable yield (Catch-MSY), extension of Catch-MSY (CMSY), optimized catch-only model (OCOM), Regression tree models Zhou-boosted (Zhou-BRT), and stochastic surplus production model in continuous-time (SPiCT), the average (maximum-minimum) maximum sustainable yield (MSY), current biomass to the biomass of MSY (B/BMSY), the ratio of the current fishing mortality to fishing mortality rate of MSY (F/Fmsy), and saturation (S=B/K) ratio were obtained. The maximum sustainable yield (MSY) in several models, the ratio of current fishing mortality to fishing mortality rate of MSY (F/Fmsy), and the current biomass to MSY biomass (B/BMSY) did not differ substantially from the one-sample t-test (P<0.05). The study’s previous year’s results (mean of B/BMSY=0.94±0.16) indicated that the Kawakawa stock’s exploitation ratio is full fishing (full exploitation), and no proposals for increasing the exploitation ratio or fishing effort were made.
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