Estimation of life history parameters, biological reference points, and associated uncertainties for black marlin (Makaira indica) n the waters off eastern Taiwan
Date Issued
2008
Date
2008
Author(s)
Fang, Huei-Ping
Abstract
Age, growth, and mortality of black marlin (Makaira indica) in the waters off eastern Taiwan were estimated based on the length data using MULTIFAN, and applied to the per-recruit analyses with uncertainty incorporated into the parameters. Length data of 5,160 black marlin were collected at Shinkang Fish Market of Taitung during July 2004 to May 2007, of which 731 were males, 4,225 were females, and 204 were sex-unknown. Male black marlin were not discussed in this study due to the sample size of length data, which is not enough to analyze. In the search of MULTIFAN, the best fitting results were obtained when Month 1 was September, the number of sample was 12, and the length interval was 5 cm can obtain. Twelve age-classes were discriminated in Month 1 sample, and the corresponding von Bertalanffy growth parameters are: growth coefficient (K) was 0.090 yr-1, asymptotic length (L∞) was 390.1 cm and age at zero length (t0) was -2.88 yr. The lifespan was 30.41 yr. The estimates were 0.55 and 0.57 yr-1 for total mortality rates (Z), 0.17 and 0.20 yr-1 for natural mortality rates (M), and 0.35 to 0.40 yr-1 for fishing mortality rates (F), with the exploitation rates (E) being 0.27 - 0.30. Based on the yield-per- recruit analyses, the current fishing mortality (FCUR = 0.37 yr-1) exceeded the target reference point (F0.1 = 0.31 yr-1), and the optimal age at first capture (tc) was suggested to be 6 yr. Increasing the fishing effort could produce the maximum yield, but also result in the risk of overexploitation. For the spawning- biomass-per-recruit, FCUR (0.37 yr-1) also exceeded the target reference point (FSSB40 0.16 yr-1) and limit reference point (FSSB25 = 0.28 yr-1). The sensitivity analysis suggested that the natural mortality was the most important impact factor on estimating F0.1, FSSB40, and FSSB25. The probability of FCUR exceeded F0.1 and FSSB40, and FSSB25 are more than 85% and about 50% respectively for the currently understanding of natural mortality (mean ± SE). Therefore, the stock condition and developments in the fishery need to be monitored closely for sustainable exploitation of this stock.
Subjects
black marlin
Makaira indica
age and growth
mortality
per-recruit analyses
uncertainty
SDGs
Type
thesis
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