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Investigating uncertainty in the estimation of growth and natural mortality parameters and sensitivity analysis for optimal catch length estimation of two Species, leaping mullet (Chelon saliens ) and golden grey mullet (Chelon auratus )
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Parviz Zare *   |
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Abstract: (78 Views) |
The aim of the present study is to estimate the optimal catch length for two mullet species , namely the leaping mullet (Chelon saliens) and the golden grey mullet (Chelon auratus), while considering uncertainty and sensitivity analysis. To record length, weight, and age data, 50 and 32 specimens of these two species were collected respectively from seining catches along the Golestan coasts during the period from October 2022 and April 2023. The parameters of infinite length (L∞ ) and growth rate (k) were estimated using two methods: Ford-Walford and nonlinear least squares, while the natural mortality rate (M) was calculated using ten different approaches. The optimal catch length (Lopt ) for the two fish species was estimated under two scenarios: (1) calculating natural mortality from growth parameters estimated by the Ford-Walford method, and (2) calculating natural mortality from growth parameters estimated by the nonlinear least squares method. The age composition ranged from 0 to 7 years (with a fork length range of 13.8-28.8 cm) for the leaping mullet and 1 to 13 years (with a fork length range of 13.9-52.0 cm) for the golden grey mullet. The length-weight relationship analysis revealed slope values (b) of 2.81 for the golden grey mullet and 3.04 for the leaping mullet. Using the Ford-Walford method, the asymptotic fork length (L∞) and growth rate (K) were estimated at 30.7 cm and 0.25 year⁻¹ for the leaping mullet, and 61.3 cm and 0.11 year⁻¹ for the golden grey mullet, respectively. Nonlinear least squares analysis yielded L∞ and K values of 25.2 cm and 0.25 year⁻¹ for the leaping mullet and 47.7 cm and 0.16 year⁻¹ for the golden grey mullet. These same parameters estimated by the nonlinear least squares method for the leaping mullet were 25.2 cm fork length and 0.25 per year, and for the golden grey mullet, they were 47.7 cm fork length and 0.16 per year. The range of estimated natural mortality rates varied from 0.176 to 0.543 for the golden grey mullet and from 0.4 to 1.23 for the leaping mullet. The optimal catch length for the leaping mullet varied between 16.3–22.3 cm (mean: 18.6 cm) in Scenario 1 and 17.3–21.1 cm (mean: 19.6 cm) in Scenario 2. For the golden grey mullet, optimal lengths ranged from 24.1–42.3 cm (mean: 29.3 cm) in Scenario 1 and 23.6–33.3 cm (mean: 26.9 cm) in Scenario 2. The differences in optimal catch length calculations between Scenarios 1 and 2 were 18.2 cm and 9.7 cm for the golden grey mullet and 5.9 cm and 3.8 cm for the leaping mullet, respectively. These results indicate the significant impact of growth parameters and natural mortality on the estimation of optimal catch length. The final recommendation of this study for sustainable fishing management and the formulation of related regulations is to set the optimal catch lengths for the leaping mullet and golden grey mullet at 20 cm and 26 cm, respectively.
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| Keywords: Uncertainty, Growth, Natural mortality, Sensitivity analysis, Optimal catch length, Mullet |
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Full-Text [PDF 1150 kb]
(14 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2025/03/5 | Accepted: 2025/05/27 | Published: 2025/06/27
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