Age, growth, mortality and population structure of the oyster, Crassostrea madrasensis, in the Moheskhali Channel (southeastern coast of Bangladesh) |
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Authors: | S. M. Nurul Amin M. Zafar A. Halim |
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Affiliation: | Institute of Marine Science and Fisheries, University of Chittagong, Chittagong, Bangladesh;;Current address: Laboratory of Marine Science and Aquaculture, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia |
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Abstract: | The population structure, age, growth, mortality and harvest intensity of the oyster Crassostrea madrasensis were examined in the Moheskhali Channel, Bangladesh between June 2003 and May 2004. The channel is a representative habitat for the area. C. madrasensis monthly length frequency data were analyzed using FiSAT software for estimating population parameters, including asymptotic length ( L ∝ ), growth co-efficient ( K ) and recruitment pattern to assess the status of the stock. Asymptotic length ( L∝ ) and growth co-efficient ( K ) were 20.88 cm and 0.35 year−1, respectively. The growth performance index (φ') was calculated with 2.18. The growth pattern showed negative allometric growth ( b < 3), with an asymptotic weight ( W ∝ ) of about 1124.6 g. The oyster attained an average length of 6.17 cm at the end of 1 year. Total mortality ( Z ) by length-converted catch curve was estimated at 1.78 year−1, fishing mortality ( F ) at 0.77 year−1, and natural mortality ( M ) at 1.01 year−1. The exploitation level ( E ) of C. madrasensis was 0.43, while the maximum allowable limit of exploitation ( E max) was 0.45 for the highest yield. The recruitment pattern was continuous, displaying a single major peak event per year. Habitat temperatures were 25.5–31.0°C (mean ± SD, 29 ± 1.62°C); salinity range was from 12.36 to 26.0 ppt (mean ± SD, 19.6 ± 4.7 ppt). The exploitation level (0.43) indicated that the oyster stock was exploited at almost maximum yield in this channel. |
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