Temporal Variation of Biometric Indices for Megalaspis cordyla (Linnaeus, 1758) from the Bay of Bengal, Bangladesh
Temporal Variation of Biometric Indices for Megalaspis cordyla (Linnaeus, 1758) from the Bay of Bengal, Bangladesh
Most. Shakila Sarmin1,2, Md. Ashekur Rahman1,2, Most. Farida Parvin2,3, Mst. Shefaly Khatun4, Kazi Ahsan Habib5, Wasim Sabbir6, Jun Ohtomi7 and Md. Yeamin Hossain1*
ABSTRACT
This study described the population sizes structure, growth pattern, maturity size (Lm), and optimum catchable size (Lopt) of Megalaspis cordyla. Fish were sampled (male = 720, female = 793) from commercial vessels operating in the Bay of Bengal (BoB), Bangladesh between January-December 2020. All lengths (TL, total; FL, fork; SL, standard length), were taken using a fish measuring board to 0.01 cm as well as a digital balance is used to weigh body weight (BW) to 0.01 g precision. The size structure (length-frequency distributions, LFDs) indicated that the males with TL 22.0-22.9 cm and females with 29.0-29.9 cm size group were statistically more appeared. The TL and BW varied between 11.5-53.0 cm and 27.6 to 1228.0 g for males, and 18.2-45.0 cm and 57.0 to 728.0 g for females. The length-weight relations (LWRs) were significantly correlated (p < 0.0001), with values of r2 ≥ 0.961. The monthly co-efficient (b) revealed negative allometric growth (< 3.0) of all LWRs for both sexes, excluding males showed isometric growth in December (TL vs. BW). Additionally, length-length relationships (LLRs) indicated notable relation (p < 0.0001), with all r2 ≥ 0.991. The estimated Lm was 27.82 and 23.92 cm for male and female of M. cordyla, separately. The assessed Lopt were 24.87 cm for females and 29.13 cm for males. Accordingly, this research will be a guide to the study of stock assessment, physiology, and biology for M. cordyla in the BoB and the related ecosystems.
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