Growth, Maturity and Form Factor of Mola Carplet (Amblypharyngodon mola) from the Ganges River, Northwestern Bangladesh

摘要

The current study presents the first complete and comprehensive description of population structure, growth pattern (length-weight relationships, LWRs; length-length relationships, LLRs), maturity (size at first sexual maturity; Lm), form factor (a3.0) and natural mortality (MW) of Amblypharyngodon mola (Hamilton, 1822) in the Ganges River, northwestern Bangladesh. Additionally, asymptotic weight (Wα), a3.0, Lm and MW of this fish species from different water bodies worldwide were calculated. Seasonal samples of A. mola were collected from the Ganges River, northwestern Bangladesh during November 2015 to October 2016 from the fishers’ catch using cast net (mesh size ranges: 1.5 - 2.0 cm). The total length (TL) was measured to the nearest 0.1 cm using digital slide calipers, and the total body weight (BW) was measured using an electronic balance with 0.1 g accuracy for each individual. The growth pattern was estimated through LWR as BW= a*TLb, where a and b are regression parameters. Also, a3.0 was calculated using the equation: a3.0 = 10log a-s(b-3), where a and b are regression parameters of LWRs and s = -1.358, is the regression slope of log a vs. b. Furthermore, Lm of A. mola was calculated using the empirical equation, log (Lm) = -0.1189 + 0.9157 * log (Lmax), where Lmax = maximum observed TL. A total of 308 individuals of A. mola were analyzed, where minimum and maximum TL was 3.9 cm and 8.1 cm, respectively, and BW was 0.5g and 5.8 g, correspondingly. The highest number (49.00 %) of its population stands at 6.00 cm size group. The b value of LWR indicated positive allometric growth, the a3.0 was 0.0129, the Lm was 5.16 cm in TL and Mw was 1.75 year-1 of A. mola in the Ganges River, northwestern Bangladesh. These findings can be very effective for the sustainable management of this fish species in the Ganges River and its ecosystems.