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Biometrics of the rare fish Rhinomugil corsula (Hamilton, 1822) (Mugiliformes: Mugilidae) in the Ganges, Northwestern Bangladesh
Authors: Md. Yeamin Hossain, Md. Foyzul Hassan Fahad, Md. Mosaddequr Rahman, Nipa Chaki, Saleha Jasmine, Zoarder Faruque Ahmed, Jun Ohtomi
Number of views: 455
Objective: To investigate biometrics of the Rhinomugil corsula (Hamilton, 1822) (R. corsula),
including length-weight relationships (LWRs), condition factors (Allometric, KA; Fulton’s, KF;
Relative, KR; Relative weight, WR), and sex ratio and length-frequency distributions in the Ganges
(Padma River), Northwestern Bangladesh.
Methods: Monthly sampling was conducted using traditional fishing gears during June to August
2012. Total length was measured to the nearest 0.01 cm using digital slide calipers, and total body
weight was measured using an electronic balance with 0.01 g accuracy. The LWR was calculated
using the expression: W= a×Lb
, where the W is the body weight , L is the total length , a and b are
the parameters of the regression.
Results: A total of 350 specimens ranging from 8.59-15.71 cm in total length and 9.57-32.59 g in
body weight were analyzed during this study. The overall sex ratio was not significantly different
from the expected value of 1:1 (χ2
=2.57, P>0.05), but there was significant difference in the
length-frequency distributions between the sexes (P=0.03). The allometric coefficient b for the
LWR indicated negative allometric growth (b≈3.00) in males, female and combined sexes. Results
further indicated that KF was not significantly different between the sexes (P=0.57). However, the
mean WR of R. corsula showed significant differences from 100 for males (P=0.03) and females
(P<0.001) in this study, indicating the imbalance habitat with food availability relative to the
presence of predators.
Conclusions: This study reported the first description of biometric relationships for R. corsula,
which would be useful for the sustainable conservation of this rear fishery in Bangladesh and also
neighboring countries.