M. R. Islam
Department of Fisheries Biology and Genetics, Hajee Mohammad Danesh Science and Technology University, Dinajpur-5200, Bangladesh
M. G. Azom
Faculty of Fisheries, Hajee Mohammad Danesh Science and Technology University, Dinajpur-5200, Bangladesh
Growth Factor; Small fishes; Atrai river
Dinajpur district of Bangladesh.
Variety and Species
Five fish species (A. jaya, G. cenia, G. youssoufi, S. bacaila and S. phulo) were caught monthly (by fishermen) using seine net (15 × 3.5 m2, 4 mm), gillnet (12 × 0.9 m2, 15 mm) or cast net (4 × 6.75 m2, 8 mm) from July to December, 2015 in the Atrai River (25.924° N 88.724° E) of Dinajpur district of Bangladesh. The captured fishes were immediately (within 1.5 hours) transported to laboratory using ice box. Total length (TL) and standard length (SL) were measured with a vernier caliper to the nearest 0.1 cm. Body weight (BW) were taken with a digital balance (HD-602ND, MEGA, Japan) to the nearest 0.1 g. Length-weight relationships (LWRs) were calculated through logarithmic transformation of linear regression equation as log BW = log a + b log TL, where BW is body weight (g), TL total length (cm) of fishes, a intercept and b slope of regression curve (Islam et al., 2017; Islam et al., 2018). The log-log plots for LWRs were exploited to eliminate the outliers (Froese, 2006). To estimate the condition (Fulton’s, CFf and relative body weight, BWr) and form (a3.0) factors, regression parameters a and b were obtained from previously calculated LWRs (log TL vs. log BW) followed by Islam and Mia (2016). Where, the earlier values of a and b are noted as 0.010 and 2.899 for A. jaya, 0.006 and 3.059 for G. cenia, 0.012 and 3.004 for G. youssoufi, 0.009 and 2.755 for S. bacaila, and 0.004 and 3.222 for S. phulo, respectively in the Atrai River, Dinajpur, Bangladesh. However, condition factors (CFs) were measured to recognize the health condition of these fishes where Fulton’s condition factor was calculated as CFf = (BW× 100)/TL3 (Fulton, 1904) and relative body weight as BW =(BW/aTLb) × 100 (Froese, 2006). Where, BW is body weight (g), TL total length (cm) while a and b are regression parameters previously estimated from LWRs by Islam and Mia (2016). According to Froese (2006), form factor (a3.0) was estimated through an equation as a 3.0 = 10 log a – S (b-3),where a and b (formerly computed) from LWRs as regression parameters. Then, mean slope S = -1.358 was used to calculate a 3.0 for these fish species. Using CFf and BWr values,one-way analysis of variance (ANOVA) and one-way analysis of similarities (ANOSIM) were tested to noticedissimilarities (p < 0.05) among fishes. Two-dimensional nonmetric multidimensional scaling (nMDS) was taken to measure the remoteness among fishes after logarithming transform of CFf and BWr values. All statistical tests were done using SPSS (IBM corporation, version 22), PAST (Paleontological statistics, version 3.10) software and Microsoft Office Excel, 2013.
Bangladesh J. Sci. Ind. Res. 53(2), 155-160, 2018
Journal