Temporal variations of sex ratio and growth pattern of critically endangered catfish Clupisoma garua from the Ganges river of north-western Bangladesh

Abstract

This research work states the temporal variations of sex ratio (SR), length-frequency distributions (LFDs), growth type based on length-weight relations (LWRs) and length-length relations (LLRs) of <em>Clupisoma garua </em>from the Ganges river of north-western Bangladesh. A total of 1200 specimens (male=630, female=570) were sampled using traditional fishing gears during May 2014 to April 2015. Then, total length (TL), standard length (SL) and fork length (FL) were taken to about 0.1 cm, and body weight (W) was taken to 0.1 g accuracy. The overall SR (male: female=1.0:0.90) did not vary statistically from the expected ratio of 1:1 (<em>df</em> =1, <em>χ</em><em>2</em> = 3.00, p>0.05). However, monthly variations of SR indicate males were higher in each month except June-August when females were greater in percentage. The LFDs showed that in males <em>C. garua</em>, ranged from 3.8-25.9 cm TL and females 3.9-26.3 cm TL. The LFDs for both sexes did not pass the normality; and Mann-Whitney U-test showed significant differences between sexes (p<0.001). The overall growth pattern was negative allometric (<em>b</em><3.0) in both sexes, although analysis of covariance (ANCOVA) reveals significant difference in LWRs between genders (p<0.001). The LLRs (TL <em>vs.</em> FL and TL <em>vs.</em> SL) of <em>C. garua</em> were highly significant (p<0.001) with all <em>r²</em> values >0.975. Finally, the findings of this study will be helpful for fishery biologists and conservationists to recommend adequate policy for the sustainable fishery of <em>C. garua</em> in the Ganges river and surrounding ecosystem.