Condition, length–weight and length–length relationships of the silver hatchet Chela, Chela cachius (Hamilton, 1822) in the Old Brahmaputra River of Bangladesh

Abstract

The silver hatchet chela, Chela cachius (Hamilton, 1822), is a cyprinid freshwater species, commercially important for both subsistence and artisanal fisheries in Bangladesh. This study describes the length–weight relationship (LWR), length–length relationship (LLR) and the condition of this minnow species from the Old Brahmaputra River in Bangladesh. In this study, 12 monthly samples totalling 2400 specimens (1172 male; 1228 female) collected from November 2004 to October 2005 were used to conduct this study. For each individual, the total length (TL), fork length (FL) and standard length (SL) as well as body weight (BW) were measured. The overall sex ratio showed no significant difference from the expected value of 1:1 and the analysis of covariance (ANCOVA) revealed no significant difference between LWRs of male and female for the pooled data over a year. Parameters of LWRs of combined gender varied monthly with high coefficients of determination (r 2 > 0.751; p < 0.001). All the LLRs (SL vs. FL, FL vs. TL and SL vs. TL) exhibited strong correlations (r 2 > 0.886; p < 0.001) and ANCOVA analyses further indicated that LLRs did not differ between males and females. The relative-condition factors with regard to both months and SLs varied in all gender groups. Females maintained similar mean condition throughout life and showed more plumpness than both males and combined genders in all months. Finally, the results should be useful for the sustainable management of this minnow species in Old Brahmaputra River and adjacent water-bodies.