Length-weight relationship and condition factors of congaturi halfbeak (Hyporhamphus limbatus) in the Kangsha river of Netrokona, Bangladesh

The Congaturi halfbeak, Hyporhamphus limbatus (Valenciennes, 1847) belonging to the family Hemiramphidae is a significant indigenous fish species in Bangladesh. This research work was carried out to analyze the monthly length-weight relationships (LWR) with the construction of generalized relationships of body weight to standard length measurements and the condition of H. limbatus for males and females separately. A total of 524 specimens (228 males and 296 females) used in this study were sampled from the Kangsha River in Netrokona, Bangladesh over a year from September 2020 to August 2021. The results revealed that length-weight relationships were highly correlated (r>0.730) in H. limbatus. The parameters of the equation W=aLb describing the relationships between body weight and standard length for male and female varied monthly. The generalized LWR was fitted with the pooled data of all monthly samples for male and female separately. In case of male, the parameters of equations (a) varied monthly from 3.30 to 7.24 and the slope of equations (b) varied from 2.02 to 3.68. In case of female, the coefficient of equations (a) varied monthly and it ranged from 4.2905 to 9.504 and the slope of equations (b) varied from 2.18 to 3.92. The higher value of regression co-efficient (b) was found either due to maturation of gonad or due to favorable feeding environment. In case of males, fish growth was both positive and negative allometric. In case of females, fish growth was negative allometric except in September, December, June and July. Monthly relative condition factors based on CFBW values ranged from 1.0187 to 1.2070 for male, the lowest condition factor appeared on October 2020 and the highest was on May 2021. In case of female the relative condition factors based on CFBW ranged from 1.1117 to 1.4281, the lowest condition factor appeared on February 2021 and the highest condition factor appeared on April 2021 for female. It has been used as an index of growth and feeding intensity to be detected seasonal variation in the condition of fish and the average storage of population.