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The near-threatened Ailia coila, commonly referred to as Gangetic ailia, is a catfish species in the Ailiidae family that is indigenous to Bangladesh, Pakistan, Nepal, and India. This study describes the comprehensive explanation of life-history traits of Ailia coila, including length-frequency distribution (LFD), growth pattern (length-weight relationships, LWRs and length-length relationship, LLR), form factor (a3.0), condition factors (allometric, KA; Fulton’s, KF; relative, KR and relative weight, WR), size at first sexual maturity (Lm), optimum catchable length (Lopt) and natural mortality (Mw) from the Tetulia River in southern Bangladesh. Additionally, Lα, a3.0, Lm, Mw and Lopt from various water bodies worldwide using the existing literature were calculated in this study. A total of 316 samples were randomly collected occasionally using traditional gear for a year from July 2021 to June 2022. With an accuracy of 0.01 cm and 0.01 g, each fish’s total length (TL), standard length (SL), and body weight (BW) were measured. The group from 10.00 to 10.99 cm TL was numerically leading and the b values of LWRs indicate positive allometric growth. The a3.0 was 0.005 and KF was the best for assessing the well-being of A. coila. Additionally, WR indicates that the habitat was imbalanced with higher predators. The calculated Lm, Lopt and Mw were 9.19 (~ 9.2 cm TL), 10.7 cm TL and 1.37 year−1 for A. coila in the Tetulia River, respectively. These insights are vital for future research and recommending suitable management strategies for A. coila in the Tetulia River and neighboring basins.

The near threatened gangetic scissortail rasbora, Rasbora rasbora (Hamilton, 1822), is an economically important, and nutritionally valuable freshwater food fish in south Asian countries. The present study provides the first inclusive explanation on life-history traits of R. rasbora in the Payra River, southern Bangladesh. This species invites research interest due to its nutritional demand and IUCN red list status. Sampling was carried out using different traditional fishing gears during July to December 2019. For each individual, total length (TL) and standard length (SL) were measured to the nearest 0.01 cm using digital slide caliper, while body weight (BW) was taken by an electronic balance with 0.01 g accuracy. A total of 215 specimens were measured ranging from 2.6-12.5 cm TL and 0.22-10.65 g BW during this study. The 4.00 to 4.99 cm TL was numerically leading group of the total population. The allometric coefficient (b) of the length-weight relationships (LWRs) indicates negative allometric growth pattern (b<3.00) for R. rasbora in the Payra River. The results also indicate that the LWRs were highly significant (p<0.001) with r2 values >0.963. In addition, The LLR (SL vs. TL) was highly significant (p<0.0001) with a coefficient of determination values of 0.988. The estimated form factor (a3.0) was 0.007 indicating this fish is elongated in body shape and the size at first sexual maturity (Lm) for combined sexes of R. rasbora was calculated as 7.96 (~8.00) cm TL in the Payra River. The allometric condition factor (KA) varied from 0.0063 to 0.0570 and Fulton's condition factor (KF) varied from 0.3933 to 4.1844. However, KF tended to be lower after 9.0 cm for combined sexes, which may indicate the start of sexual maturation and therefore Lm could be around 8.0 cm TL for R. rasbora. The knowledge about the biological aspects of gangetic scissortail rasbora may be used for improved management tools in the future. [ABSTRACT FROM AUTHOR]