Climate‐Resilient Aquaculture: Recirculatory Aquaculture Systems–Based Seed Production for <i>Heteropneustes fossilis</i> in Bangladesh

ABSTRACT Aquaculture in Bangladesh heavily relies on hatchery‐produced seeds but encounters climate change challenges. In an experimental study, two distinct recirculatory aquaculture systems (RAS) were employed: large‐RAS (LRAS) and mini‐RAS (MRAS). They were utilized for broodstock rearing, breeding, seed production and larval rearing of Heteropneustes fossilis , aiming to assess the overall suitability of RAS for seed production as an adaptation strategy in response to climate change. During the four‐month rearing period in LRAS, both male and female fish showed significant increases in length, weight gain and specific growth rate, accompanied by higher survival rates, particularly in developing broodstock. Breeding of H. fossilis was characterized by high fertilization (95%) and hatching rate (98%). Following 27 days of rearing in MRAS and the aquarium, the larvae exhibited adult‐like characteristics, showing an average length and weight of 2.6 ± 0.211 mm and 0.115 ± 0.088 g, respectively. By day 60 in LRAS, there was a notable increase in both the average length and weight of larvae to 6.55 ± 1.49 mm and 3.158 ± 0.64 g, accompanied by surface water air engulfment and heightened nocturnal activity. The relative condition factor (Kn) assesses the overall growth, health and well‐being of fish by comparing the observed weight to the expected weight based on the length–weight relationship, with a Kn of 1.25 for larvae in LRAS, indicating favourable growth. Subsequent larvae rearing in MRAS jars, aquarium tank, and LRAS tank for 10, 20 and 30 days, respectively exhibited noticeable length and weight gain with higher specific growth rates. These findings highlight the effectiveness of RAS in optimizing broodstock development, enhancing seed production efficiency and ensuring the quality of H. fossilis seed under controlled conditions. Implementing RAS can significantly contribute to climate‐resilient aquaculture, offering a sustainable solution for fish seed production in Bangladesh.