Breeding performance and growth pathways in rainbow trout: towards sustainable aquaculture practices

The genetic improvement of rainbow trout (Oncorhynchus mykiss) through strategic cross-breeding and comprehensive broodstock management is essential for sustainable Coldwater aquaculture development. This study evaluated cross-breeding performance, age-dependent broodstock efficiency, incubation technology impacts, and seasonal reproductive patterns of rainbow trout populations from three distinct sources: South Kashmir (n = 220), North Kashmir (n = 180), and commercial hatchery stock (n = 200) from the union territory (UT) of Jammu and Kashmir (J&K) of India. Six cross-breeding combinations were established alongside evaluation of broodstock age groups (2+, 3+, 4 + years) and a comparative analysis of traditional mesh versus modern steel incubation systems. Growth performance was monitored over six months (180 days), with comprehensive fecundity assessments conducted during the spawning season (December-February). Results revealed significant heterosis effects in cross-bred progeny, with N×S crosses showing the highest growth performance (mean weight: 28.4 ± 3.2 g, total length: 18.7 ± 1.8 cm) compared to pure-bred controls. Age-dependent analysis demonstrated that 3 + year broodstock achieved optimal performance with relative fecundity of 1,998 ± 65 eggs/kg and 78.2% hatchling survival, while 4 + year broodstock showed a significant decline (1,576 ± 54 eggs/kg, 55.4% survival). Modern steel incubation trays significantly improved overall survival from fertilization to fry (50.9%) compared to traditional mesh systems (27.8%), representing an 83.1% relative increase. Seasonal patterns revealed peak egg production in February (942 eggs/female) with the highest survival rates in January. The specific growth rate (SGR) ranged from 1.82 to 2.14%/day across crosses, with feed conversion ratios (FCR) varying from 1.32 to 1.68. Heterosis for body weight was highly variable, ranging from − 0.7%, indicating outbreeding depression, to a remarkable + 45.3%, demonstrating exceptional hybrid vigor. The study establishes that integrated genetic improvement strategies combining strategic cross-breeding, optimized broodstock management, and advanced incubation technology significantly enhance both reproductive performance and growth outcomes, providing a comprehensive foundation for sustainable rainbow trout aquaculture development.