Abstract
Rainbow trout (Oncorhynchus mykiss) is among the most widely translocated fish species in the world. The current study evaluated the spawning interactions between naturalized and wild rainbow trout from a high-altitude second-order stream, in Kenya. Data on total length, weight, condition factor, fecundity, fertilization, egg diameter and fry survival were collected on spawning rainbow trout between March to December 2022. Length-weight showed parabolic equations as W = 0.0144L2.900, W = 0.0069L.3.0285 and W = 0.00027L3.175 for wild fish stock, hatchery-reared and wild × hatchery-reared rainbow trout respectively. Total fecundity differed significantly among the hatchery-reared, wild fish, and the cross of the two (P = 0.0045). The fertilization rate showed significant differences (P = 0.0057), with no discernible difference observed between the hatchery-reared and crossed. There was a positive correlation between the total fecundity to female egg weight, female body weight, fertilization rate and eyed egg survival in all the populations. We recommend the use of crossed (wild and hatchery-reared) populations for fry production for use in aquaculture since they presented the highest fecundity and gives the best outcome of fry with high survival.
Keywords: Naturalized Rainbow trout, Aquaculture, Tropical streams, Fish Fecundity.