BROODSTOCK MANAGEMENT, FECUNDITY, EGG QUALITY AND THE TIMING OF EGG-PRODUCTION IN THE RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

The full potential of rainbow trout hatcheries can be attained only if the hatcheries can provide producers with regular supplies of high quality eggs and fry every week of the year. This review assesses aspects of brookstock management central to determining total number of eggs produced, quality of eggs, and timing of maturation and spawning. The effectiveness of hatchery programmes in supporting an expanding rainbow trout market is profoundly affected by the conditions under which the broodfish are maintained, their husbandry, and the stock selected for production. The paper examines factors that can critically affect fecundity, egg production, egg quality, spawning time, and maintenance of egg supplies. The discussion also outlines methods of manipulating spawning and areas requiring further advancement of knowledge if progress is to continue in optimising egg and fry production.