QUALITY IN FISH - WHAT MAKES A GOOD EGG

Factors affecting egg quality are determined by the intrinsic properti es of the egg itself and the environment in which the egg is fertilize d and subsequently incubated. Egg quality in fish is very variable. So me of the factors affecting egg quality in fish are known, but many (p robably most) are unknown. Components that do affect egg quality inclu de the endocrine status of the female during the growth of the oocyte in the ovary, the diet of the broodfish, the complement of nutrients d eposited into the oocyte, and the physiochemical conditions of the wat er in which the eggs are subsequently incubated. In captive broodfish, the husbandry practices to which fish are subjected are probably a ma jor contributory factor affecting egg quality. Our knowledge of the ge netic influences on egg quality is very limited indeed. We know that p arental genes strongly influence both fecundity and egg quality, but a lmost nothing is known about gene expression and/or mRNA translation i n fish oocytes/embryos. This is surprising because the products synthe sized in ovo and the mechanisms controlling their expression are likel y to play a central role in determining egg quality. The genetic mecha nisms underpinning oocyte and embryo growth and development are a prio rity for research.