Epsilon Open Archive

Abstract

The Swedish Arctic charr breeding programme was established in the early 1980's. Over 25 years of selective breeding has resulted in a fast-growing, late-maturing strain of charr called the Arctic Superior. However, the reproductive success of this strain is far from satisfactory. Egg hatching rates are erratic and often very low compared to other salmonid species in Scandinavian aquaculture. Securing a reliable supply of eggs and stocking fish is imperative to a continued expansion of the Swedish Arctic charr farming industry. The aim of this essay is to look into the biological and physical factors affecting gamete quality and offspring survival in fish and elucidate the most crucial of these factors concerning the Arctic Superior.
I believe that physical factors regarding the holding conditions are the cause of the problem, rather than biological traits attained as by-products of the breeding process. I suggest high temperature to be the main factor behind the problems of poor reproductive success. However, it is unlikely the only explanation to the problem.
Timing of spawning is an important part of the problem. Spawning period is often prolonged and poorly synchronised between sires and dams. This leads to increased handling and stress of the fish, over-ripening of eggs and difficulties with fertilisation, all contributing to lower reproductive success. Spawning period can be manipulated through altered photoperiod or hormonal treatment. Hormone implants can efficiently induce ovulation and spermiation, but may have detrimental effects on gamete quality. If the environmental holding conditions are right synchronised spawning and improved gamete quality should be achieved and the use of hormones should not be needed.