2010/719 Training in endocrine diagnostic techniques and hormone analysis of thermally challenged Atlantic Salmon broodstock

By Kelli Anderson

The purpose of the research was to determine whether the endocrine profiles of plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH) changed as a result of thermal exposure, broodstock age or hormonal treatment in farmed female Atlantic Salmon. FSH promotes the production of testosterone, oestrogen and oocyte (egg) growth while LH controls oocyte maturation and ovulation. There is some evidence to suggest that fish reared at 22 °C (equivalent of a warm Tasmanian summer) have higher levels of circulating FSH compared to fish reared at 14 °C (ideal temperature) and this is probably due to abnormal oestrogen levels (and therefore feedback mechanisms) in fish reared at high temperature.

An in vitro experiment was performed in Seattle that investigated the affect of elevated temperature and hormonal treatment on the expression levels of genes involved in testosterone production in ovarian fragments isolated from Coho Salmon. For the first time, it was shown that the relative expression of several genes involved in testosterone production was impaired by increased temperature in vitro. From this trial, a suite of candidate genes that may contribute to low T levels and therefore reproductive performance in Atlantic Salmon reared at 22 °C have been identified.

These results combined with previous work demonstrate that dysfunction at multiple levels in the endocrine cascade controlling reproductive development in thermally challenged female Atlantic Salmon is likely. This work also shows that formulating management strategies that improve reproductive performance in Atlantic Salmon reared at elevated temperature is no easy feat. However, as the CRC are learning more about how reproductive physiology changes with various therapeutic, biological (i.e. age) and environmental conditions, the CRC is becoming better positioned to make informed choices that will benefit the aquaculture industry in Australia.