Feed intake control and energy metabolism for Atlantic salmon under conditions of increasingly high seawater temperature and hypoxia.

?Regulation of appetite and growth of Atlantic salmon (Salmo salar L.) and effect of water oxygen, temperature and dietary energy? The PhD investigates how appetite and growth of salmon are influenced by low oxygen and high temperature, as well as high dietary energy. The studies show that high temperature reduces appetite and growth, even at optimal oxygen conditions. Low water oxygen resulted in an impairment of the energy metabolism, which contributes to reduced growth at both optimal and high temperatures. Feeding high dietary energy had a positive effect on both growth and energy metabolism. The hormone ghrelin indicated meal anticipation similar to that of humans and other vertebrates.

This PhD aims at elucidating how protein and energy is utilised under hypoxic conditions and elevated sea water temperatures and how this affects feed uptake and growth in terms of regulation of ghrelin, leptin and the GH-IGF axis in farmed Atlantic salmo n. The back ground of this PhD study is based on the expected effects of global warming on fish farming conditions in Norway. Current warm summer conditions already have a significant documented impact on salmon production, and these problems are forecast to increase markedly in coming years due to local effects of global warming and predicted increases of up to 1.5 to 2°C for the Norwegian seawater temperature this century. The aim of this PhD study is to gain further knowledge on the nutritional dietary signalling and nutrient partitioning under sub-optimal conditions in order to still enable optimal fish farming in the future. During the two first years of the PhD there are 4 fish trials planned followed by one publication each, while the last year wil l mainly be used to write up the final PhD thesis. The fish trials aim at investigating sea water adapted salmon of different sizes held at sufficient and hypoxic oxygen conditions (<90% and <70% dissolved oxygen) and optimal and high water temperatures ( 12-13°C and 15-19°), respectively. Fish will be fed diets of different protein:energy ratios and effects on the hormonal regulation of feed intake, appetite and growth will be elucidated. Regulation will be described by the hormones; cortisol, ghrelin and IGF binding proteins (IGBPs), together with the GH-IGFs and IGFBPs mRNA levels, all which will be analysed at NIFES. In order to learn about the analytical methods and how to conduct them on own samples I will make regular visits to NIFES and UiB for tra ining, discussions, courses and updates on progress throughout the PhD study.