The effect of temperature and ration size on the growth, body composition,and energy content of juvenile coho salmon

Juvenile (post-smolt) coho salmon (Oncorhynchus kitsuch) were held in fresh water in the laboratory at 5, 10, 15, and 18 degrees C for 8 weeks and fed freshly thawed, juvenile alewives (Alosa pseudoharengus) at rates equal to 1 and 2 % of their wet body weight/day, and also at the ad libitum or unre stricted ration rate. Most rapid growth in weight (1.2% wet body weight/day ) occurred among fish fed the ad libitum ration at 15 degrees C; growth was most rapid at about 10 degrees C for fish fed the 2% ration (0.7% /day), a nd the 1% ration (0.1% /day). Gross conversion efficiency was highest at 10 degrees C for all three ration levels. Gross body constituents and energy content of the test fish changed with temperature and ration during the stu dy. Growth rate was positively related to lipid, energy content, and ration ; lipid and energy content were positively related to water temperature; li pid, energy content, growth rate, ration, and water temperature were negati vely related to water content; and protein was not related to any of the te st variables. At the end of the study, water (68.7 to 76.4%) and lipid (3.5 to 10.4%) content were more variable than ash (1.8 to 3.1%), carbohydrate (0.1 to 1.9%), and protein (16.9 to 19.4%) content. Energy content of the f ish increased with ration and was highest for each ration level at 15 degre es C.