Utilization of Pacific hake offal meals of different ash content as protein sources for shinook salmon in sea water
Creators: name: Toy, Brian
Publisher: name: University of British Columbia
Year: 2008

description: Present demands for fish meal by the aquaculture industry in British Columbia exceed domestic supplies. The development of fisheries and onshore processing for domestically underutilized fish species have been identified as means of increasing the supply of fish waste for reduction into fish meal (DPA Group, 1988; Silver and Macleod, 1991). Pacific hake (Merluccius productus), with its large biomass and recent changes in quota allocations, is considered the most promising species for domestic exploitation (Silver and Macleod, 1991; Simpson, 1992). The following study was conducted to a) identify what impact high levels of ash in hake offal press cake meal would have on growth and various physiological parameters, and b) to compare press cake meals produced from non-deboned and deboned roe herring (Culpea harengus) and hake offals as protein sources for sea water-adapted chinook salmon (Oncorhynchus tshawytscha). In Experiment 1, chinook salmon from the Robertson Creek strain were fed to satiation on diets containing either 13.4, 18.1, or 23.1% ash. Hake offal press cake meal was the sole protein source and all diets were formulated to be isonitrogenous (protein = 48%) and isocaloric (37.4 kcal of estimated metabolizable energy/kg dry diet). During the 42-day trial, there were no significant differences in fish growth, appetite or feed efficiency. The concentrations of supplementary minerals in the diet were sufficient to maintain normal growth and development in the fish. Dietary ash levels had no impact on the terminal plasma concentrations of calcitonin or teleocalcin, gastrointestinal pH values, or gross morphology. Attempts to correlate hormonal levels to the amounts of feed in the gastrointestinal tract were unsuccessful. Elevated levels of calcitonin seemed to be related to the maturation state of some of the fish. In Experiment 2, chinook salmon in sea water were fed to satiation on diets containing press cake meals made from deboned or non-deboned hake offal or roe herring. The diets were formulated to be isocaloric (36.8 kcal of estimated metabolizable energy/ kg dry diet) and to contain either 35 or 48% protein which originated solely from one of the four test meals. A high protein diet (48% protein) based on freeze dried hake fillets was used as a positive control. High protein diets supported better growth and feed consumption than the low protein diets. By the end of the experiment, fish fed the low protein diets had higher percentages of carcass lipid and correspondingly lower percentages of carcass protein than fish fed the high protein diets. Feeding behavior differed between fish consuming the low and high protein diets. In the former case, the fish would stop feeding sooner and would actively pursue, capture, and mouth the pellets before expelling them. Very little of the mouthing behavior was displayed by fish on the high protein diets.. Amongst the fish fed the high protein diets, deboning of roe herring offal tended to improve growth, feed consumption, feed efficiency, protein efficiency ratio, body protein content, productive protein value, instantaneous protein gain, and instantaneous lipid gain, whereas the opposite was true for those receiving the deboned hake offal. Examination of the performance data suggested that the amount and availability of dietary arginine, rather than the level of ash, was the limiting factor for growth of fish receiving diets based on deboned hake offal. Fish fed the low protein diets containing deboned hake or herring meal exhibited different trends of performance to those described above for fish ingesting the high protein diets. In this case, deboning had no effect on the performance of chinook salmon fed the hake meal or herring meal diets. Despite the concentrations of arginine in the low protein hake meal diets not meeting estimated requirements and the arginine concentrations in the herring meal diets meeting the requirements, the fish consuming the hake diets tended to have the better growth performance and feed efficiency. However, the trend was not supported by the productive protein value. It can be concluded, therefore, that for the fish eating the low protein diets the hake and herring offal meals were of equal nutritional value. This study indicates that deboning the hake offal was unnecessary and that chinook salmon seemed to be able to utilize hake offal press cake meal as effectively as the herring offal press cake meal.