The Growth Rates And Feed Conversion Efficiency Of Rainbow Trout Salmo Gairdneri When Held At Temperatures Below 5 Degrees Celsius

Author : Wayne A. Wurtsbaugh
Publisher :
ISBN 13 :
Total Pages : 138 pages
Book Rating : 4.:/5 (1 download)

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Download or read book Effects of Temperature Ration and Size on Growth of Juvenile Steelhead Trout, Salmo Gairdneri written by Wayne A. Wurtsbaugh and published by . This book was released on 1973 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of temperature, temperature fluctuation, and fish size on the growth of juvenile steelhead trout (Salmo gairdneri) were studied in experiments which lasted 10 to 25 days. Groups of fish were fed at ration levels varying from near-starvation to repletion. Decelerating, curvilinear relationships between rates of food consumption and growth were defined in most of the experiments. At ration levels near maintenance, temperatures elevated 3 and 6 C above the seasonal ambient temperatures decreased the growth of the trout. As feeding rate increased, the detrimental effect of temperature on growth was ameliorated. At repletion feeding levels, elevation of temperature up to approximately 17 C increased trout growth rates by increasing the maximum food consumption rates of the fish. With temperature increase from 6.9 to 22.5 C the maintenance rations of the trout increased from 2.2 to 7.4% body weight/day. Large diel temperature fluctuations of 4 and 8 C did not increase growth rates and in some cases decreased growth rates to levels below those of fish kept at constant temperatures. Increase of fish size from 0.58 to 3.36 g decreased the maintenance rations (per gram of tissue) of the trout. This decrease was attributed to decreases in metabolic rate that are associated with increases in fish size. As a consequence of this size-dependent change in metabolic rate, large fish grew faster than small fish at low ration levels. However, at ration levels greater than 9%/day, small fish grew faster than large fish. At the highest ration levels fed (9- 12%/day) gross food conversion efficiency of the large fish began to decline, while efficiencies of small fish continued to increase with increases in ration size. Periodic sampling of steelhead trout in a small coastal stream indicated that growth rates of these wild trout ranged from -0.18 to 1.6%/day. Food consumption rates of the wild trout were estimated to range from 2.0 to 7.6%/day; considerably less than the maximum consumption rates of trout kept in the laboratory. At these food consumption rates it is estimated that increases of stream temperature above the normal seasonal temperatures would decrease the growth rates of wild steelhead trout.