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Effect of Hatchery Rearing Conditions on Stream Survival of Brown Trout
Author(s) -
Eipper Alfred W.
Publication year - 1963
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1963)92[132:eohrco]2.0.co;2
Subject(s) - stocking , hatchery , trout , brown trout , salmo , biology , fishery , zoology , acclimatization , ecology , fish <actinopterygii>
Groups of brown trout (Salmo trutta) which had experienced normal and temperature‐retarded growth in the hatchery were stocked in a 5‐mile section of Fall Creek, New York, to compare their natural mortality rates during the season directly following spring stocking. “Normal” trout were reared in Cortland, New York, hatchery water averaging 54° F. and varying annually from 39 to 60° F.; “retarded” trout were reared in a different water supply at Cortland which remained at approximately 47° F. year‐round. Observations on movement (from tag returns), rates of exploitation (from creel census), and total mortality (from electrical inventories in June and September) provided the data needed to compute natural mortality rate (n) of each experimental lot in the first and second parts of both the 1949 and 1950 seasons. Yearling and 2‐year‐old retarded trout usually had higher natural mortality than did yearling normals in both parts of both seasons. The higher mortality rates among the retarded trout were particularly evident in the second parts of the seasons, when higher water temperatures prevailed. At time of stocking in 1949, yearling normals had harder body fat (lower iodine number) than the yearling retarded trout. In a 6‐week test in Cascadilla Creek in the spring of 1951, yearling normals again had lower natural mortality than yearling retarded trout, although water temperatures never became critically high. These findings suggest that characteristics of the hatchery water supply can influence natural mortality rate of brown trout after stocking. High‐temperature acclimation may be one component of this influence, but apparently it is not the only component.