Stranding of pond- and hatchery-reared juvenile brown trout, Salmo trutta L., during draw-down of a pond |
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| Authors: | T HESTHAGEN O HEGGE |
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| Institution: | Norwegian Institute for Nature Research, Trondheim, Norway;Environmental Administration, Statsetatenes Hus, Lillenhammer, Norway |
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| Abstract: | Abstract. One thousand each of pond and hatchery reared 0+ brown trout, Salmo trutta L., were fin-clipped and released in a 1300-m2 large earthen pond. The pond was drawn down 5 days after the introduction, and descending individuals were caught in a trap at the outlet. A total of 904 pond-reared and 890 hatchery-reared fish were recaptured, i.e. a loss of 9·6 and 110% respectively, A total of 25 pond-reared and 16 hatchery reared fish were recorded stranded in the pond during the draw-down, accounting for 2·7 and 1·8% of total recoveries.
Pond-reared fish descended significantly earlier than did hatchery fish. Most individuals descended during the first 4·5h (75-83%). However, the final recoveries were made 10 days (233h) after the first descent. |
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