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Effect of supplementary stocking of juvenile brown trout, Salmo trutta , on yield in a Norwegian mountain reservoir
Author(s) -
HESTHAGEN T.,
JOHNSEN S. I.,
GRAN R.
Publication year - 2010
Publication title -
fisheries management and ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 55
eISSN - 1365-2400
pISSN - 0969-997X
DOI - 10.1111/j.1365-2400.2010.00735.x
Subject(s) - stocking , salmo , brown trout , fishery , juvenile , fishing , biology , trout , hatchery , zoology , fish <actinopterygii> , ecology
The effect of supplementary stocking of juvenile (age 0+), hatchery‐reared, brown trout, Salmo trutta L., on annual yields was assessed in a Norwegian mountain reservoir between 1979 and 2007. Fishing was mainly carried out by local fishermen with benthic gillnets. During the study period, annual stocking ranged from 0 to 52 500 fish (19.8 ha −1 ). No stocking has been carried out since 1997. Annual yield varied from 1650 to 5653 kg, corresponding to 0.62–2.13 kg ha −1 . Exploitation rate in terms of number of gillnets and mean weight of 6+ fish (age when catchable size was reached) explained 64% of the variability in catches. Stocked fish contributed very little to the yield or catch‐per‐unit‐effort, exhibiting no positive correlation with stocking density. The lack of contribution from stocked fish was probably caused by a competitive bottleneck in the eroded epibenthic zone, causing high juvenile mortality. If stocking continues, it is recommended that fish with body lengths >15–20 cm are used.