Evaluating technical improvements for downstream migrating diadromous fish at a hydroelectric plant

• Technical improvements to ameliorate downstream passage for diadromous fish have rarely been eval-uated in regulated rivers in northern Europe. The current study evaluated rehabilitative measures for downstream migrating Atlantic salmon, brown trout and European eel at a hydroelectric plant in south-ern Sweden. Smolts (N= 66), kelts (N= 20) and silver eels (N= 55) were caught, radio-tagged and tracked whilst passing the facilities in spring (salmonids) and fall (eels) of 2007. A surface gate in combination with a 90 mm-spaced turbine intake rack had a fish guidance efficiency ranging from no effect for eels and trout smolts to 50% for trout kelts. A siphon discharging water from the bottom of the same 90 mm rack did not bypass any tagged fish, and only a few untagged eels. The poor function of the measures was attributed to the failure of the rack to stop smolts and eels from entering the turbines. The kelts, on the other hand, could not pass through the rack, and instead took a long time to locate the surface bypass entrance. The conditions for downstream migrating fish have improved at the hydroelectric plant, but the total losses remain quite high for the studied groups (10–67%), and there is a need for a new rehabilitative measure that effectively allows all fish to bypass the turbines.

Ämnesord

NATURVETENSKAP  -- Biologi -- Annan biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Other Biological Topics (hsv//eng)

Nyckelord

Fish guidance efficiency

Surface bypass

Siphon

European eel

Anadromous trout

Atlantic salmon

Biology

Biologi

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