Annual and diel activity cycles of a northern population of the large migratory cyprinid fish asp (Leuciscus aspius)

Little is known about the exact movement parameters of migratory cyprinids listed as conservation priorities. A northern population of predatory asp, listed on the Bern Convention Appendix III, was studied in a near natural lake–river ecosystem by tracking adult fsh tagged with acoustic transmitters for 32 months. Activity levels in terms of swimming speed, swimming distance and movement range were four times higher during the warmer part of the year (water temperatures>12–15 °C, April/May–September), which coincides with their main feeding period, than other times of the year. All fsh had an annual riverine movement range larger than 40 km (max 110 km). Asp activity was afected by light, habitat type and water discharge. For most of the year, activity levels, in terms of number of movements per time unit, were higher during dawn and dusk than during day and night. Under poor light conditions and low temperatures, activity was also relatively high during the day. Fish were more likely to swim upstream around sunrise or during the day than during other diel periods. Knowledge about highactivity periods, which may render the fsh vulnerable to fshing and other impacts, can be used to develop and evaluate fshing regulations. Large annual movement ranges highlight the need for extensive continuous river systems open for migration between essential habitats. This study emphasises the need for region-specifc research on the ecology and behaviour of fsh populations in order to facilitate protection of the populations in the face of negative human impacts.publishedVersio

Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)

To study the effects of a dispersal barrier on migration of the semi-anadromous vimba bream in the Pärnu River, Estonia, we tagged thirty fish with acoustic transmitters and released above the barrier. Tagged fish showed variation in behaviour, and 16 different spawning movement patterns were identified. Several fish moved > 25 km upstream. Batch spawning was suggested by stops in up to four different spawning areas. The Fish descended to the sea after spawning in spring; females earlier than males. After spending on average 137 days in the sea, they returned to the river during autumn and stayed in the river on average 174 days until the next spawning. The fish were most active during sunrise and sunset. In conclusion, the study shows that the dam prevents a diversification of migration behaviour and the associated expansion of spawning areas. A more efficient fishway could promote population growth and improve stock status.Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)publishedVersio

Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)

To study the effects of a dispersal barrier on migration of the semi-anadromous vimba bream in the Pärnu River, Estonia, we tagged thirty fish with acoustic transmitters and released above the barrier. Tagged fish showed variation in behaviour, and 16 different spawning movement patterns were identified. Several fish moved > 25 km upstream. Batch spawning was suggested by stops in up to four different spawning areas. The Fish descended to the sea after spawning in spring; females earlier than males. After spending on average 137 days in the sea, they returned to the river during autumn and stayed in the river on average 174 days until the next spawning. The fish were most active during sunrise and sunset. In conclusion, the study shows that the dam prevents a diversification of migration behaviour and the associated expansion of spawning areas. A more efficient fishway could promote population growth and improve stock status.Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)publishedVersio

Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)

To study the effects of a dispersal barrier on migration of the semi-anadromous vimba bream in the Pärnu River, Estonia, we tagged thirty fish with acoustic transmitters and released above the barrier. Tagged fish showed variation in behaviour, and 16 different spawning movement patterns were identified. Several fish moved > 25 km upstream. Batch spawning was suggested by stops in up to four different spawning areas. The Fish descended to the sea after spawning in spring; females earlier than males. After spending on average 137 days in the sea, they returned to the river during autumn and stayed in the river on average 174 days until the next spawning. The fish were most active during sunrise and sunset. In conclusion, the study shows that the dam prevents a diversification of migration behaviour and the associated expansion of spawning areas. A more efficient fishway could promote population growth and improve stock status

Behaviour and mortality of downstream migrating Atlantic salmon smolts at a small power station with multiple migration routes

Salmon smolts were released upstream of a run‐of‐river hydropower site and recaptured downstream for inspection. Descending fish behaviour through three possible migration routes (turbines, fishway, spillway) was analysed using telemetry, fyke nets and diving. Tagged smolts did not follow the main water flow; over 70% used the fishway, which received only about 10% of the flow. The turbines received about 80% of the water, but <25% of the smolts. Smolts were not fully stopped from entering the turbines by the 25‐mm bar racks. Mortality of smolts passing through the Kaplan turbines was at minimum 36%. No mortality was found in fish moving through the fishway or spillway. This shows that small and fast‐rotating Kaplan turbines can cause relatively high mortality. No mortality in alternative migration routes resulted in a total mortality for descending smolts at the hydropower station of 8.5%, emphasising the importance of providing functional alternative migration routes. acoustic telemetry, delayed mortality, diel activity, fish passage, Kaplan turbine, salmon managemen