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Mismatch between fishway operation and timing of fish movements: a risk for cascading effects in partial migration systems.

van Leeuwen CH, Museth J, Sandlund OT, Qvenild T, Vøllestad LA - Ecol Evol (2016)

Bottom Line: Here we hypothesized that restricted seasonal opening times of fishways can importantly reduce their effectiveness by interfering with the timing of fish migration, for both spring- and autumn-spawning species.We show in a theoretical framework how restricted opening times of fishways can induce shifts from migratory to resident behavior in potamodromous partial migration systems, and propose that this can induce density-dependent effects among fish accumulating in lower regions of rivers.Fishway functionality is inadequate if there is a mismatch between natural fish movements and fishway opening times in the same river system, with ecological and possibly evolutionary consequences for fish populations.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences Centre for Ecological and Evolutionary Synthesis (CEES) University of Oslo Post Office Box 1066 Blindern 0316 Oslo Norway.

ABSTRACT
Habitat fragmentation is a growing problem worldwide. Particularly in river systems, numerous dams and weirs hamper the movement of a wide variety of species. With the aim to preserve connectivity for fish, many barriers in river systems are equipped with fishways (also called fish passages or fish ladders). However, few fishways provide full connectivity. Here we hypothesized that restricted seasonal opening times of fishways can importantly reduce their effectiveness by interfering with the timing of fish migration, for both spring- and autumn-spawning species. We empirically tested our hypothesis, and discuss the possible eco-evolutionary consequences of affected migration timing. We analyzed movements of two salmonid fishes, spring-spawning European grayling (Thymallus thymallus) and autumn-spawning brown trout (Salmo trutta), in Norway's two largest river systems. We compared their timing of upstream passage through four fishways collected over 28 years with the timing of fish movements in unfragmented river sections as monitored by radiotelemetry. Confirming our hypothesis, late opening of fishways delayed the migration of European grayling in spring, and early closure of fishways blocked migration for brown trout on their way to spawning locations during late autumn. We show in a theoretical framework how restricted opening times of fishways can induce shifts from migratory to resident behavior in potamodromous partial migration systems, and propose that this can induce density-dependent effects among fish accumulating in lower regions of rivers. Hence, fragmentation may not only directly affect the migratory individuals in the population, but may also have effects that cascade downstream and alter circumstances for resident fish. Fishway functionality is inadequate if there is a mismatch between natural fish movements and fishway opening times in the same river system, with ecological and possibly evolutionary consequences for fish populations.

No MeSH data available.


Related in: MedlinePlus

Map of the study systems Lågen River and Glomma River, Norway. Migration barriers in the rivers are indicated by (red) bars with underlined (red) names, river names are in italic, and lake names in boldface.
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ece31937-fig-0001: Map of the study systems Lågen River and Glomma River, Norway. Migration barriers in the rivers are indicated by (red) bars with underlined (red) names, river names are in italic, and lake names in boldface.

Mentions: The rivers Glomma and Gudbrandsdalslågen (hereafter Lågen) are the two largest rivers in southeastern Norway (Fig. 1). In Glomma River, the study area covers the 236 km river section from the town of Elverum (60.832°N; 11.613°E) in the south to the dam and power plant at Røstefossen (62.507°N; 11.264°E) in the north. Downstream of Elverum salmonid densities decrease and the fish communities change significantly. The upper limit of the study site was the impassable dam at Røstefossen. The study area also included 26 km of the tributary Rena River up to Lake Storsjøen (61.394°N; 11.364°E). Within this section of the Glomma and Rena rivers, which in the natural condition was open to two‐way fish migration, there are four hydropower dams with fishways (Fig. 1, Table S2).


Mismatch between fishway operation and timing of fish movements: a risk for cascading effects in partial migration systems.

van Leeuwen CH, Museth J, Sandlund OT, Qvenild T, Vøllestad LA - Ecol Evol (2016)

Map of the study systems Lågen River and Glomma River, Norway. Migration barriers in the rivers are indicated by (red) bars with underlined (red) names, river names are in italic, and lake names in boldface.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834326&req=5

ece31937-fig-0001: Map of the study systems Lågen River and Glomma River, Norway. Migration barriers in the rivers are indicated by (red) bars with underlined (red) names, river names are in italic, and lake names in boldface.
Mentions: The rivers Glomma and Gudbrandsdalslågen (hereafter Lågen) are the two largest rivers in southeastern Norway (Fig. 1). In Glomma River, the study area covers the 236 km river section from the town of Elverum (60.832°N; 11.613°E) in the south to the dam and power plant at Røstefossen (62.507°N; 11.264°E) in the north. Downstream of Elverum salmonid densities decrease and the fish communities change significantly. The upper limit of the study site was the impassable dam at Røstefossen. The study area also included 26 km of the tributary Rena River up to Lake Storsjøen (61.394°N; 11.364°E). Within this section of the Glomma and Rena rivers, which in the natural condition was open to two‐way fish migration, there are four hydropower dams with fishways (Fig. 1, Table S2).

Bottom Line: Here we hypothesized that restricted seasonal opening times of fishways can importantly reduce their effectiveness by interfering with the timing of fish migration, for both spring- and autumn-spawning species.We show in a theoretical framework how restricted opening times of fishways can induce shifts from migratory to resident behavior in potamodromous partial migration systems, and propose that this can induce density-dependent effects among fish accumulating in lower regions of rivers.Fishway functionality is inadequate if there is a mismatch between natural fish movements and fishway opening times in the same river system, with ecological and possibly evolutionary consequences for fish populations.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences Centre for Ecological and Evolutionary Synthesis (CEES) University of Oslo Post Office Box 1066 Blindern 0316 Oslo Norway.

ABSTRACT
Habitat fragmentation is a growing problem worldwide. Particularly in river systems, numerous dams and weirs hamper the movement of a wide variety of species. With the aim to preserve connectivity for fish, many barriers in river systems are equipped with fishways (also called fish passages or fish ladders). However, few fishways provide full connectivity. Here we hypothesized that restricted seasonal opening times of fishways can importantly reduce their effectiveness by interfering with the timing of fish migration, for both spring- and autumn-spawning species. We empirically tested our hypothesis, and discuss the possible eco-evolutionary consequences of affected migration timing. We analyzed movements of two salmonid fishes, spring-spawning European grayling (Thymallus thymallus) and autumn-spawning brown trout (Salmo trutta), in Norway's two largest river systems. We compared their timing of upstream passage through four fishways collected over 28 years with the timing of fish movements in unfragmented river sections as monitored by radiotelemetry. Confirming our hypothesis, late opening of fishways delayed the migration of European grayling in spring, and early closure of fishways blocked migration for brown trout on their way to spawning locations during late autumn. We show in a theoretical framework how restricted opening times of fishways can induce shifts from migratory to resident behavior in potamodromous partial migration systems, and propose that this can induce density-dependent effects among fish accumulating in lower regions of rivers. Hence, fragmentation may not only directly affect the migratory individuals in the population, but may also have effects that cascade downstream and alter circumstances for resident fish. Fishway functionality is inadequate if there is a mismatch between natural fish movements and fishway opening times in the same river system, with ecological and possibly evolutionary consequences for fish populations.

No MeSH data available.


Related in: MedlinePlus