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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

Daily movement for European grayling (A) and brown trout (B) over months of the year. Data are shown as the average movement over all tagged individuals (n = 180 and 275, respectively). Upstream movement is indicated as positive, downstream movement as negative. P‐values of one‐sample t‐tests testing for a significant difference in movement from 0 m are indicated for each month for the rivers combined. Error bars indicate standard errors of the mean, more statistical details in Table S3. (C) Fishway operation over months of the year. Gray bars indicate when the fishways are open. Error bars indicate SD around the mean opening and closing times during the years 1985–2011. (D) Average number of fish passing the four fishways per year indicted over months. Data are summed for the four fishways but averaged over 1985–2011. Error bars indicate SE. (E) River discharges in the two rivers. Indicated for the four different migration barriers in Glomma River and the two upstream barriers Eidefoss power plant and Rosten waterfalls in Lågen River. The solid (blue) line depicts the average river water temperature in Glomma River, and the dashed (green) line the average river water temperatures for Lågen River, both in relation to the right‐hand vertical axis.
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ece31937-fig-0002: Daily movement for European grayling (A) and brown trout (B) over months of the year. Data are shown as the average movement over all tagged individuals (n = 180 and 275, respectively). Upstream movement is indicated as positive, downstream movement as negative. P‐values of one‐sample t‐tests testing for a significant difference in movement from 0 m are indicated for each month for the rivers combined. Error bars indicate standard errors of the mean, more statistical details in Table S3. (C) Fishway operation over months of the year. Gray bars indicate when the fishways are open. Error bars indicate SD around the mean opening and closing times during the years 1985–2011. (D) Average number of fish passing the four fishways per year indicted over months. Data are summed for the four fishways but averaged over 1985–2011. Error bars indicate SE. (E) River discharges in the two rivers. Indicated for the four different migration barriers in Glomma River and the two upstream barriers Eidefoss power plant and Rosten waterfalls in Lågen River. The solid (blue) line depicts the average river water temperature in Glomma River, and the dashed (green) line the average river water temperatures for Lågen River, both in relation to the right‐hand vertical axis.

Mentions: The telemetry data were used to study the timing of fish movements in free‐flowing, unfragmented sections of the rivers. We determined whether or not species moved significantly up‐ or downstream during particular periods of the year, by classifying all movement as either upstream (positive) or downstream (negative), and averaging this per species per month. As the study systems are comparable in both biotic and abiotic characteristics and showed consistent patterns of fish movement (see Fig. 2E and Table S3 for details), the telemetry observations were pooled over 3 years to increase sample sizes and to describe behavior that is consistent over multiple years and river systems. Data were standardized to movement per day to account for differences in time intervals between consecutive detections (on average once per week). Whether or not average daily movement was significantly different from zero movement was determined per month by two‐tailed one‐sample t‐tests, separately per species (and by river system in Table S3). In addition, for each individual fish we calculated the length of the river section it used per month, defined as the maximum distance between the two extreme positions in the rivers where an individual was located.


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)

Daily movement for European grayling (A) and brown trout (B) over months of the year. Data are shown as the average movement over all tagged individuals (n = 180 and 275, respectively). Upstream movement is indicated as positive, downstream movement as negative. P‐values of one‐sample t‐tests testing for a significant difference in movement from 0 m are indicated for each month for the rivers combined. Error bars indicate standard errors of the mean, more statistical details in Table S3. (C) Fishway operation over months of the year. Gray bars indicate when the fishways are open. Error bars indicate SD around the mean opening and closing times during the years 1985–2011. (D) Average number of fish passing the four fishways per year indicted over months. Data are summed for the four fishways but averaged over 1985–2011. Error bars indicate SE. (E) River discharges in the two rivers. Indicated for the four different migration barriers in Glomma River and the two upstream barriers Eidefoss power plant and Rosten waterfalls in Lågen River. The solid (blue) line depicts the average river water temperature in Glomma River, and the dashed (green) line the average river water temperatures for Lågen River, both in relation to the right‐hand vertical axis.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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

ece31937-fig-0002: Daily movement for European grayling (A) and brown trout (B) over months of the year. Data are shown as the average movement over all tagged individuals (n = 180 and 275, respectively). Upstream movement is indicated as positive, downstream movement as negative. P‐values of one‐sample t‐tests testing for a significant difference in movement from 0 m are indicated for each month for the rivers combined. Error bars indicate standard errors of the mean, more statistical details in Table S3. (C) Fishway operation over months of the year. Gray bars indicate when the fishways are open. Error bars indicate SD around the mean opening and closing times during the years 1985–2011. (D) Average number of fish passing the four fishways per year indicted over months. Data are summed for the four fishways but averaged over 1985–2011. Error bars indicate SE. (E) River discharges in the two rivers. Indicated for the four different migration barriers in Glomma River and the two upstream barriers Eidefoss power plant and Rosten waterfalls in Lågen River. The solid (blue) line depicts the average river water temperature in Glomma River, and the dashed (green) line the average river water temperatures for Lågen River, both in relation to the right‐hand vertical axis.
Mentions: The telemetry data were used to study the timing of fish movements in free‐flowing, unfragmented sections of the rivers. We determined whether or not species moved significantly up‐ or downstream during particular periods of the year, by classifying all movement as either upstream (positive) or downstream (negative), and averaging this per species per month. As the study systems are comparable in both biotic and abiotic characteristics and showed consistent patterns of fish movement (see Fig. 2E and Table S3 for details), the telemetry observations were pooled over 3 years to increase sample sizes and to describe behavior that is consistent over multiple years and river systems. Data were standardized to movement per day to account for differences in time intervals between consecutive detections (on average once per week). Whether or not average daily movement was significantly different from zero movement was determined per month by two‐tailed one‐sample t‐tests, separately per species (and by river system in Table S3). In addition, for each individual fish we calculated the length of the river section it used per month, defined as the maximum distance between the two extreme positions in the rivers where an individual was located.

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