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Migratory passage structures at hydropower plants as potential physiological and behavioural selective agents.

ABSTRACT: Anthropogenic activities affect fish populations worldwide. River dams have profound impacts on ecosystems by changing habitats and hindering migration. In an effort to counteract such effects, a range of mitigation measures have been installed at hydroelectric power plants. However, not all individuals in a population use these measures, potentially creating strong selection processes at hydroelectric power plants. This may be especially true during migration; fish can get heavily delayed or pass through a hydropower turbine, thus facing increased mortality compared with those using a safe bypass route. In this study, we quantify migration route choices of descending wild passive integrated transponder (PIT)-tagged Atlantic salmon smolts released upstream from a hydroelectric plant. We demonstrate how only a few metres' displacement of bypass canals can have a large impact on the fish guidance efficiency (FGE). The proportion of fish using the bypasses increased from 1% to 34% when water was released in surface gates closer to the turbine intake. During a period of low FGE, we observed two different smolt migratory strategies. While some individuals spent little time in the forebay before migrating through the turbine tunnel, others remained there. We suggest that these groups represent different behavioural types, and that suboptimal mitigation measures at hydropower intakes may, therefore, induce strong selection on salmon behavioural traits. The ultimate outcome of these selection mechanisms is discussed in light of potential trade-offs between turbine migration mortality coast and optimal sea entrance timing survival benefits.

SUBMITTER: Haraldstad T

PROVIDER: S-EPMC6894575 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Migratory passage structures at hydropower plants as potential physiological and behavioural selective agents.

Haraldstad Tormod T Haugen Thrond Oddvar TO Kroglund Frode F Olsen Esben Moland EM Höglund Erik E

Royal Society open science 20191113 11

Anthropogenic activities affect fish populations worldwide. River dams have profound impacts on ecosystems by changing habitats and hindering migration. In an effort to counteract such effects, a range of mitigation measures have been installed at hydroelectric power plants. However, not all individuals in a population use these measures, potentially creating strong selection processes at hydroelectric power plants. This may be especially true during migration; fish can get heavily delayed or pa ...[more]

PMID: 31827840

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Project description:Fishways have been widely used for upstream passage around human-built structures, but 'success' has varied dramatically. Evaluation of fishway success has typically been conducted at local scales using metrics such as fish passage efficiency and passage time, but evaluations are increasingly used in broader assessments of whether passage facilities meet population-specific conservation and management objectives. Over 15 years, we monitored passage effectiveness at eight dams on the Columbia and Snake rivers for 26,886 radio-tagged spring-summer and fall Chinook Salmon O. tshwaytscha, Sockeye Salmon O. nerka, and summer steelhead O. mykiss during their migrations to spawning sites. Almost all fish that entered dam tailraces eventually approached and entered fishways. Tailrace-to-forebay passage efficiency estimates at individual dams were consistently high, averaging 0.966 (SD = 0.035) across 245 run×year×dam combinations. These estimates are among the highest recorded for any migratory species, which we attribute to the scale of evaluation, salmonid life history traits (e.g., philopatry), and a sustained adaptive management approach to fishway design, maintenance, and improvement. Full-dam fish passage times were considerably more variable, with run×year×dam medians ranging from 5-65 h. Evaluation at larger scales provided evidence that fishways were biologically effective, e.g., we observed rapid migration rates (medians = 28-40 km/d) through river reaches with multiple dams and estimated fisheries-adjusted upstream migration survival of 67-69%. However, there were substantive uncertainties regarding effectiveness. Uncertainty about natal origins confounded estimation of population-specific survival and interpretation of apparent dam passage 'failure', while lack of post-migration reproductive data precluded analyses of delayed or cumulative effects of passing the impounded system on fish fitness. Although the technical fishways are effective for salmonids in the Columbia-Snake River system, other co-migrating species have lower passage rates, highlighting the need for species-specific design and evaluation wherever passage facilities impact fish management and conservation goals.

Project description:BackgroundHuman disturbance alters animal movement globally and infrastructure, such as roads, can act as physical barriers that impact behaviour across multiple spatial scales. In ungulates, roads can particularly hamper key ecological processes such as dispersal and migration, which ensure functional connectivity among populations, and may be particularly important for population performance in highly human-dominated landscapes. The impact of roads on some aspects of ungulate behaviour has already been studied. However, potential differences in response to roads during migration, dispersal and home range movements have never been evaluated. Addressing these issues is particularly important to assess the resistance of European landscapes to the range of wildlife movement processes, and to evaluate how animals adjust to anthropogenic constraints.MethodsWe analysed 95 GPS trajectories from 6 populations of European roe deer (Capreolus capreolus) across the Alps and central Europe. We investigated how roe deer movements were affected by landscape characteristics, including roads, and we evaluated potential differences in road avoidance among resident, migratory and dispersing animals (hereafter, movement modes). First, using Net Squared Displacement and a spatio-temporal clustering algorithm, we classified individuals as residents, migrants or dispersers. We then identified the start and end dates of the migration and dispersal trajectories, and retained only the GPS locations that fell between those dates (i.e., during transience). Finally, we used the resulting trajectories to perform an integrated step selection analysis.ResultsWe found that roe deer moved through more forested areas during the day and visited less forested areas at night. They also minimised elevation gains and losses along their movement trajectories. Road crossings were strongly avoided at all times of day, but when they occurred, they were more likely to occur during longer steps and in more forested areas. Road avoidance did not vary among movement modes and, during dispersal and migration, it remained high and consistent with that expressed during home range movements.ConclusionsRoads can represent a major constraint to movement across modes and populations, potentially limiting functional connectivity at multiple ecological scales. In particular, they can affect migrating individuals that track seasonal resources, and dispersing animals searching for novel ranges.

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Migratory passage structures at hydropower plants as potential physiological and behavioural selective agents.

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Migratory passage structures at hydropower plants as potential physiological and behavioural selective agents.

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