| 1. |
- Sunde, Johanna, et al.
(författare)
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Variation in salinity tolerance between and within anadromous subpopulations of pike (Esox lucius)
- 2018
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Environmental heterogeneity is a key determinant of genetic and phenotypic diversity. Stable andhomogenous environments tends to result in evolution of specialism and local adaptations, whiletemporally unpredictable environments may maintain a diversity of specialists, promote generaliststrategies, or favour diversified bet hedging strategies. We compared salinity tolerance between twoanadromous subpopulations of pike (Esox Lucius) that utilize freshwater spawning sites with differentsalinity regimes. Eggs from each population were artificially fertilized and incubated in a salinitygradient (0, 3, 5, 7, and 9 psu) using a split-brood design. Effects on embryonic development, hatchingsuccess, survival of larvae, and fry body length were compared between populations and families.The population naturally spawning in the stable freshwater habitat showed signs of specialization forfreshwater spawning. The population exposed to fluctuating selective pressure in a spawning area withoccasional brackish water intrusions tolerated higher salinities and displayed considerable variation inreaction norms. Genetic differences and plasticity of salinity tolerance may enable populations to copewith changes in salinity regimes associated with future climate change. That geographically adjacentsubpopulations can constitute separate units with different genetic characteristics must be consideredin management and conservation efforts to avoid potentially negative effects of genetic admixture onpopulation fitness and persistence.
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| 2. |
- Tamario, Carl, et al.
(författare)
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Nature-like fishways as compensatory lotic habitats
- 2018
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Ingår i: River Research and Applications. - : Wiley. - 1535-1459 .- 1535-1467. ; 34, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- Damming of rivers disrupts migration of fish and results in lotic habitats being both scarcer and spaced further apart, ultimately affecting riverine fish communities. Nature-like fishways are often designed as bypass channels, constructed with natural materials that reroute part of the water around weirs and dams, restoring longitudinal connectivity as well as forming nature-mimicking habitats. We evaluated the potential of such bypasses to function as compensatory lotic habitats by comparing fish fauna in 23 bypasses to adjacent lotic stream habitats in a same-river pairwise design. Bypasses were narrower, shallower, and less shaded than adjacent stream habitats, but very few significant differences could be detected in the fish communities, indicating the potential of such nature-like fishways to constitute compensatory lotic habitats for fish. Analyses also indicated how bypass design may be altered to favour or disfavour certain target species. Generally, narrower and shallower bypasses with high gradient favoured brown trout (Salmo trutta), whereas European eel (Anguilla anguilla) were more abundant at sites with lower gradient. Finally, to increase the impact of these compensatory habitats on running water ecosystems, we suggest that the size of bypasses should be maximized in areas where natural stream habitats have been lost.
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| 3. |
- Watz, Johan, 1977-, et al.
(författare)
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Enhancing upstream passage solutions for juvenile eels : Effects of climbing substrate and ramp placement
- 2018
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Konferensbidrag (refereegranskat)abstract
- Juvenile anguillid eels migrating into inland waters often face migration barriers. Upstream passage solutions normally consist of inclined ramps lined with a wetted climbing substrate. In this study, we compared the performance of three commonly used substrate types in a controlled experiment, using European eel as the test species. We also analyzed climbing behavior with videography and validated the experimental results under natural conditions at a hydropower plant. In addition, we investigated the effects of ramp placement. Studded substrate attracted more approaches and climbs and passed more eels at a higher climbing velocity than open weave and bristle substrates, results that were confirmed by the field validation. Moreover, ramps placed in the tailrace caught more eels in low than in high water velocities. To conserve anguillid eels, both safe routes for downstream-migrating adult silver eels and improved recruitment at the freshwater feeding life stage must be achieved. Optimizing ramp position and equipping upstream passage solutions with functioning climbing substrate are key factors to enhance the performance of eel ramps.
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