Size-related changes in habitat selection by larval grayling (Thymallus thymallus L.) |
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| Authors: | M Nykänen A Huusko |
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| Institution: | Kainuu Fisheries Research and Aquaculture, Finnish Game and Fisheries Research Institute, Paltamo, Finland |
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| Abstract: | Abstract – In a medium-sized river in northern Finland, larval grayling shifted with growth from shallow habitats with slow velocities, fine substrata and abundant vegetation cover to deeper sites with swifter velocities, coarse substrata and sparse vegetation cover within 3 weeks. Small (17–21 mm) larvae preferred water depths 10–30 cm, substrata dominated by mud or sand (<2 mm), 10–70% vegetation cover and water velocities <10 cm · s?1. Middle-sized (22–25 mm) larvae preferred 30–90 cm depths, sandy substrata, <40% vegetation cover and velocities <10 cm · s?1. Large (26–31 mm) larvae preferred >50 cm depths, substrata dominated by sand or boulders, <20% vegetation cover and 10–50 cm · s?1 velocities. The strict habitat requirements of the smallest larval group suggest that these habitats, in particular, are important to the early survival of grayling. |
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| Keywords: | habitat shift larvae fish size group habitat preference |
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