The ecology of salmonids is tightly linked to their spawning habitats, but the link between spawning site selection and phenology is poorly understood. To address this, we studied the Arctic charr (Salvelinus alpinus) from the postglacial lake Thingvallavatn (Iceland) through a multidisciplinary approach involving aerial surveys, behavioural observations, temperature monitoring and embryo rearing experiments. Aerial footage revealed that most nests (i.e. redds) were established in shallow parts of the spawning area, and we reported through direct observations trends for stronger male–male competition and for more frequent courtship behaviours in shallow than in deep redds. While water depth did not correlate with temperature at the time of spawning, the temperatures recorded at the shallow redds were consistently lower in the two months following the video recordings, likely because of the proximity of glacial outlets. Laboratory experiments demonstrated that the temperature regimes in shallow waters can delay hatching with about a month, likely impacting the phenology of the offspring. The viability of the Arctic charr in Thingvallavatn may thus depend on physical features like groundwater springs and upwelling water flows acting as “temperature shelters”.
Bibliographical noteFunding Information:
This study greatly benefited from the intellectual input of Sigurður Snorasson. We thank Skúli Skúlason, Neil Metcalfe, Michael Morissey and Hrefna Sigurjónsdóttir for their advice on multiple aspects of the project. We are also grateful to Rebecca Lesdalon, Cécile Rayssac, Marie Sciannamea, Dagný Rúnnasdóttir and Sylvain Moinard for their help during fieldwork. This work was achieved thanks to the compliance of Thingvellir National Park, the help from the “Arctic charr and Salmonids” research group for producing the embryos, and the support of the Department of Aquaculture and Fish Biology at Hólar University for hosting and rearing the embryos. Lastly, we thank three anonymous reviewers for their helpful comments.
© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
- Arctic charr
- habitat selection
- spawning behaviour