Líffræðifélag Íslands
Líffræðiráðstefnan 2015

Erindi/veggspjald / Talk/poster E3

Intra- vs Inter-population effects of temperature on the temporal and spatial behaviour of a stream-dwelling fish

Nicolas Larranaga (1,2), Stefán Óli Steingrímsson

1. Hólar University College, Department of Aquqculture and Fish Biology, 2. University of Iceland, Institute of Life and Environmental Science,

Kynnir / Presenter: Nicolas Larranaga

Tengiliður / Corresponding author: Nicolas Larranaga (nicolas@mail.holar.is)

There is considerable variation in the way young salmonids distribute their activity in time. Such variation can be explained in part as a response to fluctuations in local conditions (e.g. water temperature, water flow, depth). For instance, when temperature increases, fish become more active to sustain increased metabolic demand. When temperature decreases, they become more nocturnal. Salmonids' diel activity has been monitored at temperatures ranging from 7 °C up to 27 °C. However, so far, there has only been few attempts to systematically compare diel activity in rivers with marked differences in temperature. In Iceland, Arctic charr Salvelinus alpinus inhabits streams with contrasting temperature, which offers the potential to perform such comparisons. We repeatedly observed 60 juvenile Arctic charr from 3 streams (~4, 9, and 14 °C) in semi-natural enclosures during two weeks in summertime. As predicted, activity rates increased from cold to warm streams. However, the within-stream effect of temperature on activity rates decreased from cold to warm streams, indicating that the net benefits of increased activity are reduced at high temperature. Fish were also more aggregated in the warm stream but the effect of temperature varied among populations. In the cold and warm streams, aggregation decreased and increased with increasing water temperature, respectively. These results shed a light on the behavior and local adaptation of young salmonids to different thermal regimes.