Abstract
“Småblank” is the only population of Atlantic salmon in Europe living its entire life in the river habitat without performing migrations to the sea or lakes. Home range size and habitat use were compared between an unregulated tributary and hydro-power regulated parts of the main river during 2014–2017. In total, 140 småblank were tagged with radio transmitters and tracked for 4–5 months. Tagged fish tended to stay within small areas: the average 50% home range was 1123 m2 and the average 95% home range was 4416 m2. Mean distance between the furthermost positions for individual fish during tracking was 242 m, and the fish did not migrate between different stretches of the river. The small home range and non-migrating behaviour may explain why småblank are divided into several genetically distinct populations with limited gene flow. The results showed that småblank were far more stationary than what is known for other landlocked salmon populations. Use of moderate or high water velocities’ (> 50 s−1) areas with coarse river substrates implies a vulnerability to anthropogenic effects such as water diversion, dams and weirs.
Highlights
Abstract ‘‘Smablank’’ is the only population of Atlantic salmon in Europe living its entire life in the river habitat without performing migrations to the sea or lakes
Berg NTNU Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway showed that smablank were far more stationary than what is known for other landlocked salmon populations
Smablank tagged in the regulated main river had greater body length and body mass than those tagged in the unregulated tributary (Student’s t test, t = 3.86, P \ 0.001, t = 92.6, P = 0.019, n = 95)
Summary
Abstract ‘‘Smablank’’ is the only population of Atlantic salmon in Europe living its entire life in the river habitat without performing migrations to the sea or lakes. This is most likely the case for smablank, which has a lower genetic variation than anadromous Atlantic salmon, and is a unique endemic island population of Atlantic salmon (Bourret et al, 2013; Sandlund et al, 2014) It is in a precarious situation due to a variety of anthropogenic impacts on its restricted habitat area: reduced water discharge, hydro-power dams and weirs causing fragmentation and a change from lotic to lentic conditions, introduced species, and hybridization with anadromous Atlantic salmon after the construction of fishways (Sandlund et al, 2014; Karlsson et al, 2018). Maintaining population size, avoiding further habitat fragmentation and reducing negative impacts of river regulation are important for protecting this population
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