Variability in Body Shape of the Perch Perca fluviatilis Linnaeus, 1758 in Mountain and Semimountain Reaches of the Loz’va River and Adjacent Lakes (Northern Urals)

The body-shape variability of European perch populations in the mountain and semimountain reaches of the Loz’va river basin and adjacent Prostaptur and Elesinskoe lakes (Northern Urals) is examined using geometric morphometrics based on the box-truss method. Twenty-three distances between homologous landmarks are used to describe the body-shape variability of the fish. About 33% of the total shape variance in perch is due to the perch distribution along the gradient of the locations’ spacing along the stream of the river. The range of variability in body shape of perch, occurring in different stretches of the stream, is 1.3 times as great as the range of shape variability associated with the river and lakes habitats and 1.6 times as great as the range of local morphological variations determined by the habitat environment of perch in the Lake Prostaptur. A low level of the within-group diversity of body shape was established for the perch population from the lakes with a recurrent deficiency of dissolved oxygen in the water. The within-group morphological diversity is high in perch from the river with strong turbulence of mountain currents and variable water levels of the stream and water flow trajectories It may indirectly indicate a change in the ontogeny of individuals under the conditions of mountain and semimountain river flow and suggests a greater perch adaptation to recurring low dissolved oxygen levels in the lakes than to changes in the hydrodynamic regime of the mountain river.