The formation of wood jams in Kamchatka rivers and their role in juvenile fish distribution

In piedmont rivers of the Kamchatka Peninsula, wood jams play a major role in channel formation and largely determine the density distribution of juvenile fish along the river, offering them convenient habitats in areas with rapid current. It has been found that juvenile fish density in wood jams is 1.5–3 times higher than in adjoining open shoals. An analysis of data on the location and morphology of more than 200 wood jams has shown that their occurrence frequency and size depend mainly on river size (flow discharge), the type and morphology of river channel, and the type of tree stand in the floodplain.