The Effect of Increased Turbidity on Arctic Charr (Salvelinus alpinus) and Brown Trout (Salmo trutta) in a Glacier-Fed Lake

Productivity of rivers can be greatly influenced by its turbidity. In many glacier-fed rivers the low penetration of light is a limiting factor for primary production, which consequently affects the living conditions for invertebrate and fish. The Fljótsdalur hydropower plant (2007), East Iceland, is run by water from two glacier-fed rivers. The outlet from the power plant is into a glacier-fed lake, Lake Lagarfljót. The effluent from the power plant has higher level of suspended solids than originally found in Lake Lagarfljót, causing increased turbidity and reduced visibility in the lake. Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) are found in the lake, as well as in its tributaries. The main objective of our study was to observe the impact of increased turbidity on charr and trout in Lake Lagarfljót. The abundance and growth rate of both charr and trout has declined, following the change in turbidity. The diet of both fish species has shifted from being primarily aquatic to terrestrial origin. In our poster we will discuss the impacts of these changes on the fish in the lake.