Location of whitefish (Coregonus lavaretus (L.)) spawning grounds using Eurasian otter (Lutra lutra L.) spraints and prey remains

Abstract

The assessment of spawning grounds is frequently an objective of conservation management, but their locations remain scantily described for many lacustrine fish species. This study explored the use of whitefish (Coregonus lavaretus) scales in Eurasian otter (Lutra lutra) spraints and the remains of otter-predated fish to locate whitefish spawning grounds at two lakes (Ullswater and Haweswater) in the English Lake District, U.K. At Ullswater, regular spraint collections were made at a known whitefish spawning ground from the spawning season in February 2010 through to the end of the subsequent spawning season in March 2011. The frequency of spraints was several times higher during the spawning seasons and whitefish scales were almost entirely restricted to spraints collected during these periods. At the same time, motion-triggered infra-red cameras recorded otters bringing fish ashore to eat. More extensive searches around the shore of Ullswater during the spawning seasons of 2010 and 2011 found whitefish remains and high numbers of spraints in numerous other places. At nearby Haweswater, a survey of the lake’s shore during the spawning season of 2010 found remains of otter-predated whitefish only at sites on the east shore, including an area adjacent to the only known whitefish spawning ground.