Spawning migration of radio tagged landlocked Arctic Charr, Salvelinus alpinus L. in Ennerdale Lake, the English Lake District

Abstract

A sample of twenty Arctic charr, Salvelinus alpinus L. from Ennerdale lake were externally tagged, using a small radio transmitter, during their annual spawning migration. Ten fish (5 male, 5 female) were captured from each of the two spawning tributaries using electrofishing techniques. Following release, migration behaviour was observed remotely through a network of automatic radio listening stations placed at the mouths of the two spawning streams. Over 106 detections were made of tagged fish entering the two streams, during the observed spawning period of 15th November to 4th December 1996.

Time of entry and stream residence duration were examined. On average male and female charr showed no difference in initial entry time to the spawning grounds each night although charr entered Smithy Beck earlier than the River Liza. Male charr stayed resident on the spawning grounds for slightly longer than female charr although residence duration’s varied throughout the experimental period, with some fish remaining resident on the spawning grounds during daylight hours at the peak of spawning activity. Repeated migrations from the lake into one or other of the spawning tributaries was observed for 9 female and all 10 male charr. Significant differences occurred between the frequency of these repeated spawning migrations with females making on average 2.7 migration runs, whilst males made on average 6.1 migrations.

The selectivity of spawning stream was also observed with 7 of the 20 fish showing migration runs of greater than 10 minutes, into both rivers during the course of the spawning period. Male fish originally captured in the River Liza appeared to’ stray’ most, whilst male fish caught in Smithy beck showed the least straying behaviour.