Gjenfangster i Norge av havert merket i Storbritannia

Abstract

Since tagging of grey seals in Great Britain was initiated in 1951, a total of 61 seals has been recovered in coastal Norwegian waters. Most of the recovered seals had been tagged at the Orkney (35 recoveries) and the Farne Islands (17 recoveries) and captured in fishing gear on the southwestern coast of Norway. Recovery rates are highest from the Orkney and Shetland breeding stocks (about 12 and 10 per thousand) . Among the total of 61 recoveries, 58 were recovered within six months after tagging, two after three years and one after five years. We assume that after arriving in coastal Norwegian waters, the British grey seals are equally vulnerable to recovery as Norwegian grey seals of the same age. Using a known recovery rate of Norwegian grey seals, the total immigration from Great Britain is estimated to be about 14300 seals through the period 1960-1981 with an average of about 650 seals per year. There is no indication in the available information that British grey seals are recruiting to Norwegian breeding stocks or establishing new breeding colonies on the Norwegian coast.