Abstract
This report presents the final efforts and results from the tagging program of marine mammals in the North Sea carried out by Aarhus University, Stiftung Tierärztliche Hochschule Hannover (from here onwards ‘TiHO’) and NIRAS for the Danish Energy Agency (from here onwards DEA). The analysis of the data from tagged harbour and grey seals includes habitat suitability analysis and tortuosity track analysis. The data from TIHO was bought for this project and the fieldwork was carried out under German permits and HSE requirements.
The tagging program intended to tag harbour porpoises, white-beaked dolphins, killer whales, minke whales, harbour and grey seals with satellite transmitters to understand whether the pre-investigation area for the North Sea Energy Island was used for foraging or migration of these species. Data from 27 harbour seals and 15 grey seals instrumented with satellite transmitters in 2022 and 2023 provided information that was used to evaluate use of the pre-investigation area of the North Sea Energy Island in relation to migration and movement patterns of the two seal species. In addition, Aarhus University obtained permission to use data from 33 juvenile grey seals tagged at Helgoland, Germany by TIHO between 2018 and 2022 to improve the data material of the present assessment.
Capture trials of harbour porpoises and white beaked dolphins were limited by number of days with calm water and a lack of dolphins close to shore. It was attempted to tag dolphins with an ARTS - a modified air-gun normally used as a ‘line thrower’ that allows the scientists to shoots the satellite tag into the dorsal fin. This was attempted during the servicing of the PAM stations in the Energy Island pre-investigation area. However, due to very few observations close to the ship no dolphins or porpoises were tagged.
Killer whales and minke whales were likewise planned to be tagged by shooting the tag into the dorsal fins or back of the animals, however none of the species were observed during the field work.