Electronic tagging of basking sharks

The North Sea is the world’s busiest marine area and basking sharks in Europe probably undertake extensive movements between Norway and other nations via the North Sea. Pervasive potential stressors operate across the anticipated range of these animals including fisheries, aquaculture, offshore drilling, etc. Limited knowledge about where and when basking sharks are present limits the potential for effective management of the species. This study will be the first of its kind attempting to understand the movements and distribution of these animals in Norwegian waters and connectivity to other nations. However, the approaches are adopted from successful efforts in Ireland and Scotland to tag these animals. These data are essential to management of the species and mitigation of putative stressors encountered by the animals during their long lives. We will use advanced electronic tags which will be deployed into the muscle of the sharks while freely swimming next to the boat. The tagging will be done following best practice for this species, and we expect that this procedure only has a light impact on the animals ("lett belastende"). Our aim is to tag 15 individuals with pop-up satellite tags and 15 individuals with SPLASH or SPOT tags. Some of these individuals will be double-tagged with an additional pop-up tag, i.e. with either two pop-up tags or one SPOT tag in combination with a pop-up tag to get more data per individual. The tags will enable us to study both the horizontal and vertical movements of the sharks. With experts from the United Kingdom providing input on the tagging protocols, we fully expect that this procedure will be minimally invasive and highly effective for instrumenting the animals with limited stress or interference with their daily lives. Although they are likely to be stressed by the presence of a boat, the duration will be brief and the animal will have the opportunity to dive to avoid the boat if it is under any duress. We do not capture, handle, or treat the animals in any way other than applying the tag package with a tagging pole.