Animal-borne electronic instruments (tags) are valuable tools for collecting information on cetacean physiology, behaviour and ecology, and forenhancing conservation and management policies for cetacean populations. Tags allow researchers to track the movement patterns, habitat use andother aspects of the behaviour of animals that are otherwise difficult to observe. They can even be used to monitor the physiology of a taggedanimal within its changing environment. Such tags are ideal for identifying and predicting responses to anthropogenic threats, thus facilitating thedevelopment of robust mitigation measures. With the increasing need for data best provided by tagging and the increasing availability of tags, suchresearch is becoming more common. Tagging can, however, pose risks to the health and welfare of cetaceans and to personnel involved in taggingoperations. Here we provide ‘best practice’ recommendations for cetacean tag design, deployment and follow-up assessment of tagged individuals,compiled by biologists and veterinarians with significant experience in cetacean tagging. This paper is intended to serve as a resource to assist tagusers, veterinarians, ethics committees and regulatory agency staff in the implementation of high standards of practice, and to promote the trainingof specialists in this area. Standardised terminology for describing tag design and illustrations of tag types and attachment sites are provided, alongwith protocols for tag testing and deployment (both remote and through capture-release), including training of operators. The recommendationsemphasise the importance of ensuring that tagging is ethically and scientifically justified for a particular project and that tagging only be used toaddress bona fide research or conservation questions that are best addressed with tagging, as supported by an exploration of alternative methods.Recommendations are provided for minimising effects on individual animals (e.g. through careful selection of the individual, tag design and implantsterilisation) and for improving knowledge of tagging effects on cetaceans through increased post-tagging monitoring.

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Spitsbergen's bowhead whales ( Balaena mysticetus ) were hunted to near extinction in the world's first commercial whaling enterprise; this population clearly remains threatened, but nothing is known about its distribution, making assessment unfeasible. In this study, we document range, movement patterns and habitat preferences of this population, based on tagging done from an icebreaker-based helicopter. Despite their reduced abundance, Spitsbergen's bowhead whales occupy much of their historical range, stretching across the northern Barents Region from East Greenland eastward to Franz Josef Land. Unlike larger bowhead populations to the west, they do not migrate in a classical sense, but rather disperse from wintering grounds in the northernmost parts of their range during spring, returning northward again in autumn, a pattern opposite in terms of directionality compared to other Arctic bowhead whale populations. The extreme affiliation of this population with cold, ice-filled waters is a concern given ongoing climate warming and concomitant rapid sea ice habitat loss.

Environmental change and increasing levels of human activity are threats to marine mammals in the Arctic. Identifying marine mammal hotspots and areas of high species richness are essential to help guide management and conservation efforts. Herein, space use based on biotelemetric tracking devices deployed on 13 species (ringed seal Pusa hispida, bearded seal Erignathus barbatus, harbour seal Phoca vitulina, walrus Odobenus rosmarus, harp seal Pagophilus groenlandicus, hooded seal Cystophora cristata, polar bear Ursus maritimus, bowhead whale Balaena mysticetus, narwhal Monodon monoceros, white whale Delphinapterus leucas, blue whale Balaenoptera musculus, fin whale Balaenoptera physalus and humpback whale Megaptera novaeangliae; total = 585 individuals) in the Greenland and northern Barents Seas between 2005 and 2018 is reported. Getis-Ord Gi* hotspots were calculated for each species as well as all species combined, and areas of high species richness were identified for summer/autumn (Jun-Dec), winter/spring (Jan-May) and the entire year. The marginal ice zone (MIZ) of the Greenland Sea and northern Barents Sea, the waters surrounding the Svalbard Archipelago and a few Northeast Greenland coastal sites were identified as key marine mammal hotspots and areas of high species richness in this region. Individual hotspots identified areas important for most of the tagged animals, such as common resting, nursing, moulting and foraging areas. Location hotspots identified areas heavily used by segments of the tagged populations, including denning areas for polar bears and foraging areas. The hotspots identified herein are also important habitats for seabirds and fishes, and thus conservation and management measures targeting these regions would benefit multiple groups of Arctic animals.

Ocean warming is causing shifts in the distributions of marine species, but the location of suitable habitats in the future is unknown, especially in remote regions such as the Arctic. Using satellite tracking data from a 28-year-long period, covering all three endemic Arctic cetaceans (227 individuals) in the Atlantic sector of the Arctic, together with climate models under two emission scenarios, species distributions were projected to assess responses of these whales to climate change by the end of the century. While contrasting responses were observed across species and seasons, long-term predictions suggest northward shifts (243 km in summer versus 121 km in winter) in distribution to cope with climate change. Current summer habitats will decline (mean loss: −25%), while some expansion into new winter areas (mean gain: +3%) is likely. However, comparing gains versus losses raises serious concerns about the ability of these polar species to deal with the disappearance of traditional colder habitats.