The population biology and ecology of the world's northernmost harbour seals in a changing Arctic

"The population biology and ecology of the world's northernmost harbour seals in a changing Arctic" has been, and continues to be, an extremely productive research programme. Five Norwegian MSc students and one PhD have been facilitated within the project period. This population is a unique genetic entity that has been isolated from other populations for close to 1000 years. It has undergone bottlenecks in the past and displays signs of inbreeding. Its low genetic diversity makes it vulnerable to chance events such as disease epidemics, which are common in this seal species elsewhere. Thus, we conducted several disease studies in our programme including - Phocine herpersvirus 1 testing, which found this disease to be endemic to this population though no outbreak events have been documented. Svalbard?s harbour seals were found to be free of Toxoplasma gondii. Steoscopic photographic aerial surveys conducted in our programmes estimate that there are approximately 2000 harbour seals in this population (2 x previous estimates). Distributional expansion also suggests that this population is increasing. Seasonal distribution and habitat use of Svalbard harbour seals were determined in this research programme using satellite-tracking devices, which showed that juvenile and adult seals remained in coastal areas throughout the year. They haulout mainly on the west coast islands, avoiding areas with heavy ice concentrations during the winter though they did haul out on drifting ice near the shelf edge. Atlantic Water in the West Spitsbergen Current was a particularly important foraging habitat, which explains the dominance of temperate fishes, such as Atlantic cod and haddock in their current diet, which has changed markedly over the last decade. The seals dove to average depths of 41 m for periods of a few minutes. During the winter, dives were deeper, tracking the depth of Atlantic water. Pups in this population dive to depths half those of older animals and their diving did not track upwelling phenomena, suggesting that they targeted different prey than older individuals. Aquatic skills developed quickly in young animal, showing steep linear increases in skill from birth until an age of about 50 days. Home range size increased markedly during the first 60 days of life, and then showed an overall decrease throughout the rest of the first year of life. Predator studies, focussed on the Greenland shark, have produced a lot of new knowledge about this extraordinary animal in Svalbard. This large, numerous arctic shark occupies waters from the surface to significant depths (over 1500 m), over a range of temperatures including below-zero waters. They feed primarily on gadoid fishes and marine mammals. Most of the seals are live-captured given the condition of the material in the fish stomachs, despite the fact that this shark is the slowest swimming fish for its size on the planet. Its cryptic colouration and slow approach speed appear to allow it to get close enough to sleeping seals to employ suction feeding. Given their high trophic feeding habits in Svalbard, contaminant levels were explored in the sharks in a comparative study that showed considerable regional variation, likely reflecting dietary differences across the Arctic. Contaminant levels are sufficiently high in these long-lived sharks that vitamin homeostasis might be being impacted. Exploration of fatty-acids in the diet of Greenland sharks showed that their diet varies a lot regionally and also interannually. Our genetics studies demonstrated that: Atlantic sleeper sharks do not show population subdivisions; that this species is distinguishable from the closely related Pacific sleeper sharks based on mitochondrial DNA and nuclear DNA markers; and that some mating occurs between the two species. CTD data collected by tags deployed on the harbour seals in our study have shown that cross-frontal exchange of Atlantic Water, driven by buoyancy forcing and wind stresses, induces upwelling events, which are the source of heat that melts drift ice on the shelf. The larger volumes and increased temperatures in this water are likely a major driver of losses of sea ice in Svalbard over the past decade. Harbour seals are likely to be "climate winners" in a Svalbard context, while arctic endemic seals are likely to all be losers. This study contributed to developing methods for assessing species vulnerability to climate change and provided a large volume of novel data on how animal populations are responding to dramatic environmental change in the Arctic as well as providing an important new oceanographic data set for Svalbard.

Several harbour seal populations in northern parts of the Atlantic and Pacific Oceans have recently declined precipitously. The collapses of these populations have been attributed to climate-change-induced regime shifts, concomitant shifts in predator-ind uced mortality on harbour seals, altered competitive stresses and unknown causes. Little is known about the status or the ecological needs of the harbour seal population on Svalbard (or several other harbour seal 'populations' within the Nordic Arctic). T his research programme will determine the current abundance and most probable population trend of this vulnerable, Red-listed, harbour seal population, which is the world's northernmost population of this species - breeding on the West Coast of Spitsberge n. It will assess possible community changes taking place in the region due to climate change via determining what harbour seals are eating, and what is eating them. It will facilitate sample collections for several international programmes dealing with t hreats to Arctic biodiversity as well as providing a vast, year-round oceanographic data set for a region of key importance to climate modelling for the Barents Region. In collaboration with a Nordic Arctic programme, stock identities will be determined a nd an adaptive management plan with be created for this species, within the Atlantic Arctic. Svalbard's harbour seals are a vital reference population, because they are the only arctic population of this species that is protected from human harvesting.