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MARINFORSK-Marine ressurser og miljø

Effects of multiple stressors on Norwegian killer whales: MULTIWHALE

Alternative title: Samlede effekter av ulike stressfaktorer på norske spekkhoggere: MULTIWHALE

Awarded: NOK 12.5 mill.

Killer whales are among the oceans’ greatest predators. Pollution is concentrated up marine food webs, and killer whales at the top are particularly vulnerable. Man-made pollutants build up in the blubber of whales, which can then be released into the bloodstream when the fat is utilised during stressful situations, such as persistent disturbance or starvation. The pollutants can lead to harmful effects such as impaired reproductive and immune systems, potentially affecting the population. The aim of MULTIWHALE is to study the cumulative effects of three stressors in Norwegian killer whales: pollutants, disturbance from human activities, and fluctuating food sources. We investigate the effects of these stressors at both individual and population levels, taking into account that some killer whales are more vulnerable to pollutants by eating seals in addition to fish. To achieve these aims, skin and blubber samples are collected from killer whales using a minimally-invasive biopsy system. Each sample can provide information on pollution levels, diet, stress levels, health responses and genetics. Every sampled killer whale is photographed and matched to a database with information on where the it has previously been seen, with whom, if it has had offspring, and an estimation of age. Combined, this makes it possible to forecast the long-term effects of multiple stressors and population development. The COVID-19 pandemic led to restrictions on tourism in Norway, and provided us with a unique opportunity to collect samples from undisturbed whales in 2020. We aspire to use the MULTIWHALE results to understand how harmful emerging and legacy pollutants affect the killer whales when they are simultaneously exposed to multiple stressors. Results will be communicated to stakeholders to help develop sustainable tourism and wildlife conservation. MULTIWHALE is a broad national and international collaboration, and includes members from all stages of the scientific carrere.

The research project MULTIWHALE addresses the urgent and complex challenge of how multiple stressors affect individual killer whales and populations, and how these responses can vary across time and between ecological groups of whales. The stressors we focus on are anthropogenic contaminants (including both legacy and emerging contaminants of concern), disturbance from tourism (boat traffic/whale-watching) and nutritional status (fluctuating prey resources). We investigate the response to these stressors in the context of intra-species variability in risk: some killer whales eat marine mammals in addition to fish and are thus exposed to higher levels of contaminants. We analyse how the difference in contaminant exposure affects the response to other stressors in these whales and, using modelling, how it affects population development and viability. Using long time trends from analysing archived teeth, we compare contaminant (mercury) and diet variation between whales in two periods of contrasting ecosystem states: 1960-1980 (collapse of the Norwegian Spring Spawning herring) vs. 1995-2015 (“recovered” ecosystem) to understand killer whale response and exposure to long term human impacts. The project team is composed of national and international leading experts on killer whale population and behaviour, gene expression, chemical analyses of legacy and emerging contaminants, dietary descriptors and health responses, population genetics and modelling - ensuring broad expertise and feasibility when assessing the effect of human interactions on whales status and health. We will work closely with our killer whale partners in Canada to exchange knowledge and protocols, and harmonise our methods to ensure future comparison across regions and populations. The MULTIWHALE results are relevant for understanding human impacts on killer whales, their harvestable prey resources (seal and fish) and for development of sustainable tourism.

Funding scheme:

MARINFORSK-Marine ressurser og miljø