Researchers say the rise indicates ‘a genuine cause for concern’.
The number of marine mammal strandings has risen in the last 30 years across all species of dolphins, whales and porpoise native to Scottish waters.
Researchers at the University of Glasgow used a 30-year dataset collected by the Scottish Marine Animal Stranding Scheme to analyse distribution and trends in marine mammal strandings.
The data revealed rising stranding rates across all cetacean species. However, common dolphins and baleen whales showed an exponential increase in strandings, suggesting they are facing unprecedented pressures in Scottish waters.
Researchers say the exact reasons for the strandings are difficult to pinpoint. However, declining fish stocks, noise pollution, rising sea temperatures and cascading impacts from chemicals and plastics are being attributed to the rise.
Rachel Lennon, lead author and PhD researcher at the University of Glasgow, said: ”Fisheries interactions are recognised as a critical threat for marine mammals, especially for baleen whales in Scotland. As populations begin to recover from the impacts of historic whaling, reports of entanglement have increased.
“While determining the exact causes of strandings can be complex, identifying these emerging trends provides a vital starting point for targeting future research. It also underscores the value of long-term stranding programmes as practical monitoring tools that can help guide conservation strategies and policy interventions.”
The study included 5,147 cetaceans stranded in Scotland between 1992 and 2022. Harbour porpoises accounted for more than half of all the strandings (2,676, 52%), followed by pelagic dolphins (1,217, 24%), common dolphins 494, 10%), baleen whales (479, 9%), and deep divers (281, 5%).
Stranding rates for baleen whales and common dolphins remained consistently low during the first two decades of the study, but reports rose sharply from 2010, followed by an exponential increase.
The data, published in Scientific Reports, also revealed a disproportionate rise in strandings among juveniles of both species, indicating that younger animals may be particularly vulnerable.
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