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Prey depletion threatens health of marine mammals

Published Tuesday, 25th August 2020 in Scottish Marine Animal Stranding Scheme news

Dolphin eating fish
A reduction in the number and quality of fish could impact mammals such as dolphins.

The link between reductions in the numbers and quality of fish and squid and the health of marine mammals that feed upon them in parts of northern European waters has been highlighted in a new report.

The report, which involved the Scottish Marine Animal Stranding Scheme (SMASS ) - part of Scotland’s Rural College, raised particular concerns about the deteriorating state of several marine ecosystems, such as the Baltic, and highlighted the ‘unfavourable status’ of important prey such as Iberian sardine, cod and herring in the Baltic and sand eels, cod and whiting in the North Sea.

The research was published by ASCOBANS (Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas).

Researchers from the Resource Depletion Working Group highlighted the role that prey depletion could have on the health of many important cetacean species, particularly smaller species such as harbour porpoise which have high metabolic requirements and limited capacity to store energy

They also said the changing availability of prey, together with climate change and warming seas, had caused several small cetacean species to shift northwards, potentially increasing the hazards experienced by these animals.

Dr Andrew Brownlow, head of SMASS which is part of the working group, said: “This report highlights why we need to adopt a whole ecosystem approach when monitoring the health and resilience of some of our most iconic cetacean species.

“Many of our marine mammal species are subject to a range of human-induced pressures, both directly, such as bycatch, noise or disturbance, and indirectly through ecosystem change as a function of climate change.

“Human activity has significantly changed the distribution, diversity and abundance of many important prey species, but to effectively understand the full impact of depletions in food supply, we also need to factor in all the other stressors affecting cetacean populations. This is why we are encouraging member countries to support monitoring and research in this area.”

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