Publication Date:
2024-03-28
Description:
With global increases in anthropogenic pressures on wildlife populations comes a responsibility to manage them
effectively. The assessment of marine ecosystem health is challenging and often relies on monitoring indicator
species, such as cetaceans. Most cetaceans are however highly mobile and spend the majority of their time
hidden from direct view, resulting in uncertainty on even the most basic population metrics. Here, we discuss the
value of long-term and internationally combined stranding records as a valuable source of information on the
demographic and mortality trends of the harbour porpoise (Phocoena phocoena) in the North Sea. We analysed
stranding records (n = 16,181) from 1990 to 2017 and demonstrate a strong heterogeneous seasonal pattern of
strandings throughout the North Sea, indicative of season-specific distribution or habitat use, and season-specific
mortality. The annual incidence of strandings has increased since 1990, with a notable steeper rise particularly
in the southern North Sea since 2005. A high density of neonatal strandings occurred specifically in the eastern
North Sea, indicative of areas important for calving, and large numbers of juvenile males stranded in the
southern parts, indicative of a population sink or reflecting higher male dispersion. These findings highlight the
power of stranding records to detect potentially vulnerable population groups in time and space. This knowledge
is vital for managers and can guide, for example, conservation measures such as the establishment of time-areaspecific limits to potentially harmful human activities, aiming to reduce the number and intensity of humanwildlife conflicts.
Keywords:
Surveillance programme
;
Wildlife monitoring
;
Marine mammal
;
Mortality
;
North Sea
;
Harbour porpoise
;
Phocoena phocoena
Repository Name:
National Museum of Natural History, Netherlands
Type:
info:eu-repo/semantics/article
Format:
application/pdf
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