Populations of harbor porpoises off the coast of Western Europe have remained stable over the past decade, but pods have migrated further south, according to the results of a recent study.
SCANSII Project -- a multinational research project led by the University of St. Andrews in Scotland in collaboration with twelve institutions, including the Spanish Cetacean Society -- recently unveiled its latest decade of population research.
The main result is that the porpoise population has remained the same but there has been a trend to move from the north to areas further south," said José Antonio Vázquez from the Spanish Cetacean Society.
The SCANSII Project focuses on populations of harbor porpoise and other small cetaceans in the waters of the European Atlantic shelf and the North Sea. It issues recommendations to governments and other institutions for marine life monitoring and economic sustainability, as well as evaluates trends in relative species abundance.
Creating a robust management framework that enables us to assess the impact of bycatch and recommend safe bycatch limits for each species is another of the aims we sought for years to achieve," Vázquez said.
The survey covered an area of more than 1.3 million square kilometers, collecting records of 13 species of cetacean: the harbor porpoise, the common bottlenose dolphin, the white-beaked dolphin, the short-beaked common dolphin, the common minke whale, the Atlantic white-sided dolphin, the striped dolphin, Risso's dolphin, the long-finned pilot whale, the killer whale, Cuvier's beaked whale, the fin whale and the sei whale.
The harbor porpoise is the most abundant of all the cetaceans observed in the survey area.
"Absolute abundance estimates were obtained for the first five species in the area of study. The harbor porpoise, standing at 375,358, is the most numerous in these waters, followed by the common dolphin, the common minke whale and the white-beaked dolphin. The common bottlenose dolphin is the least numerous with only 16,485 recorded," Vázquez said.
The survey yielded the first-ever abundance estimates for species such as the bottlenose dolphin and the common dolphin over the entire North European Atlantic continental shelf.
"As such the absolute abundance estimates obtained allow us to contextualize quantitatively the effect of bycatches on current populations, as well as to create predictive models that enable us to include various hypothetical situations for the development of bycatches and how these affect size evolution in the population in the medium- and long-term future," Vázquez said.
A scientific paper detailing the survey's results is published in the journal Biological Conservation.