Harbor porpoises on the decline in the German North Sea

January 07, 2021

The North Sea is a heavily trafficked area, with major shipping routes crossing its waters, and fisheries, offshore oil rigs, and wind farms populating its waves. All this activity inevitably has an effect on marine wildlife, and scientists are particularly interested in how the harbor porpoise population has fared in the face of such disturbances.

The harbor porpoise is known as a "sentinel species" - animals which indicate the health of an ecosystem and point to potential risks (think of the canary in the coal mine). According to a recent study published in Frontiers in Marine Science, their population is declining in the German North Sea.

"The trend seen here is concerning," says Dr Anita Gilles of the University of Veterinary Medicine Hannover, Germany, one of the study's authors. Particularly troubling is the fact that harbor porpoises have experienced a strong decline in protected areas, such as the Special Area of Conservation (SAC) Sylt Outer Reef, which was specifically designated to keep marine life safe. In that particular region, the harbor porpoise population declined by an average of 3.79% per year. In the south, however, the population increased, indicating a possible shift in distribution. Overall, the harbor porpoise population declined by 1.79% per year in the German North Sea.

In order to get an accurate abundance estimate, Gilles and her colleagues used a system in which the surveyed area was divided by transects into smaller blocks, then observed by plane. "Knowing the abundance of a population is at the heart of ecology, but extremely challenging for mobile species in a rapidly changing marine environment like the North Sea," she says. Their system is a standard method to determine wildlife population sizes, and includes measures to ensure accuracy, such as doubling back to account for diving porpoises. Additionally, an innovative analysis framework, developed by co-author Sacha Viquerat and based on the Bayesian paradigm, was implemented for trend analysis.

The study is also noteworthy for its two decades-long time span. "After almost 20 years of systematic data collection... we now have a wealth of data at hand," says Gilles. This data, while troubling, can help drive legislation to aid conservation efforts. "Abundance, distribution, and trends are key for EU and other legislative instruments, and for marine conservation management in general."

Moreover, co-author Dominik Nachtsteim is hopeful that their survey design and data analysis methods can be used in other regions where a dedicated monitoring concept needs to be implemented. Their study limited itself to the German North Sea, meaning that population counts and observed trends in the broader North Sea are missing.

As for why there are fewer harbor porpoises today than there were 20 years ago, Gilles and her colleagues hypothesize it might be due to an increase in human activities, a change in prey availability, a distribution shift. "Most probable, it is a mixture of different causes and cumulative effects," says Gilles. But because their study was focused on data collection and not understanding causes, "We urgently need more research into the drivers of change."
-end-


Frontiers

Related Conservation Articles from Brightsurf:

New guide on using drones for conservation
Drones are a powerful tool for conservation - but they should only be used after careful consideration and planning, according to a new report.

Elephant genetics guide conservation
A large-scale study of African elephant genetics in Tanzania reveals the history of elephant populations, how they interact, and what areas may be critical to conserve in order to preserve genetic diversity of the species.

Measuring the true cost of conservation
BU Professor created the first high-resolution map of land value in the United states.

Environmental groups moving beyond conservation
Although non-governmental organizations (NGOs) have become powerful voices in world environmental politics, little is known of the global picture of this sector.

Hunting for the next generation of conservation stewards
Wildlife ecology students become the professionals responsible for managing the biodiversity of natural systems for species conservation.

Conservation research on lynx
Scientists at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) and the Leibniz Institute for Molecular Pharmacology (Leibniz-FMP) discovered that selected anti-oxidative enzymes, especially the enzyme superoxide dismutase (SOD2), may play an important role to maintain the unusual longevity of the corpus luteum in lynxes.

New 'umbrella' species would massively improve conservation
The protection of Australia's threatened species could be improved by a factor of seven, if more efficient 'umbrella' species were prioritised for protection, according to University of Queensland research.

Trashed farmland could be a conservation treasure
Low-productivity agricultural land could be transformed into millions of hectares of conservation reserve across the world, according to University of Queensland-led research.

Bats in attics might be necessary for conservation
Researchers investigate and describe the conservation importance of buildings relative to natural, alternative roosts for little brown bats in Yellowstone National Park.

Applying biodiversity conservation research in practice
One million species are threatened with extinction, many of them already in the coming decades.

Read More: Conservation News and Conservation Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.