Jan. 7 (UPI) -- New survey results suggest harbor porpoises are on the decline in the German North Sea.
Scientists worry the findings, published Thursday in the journal Frontiers in Marine Science, may be evidence of worsening ecological health in the region.
The North Sea hosts a variety of potentially disruptive human activities. Its shipping routes are heavily trafficked, and its waters are crowded with fishing boats, wind farms and offshore oil rigs.
Scientists consider the harbor porpoise to be a "sentinel species," an animal that's well-being is indicative of the health of the broader ecosystem.
In the German North Sea, data suggests the harbor porpoise is even suffering in protected marine areas.
"The trend seen here is concerning," study co-author Dr. Anita Gilles, researcher at the University of Veterinary Medicine Hannover in Germany, said in a news release.
To gauge the health of Germany's harbor porpoise population, researchers divided the species' range in the German North Sea into small subsections and counted specimens from a plane.
Researchers doubled back to confirm initial counts hadn't missed diving porpoises. The team also used a form of Bayesian statistical analysis to ensure the accuracy of the tallies in each subsection.
The new data suggest that harbor porpoise numbers in the German North Sea have declined by an average of 1.79% per year over the last two decades.
"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," Gilles said. "After almost 20 years of systematic data collection ... we now have a wealth of data at hand."
Researchers expect their survey data to inform policy making decisions and influence ongoing conservation efforts.
Gilles and her colleagues hope to expand their efforts to include the rest of the North Sea. They also said they hope followup efforts can identify the most important causes of the harbor porpoise's decline.