January 14, 2021 — The following was released by NOAA Fisheries:
Harbor porpoises have rebounded in a big way off California. Their populations have recovered dramatically since the end of state set-gillnet fisheries that years ago entangled and killed them in the nearshore waters they frequent. These coastal set-gillnet fisheries are distinct from federally-managed offshore drift-gillnet fisheries. They have been prohibited in inshore state waters for more than a decade. The new research indicates that the coastal set gillnets had taken a greater toll on harbor porpoise than previously realized.
The return of harbor porpoises reflects the first documented example of the species rebounding. It’s a bright spot for marine wildlife, the scientists write in a new assessment published in Marine Mammal Science.
“This is very good evidence that if we can eliminate the deaths in fishing nets, marine mammal populations can come back in a big way,” said Karin Forney, a research biologist with NOAA Fisheries’ Southwest Fisheries Science Center who is based in Monterey Bay.
The State of California managed set-gillnet fisheries for white seabass and halibut in coastal waters off central California beginning in the 1930s. Before the 1980s, there was little solid information about the impacts of coastal set-gillnets on protected species such as marine mammals and seabirds. Harbor porpoises were vulnerable to this coastal fishery because they frequent shallow inshore waters where the nets were historically set.
The scientists estimated, based on a combination of data, that as many as 300 harbor porpoises per year may have been killed in California’s coastal set-gillnet fisheries during the 1980s. One 1994 study (PDF, 4 pages) confirmed the deaths of more than 50 harbor porpoises in Monterey Bay alone, with the authors speculating that the true number was far higher.