The state Department of Energy and Environmental Protection on Friday announced that the prohibition on the taking of alewives and blueback herring from most inland and marine waters in Connecticut has been extended for another year.

This action was initially taken in April 2002 and has been extended each successive year because there has been no improvement in population size, DEEP said in a news release. The current action extends the prohibition through March 31, 2016.

“Despite the conservation efforts taken by this agency and others over the past decade, the runs of river herring in Connecticut are still diminished,” said DEEP Deputy Commissioner Susan Whalen. “The best available data from this past year indicates that the closure of these fisheries must therefore remain in place.”

River herring is a term used collectively to refer to alewife and blueback herring. Both species are anadromous, which means they hatch in freshwater, migrate to the ocean to grow, then return to freshwater to spawn. Historically, millions of river herring returned to Connecticut’s rivers and streams each year.

More than 630,000 blueback herring passed over the Holyoke Dam on the Connecticut River in Massachusetts in 1985. By 2006, only 21 passed the Holyoke Dam, the lowest number in the history of the Holyoke Fishlift. Numbers have fluctuated since that time but have never surpassed 1,000.

In 2014 the number of fish passed was 648, DEEP said. While river herring are not typically consumed by humans, they are used as fishing bait. They are also important food to many species of freshwater and marine gamefish, as well as ospreys, bald eagles, harbor seals, porpoises, egrets, kingfishers and river otters, DEEP said.

Non-migratory alewife populations are established in several lakes and ponds in Connecticut. The DEEP prohibition does not include landlocked alewives from Amos Lake in Preston, Uncas Pond in Lyme and 10 other lakes and ponds. Rogers Lake in Old Lyme previously was on that list but with the completion of the latest fishway there, sea-run alewives can now enter Rogers Lake to spawn. To avoid any confusion between the two types of alewives, the protection has been extended to landlocked alewives in Rogers Lake.

DEEP said it is continuing its other efforts to enhance river herring stocks by transplanting adult herring from streams with healthy runs into streams where runs have been eliminated or greatly depleted, removing obsolete dams and building fishways that allow fish to migrate past remaining dams.