BANGOR, Maine (AP) — The Penobscot River is on track to see the fewest Atlantic salmon in recent years, Maine state officials said.

According to a trap count report provided by the Maine Department of Marine Resources on August 23, 520 salmon had passed through the Milford and Orono dams this year.

The species is hampered by hydroelectric dams on the Penobscot and Kennebec River that reduce their ability to reach spawning grounds upstream.

The total is the fewest fish counted, as of the same date, in four years and is the fourth-lowest total since 2000, Bangor Daily News reported.

Department officials say that a bad year does not spell disaster for the species as there are many factors that contribute to this years low numbers.

“There are many factors that might contribute to the lower run this year, the most significant likely being low survival at sea and poor freshwater survival and passage at dams for juveniles in prior years,” said Sean Ledwin, the sea run fisheries and habitat division director for the Department of Marine Resources.

Ledwin said that Salmon returns vary significantly from year to year, especially with the reduced population.