Mysterious anchovy die-off in Monterey marina

Some believe that a mysterious minor die-off of anchovy in the Monterey marina this week was caused by disease or stress induced by unusually warm water and changing west coast ocean condition, according to a City of Monterey press release.

Thursday, a large school of anchovies entered the marina so harbor staff switched on its aeration system that is turned on and off as large schools of fish swim in or out of the inner harbor.

The West Coast water temperature has risen two to five degrees over the last two months, and warm water contains less oxygen than cold water. Aerators can help by pumping oxygen into the water.

Several hours after the aeration system was turned on, some dead anchovies were seen on the surface of the water and on the bottom. Harbor staff immediately began cleaning up the dead anchovies, which en masse can create quite a stench. Some of the Monterey Classic Car Week events are being staged within smelling distance of the marina. Monterey installed the aeration system after a mass die-off of sardines in 1996. Anchovies are smaller and less oily than sardines. The dead anchovies are not expected to cause any odor issues or impede recreational activities and boating.

“We are still seeing a large biomass of anchovy alive and swimming around in the marina, which is a good sign because it shows that the aeration system is helping,” said Monterey Harbormaster Steve Scheiblauer.

For the last month, large schools of anchovy mixed with some mackerel and sardines have moved in and out of the Monterey harbor and marina, and the aeration system has been in use, according to the City of Monterey.

Although the cause of the anchovy die-off is unknown, several unusual climate conditions have occurred this summer. A record-breaking algal bloom stretches across the North Pacific from the Aleutian Islands to southern California.

The bloom coincides with warmer sea-surface temperatures throughout the West Coast and is laced with some toxic algae that may have caused whale deaths in Alaska in June and have closed some anchovy and sardine fisheries in California.

Earlier this week, an adolescent minke whale entered the Monterey harbor and got stuck on the rocks under the Coast Guard pier.

Monterey Fire Department and Harbor staff, working closely with the Coast Guard, National Oceanic & Atmospheric Administration, and a whale rescue team managed to free the 35-foot whale and get it back into the bay. Marine scientists think the whale may have been suffering from domoic acid poisoning, according to the City of Monterey.

Monterey Harbor staff are monitoring the anchovy situation around the clock and are working closely with marine scientists in the area.