Sporadic Events

Anchovies swarm in Monterey Harbor, again (2017)

School of anchovies in Monterey Harbor, September 2017. Photo by Dr. Andrew DeVogelaere, NOAA MBNMS.

Anchovies have once again appeared in Monterey Harbor, and in very dense schools numbering in the thousands.  

Every few years, often when nearshore waters are warmer than usual, anchovies and other bait fish come close to shore, and in Monterey Bay, many of them swim into the Monterey Harbor and do not swim back out.  The high number of fishes can cause a drop in oxygen, which can in turn lead to a fish die off and an awful smell in the harbor area.

To avoid the fish die-off, Monterey Harbor staff placed aerators into different parts of the harbor, forcing air back into the water, much like a bubbler in a fish tank.  This increases the amount of oxygen in the water available to the fishes and reduces the chances of a massive fish die off.

Aerator pumps oxygen into the harbor. The dense school of bait fish will deplete oxygen quickly, and without the aerators, they are doomed to death. Photo by Dr. Andrew DeVogelaere, NOAA MBNMS.

Eventually the fish will swim out of the harbor or be consumed by the numerous sea lions and birds that are feasting on them.

This is not the first time Monterey Harbor has been invaded by bait fish.  In 1995 the harbor was so full of dead fish that the smell overwhelmed the wharf and surrounding area.  Because of this issue, the City of

Monterey decided to purchase aerators (100K) and prevent future die-offs.  Since then there has not been a die-off like in 1995.  Back in 2015 it was mackerel, another schooling fish, that swarmed into the harbor, but the aerators worked and a stinky mess was avoided.  The aerators are back and working their magic.

Other harbors have also been impacted by wayward schools of anchovies.  In August 2014 anchovies invaded Santa Cruz Harbor and subsequently died, creating a horrible stench.  Despite having aerators, tons of anchovies died and with days were floating at the surface, creating oil slicks and causing people to gasp for breath.

Harbor seal looking at anchovies, which are a staple in the diet of seals. Photo by Dr. Andrew DeVogelaere, NOAA MBNMS.

To watch a video of the recent event in Monterey Harbor, see the KSBW news report here (Sept 22, 2017).

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