Dead Liberty Bay anchovies likely the result of natural processes

Scientist says predators and low-oxygen event likely to blame.

*Editor’s note: Previous reports identifying the fish as salmon fry and smelt were incorrect.

POULSBO — Hundreds of forage fish were found dead, washed ashore at the northern end of Liberty Bay on Tuesday, May 29. While the dead fish raised some concern among locals for the health of the bay, a scientist with the Department of Fish and Wildlife said the cause was likely natural.

Initially it was reported that the fish appeared to be smelt, after a biologist with the Suquamish Tribe incorrectly identified the fish in a photo provided by Kitsap News Group. Phillip Dionne, a scientist with the Department of Fish and Wildlife’s Marine Fish Science Unit, said based on the photos he had seen, the dead fish were actually anchovies.

The misidentification, Dionne said, was an “easy mistake to make.”

“As a forage fish researcher, I’m used to everybody just assuming that they’re all the same thing,” he said. “We have a species of surf smelt that is known to spawn on the beaches in Puget Sound, so people presume that that would be the fish that you find on the beach, but we do also have large schools of anchovy that periodically show up in Puget Sound and for the last couple of years we’ve had a relatively high abundance of anchovy, especially in south Puget Sound.”

As for possible explanations as to what killed the fish, Dionne said his knowledge of similar incidents and the information available, suggested natural causes were to blame.

“When we start piecing things together, we usually find a culmination of several factors. We normally see these in relatively shallow bays during periods of time when we have relatively high tidal exchange.”

Dionne explained activity by harbor seals, sea lions and other predators is often reported in these areas prior to similar anchovy kills.

“So what we think is happening is that these large schools of fish will essentially get crowded into those near-shore areas where it’s relatively shallow and that water during this time of year is starting to warm up, so when they get pushed into that warmer, shallower water, it doesn’t hold as much oxygen. There’s a lot of fish in there, essentially consuming oxygen because there’s many of them and they’re stressed out.”

The distressed fish, Dionne said, can actually create a localized, low-oxygen event which causes them to die off, or become stranded on the beach.

“Without having been on the ground, just based on the timing of it, the general locality and the picture of the fish I’ve seen, that seems to be the case,” he said. “The fact that it’s just a single species apparently, leads me to believe that sort of shallow water predator activity, localized low-oxygen is the most likely scenario.”

Assuming it doesn’t become a regular occurrence, Dionne said the issue didn’t likely pose or indicate any serious threats to the health of the bay. The scientist did, however, recommended that folks keep their dogs on a leash while walking the beaches around Liberty Bay, in order to avoid accidental ingestion.

“Sometimes fish carry parasites or bacteria that can make their pets ill, so probably best to keep them on a leash if you’re walking on beach like that,” Dionne said.

Most of the fish were found in a muddy area near the mouth of Dogfish Creek where late last month 2,000 gallons of sewage leaked from a manhole before entering the waterways and prompting the county to issue a no-contact advisory for the area. The spill affected Dogfish Creek from Highway 305 to the northern end of Liberty Bay, including all shoreline in Fish Park.

Dionne said he did not believe the two to be related.

“Because we’ve seen this in the past, in the same general area, without a sewage spill, I would guess that they’re probably unrelated.”

Dionne suggested that if anyone in the area encounters more groups of dead fish, that they contact the Department of Fish and Wildlife or Department of Ecology to report the incident.

“If it’s not a natural event, if it were to be associated with a spill or something like that, we would want to be able to get out there and sample it,” he added. “The eyes and ears of the public are a great help to us if they can report these incidents.”

________

This story was first published in the Kitsap Daily News. Nick Twietmeyer is a reporter with Kitsap News Group. Nick can be contacted at ntwietmeyer@soundpublishing.com.

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