Anchovies near the launch ramp at the Santa Cruz Small Craft Harbor scatter as a seal swims by this week. Millions of anchovies have arrived in the harbor and along much of the local coastline, attracting huge flocks of feeding birds. (Shmuel Thaler – Santa Cruz Sentinel)
SANTA CRUZ — All this week, an influx of anchovies, thousands possibly millions of the baitfish, inundated the waters near the Santa Cruz coastline, drawing swarms of sea birds and stoking concerns at the Santa Cruz Small Craft Harbor.
“They swam in here Sunday night,” said Santa Cruz Port District Harbormaster Blake Anderson. “One of my patrol guys noticed it and sent me a picture of a few fish. And then Monday morning, when I came in and actually saw how many fish, we started deploying our aerator system.”
Since Sunday, the harbor’s staff has been closely monitoring the abundance of anchovies, measuring oxygen levels and deploying the aerator system to prevent the fish horde from suffocating en masse.
The last big baitfish die-off occurred in the late summer of 2014 and led to a massive cleanup effort at the harbor and a foul fishy smell to permeate along the affected coastline. To prevent the stinky nightmare scenario from happening again, the aerators on the north and south sides of the harbor are working overtime.
“We have aerators throughout the harbor,” said Anderson. “They put oxygen back into the water. The oxygen is being depleted as the fish swim and as they breathe. It’s a lot like your home fish tank. We’re trying to aerate that water and bring more oxygen to the water.”
Anderson said that the crew at the harbor deals with similar fish issues on a seasonal basis, and it is often in the summer and early fall when the baitfish tend to swamp the shoreline and Santa Cruz Small Craft Harbor.
“Some years we have more and some we have less,” said Anderson. “This particular group of fish that’s here right now is one of the largest that we’ve seen in recent years.”
Anderson said that they have been fortunate not to experience a mass die-off in the harbor in recent years, which he said is in large part due to the help of the aerators. The fish seem to take the hint and leave after the system is switched on, because as Anderson pointed out, the devices serve a double function.
“Not only does it provide more oxygen to the water, which is ultimately what we need, we believe that it creates a nuisance sound that maybe they don’t like,” said Anderson. “We’re hopeful that that will help to drive them out of here, too.”
Anderson said that, according to their measurements, the oxygen levels in the water were at their lowest Monday morning, but have gone up through the week. However, he and the harbor staff remained on edge until the tide turned in their favor Friday morning.
“It’s a large biomass,” said Anderson. “If the fish stay in here for long enough, there are so many of them that no amount of aeration or mitigation is going to help. The biomass will just overwhelm the aeration system and that’s when we have the die-offs.”
As to why this recent anchovy school seemed larger than normal, Anderson said it could be due to numerous factors in the dynamic ocean, but to the reason behind their invasion of the harbor, Anderson did notice some anomalous behavior that could point to the anchovies’ motives.
“Up and down the coast in Santa Cruz, we’re hearing about the same thing occurring,” said Anderson. “Over at Cowell’s and Sunny Cove and Black’s Beach all the baitfish are up against the shoreline — almost in the waves. That’s also happening in South County. Our partner agencies are telling us there’s tons of bait fish near the shore. Something is pushing all of the fish in this area toward the shore.”
Anderson pointed out that this phenomenon could be caused by predators such as whales or sea lions driving the fish toward the coast, but it could also be due to ocean conditions such as a lack of oxygen further out at sea.
Avid ocean swimmer Peggy Miles, who records the ocean water temperature for the Sentinel, also noticed the larger schools of anchovies this week with the sea bird swarms in tow. Miles said that she doesn’t mind the anchovies and even enjoys swimming through the massive schools of small fish.
“I’ve been swimming in the ocean literally every morning, unless it’s unsafe, for 40 years,” said Miles. “The anchovies are amazing. It’s like big black clouds in the water, and you don’t realize that it’s fish until you get there. Then, all of a sudden the cloud separates and they never touch you. It’s kind of like Moses crossing the Red Sea.”
Miles said that when the sun hits the anchovies just right, the seemingly black mass illuminates and sparkles under the water.
“When the light hits them as they’re moving, they’re silver and they reflect and they’re just gorgeous,” said Miles. “It’s a very special experience to swim with the anchovies.”
She said that the anchovies seemed to be most active where she swims near Cowell Beach on Wednesday and dissipated Thursday and Friday, but the “convention of pelicans” and other mobs of sea birds left a lingering stink.
“With that many pelicans around, there’s probably a lot of pelican poop in the water, and that’s what was smelling fishy,” she said.
In a statement Friday afternoon, the Santa Cruz Port District announced that the most recent oxygen level measurements indicated that the situation had improved and that the aerators would be turned off.
“We are on anchovy watch 24/7 when these fish come in here because we know how bad it is when they die,” said Anderson. “It creates a huge mess and it’s very unpleasant for everyone at the harbor, so we try to do everything we can in our power to prevent these fish from dying.”
Although oxygen levels in the harbor are rising, the port district asked that boaters who observe large concentrations of fish inside the harbor and near the harbor entrance, or if boaters observe fish jumping in a large area to contact the harbor at VHF Channel 9, by phone at 831-475-6161 or after business hours at 831-471-1131.
Originally published at Aric Sleeper