Spawning salmon returning from the ocean to the Greater Lake Washington Watershed and our own Issaquah Creek are getting a helping hand to get past predators at the Ballard Locks. That is where many Issaquah chinook and coho – squeezed into a small space to navigate the fish ladder into fresh water – are getting waylaid and devoured by hungry harbor seals.
And it is not just the adult salmon that become dinner for seals. Smolts migrating from the Issaquah Salmon Hatchery out to the ocean spend several months just below the locks as they adapt to saltwater, and many become snacks for the resident harbor seals. The U.S. Army Corps of Engineers, in partnership with non-profits and tribes, is experimenting with a new noise-making technology that will deter salmon-fishing by seals and potentially improve the salmon survival rates.
According to the Seattle Times:
A new gadget is being tested at the locks, intended to startle seals to deter them. The so-called Targeted Acoustic Startle Technology, developed by scientists from the Sea Mammal Research Unit at the University of St. Andrews, is marketed by GenusWave Ltd. based in Edinburgh, Scotland. The device was made for use at fish farms, to keep seals away from net pens. The device is housed in a metal canister that looks like an upscale water bottle, and produces a sound played through two underwater speakers at randomized intervals. The sound it makes is not particularly loud or unpleasant … to a person. The acoustic technology replaces conventional, loud noisemakers that seals just get used to. The sound made by the startle device provokes a flight response — a fundamental mammalian reflex — without causing harm to the seal, or bothering salmon.”
Updated from the original post on Friday, September 25, 2020: Some of the salmon in this year’s return are sporting a highly visible plastic string, telling any observer there is something important about this fish. In particular, this Chinook was captured at the Chittenden Locks by the Muckleshoot Indian Tribe, equipped with an internal tag (acoustic transmitter) that will ping multiple receivers in fixed positions as the fish makes it way from the Locks, through the Lake Washington Ship Canal, Lake Washington, the Sammamish River, Lake Sammamish, and finally, Issaquah Creek. The main purpose of tagging the hatchery fish is to document survival during their migration from the Locks to the hatchery. The last couple of years we have noticed a difference in numbers between the Lock counts and what shows up at the hatchery so we are trying to find out if and where we are losing fish.
Wednesday, Sept. 23, 2020: The forecasted chinook return to the Issaquah Salmon Hatchery was about 4,000 fish. The number counted through the Chittenden Locks was 12,780 as of 09/20. What?!? Historically, 50 to 70% of the fish counted through the Locks make it to the Issaquah hatchery. Some of the chinook are headed to the Cedar River, where they are considered an endangered population, but most are headed our way.
Another brush with reality: this time, the males outnumbered the females almost 3 to 1! We know that pinnipeds (and our beloved orcas) prefer female chinook – they are loaded with fat and protein-filled eggs, but this season that tendency is extreme.
The WDFW set a pretty high bar to assure the safety of the staff and volunteers at the spawning shed, but the shortfall of female chinook made it a short day, resulting in 328,000 fertilized eggs — a small but significant step to the 3,200,000 chinook egg goal for the year. The holding pond is full, the creek is full, so we are on a good path to meeting the goal.
What can we conclude from this?
Salmon return forecasting is even tougher than weather forecasting. And, we need to get good data on where the female attrition is happening, and whether something can be done about that.
Please note that the WDFW is not allowing tours on Tuesdays, spawning days, as keeping staff, volunteers and possible visitors safe is paramount.
New technology is helping to remove deadly “ghost nets” that have been lost in the depths of Puget Sound. It is part of an effort that saves millions of animals every year, but managers say better reporting of these lost nets by fishermen is still needed. Read more at the Encyclopedia of Puget Sound.