Deterring Seal Predation at the Locks
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.”