Feeding the Fishies
Dec 07, 2016
By Colin Bailey
Fish scattered as I approached, but abandoned caution when I added thousands of Pink Salmon eggs to the stream. I backed away carefully, and watched from the gravel bar as young Coho and Steelhead parr darted through the cloud of eggs, food trailing from their mouths as they raced to stuff their stomachs. Sculpins wiggled in their hiding places, waiting for eggs to drift in to their lairs.
Thirty minutes later, over half of the eggs were still laying on the cobble bottom. When I returned for site clean-up 2 hours later, I stopped short. Where were the eggs? Suspicious, I crept forward, gravel grinding gently under my feet. I peered at the pool, and edged my way around to reduce the water’s glare. One moment I saw nothing, and the next I had to suppress an outburst of excitement. Leopard-patterned bodies glinted dull gold as I stared at six mature Cutthroat Trout with their tails up and their heads buried amongst the cobbles. They were greedily vacuuming the remaining eggs off the bottom. With childish glee, I gestured for the rest of the field crew to stealthily join me in observing these gorgeous animals. I am such a fish nerd.
Pacific Salmon return to streams annually to spawn, and in doing so bury their eggs in gravel until they are ready to hatch in spring. Some eggs escape the nest during spawning and end up drifting downstream to be consumed by predators. When there are enough salmon, fish that spawn later dig up the redds of earlier spawners, releasing many eggs at once. For my research, I want to understand more about egg predation. I was at the Keogh River in Port Hardy, BC trying to understand how those unburied eggs are divvied up amongst the fish in the stream. Who eats, who doesn’t, how much can different fish eat, and why?
We want to answer these questions because eggs can play a major role in the diet of fishes. For some fish, salmon eggs may be the difference between starvation and growing over the course of a year. With this information, we can learn how Pink Salmon, controlled by ocean conditions and fisheries, may affect stream fish communities, from Steelhead and Coho to Cutthroat and Sculpins.