Blog Number 10
After experiencing the spectacle of pinks spawning in September and October, all those “in your face” sights, sounds and smells of the world of salmon suddenly stopped by November here in Rocky Brook. Not a big fish to be seen or heard.
I know the eggs are there, beneath the gravel, hopefully fertilized, hopefully alive with the promise of another generation of fish. But I am not certain, for I really cannot see what is taking place.
Of course I could dig around in the gravel to find some eggs and look at them, but that just feels wrong (and is). The eggs have to remain undisturbed, left to do what eggs have done for millennia, away from human eyes, human curiosity, human meddling.
So, I am left to imagining and wondering.
I imagine that the resident dippers, rummaging around in the gravel for bugs, may be finding eggs and eating them.
I wonder if Rocky Brook at flood stage may be rearranging rocks, exposing the clumps of eggs to the force of the water, taking them downstream to who knows where.
I imagine elk walking mindlessly across the creek, their big hooves and heavy weight moving stones around, crushing eggs, making others visible to hungry predators.
I wonder if the mergansers I see in late January are here because there is something to eat, maybe emergent little fry in great numbers.
And I imagine most eggs just sitting there, minute by minute, day by day, first with a spot called an “eye” indicating that it has been successfully fertilized; then becoming a tiny embryo, curled up around the nourishing yolk.
I read what I can find about this time. I look at pictures. I understand the process, the going from embryo confined by the “shell” of the egg only to hatch and then be confined by the gravel. At this point it is called an alevin, still not a free swimming fish, but more like a fat wobbly worm wiggling around the safety provided by the gravel. There it continues to get just a little bit bigger, just a little bit tougher, just a little more able to survive in the “lots of things eat little fish” world above the gravel.
Most of all I wonder about what is called “emergence”, that moment in the salmon life cycle when it leaves the gravel, floats up to the place where air and water meet, takes a big breath to inflate its swim bladder, and begins life as a free-swimming fish, now called a fry.
I would love to observe, maybe even celebrate this magical moment, but I still have not figured out how, because I don’t know exactly when it happens.
Scientists (especially those working in a hatchery) have studied and observed this early salmon life, from fertilized egg to alevin to emergent fry. They know that in the wild its duration depends on a number of factors and varies from river to river, from year to year, and for different kinds of fish. They can make a pretty educated guess when emergence might happen, given some key information, in particular water temperature. Emergence is temperature dependent. The higher the water temperature, the faster the embryo develops and the lower the temperature, the greater the amount of days needed for fry emergence.
I asked Hoodsport State Fish Hatchery specialist Mark Cylwik how long pink salmon eggs take to hatch and emerge in the Dosewallips and/or Duckabush rivers where I live. He works where pink salmon are raised in tightly controlled conditions. This is what he wrote to me.
“Our fish live in a different environment than wild fish so everything I tell you is hatchery knowledge. Pink salmon will emerge from the stream bed before Coho since the adults return to the Hood Canal in early August and spawn early September (earlier than Coho). Once fertilization takes place, we use Temperature Units TU’s to calculate development. A TU is the average water temperature over a 24 hr. period subtracted from 32 deg F. For example if my water temp average was 45 Deg F minus 32 deg F it would equal 13 TU’s gained for that 24hr period. When your TU total equals about 1850 +/- then the baby pinks should start emerging…..at least that’s when we put them in the ponds and start feeding them at the hatchery.
Due to our water temperatures this year (2021-22), that magical happy day was January 18th.
Under hatchery conditions, Coho salmon need only 1320 TU’s to emerge. Chum and Chinook take longer, needing 1,450 and 1600 TU’s respectively.”
Based on this information, I have clearly missed this year’s pink and coho emergence. But I plan on being more prepared this fall by getting a temperature gauge for Rocky Brook. Mark said they use an Onset HOBO Water Temperature PRO V2 Data Logger. You anchor it to a location in the stream and can download the info into your lap top every month or two. I plan to look into what equipment might be best for me and will let readers know what I buy and how well it works.
So, last year’s good pink run is now out of my reach, they are now called smolts, living in salt water (since they spend little time in the rivers and streams where they were eggs and alevins).
Once again I have to do a bit of imagining and wondering.
I also dream that some day we ingenious and infinitely curious humans will develop a tiny camera which a little salmon could wear without much effort, recording its life out in estuaries, bays and the open ocean in a way which we could access. Now wouldn’t that be something?
Dennis Lloyd Kuklok