Residency and Anadromy in O. mykiss, May 25, 2011

BTW, this here fish is a hatchery steelhead that was released into the South Santiam in April or May, and was still hanging out in the river in September, where it gulped a size 16 Renegade and was then released back into the river to compete with wild rainbow, cutthroat, and chinook juveniles.

Wow, what a complex question, that faced by a rainbow/steelhead trout which is now actually a member of  Oncorhynchus, not as it formerly was, of Salmo, and as such is a member of the Pacific Salmon family.

What was the question?  Oh yes.  I am a little O mykiss (rainbow) living in Hood River.  My mom and dad might have been anadromous (like they swam to the ocean and came back) or they might have both matured somewhere in Hood River, mated and produced me.  But now, gosh darn it, I have this strong impuse to head off downstream myself, swim out into the ocean and migrate way up between Alaska and Russia in the Alaskan Gyre (Google that if you will), hang out for a few years, and then come on home to the Hood.  (play on words?)

This blog ain’t gonna answer the question completely, as this would take more time and dilligence than I have at the moment.  But here is the deal.

O. mykiss is good at exploiting habitat and ecological opportunities.  Some fascinating research in Kamchatka indicates that rivers with very fertile feed production tend to produce more “residency” in mykiss, although a proportion of the rainbow do practice anadromy (as if they need practice) and head out to sea and back, thusly becoming steelhead.

Conversely, the anadromous life history was more common in rivers where we would consider food production to be on the stingy side.  This makes sense.  If there isn’t much to eat, then let’s go to sea, grow, make lots of big eggs, and then come home to spawn.  If on the other hand, there is a ton of food in the river, then why bother?

One cool aspect of this tendency to express fundamentally an anadromous or resident life history, with lots of interbreeding among both “types” of fish, is that it shows how O. mykiss can exploit significantly different ecological conditions by mostly staying in the river to mature or mostly going to sea to mature.

But I ramble, as per usual.  Go to southern CA, at the extreme southern edge of where steelhead persist these days.  Little streams.  Harsh warm climate.  Unpredictable stream flow patterns.  And on top of all that, a few impassable dams.  O. mykiss persists above these dams, sending some number of little fish downstream over the barrier each year, and amazingly, if there is water in the creek, there may be two,or three or six or heck, even a dozen or so steelhead come back to the creek in some years.

Many studies in Columbia River, if not all, have found that resident mykiss parents can produce anadromous offspring, anadromous parents can produce off spring that mature in the river, and parental pairings can include any possible combination of anadromous and non anadromous fish.

Jon McMillan has observed non-ocean going O. mykiss spawning with anadromous steelhead in Olympic Peninsula rivers.  If it goes on in those coastal WA populations, then why not here in Oregon?

In oregon, ask the coastal biologists if we have “resident” rainbow and they will almost universally say that we do not.  My guess is that there are indeed offspring of anadromous mykiss that stay in the river and spawn with non ocean going or ocean going mates, producing mostly offspring that go to sea, but an occasional little guy or gal that matures in the river.

What about steelhead through Ballard Locks?  I find it difficult to believe that the mostly river resident rainbow in upriver tributaries don’t produce at lease a few little guys and gals who do in fact migrate to the ocean and try to return as big adults.  It may simply be that this life history is so scant that no one notices these fish, or that survival is so low that none survive to make it back through Ballard Locks, but common, there have to be a few offspring of the upriver O. mykiss that are trying to express an anadromous life history, don’t ya think?

Our Oregon coastal rivers could be an example of an ecological setting where food supplies, rationed across many species of Pacific Salmon, are slim enough that the residency life history is so rare compared to the anadromous life history.  But to think that the stay at home in the river to mature life history is completely missing in Oregon coastal mykiss populations seems a stretch, given what we have seen in most every place where we have really looked closely.

Most every place, not every place, I should add.  Let’s consider the McKenzie River, in the upper Willamette River basin.  This river is big and bold, it grows tons (not that I have weighed the critters, but a lot of rainbow at any rate) of what we call resident rainbow.  We call ‘en resident rainbow because they live out their entire life cycle in the McKenzie, Willamette, and various tributaries of same.  These O. mykiss are in a river close to 200 miles from the ocean.  There is what I would consider decent food supply in the river, and it seems that these mykiss have evolved to be stay-at-homes to such a great extent, that we don’t believe that there are any anadromous offspring of these rainbow.

Hummmmm.  If so, is this because there was such a clear disadvantabe to make the long migration to and from the ocean that the anadromous life history pretty much got weeded out of the population?  Are McKenzie mykiss derived from stream capture of an interior mykiss ancestor that had even less tendency to go clear to the ocean than to stay close to home?

So, yes, I think if one goes far enough inland, and looks at”rainbow” that have been isolated from the ocean long enough, you will see anadromy pretty much lacking from the life history expressions.

The Elwah?  I do not know enough about the specifics to be an expert and recommend a breeding program to re-establish runs of anadromous Pacific Salmon.  But your proposal should be considered.  And it really grates on my sensibilities to think about flooding the system with hatchery fish to restore anadromy to the upper basin.  I do not know exactly what has survived below and above the dam.  I am sure that a hundred years of isolation has had some genetic effects on the up and downstream mykiss.  So too, the below-dam Pacific Salmon in the Elwah, may have been influenced by hatchery programs.  Wouldn’t this be a great opportunity to restore an all wild assemblage of many species of Pacific Salmon in this gorgeous basin that has been strangled by the dam for so long?

Ooops.  Editorializing.  Again.

But hey, here’s an idea, if it is deemed essential to use hatchery fish to restore a wild run, what about limiting the program to one life cycle and prohibiting any fishing on the river for three life cycles?  I know, none of my business.  But an honest to goodness conservation/restoration effort shouldn’t get mired in harvest battles, and should give the fish a decent shot at making the re-introuduction on their own, because these are amazing resilient fish, given half a chance, and especially considering the quality of the upriver habitat in the Elwah.

And how would anyone know that there are not any anadromous mykiss returning to the Elwah from above-dam resident rainbow?

Jay Nicholas, May 25, 2011

3 thoughts on “Residency and Anadromy in O. mykiss, May 25, 2011

  1. It’s great to hear your take on these questions, Jay. I can confirm the presence of mutiple rainbow life histories in coastal streams, just barely. We’ve got isolated populations of true, resident rainbows tucked in a few nooks and crannies. We’ve also got a handful of big fat ‘bows that appear in late spring and summer. The couple I’ve handled were clearly rainbows, but had cutthroat marks under their jaws. Very deep bodies, very vibrant coloration. I doubt either of those fish survived their releases, due to the fact that they were caught with bait while salmon fishing.

    An important aside to this conversation: I strongly believe that the only way we’ll ever have vibrant, diverse populations of “resident” trout in Oregon’s coastal rivers is to eliminate the use of bait. Our coastal trout are the unfortunate casualties of salmon and steelhead anglers who use bait, especially in spring and summer. They also get taken out by the white-bucket-load by locals who are very comfortable breaking whatever laws might be in place. Now ODFW has rekindled cutthroat harvest on the north coast, so any rainbow that has to survive a summer in one of those rivers is dead meat.

    The McKenzie is being “managed” for only one rainbow life history, while the size of the basin and the predominance of anadromous and estuarine life histories implies there was a lot more to the story before we effed things up so royally. One can only imagine the migratory rainbows, cutts, and bulls/dollies that migrated throughout the Willamette basin. Along with the greatest run of spring chinook on earth, now virtually toast. In Kamchatka, the most productive rivers host up to six distinct O. mykiss life histories. So I’ll bet the McKenzie had more than one, steelhead or no.

    Thanks, as always.

  2. Jay,

    Thanks for the amazingly timely response – with an appropriate photo to boot!

    I have not really invested my self in the Elwah process as I should, but did hear that the state and tribe had already agreed to a hatchery program that includes the existing chambers creek stock. I believe it includes up-river reintroductions, but perhaps I am wrong -guess I will need to get off my butt. At least there is going to be a closure for 4 (?) years. Sad though, I will miss the trout fishing in the upper watershed until it reopens. The best trout river fishing in western Washington IMHO, can’t wait to see what they have to show us.

    Wes

  3. Jay, I’m glad to see that the science is finally starting to show what we were sure of back in the late ’60’s. By we, I am referring to Dr. John Fryers fish pathology lab at OSU. DNA studies were in their infancy at the time, but we realized just what you are saying. The gene pool is the same and we suspected that food abundance in the river dictated how many offspring smolted and how many stayed to become “resident” trout and it didn’t matter much whether their parents were “steelhead” or native trout.

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