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The only rover I am aware of that has sufficient monitoring is the Wind river. Every year they trap out migrating smolts, and mark them and every year when they return they get counted.
What they find on the Wind river is that once the adult population hits 500 there is not a significant increase in the production of juveniles. Therefore the habitat is fully seeded at 500 fish. Over 500 does not add anything to the next generations population. Most years the population is significantly over that. I was pretty much against the whole carrying capacity thing for a long time but at least on the Wind river the habitat appears to not be able to produce any more fish.. Now the one caveat. The Wind river is still planted with large numbers of Spring chinook I suspect that those Chinook juveniles may push some steelhead into less suitable habitat and cause some mortality. Maybe moving that non-native run somewhere else would increase juvenile steelhead production.
 

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Is the article hosted or available anywhere other than on facebook?

Now the one caveat. The Wind river is still planted with large numbers of Spring chinook I suspect that those Chinook juveniles may push some steelhead into less suitable habitat and cause some mortality. Maybe moving that non-native run somewhere else would increase juvenile steelhead production.
This would be hard to dispute in my opinion. How much time do these particular Chinook parr spend in the system?

Thanks
 

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Was able to access the article outside of fb: http://www.wildsteelheaders.org/how-many-steelhead-can-you-fit-into-a-school/ Interesting read.

"As we see here, more fish can occupy a given amount of habitat if they are diverse in size, because diversity in size - which is due to differences in spawn timing - results in fish competing for slightly different habitats."

Totally agree with above quote from article. Food has got to be a significant factor as well though.

 

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At what point does the gene pool become full? Is it at 500 fish? Or is it at 1000? My questions have nothing to do with carrying capacity but more to do with survival of the most capable. Sometimes I wonder if there is to much emphasis put on the minimum number needed to maintain the population at the detriment of the population's ability to produce the most fit to adapt and survive.
 

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"The authors conducted an experiment in artificial stream channels by spawning early and late emerging steelhead, the timing of which was about a month apart."

I'm going to take a wild guess here and wager that this artificial stream channel had no resident juveniles of other species occupy any of the preferred locations of the steelhead juveniles. In other words, not a real life situation.

By their own words; "Because early emerging fish got there first and it is easier to defend a territory than it is to acquire a new one." it would seem that if other species were inhabiting the territory it would bode ill for the newly arrived fish to try and acquire it.
 

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Sg -
The Chandler/Bjornn article was in the TAFS in 1988; vol. 117 issue 5.

According to the abstract the study of the fry early and late emerging fry were held in artificial channels with the earlier fish both larger and more robust than the later fish. When the two were held in the same channel the early fish dominated but the over all numbers were greater than when held together. The kicker in the study was that the fish were held 1 to 2 months. As we know that is only a small portion (less than 5% of the time) that juvenile steelhead spend in freshwater. In much of the steelhead world that early freshwater period of the newly emergent fry is rarely the smolt production (carrying capacity) bottle neck. That certainly the case on the north sound rivers; typically for the steelhead in that area the production bottle neck is more often the over-wintering habitat of either the first year fry and the second year parr.

WW raised a critical point in that in a basin like the Skagit the steelhead fry/parr are sharing the water with a variety of species (cutthroat, bull trout, coho, Chinook, pink, whitefish, etc.)all of which of individual habitat preference in which they do the best. As a result the fish partition the habitat with each species dominating the habitat in which they are best suited. In basins with less diversity of species or some species at depressed levels there is more potential for a species like steelhead (a higher carrying capacity).

On the north Sound rivers the wild steelhead spawning timing is determined by the constant tug-a-war between the pull to spawn early (emerge early) and produce larger fry and the pull to spawn later so that the newly emerging fry avoid the hazards of the snow melt run-off.

Curt
 

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At what point does the gene pool become full? Is it at 500 fish? Or is it at 1000? My questions have nothing to do with carrying capacity but more to do with survival of the most capable. Sometimes I wonder if there is to much emphasis put on the minimum number needed to maintain the population at the detriment of the population's ability to produce the most fit to adapt and survive.
Hi Kerry,
Your question is directed at fields of conservation biology called minimum viable population and population viability analysis. In the case of steelhead, remember that the best evidence at present indicates that the resident rainbows are part of the same gene pool as ocean-going steelhead. Therefore, they are a reservoir of genetic diversity too.
Over the long-term, genetic diversity is probably the more important consideration than is "most capable". There is significant variability in all the various environments that steelhead experience during their lives. The most resilient population is one which contains enough genetic diversity that there are always some individuals that will thrive under the new conditions.
For example, biologists always tell the story of the amazing homing abilities of salmonids; the adaptive explanation is that this facilitates a population evolving to match the specific local conditions of a specific watershed. Yet, somebody needed to seed the rivers in the first place, especially with the dynamics of ice ages. Therefore, there are situations when straying is a positive characteristic. The offspring of the first fish to spawn into a pristine watershed will experience little competition and should experience solid growth and reproduction. A healthy steelhead/rainbow trout population will have some individuals that stay at home (residents) and others that migrate out (steelhead), some that spawn in the same watershed and others that are more adventurous.
Steve
 

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Thanks Steve. I know a little about the multiple life histories of steelhead. My questions were a bit rhetorical to reflect my feelings that sometimes we focus to much on minimum numbers to maintain a population over the need for diversity to maintain a population.
 

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Thanks Steve. I know a little about the multiple life histories of steelhead. My questions were a bit rhetorical to reflect my feelings that sometimes we focus to much on minimum numbers to maintain a population over the need for diversity to maintain a population.
Yup. I'm slowly coming around, but I've long been a doubter of the argument that our rivers are operating at maximum carrying capacity. I think my biggest mental hurdle to get over has been the fact that an agency (WDFW) that manages fisheries has adopted a policy of managing fisheries to achieve something as close to the minimum escapement as possible. Always seemed to me that carrying capacity was an argument of convenience, used to justify overfishing in years when the rivers prove themselves capable of far more than their assumed capacities.

I still question whether allowing more salmon and steelhead spawners (even if they won't create more smolts) to survive wouldn't improve the overall capacity of some systems, simply by providing more nutrients (food) to the system, but those in the know don't seem to lend that much credence.

All I'm sure of is that steelhead are a tough nut to crack.
 
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