WN1A -
Question # 2 - Why are the resident fish doing well and the steelhead are not?

I think a major factor in the success of the resident form is the fact that the anadromous form is not. With the current marine survival conditions for steelhead I believe that there is lot of freshwater habitat that is no longer capable of sustaining the anadromous life history and the resident form is taking advantage of the available habitat.

May be this example will help explain my thinking. For steelhead a potential measure of the productivity of the freshwater habitat would be the number of the smolts/spawning female that habitat can produce. In good times it an average smolts/female value of 35 might fairly representative. Let's assume that we have a river basin with two equal forks; one with excellent habitat and the other with degraded habitat. Further let's assume that the basin productivity is 35smolts/female. However the value in the good habitat fork is 45 smolts/female and in the degraded fork it is only 25 smolts/female.

During good times fish spawning in both forks will be successful and likely to produce more than enough adults to replace themselves. However look what would happen with smolt to adult survival drops to say 5% (at least a few managers feel that currently PS survivals may be that low or lower). In the good fork at 5% survival those 45 smolts would still produce more than 2 adutls however in the degraded fork at 5% survival those 25 smolts would produce only 1.25 adults. In short that fork has become a population sink and if those conditions last for any length of time steelhead would virtually disappear from that degraded habitat. That would leave empty freshwater habitat for the resident form and even in the habitat with little competition from the anadromous juveniles they would be able to increase in abundance to fill that habitat.

BTW -
It is by that same mechanism that when marine survival drops for an anadromous fish both the productivity and carrying capacity of the basin drops. The lower the marine survival rates the lower the carrying capacity becomes. It is for that reason that in tough times like we are currently in it is so damn tough to increase the number of spawners. There just isn't the habitat to support more fish. Further even if all fishing were to end for a number of years there would not be the expected increase in run sizes unless that survival increases.

Tight lines
Curt

WN1A -
Question #3 - early marine mortality of steelhead smolts.

No I had not read that report before. However if you are interested in such things you may wish to check out -


Moore, M. E., B. A. Berejikian, E. P. Tezak. 2010. Early marine survival and behavior of steelhead trout (Oncorhynchus mykiss) smolts through Hood Canal and the Strait of Juan de Fuca. Canadian Journal of Fisheries and Aquatic Sciences, 139(1):49-61.

I believe that there is summary on the Native Fish society's web site; if you like I probably can find a link to that summary.

Back to the questions. The Hood Canal study found a similar level of mortaltiy (50 to 60%) though in that case the mortality occured over several weeks (at a rate of 2/7%/day) as the fish move through the canal and out into the Straits.

I think it has been pretty well accepted that the smolts experience pretty high mortalities when they first hit the salt and with time and growth the mortality rates drop fairly dramatically. I have to wonder that as the smolts leave the river the many are either not very fit for survival in that environment or just unlucky. Those fish are fated to become fodder to some predator and it is just a matter of time until they do so. If they hit a high density of predators they die quickly; if not it may take a little longer.

Once the smolts get by that initial predation it seems to me that the factor the ultimately determines their over all survival is the forage availability in the open ocean though you know more about such things than I do.

Quyestion # 4 -
Yes I did read all of your post.

Tight lines
Curt

Dave -
Regarding the fate of those legal rainbows planted in rivers.

Soem 50 years ago there was several studies look at that issue; some of which was done in Montana. Basically what was found was that shortly after the fish were released (within weeks) the vast majority of the uncaught fish just disappeared never to be seen again. They either eaten by predators were failed to adapt to a natural situation and either starved to death or were washed downstream.

What the folks in Montana found was while the hatchery trout were in the river they tended to push out the wild fish and once the hatchery fish were caught or disappeared there were less trout in the system than before the fish were released. This of course was why they went to wild trout management.

It took States like Washington much longer time to end those programs, mostly because of the political popularity of such programs. That was compound of course by the fact the various PUDs and other used the planting of those fish as part of their mitigation packages.

One interesting side note from those stream catchable plants is that they seem to have left little genetic foot print on our local populations. Virtually all the rainbows used in those programs were from brood stocks that had long histories of domestication and were genetically very different than the native rainbow/steelhead stocks. I recall in one case where the genetic profile of the Cedar River steelhead/rainbow trout was examined. For a couple of decades (late 1940s into the 1960s) 10,000s of catchable hatchery rainbows were released into the Cedar yet 30 some years later there was little or no evidence of those fish successfully interaction with the native stocks.

Tight lines
Curt

Thanks Curt. The info from the studies seems very consistent with what I noticed.

I'm glad they discontinued those plants but they sure did entertain the kids for a week or two.

Smalma

Thanks for the response to my questions. I do think that it would be useful to know the sex ratio of the resident rainbows in different rivers. The John McMillan article that Double Haul posted a link to has some info about the ratios in the Sol Duc and Calawah. That paper views the Sol Duc and Calawah as having a relatively healthy wild steelhead population. It would be interesting to have a comparsion study in a system with a poor wild steelhead population. It is interesting that you point out that broodstock programs should have some resident rainbow input. I did come across a paper related to Kamchatka steelhead that stated any recovery program that did not involve resident rainbow was poorly designed.

I am interested in the early marine mortality of all smolts, the physiological transformation from freshwater to saltwater is a key life history stage. Unhealthy smolts, small size, impaired swimming speed, and other problems increase the probability of mortality. The birds and seals are probably improving the chances of the healthy smolts by getting rid of unhealthy fish that would compete with them only to die later.

I did check out the report. One of the advantages of being a retired UW staff is that you have access to the UW libraries online services which includes free downloads of journal articles. It was a bit of detective work to find the article though, the citation was the wrong journal. I checked the NMFS Northwest Science Center publications site and it was the same as your post but there is no issue 139 of the Canadian Journal of Fisheries and Aquatic Sciences. A bit of google searching turned up the correct journal, posted below.

Moore, M.E., B.A. Berejikian, and E.P.Tezak. 2009. Early marine survival and behavior of steelhead trout (Oncorhynchus mykiss) smolts through Hood Canal and the Strait of Juan de Fuca.. Trans. Am. Fish. Soc. 139:49-61

I found it interesting that many of the steelhead smolts had an extended residency in Hood Canal, that they migrated to the bridge in a few days then turned around and went south and hung around for some time. The mortality in Hood Canal was not so high, the majority of the mortality was between the bridge and the Juan de Fuca detector array. There is some question of the ability of the arrays to detect steelhead because of the migration routes, in the center of the straits and possibly out of range. Fish that are not detected are enumerated as a mortality. While ocean conditions are commonly viewed as the major determinant of smolt to adult returns I think the health of the smolts leaving the river is of equal importance.

I do think it is important to sort out the questions of plasticity, phenotype, genotype and the relationships of populations within rivers and populations in different river systems. How local environmental conditions and how more regional environmental conditions interact to influence population structure. The paper below is an interesting look at the Dean River wild steelhead population structure. It is particularly interesting because sport fishermen participated in the sampling. It was referenced in the John McMillan article, I was surprised to see I have coffee every morning with one of the co-authors so I can't be too critical. The abstract is available online but the paper requires a subscription or a trip to the library.

Hendry, MA, JK Wenburg, KW Myers, AP Hendry. 2002 Genetic and phenotypic variation through the migratory season provides evidence for multiple populations of wild steelhead in the Dean River, British Columbia. Trans. Am. Fish. Soc. 131:418-434.