scoobydope said:
Every July, once the Chilliwack/Vedder re-opens for the beginning of Salmon season, there's a rush of people to the river.
I am usually one of the people in that rush, and have -- in the past -- been really quite disturbed by watching some little family with tiny little fishing rods and a bucket of worms, yanking out the little 8 inch "hatchery rainbows". Usually, they appear to stick to their daily quota of 4 (but not always, unfortunately).
My old thought process on this activity was "Leave them alone! Those little "hatchery rainbows" are actually steelhead smolts, so fer christs sake, release them back! Come back in a couple of years and catch him when he's 12 pounds. No WONDER I have such a hard time catching any steelhead in the winter, these bastages are killing off the entire brood of babies"
Well, here I am a couple of decades later, with as many years under my belt on that river system, and I've been hearing alternate theories that I'd like to verify: (any fisheries people, please chime in)
Theory goes: The smolts are released in April or May, and should be OUT of the river system by July. Any that are still hanging around should not be there, they should be off to the ocean to start their steelheadedness. If they are still in the Vedder, they start to compete with the wild trout population, and result in an imbalanced ecosystem between hatch/wild. If you catch a straggler hatch in July, get him out of the river.
Anyone? Anyone? Beuller? Beuller?
Sorry for the delay...
Well Scoobydope, your
old thoughts on the issue are fairly common amongst us fishermen and women, I too felt this way at one time...it is a natural reaction I think for those who care about the fish and want to see more of them return each year.
Some of the reasons you see given when attempts are made to explain the opening on these little guys is that these juveniles become predators of the wild fish, or to remove those of small size because they arent likely to survive anyways, this is not really correct. Your more recent understanding of the theories are more accurate. Typically hatchery produced steelhead juveniles are raised to the yearling stage in the vedder, more specifically labeled as "yearling smolts" in the data as they are of a size and age group that is expected to smoltify and head out to the ocean relatively quickly.
http://pacgis01.dfo-mpo.gc.ca/Docum...DValue=107#Steelheadreleased fromChilliwack R
Part of the problem is however that hatchery supplementation is quite complicated for many reasons.... Those released do not always do what they are supposed to do, increased numbers of released fish does not always equate to more returning adults and other various factors come into play in fisheries management decisions, not the least of which are the impacts that hatchery supplementation can have on all of the wild stocks, in the different species, both salmon and steelhead, and in the varying age groups and stages of development that you might find in the river at this time.
The negative effects our interference can have is reasonably well studied and there are a large amount of papers out there. In addition to that, studies of wild populations and ecological "truths", like the concepts of carrying capacity, competition and predation factor in as well. All of these things together help shape fisheries policies and in turn dictate the strategies for hatchery supplementation. On a river like the vedder which has a large wild steelhead population, (but this applies to pretty much any hatchery supplemented river in BC whether the wild populations are large or small), policies are very clear to minimize impacts on wild stocks. Some of the strategies in place to facilitate this policy include manipulating release age and size, release location, imprinting, etc, etc.
Now one of the impacts despite all of these efforts can be in how some of the fish we produce interact with wild stocks after their release. As scoobydope mentions, they are then expected to head for the salt and begin their "steelheadedness", but some do not, they residualize. Now residualization is not fully understood, but it does occur in both hatchery stocks and wild populations...
This large hatchery clipped residualized fish was caught on the vedder river during steelhead season,
but they are a relatively rare find for the most part.
Residualization basically means that a juvenile steelhead, wild or hatchery, does not migrate to the ocean but stays in river becoming a resident fish. The frequency with which it happens does vary quite a bit, but on average it is expected around 5-6% of hatchery stock try to stay in river, but some reports have it as high as 17%. as such you might see anywhere from roughly 5000-20,000 hatchery juveniles trying to stay in river in any given year, of course not all of these will survive, but a percentage will, so you can see how it might be desireable to remove those from the system. Many strategies are employed to minimize this occurrence, including releasing fish further downstream, using acclimation ponds, etc., but suffice it to say when these fish residualize and stay in river they can have a negative impact on wild populations mainly through competition, but also to a small extent through piscivory/predation, etc especially when rivers are already operating at or near carrying capacity.
So what we see are strategies in place like those regulations on the vedder that encourage harvesting of hatchery individuals after their migration period was expected to have ended. This removes them from the system, relieving some of the competitive stressors on wild fry and parr in both salmon and steelhead that are also in the river at that time.
It is not a perfect system of course. Much of the problem arises when those partaking in this fishery indiscriminately harvest fish regardless of wild or hatchery status. This can result in some detriment to wild fish in the same age group and thus begins another argument against this opening for the hatchery juveniles. Of course, one is considered the lesser of two evils but arguably most of the wild stock that had been in river and ready to begin their smoltification would have left by now as well, so those that remain might have been the wild version of the residualized rainbow so it still will have been good to remove them anyways.
Lastly I will point out to anyone who didn't know it already, the vedder is one of the best steelhead rivers around with a healthy and large wild population that fisheries managers have managed to keep that way despite large returns of hatchery fish, so it would seem that the strategies are effective in minimizing the negative impacts of our interference. Considering the extreme fishing pressure, heavily populated area the river runs through and all our other influences on the ecosystem, clearly fisheries managers and hatchery staff are doing an excellent job on this river. So although it is perhaps counter intuitive at first to remove fish from the system in order to ensure more return, it does seem to be working and has proven itself time and time again over many, many generations. The most likely reasons people have a hard time catching steelhead in the vedder are inexperience and competition from other anglers, not lack of fish. This usually also proves itself true as each generation of angler gains experience fishing for them and starts to catch more and more fish as they become better anglers over the years.
I hope that helps explain things a bit, and I've linked a few pdf files here for additional reading if anyone is interested, some more recent articles on residualization, etc, etc, a little bit dry reading in places but if you sort through a bit and read some of the discussions and other subsections it's not too bad.
Here is some additional reading of interest on survival rates and release strategies as well, not exactly this question about harvest of these juvenile hatchery steelhead, but potentially an interesting sidebar for some...
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0014779
Don't forget to see the attached papers as well for more reading if you find this stuff interesting, there are lots out there, these are just a few that were easier to find and are representative of the many of the details.
Cheers,
Rib
:cheers: