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Thread: Salmon feeding in freshwater?

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    Member fishNphysician's Avatar
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    Default Salmon feeding in freshwater?

    Salmon Feeding in Fresh Water?

    Many anglers have long known that mature Pacific salmon (Oncorhynchus spp.) will strike at objects that resemble eggs while in fresh water. Concurrently, there has been a deeply entrenched belief held by both scientists and anglers that mature Pacific salmon cease feeding in fresh water, with numerous explanations having been developed to explain this behaviour, such as ‘instinct’, ‘aggression’, or a fish being ‘territorial’. It has even been stretched as a way for adult salmon to eliminate potential competitors that their offspring might encounter as juveniles. As a much simpler explanation, Pacific salmon continue to feed because it provides them with nourishment.
    A group of researchers set out to test whether Pacific salmon do in fact feed, and try to unravel some of the myth around why they may feed. They looked at the feeding on eggs within adult Chinook Salmon, Chum Salmon, and Coho Salmon. Overall, 13% of stomachs examined contained eggs (up to 30% observed for Coho Salmon), and feeding rates were estimated at up to 14 eggs per day. Feeding experiments in a lab revealed that mature salmon could digest eggs, as fed salmon maintained significantly higher body mass than unfed salmon. The researchers in this study determined that the energy from consumed eggs could potentially allow salmon to migrate up to an additional 3.8 km per day of feeding, or extend the duration of spawning activity by up to 12%.
    The researchers found that the energetic gains associated with egg consumption in Pacific salmon may thus be particularly important for precocial males (jacks). Alternatively, one of the most surprising findings was that large individuals were no less likely to feed than their smaller counterparts. The highest feeding prevalence was observed in adult female Coho Salmon from the Quinsam River, BC, in which 40% of the sampled females had consumed eggs. Importantly, female salmon may continue to feed in fresh water not only to offset the relatively higher costs of breeding that they incur, but to obtain physiologically important resources, such as carotenoids and dietary protein.
    Although there is still a lot of uncertainty on why adult Pacific salmon will feed while in fresh water, the researchers conclude; given that Pacific salmon stocks show high homing to their stream of birth, it is possible that many populations have evolved local adaptations to their specific migration and spawning requirements that include nutrients from salmon eggs from their own species or other salmon species. Such a dependence on supplemental energy from freshwater feeding could explain why some populations fail to recover even when released from fishing pressure, as lower abundances of salmon (all species) may remove feeding opportunities that some populations and species depend on to successfully complete migration and spawning.

    More here....

    http://publish.uwo.ca/~bneff/papers/...n%20salmon.pdf
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    Supporting Member bullbuster's Avatar
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    A fascinating study on a subject dwelled upon by thousands of guys with time to consider such things. This could really explain why reduced pressure fish do continue to decline in population.

    Changes the way we think of salmon runs.

    Thanks for posting this information. I love it.
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    I'm not chumming, I am assisting current runs of salmon to sustain the species for future runs. Ya, that is a bead on my fly rod, pleasure don't need to be resisted does it? Sorry, fishnMD. Great read, first question is before fishers using eggs what did the first run salmon have to feed on?

    George

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    Very interesting indeed, this does however not explain the non recovery of populations that are excluded from fishing. Nowhere does it state that salmon are actively predating and attacking laid eggs, rather feeding on egg escapees that would have a low chance of survival anyway.

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    Member c6 batmobile's Avatar
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    Quote Originally Posted by George Riddle View Post
    I'm not chumming, I am assisting current runs of salmon to sustain the species for future runs. Ya, that is a bead on my fly rod, pleasure don't need to be resisted does it? Sorry, fishnMD. Great read, first question is before fishers using eggs what did the first run salmon have to feed on?

    George
    Theyve always fed on eggs. We just figured out a way to make the packaging more appealing and deadly for them.

    Just goes to show you why eggs are such an effective tool on the river and why bans on eggs can help restrict catch rates.

    Good read doc.
    Makin fur fins and feathers fly.

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    There's nothing more suicidal than a Kenai silver gluttonously sucking down a glob of eggs plunked, bounced, or trailing from a diver.

    Let 'em eat long enough and the whole works is all the way down in their stomach. I gut- and gill-hooked more than my fair share as a young lad.
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    Reds suck eggs with aplomb too. Guys doing nothing but flossing are really missing out.

    Caught my fair share of dark humpies while skating caddis dry flies for Dollies, too.

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    Quote Originally Posted by captainkim View Post
    Very interesting indeed, this does however not explain the non recovery of populations that are excluded from fishing. Nowhere does it state that salmon are actively predating and attacking laid eggs, rather feeding on egg escapees that would have a low chance of survival anyway.
    It actually does, cap, if you'll read it again. If certain runs of salmon actually require food, such as salmon eggs in the water, to make it as far as their spawning grounds, and there are fewer eggs in the water than necessary to sustain them, then they will not be able to travel as far upstream, and may not be able to reach an area where spawning can occur successfully. Early run spring chinook will still encounter eggs in the water from the preceeding fall's coho, chum, sockeye and pinks. In the Kenai, as silvers are still spawning in small numbers well past Christmas, there will still be some of their eggs available in the water for the first of the kings to consume. This research line could establish a much closer link between runs of different species, and interdependence on each other for their success. So even if fishing is halted, if there are still far fewer fish in the water to produce eggs for each other to snack on, spawning success and run recovery will be hampered.

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    Ok I am open to the possibility that salmon feed in river, but how can they actually prove the fish are striking to consume food rather then instinct or aggravation? Can they show the digestive system is was working in the stream? I mean if this stuff is true it actually accounts for a lot of things I have seen fish do on the river.

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    If this study is true, we could effectively boost future years' runs by closing the drainage areas to all king fishing, then systematically chumming the water with eggs to assist the full run making it to their predestined spawning grounds. A few years of this and the water should be boiling with kings in June. That is if this study can be taken at face value. It certianly wouldn't hurt to give it a shot. Along with putting seasonal fish cops to along the troubled areas like the Susitna areas accessable from the Parks Hwy to make sure the run is as close to absolutely undisterbed as achievable. I would gladly go along with putting this idea to a five year test.

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    Quote Originally Posted by kenaibow fan View Post
    how can they actually prove the fish are striking to consume food rather then instinct or aggravation?
    They asked them. You just have to read the article more closely.
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    Quote Originally Posted by scott_rn View Post
    They asked them. You just have to read the article more closely.
    I guess I deserve that…………….

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    I have been saying for years salmon are just like humans. I often have the same reaction upon receiving a come-hither glance from my wife. The journey to the bedroom has me passing by the aroma of the kitchen. Side tracked I do get in picking up a quick energy boosting snack and some red bull which enables me to complete the trip and accomplish the ritual.
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    Quote Originally Posted by JediMasterSalmonSlayer View Post
    quick energy boosting snack
    Also known as Viagra....
    "The North wind is cold no matter what direction it's blowing"

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    If you want more salmon in our rivers we need to put a bounty on pike, or before long we won't have anything but farmed salmon. They are killing all the fry before they can return to the ocean. It is just a matter of time. Take a look at the size of the pike they are pulling out of the Susitna river drainage. They keep getting bigger every year.
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    I didn't see that this study mentioned Sockeye, which while they may rarely strike them, do not feed on eggs or anything else after their return to fresh water.

    IF these fish are actively feeding in freshwater, and this is essential to their journey and spawning success, why are Sockeye so successful considering that they do not feed, and their journey is usually longer than Kings/Cohos as many of them spawn in the headwaters of our rivers?

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