Results 1 to 9 of 9

Thread: Chinook and the marine environment

  1. #1
    Member
    Join Date
    Nov 2006
    Location
    Anchorage
    Posts
    1,293

    Default Chinook and the marine environment

    Chinook salmon and the marine environment

    Edward Farley, ed.farley@noaa.gov
    NOAA – Alaska Fisheries Science Center
    Joe Orsi, joe.orsi@noaa.gov
    Jim Murphy, jim.murphy@noaa.gov
    Phil Mundy, phil.mundy@noaa.gov
    Wyatt Fournier, wyatt.fournier@noaa.gov
    Kate Myers , kwmyers@u.washington.edu


    Chinook salmon are an important cultural, commercial, and sport salmon species to the people of Alaska.
    Recent sharp declines in Chinook salmon returns to Alaska’s rivers have lead to disaster declarations by the State of Alaska and Federal Government for some communities. The question is: “where have all the salmon gone?” Chinook salmon are anadromous, meaning their life cycle is dependent on environmental conditions in both freshwater and marine environments. Understanding the potential impacts of climate change on Chinook is complicated by the wide disparity between the effects of climate change on freshwater habitats, where long term temperatures are sharply increasing, and on the marine environment where warming occurs only very slowly, if at all. Mortality can be high and variable in both of these environments, but scientists believe the recent synchronous decline in Alaska’s Chinook salmon returns is largely due to factors impacting their survival in the marine environment. We provide data on climate, distribution, migration, and diet of Chinook salmon in order to describe their marine ecology and understand effects of climate on the timing of the life cycle (phenology). The following hypotheses explaining the decline in Alaska’s Chinook populations will also be discussed: 1) match – mismatch hypothesis: early marine mortality operating for all Alaskan Chinook salmon is the mismatch between
    timing of the life cycle in freshwater and the annual cycle of productivity in the marine environment, which is caused by the differential effects of climate change in the continental spawning and rearing areas and the nearshore marine environment; 2) critical size and period hypothesis: where climate change is effecting growth and energetic status during the first year at sea impacting marine survival over winter; 3) reduced size at age hypothesis: harvest on larger Chinook salmon has reduced fecundity in adult spawning populations leading to lower productivity.


    This was the keynote speaker at the recent Alaska Marine Science Symposium held here in anchorage. Here is a link to the agenda/abstracts from which the above was copied.
    http://www.alaskamarinescience.org/d...racts_2013.pdf


    So in other threads you can read about how one user group is better or worse than another. This is ongoing in the disguise of conservation discussions, but I never, ever hear the above brought up. Why is that? I think it’s because most in those threads have agendas pushing what they want.

    What Farley and the others are saying is likely correct. So talk about trawler bycatch, ESSN vs drift vs in-river guides and semantics of what overescapement is….while the barn burns down around you. All of that is real, but notice it’s not listed above as a possible overall cause. While limited and decreased surplus has and likely will continue to depress overall harvest understand it might simply be a blip, or an anomaly. It likely ISN”T, and this might continue. So we’ll be reduced to allocative discussions disguised as conversations about Chinook health overall.

    In my opinion mankind’s impacts overall are having an impacts on Chinook as an apex predator earlier than in other species. However, it could be cyclic, PDO, or various other things. I have a feeling Farley knows a heck of a lot more than I do in regards to this though, and will simply go with his keynote statements above.

    So what can/should we do about Chinook?

  2. #2
    Member fishNphysician's Avatar
    Join Date
    Jun 2006
    Location
    Aberdeen WA
    Posts
    4,516

    Default

    Since this is the only one we can control, let's start here...


    3) reduced size at age
    hypothesis: harvest on larger Chinook salmon has reduced fecundity in adult spawning populations leading to
    lower productivity.
    "Let every angler who loves to fish think what it would mean to him to find the fish were gone." Zane Grey
    http://www.piscatorialpursuits.com/uploads/UP12710.jpg
    The KeenEye MD

  3. #3

    Default Chinook and the marine environment

    No doubt we can control a portion of this, however it was my understanding that the size of chinook are decreasing region-wide. I have no idea if the data shows this or not, but one would think that if selective harvest was the dominating factor here, we would see decreased size and age at return as much more prominent on rivers like the Kenai than in other systems where harvest is more spread across the age range. I will say that when I ran the numbers this summer, the recent 10 year average weight of the fish in the ESSN Chinook harvest (at I think it was just over 20lb.) is down about 25% from a 10 year average in the 80's Not only that, but in recent years, around 40% of the commercial harvest consists of age 1.1 and 1.2 fish. (Jacks, and just larger) This is significantly higher than in years past.

    Also, I have read that some biologists believe that while age at maturity has a definate genetic component, when these stocks' survival rates decrease in the marine environment, they are more likely to return early, thus increasing the probability that they will successfully reproduce. Again, don't know if this is true or not, but it makes sense.

  4. #4

    Default

    Quote Originally Posted by smithtb View Post
    I will say that when I ran the numbers this summer, the recent 10 year average weight of the fish in the ESSN Chinook harvest (at I think it was just over 20lb.) is down about 25% from a 10 year average in the 80's Not only that, but in recent years, around 40% of the commercial harvest consists of age 1.1 and 1.2 fish. (Jacks, and just larger) This is significantly higher than in years past.
    smithb, I'm not a commercial fisherman and don't take this as "anti" but I have a question about this statement. When did the mesh size change for the ESSN? Could "selective harvest" mean that larger kings on average were gilled in the '80's than the last 10 years due to mesh size? Or, maybe I should ask it this way: does mesh size not matter when it comes to king salmon harvest and the weight data prior to the change would be the same as after the mesh size change? Apples to apples? Am I off base with this observation/thought?

  5. #5

    Default Chinook and the marine environment

    ADFG Has done studies that show a link between mesh size and average harvest age on the Yukon, however this was using king gear. I believe the study focused on the difference between 8.5" and 7-7.5" mesh, and its effect on selective harvest.

    In UCI, max mesh size has been limited to 6" (sockeye gear) for many years. I believe this limit was introduced in the 60's or 70's, during the last down cycle of king abundance. The overwhelming majority of gillnetters use mesh size under 5-1/2" as it is much more efficient at harvesting sockeye.

    This smaller mesh size is part of the reason the average age of kings harvested in UCI gillnets is low. Large kings don't get gilled as easily, and are much more likely to break through.

    Interestingly, when everyone thought that the harvest of KRLKR's was split fairly evenly between the commercial and sport grups, the selective harvest of smaller kings in the commercial industry combined with the selective harvest of larger kings in the sport industry made for a fairly even harvest across the age range. Now that the new data shows that the commercial industry only takes about 1/3 of the harvest, that could change.

  6. #6
    Member
    Join Date
    Apr 2007
    Location
    Vancouver, Washington
    Posts
    1,206

    Default

    Quote Originally Posted by smithtb View Post
    No doubt we can control a portion of this, however it was my understanding that the size of chinook are decreasing region-wide. I have no idea if the data shows this or not, but one would think that if selective harvest was the dominating factor here, we would see decreased size and age at return as much more prominent on rivers like the Kenai than in other systems where harvest is more spread across the age range. I will say that when I ran the numbers this summer, the recent 10 year average weight of the fish in the ESSN Chinook harvest (at I think it was just over 20lb.) is down about 25% from a 10 year average in the 80's Not only that, but in recent years, around 40% of the commercial harvest consists of age 1.1 and 1.2 fish. (Jacks, and just larger) This is significantly higher than in years past.

    Also, I have read that some biologists believe that while age at maturity has a definate genetic component, when these stocks' survival rates decrease in the marine environment, they are more likely to return early, thus increasing the probability that they will successfully reproduce. Again, don't know if this is true or not, but it makes sense.
    TB - You are correct. When harvest rates in the ocean are high enough, Chinook salmon stocks will appear to be returning at an earlier age. While this isn't exactly true, the mechanism (open ocean harvest) does not allow Chinook salmon to reach a large body size. They get caught before they have a chance. Nobody releases a 50lb Chinook salmon hoping it will grow to 80lbs. Those 50lbers get bonked. Over time, the only fish that survive long enough to spawn are those that spend the least amount of time in the ocean - i.e., smaller fish. So it appears that the stocks are getting smaller, when in fact it's just differential survival across size classes. This effect is not often seen in freshwater since the fish returning to spawn (at whatever size) have already reached their terminal size. That is, they've stopped growing and are focusing on reproduction, not on increasing body size.

  7. #7

    Default Chinook and the marine environment

    Coho,

    I was not speaking specifically of factors related to marine harvest, but rather more to natural marine conditions, like water temps, abundance of feed, etc. that many think are at play now. The thinking was that unfavorable conditions may trigger a natural instinct to return early as a mode of protection. I dunno.

    Thanks for the conversation.

  8. #8

    Default Chinook and the marine environment

    Coho,

    I was not speaking specifically of factors related to marine harvest, but rather more to natural marine conditions, like water temps, abundance of feed, etc. that many think are at play now. The thinking was that unfavorable conditions may trigger a natural instinct to return early as a mode of protection. I dunno.

    Thanks for the conversation.

  9. #9
    Member
    Join Date
    Nov 2006
    Location
    Anchorage
    Posts
    1,293

    Default

    Quote Originally Posted by Cohoangler View Post
    TB - You are correct. When harvest rates in the ocean are high enough, Chinook salmon stocks will appear to be returning at an earlier age. While this isn't exactly true, the mechanism (open ocean harvest) does not allow Chinook salmon to reach a large body size. They get caught before they have a chance. Nobody releases a 50lb Chinook salmon hoping it will grow to 80lbs. Those 50lbers get bonked. Over time, the only fish that survive long enough to spawn are those that spend the least amount of time in the ocean - i.e., smaller fish..

    Cohoangler, what ocean harvest are you talking about? I'm not aware of any that would have a state wide/north coast wide effect. Also where/why is everyone thinking it's ocean harvest? Reading Farleys papers, I think it's coastal harvest and inriver harvest that then leads to smaller fish, that then leads to fecundity issues, and then #1 and #2 come in.

    Doc, your statement stuck me as sad in a way. You said the only one we can do anything about is #3, when the preceding reasons are given more credence in the overall situation. Both CAN be dealt with, but we just won't do it. That was kind of my point in posting it, that the arguments in regards to catch and kill/Catch and Release/ESSN vs drifters vs guides. It is so much bigger than that. The issue when it comes down to harvest (surplus yields) and our desire for our own portion of that harvest is all about allocation............not Chinook stock health, or biology in almost all cases. So saying one group or another has "caused" this is rediculous when it's everyone on the planet and our disregard for it that is causing this.


    An intersting point, imo, is if 1-3 are correct, what does the release of 5billion smolt from stocking have? Those smolt are healthier, bigger, and likely can outcompete the wild chinook that are a much smaller slice of the overall biomass. I'm not saying to stop enhancement, but it's obviously a factor no one wants to talk about.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •