St Croix River Thermocline

  • mark_johnson
    St. Croix River
    Posts: 940
    September 8, 2011 at 2:59 am #1272551

    Have you guys ever noticed how the thermocline on the St. Croix appears alot more pronounced at certain times? Today was one of those days so we sent the Marcum camera down and ended up finding a massive cloud of bait just inside the thermocline at 45+ feet. Not sure exactly what they are but it was thick enough to read on the sonar at almost 50ft. Surface temp was 74.5, at 25fow it was 71 and it dropped fast after 40fow down to 61 degrees in 47fow. There were fish in the area too but nothing was biting…probably full already.

    Youtube Video

    James Holst
    Keymaster
    SE Minnesota
    Posts: 18926
    September 8, 2011 at 3:14 am #993537

    That’s dang cool. If that was in salt water I would be guessing krill or something similar given the density of the little buggers. I wish there was an easy way to ID them. Regardless… cool video.

    mark_johnson
    St. Croix River
    Posts: 940
    September 8, 2011 at 3:34 am #993540

    Its hard to tell what it is but there are two distinct little critters in that cloud, some look like daphnia or something similar and the other long skinny ones could be some type of larvae hatch or a very immature fish or minnow. Either way it’s WAY too much competition for my bait!

    drifter295
    Hastings MN
    Posts: 413
    September 8, 2011 at 10:13 am #993549

    very cool, thanks for sharing.

    mplspug
    Palmetto, Florida
    Posts: 25026
    September 8, 2011 at 10:14 am #993550

    Sure hope they aren’t silver carp larvae

    The mass of the fish makes me think they must be shad larvae newly hatched from this year?

    JasonP
    Twin Cities
    Posts: 1368
    September 8, 2011 at 11:50 am #993560

    Very cool vid…some type of macroinvertabrate….crappies shouldn’t be too far I would think.

    JP

    Brian Klawitter
    Keymaster
    Minnesota/Wisconsin Mississippi River
    Posts: 59992
    September 8, 2011 at 1:23 pm #993585

    From our catfish biologist at the MN DNR:

    Looks like the one of the guesses was correct. There are daphnia darting around in there. The other dense cloud looks like chironomid (midge) larvae. Here is a decent website that explains some stuff about chironomids. http://lakes.chebucto.org/ZOOBENTH/BENTHOS/xiii.html

    I’ve heard of this occurring on depth finders before and hearing the explanation of a chironomid hatch. First time I have seen video of it though. Pretty cool.

    Note new e-mail address is in effect

    Joel Stiras
    Metro Catfish Project Lead
    1200 Warner Road
    St Paul, MN 55106
    651-259-5806

    [email protected]

    corey_waller
    hastings mn
    Posts: 1525
    September 8, 2011 at 1:30 pm #993589

    asian carp fry? that is actually pretty darn cool just goes to show there is lots of fish food in the river. nice work

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