Stomach Contents

Fish make the best surveyors. So take advantage of their hard work scouring the lake from bottom to top to figure out what's going on in the lake!

Below are some pictures of commonly found food items. Following the pictures are instructions for examining stomach contents by "fluidizing."

Trout stomach and contents spread out in white dish.
Before full fluidization, seeing the stomach contents can be difficult. Photo credit: Don Wicklund
Small freshwater shrimp are easily observed floating in white dish
After being fluidized, these scuds, a common name for a freshwater shrimp of the Genus Gammarus, a crustacean, are plainly visible. Scuds give fish flesh a red color. Photo credit: Jonathan Leathers
Trout stomach split open and shown stuffed with scuds
A stomach bulging with groceries. Photo credit: Jonathan Leathers
Dragonfly numph shown on white background alongside a pencil with eraser. The nymph is about the same length as the eraser and metal part of the pencil.
A tasty dragonfly nymph. Dragonflys are typically found in warmer waters, with emergent vegetation that the aquatic insects can crawl up onto to emerge as winged adults. Photo credit: Don Wicklund

Instructions for examining stomach contents:

  1. Open the stomach, put contents into a white-bottomed vessel: plastic tub, paper plate, Tupperware, what have you.
  2. Add a little water, 1/4 to 1-inch, and "fluidize" the contents. The contents open up like a book.
  3. If you can identify the stomach contents, please include that info in the stomach contents section of your Survey Report.
  4. If stumped, send a close-up picture to Rich O'Connell to ID, or bring a sample to a meeting.

    Please forward the photos to Rich:

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    Please include relevant info, such as:

    • Lake name (which won't be published but is helpful)
    • General location (Eastern Washington, Alpine Lakes Wilderness, etc.)
    • Elevation
    • Date
    • What you were fishing with
    • Weather
    • Any other pertinent conditions.

    But mostly take your digital camera and send some good close-up photos for identification.

  5. Rich O'Connell will respond and you can then update your Survey Report.

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Brown trout shown next to two salamanders found in its stomach.
A brown trout and stomach contents
Dragonfly larvae shown on snow.
Dragonfly Nymphs
Tiny red copopods shown in white dish with larger mosquitoe larvae.
Copepods
Three pond skippers shown on palm of hand.
Pond Skippers
Cut open fish showing stomach and eggs.
Fish guts
Stomach contents in pain all lumped together.
Fish stomach content before separation
Fish stomach bursting with tiny freshwater clams.
Fresh water clams in fish stomach
Stomach contents in pan with knife for scale.
Identifying bugs from fish stomach contents
Salamander shown in freshly opened stomach.
Salamander in fish stomach
Mostly digested salamander remains.
Salamander remains
Pan with various items including fir needles.
Miscellaneous fish stomach contents
Squeezing contents out of freshly cut stomach.
Squeezing fish stomach contents into pan to identify
Small tadpoles shown in palm of hand.
Tadpoles
Large dragonfly nymph sittng on offal on a rock.
Nymphs in stomach
Holding open cleaned fish to show off red flesh.
Red meat
Stomach and miscellaneous small items in a white bowl.
Stomach contents
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