Fish Fry Day: Sifting Through Seagull “Deposits” for Fish Facts

We apologize for the unsavory nature of this post on the day we celebrate Wisconsin’s fabulous fried fish culinary tradition, but we promise to leave out the gory details!

Panorama of the Crystal Mixing crew getting ready for 2013. Photo: Goisa Golub
Panorama of the Crystal Mixing crew getting ready for 2013. Photo: Goisa Golub

After a summer spent in the shimmering waters of Crystal Lake, the Crystal Mixing Crew is hunkered down in the lab processing the samples they collected in the field. You can read up on the details here. In the meantime, grad student, Zach Lawson, sent in these pics of how a fish goes from its aquatic habitat to a more scientific one in six easy steps.

To quote Zach, “Digging through gull deposits is not our ‘favorite’ method of answering scientific questions, but knowing the age of the [fish] that exhibit signs of stress helps us understand the impact this whole lake experiment had on the population.”

Step One: Gulls take advantage of stressed smelt thrashing at the surface of Crystal Lake as the water temp approaches 20 Celsius, feasting on the invasive fish.

Gulls take advantage of stressed smelt thrashing at the surface of Crystal Lake as the water temp approaches 20 Celsius

Click on images for a bigger pictures.

Step Two: After their fishy feast, the gulls “deposit” the remains on the Crystal Lake experiment’s instrumented buoy.

After their fishy feast, the gulls "deposit" the remains on the Crystal Lake experiment's instrumented buoy.

Step Three: Researchers pick through the gull “leavings” and extract and clean [not pictured] the smelt otoliths left behind.

Researchers picked through the gull "leavings" and extracted and cleaned [cleaning process omitted] the smelt otoliths left behind.

Step Four: It’s a dirty job, but someone’s got to do it. Otoliths, also called fish “earbones” are cleaned and mounted in blocks of epoxy.

It's a dirty job, but someone's got to do it. Otoliths, also called fish "earbones" are cleaned and mounted in blocks of epoxy.

Step Five: Using a sectioning saw, a thin slice of otolith is cut and then affixed to a glass slide.

Using a sectioning saw, a thin slice of otolith is cut and then affixed to a glass slide.

Step Six: Safe (and sanitized) on the slide, the otolith can be examined under a microscope to get at the age of the fish that were thermally stressed and providing the gulls’ feast.

Safe (and sanitized) on the slide, the otolith can be examined under a microscope to get at the age of the fish that were thermally stressed and providing the gulls' feast.

That’s all there is to it – we wish the crew luck and resilient eyeballs as they stare through their ‘scopes, counting otolith rings until the lakes begin to thaw!

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