Trout Lake Research Rewind: Fyke Nets & Native Mussels

by Riley Steinbrenner

Week Seven

This summer, CFL graduate students Martin Perales and Holly Embke are busy catching fish on their two study lakes–Sandy Beach Lake and McDermott Lake in Iron County–using a lot of different methods. One of these involves a net called a Fyke net. Fyke nets are generally used to trap smaller fish near the shoreline, such as yellow perch, rock bass and bluegill that are only a few months old, or what scientists and fisheries managers call “young of the year” (YOYs). The first half of the Fyke net forms a curtain-like wall that is attached to the shoreline and runs out into the lake. Fish swimming in nearshore waters run into the wall and turn to head out to deeper water. Following the wall, they are led into the tunnel-like part of the net through a series of hoops that lead them to a “dead-end.” But not for the fish! These nets are usually harmless, holding fish in the last section of the net until researchers can come by, lift it out of the water, take measurements and toss them back in.
After catching fish, Martin and summer undergraduate students, Matt Chotlos and Liddy Ginther, took them back to shore where Holly and Ishita Aghi, another summer undergrad here on station, measured their weights and lengths. Since numbers of the fish could reach up to the thousands, Holly and Ishita only weighed the first 30 of each species, as they could then apply an average weight to the sample. The team repeated this for five locations around Sandy Beach Lake, and will do so on McDermott Lake as well. 
By trapping and identifying fish once a month this summer, as well as electrofishing, clover trapping and seining, they hope to get a “baseline” profile of the different populations of fish that inhabit the lakes before they start removing bass next summer. Since all these fish are interconnected through the food chain, Martin and Holly believe they will observe large fluctuations in the fish species as bass become disconnected from the top of the food chain. But the only way to find out if that hypothesis is supported, is by first establishing a baseline. And that means a lot more Fyke nets are in their future!
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This week, CFL graduate student, Vince Butitta, and summer undergraduate student, Liddy Ginther, joined us at Trout Lake Station to collect native freshwater mussels. Vince currently conducts a survey on these mussels to observe how different environmental characteristics, such as water temperature and chemistry, affect their growth. In order to do so, he must collect older mussels, which have at least over 15 rings – the age of mussels can be determined by the amount of rings on their shell, just like trees!
Vince explained that while most mussels are found in rivers and streams, lakes are a refuge for them, as the mechanical wear-down from fast-moving rocks and sand isn’t as much of a concern. However, slight changes in the lake’s water chemistry such as an increase in carbon dioxide, the gas infamously known for its role in global warming, can severely harm a mussel. An increase in carbon dioxide in the water is what causes mussels to deteriorate, as the increase in acidity eats away at the calcium carbonate mussels use to make their protective shells.
By taking the shells back to Hasler Lab in Madison and examining them at the molecular level, Vince’s objective is to see if the older mussels are struggling or thriving and if conditions in the ecosystems from which they came could help explain why.
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