The night shift begins! Electrofishing 15 Michigan lakes
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Joe Nohner is a CSIS PhD student who's studying largemouth bass, specifically how habitat helps baby largemouth survive and grow, and the socioeconomic factors that influence landowners’ habitat management choices. He's also a passionate fisherman who aims to understand the layers and layers of complexity to solve ecosystem problems. This is an excerpt from Joe's blog, Fishing for Habitat.
July 21, 2014
Our team has started conducting nighttime electrofishing surveys of 15 Michigan lakes, meaning long days and lots of excitement!
I mentioned in my previous post that our big research question is, “what habitats are best for largemouth bass?” We are using net pens to confine fish to particular habitats and follow their growth, but of course fish can swim from habitat to habitat in many lakes. So, we are complementing the net pen research with a study of largemouth bass populations across lakes that provide different habitats. Some lakes have lots of aquatic vegetation while others have only a few spots. How much is enough? How much is too much? These are questions that have been addressed in the fisheries research to some extent, but most studies are from southern lakes choked with vegetation. Not much use up in Michigan! So, we are setting out to study these questions by comparing the largemouth populations of many lakes to maps of aquatic vegetation and other habitat characteristics.
That means we get to go out and catch thousands of fish. The best way to do that is electrofishing. Here’s what it looks like from my perspective on the boat.
We conduct a number of sampling runs on each lake in different habitats. If you watch closely, you’ll notice that many of the bass we catch are near aquatic vegetation or docks. That’s fairly typical for us, and is consistent with our hypothesis that largemouth are relating to this structure. Of course, this will not be a surprise to the fishermen out there!
Each fish we catch, we mark a GPS position and put in a special compartment in the live well. We record the length and weight of the fish, remove about five scales to determine its age in the lab, and for some fish we pump their stomachs to see what they are eating. All of this information will help us put together a composite picture of what is happening between the lakes in our study, as well as some indication of what happens where in each lake (Where are the big fish? Where are the young fish? Where are the fish with full stomachs? etc. etc.). This fall and winter, we will have a lot of fun sorting through fish puke and determining ages from scales under the microscope. I’ll use computer mapping programs to build statistical models and test our hypotheses. But, for now, we are putting in long hours and enjoying the outdoors.
