Electro fishing in the Great Lakes

Text by Roger F. Thoma.

Here we are on a Lake Erie tributary sampling fish populations (electro-fishing) during the day. This is the Toussaint River lacustuary. We are at the mouth of the river where it joins Lake Erie and forms a wide area affected by lake water levels. Many people call these areas estuaries in the Great Lakes. I prefer the term lacustuary. Lacustuary is a word I created to use instead of estuary. The biological processes occurring in estuaries are so different from what occurs in a lacustuary that I felt it was important not to get the two phenomena confused, ergo the new word.

Here is another picture of the Lake Erie electrofishing sampling boat. This one is a little closer up. I'm at mid ship, Steve White is in the stern, and Mat Raffinburg is at the bow. We're in the same lacustuary system as the other picture.

The Great Lakes were formed by continental glaciers that scooped out the large pits that are now the lakes. When the glaciers first retreated Lake Erie was much smaller and shallower because the glaciers (over a mile thick) had depressed the eastern end of the land with their weight. Because the lake was shallower, this allowed tributary streams to erode valleys in the area that is now the lake's edge. As the land rebounded (the Niagara escarpment) Lake Erie's water level began to rise and flooded the tributaries thus creating what I call lacustuaries. Many estuaries were also formed during glacial epochs when ocean levels were lowered and much water was locked up as ice on the continents. Like estuaries, lacustuaries are subject to tidal like influences, though these movements are mostly caused by winds pushing the lake water from one end of the lake to the other. This can frequently result in over a six foot water level difference from one end to the other!

Here we are sampling on Lake Erie at night. Mat Raffinburg is on the front dipping out fish as they rise to the electrical current. We sample the Lake proper at night and wetland/lacustuary areas during the day. This then allows me to work 24 hours a day which makes my bosses very happy (just joking)!

Steve Fouts records chemical data to go with our fish data. As you may have noticed, at night all the scenery looks the same.
Bill Zawiski hauls a fish on board as we sample the Black River lacustuary. Its only a carp (Cyprinus carpio) but its big enough to see. Bill works with
me at my Twinsburg office and frequently helps out when I'm short handed. Bill knows more about permits and chemical limits than anybody else I know.


Great Lakes Fish

Great Lakes Exotics