“Most Wisconsin fish species, from sturgeon to smallmouth, spawn in one of two standard modes. The first is broadcast spawning, where males fertilize eggs dropped by females as they swim across spawning grounds. The second main type of spawning happens with a male or female building a nest for the eggs and sometimes with one of the adults guarding the nest after the female lays the eggs.
“The freshwater drum is an interesting spawner in several ways. First, the males make an audible drumming noise as spawning approaches. The other drum oddity is that drum eggs float, which is typical of saltwater fish, but very rare for freshwater species.
“Burbot is another species unique in its spawning, though more so in the timing. Burbot spawn in the dead of winter, under the ice, making large, writhing spawning ‘balls’ with many adults slithering together as they procreate.
“Creek chubs are also a noteworthy spawner. Many fish species scoop nests with their powerful tail fins, but the chub does it with its mouth. The male chub digs out a spawning depression in gravel by relocating rocks by mouth, one at a time, usually placing them in a ridge or a pile that you can see if you wade in a stream where chubs have spawned.”