Methods:
A field experiment will be conducted at the University of Michigan’s Biological Station on Douglas Lake from May 14th until August 18th. Study sites will be selected by visual surveys for black crappie nesting colonies with the presence of eggs and adult black crappies exhibiting nesting behaviors. GPS coordinates of the nest will be recorded to prevent repetition along with a series of environmental variables such as light and temperature will be quantified alongside abiotic factors such as nest location and depth relative to the boat.
All motorized vehicles in the area will be categorized according to their distance from the nest: 0-5 meters, 5-10 meters, 10-15 meters, or 15-20 meters. A series of background noise readings will be recorded using a hydrophone (DolphinEar DE200). The hydrophone will be lowered to approximately 15 cm off the substrate, directly adjacent (less than 1 meter) to the target nest to measure the sonogram of background noise continuously for three minutes. The background noise will be later compared to a control recording made in an area of Douglas Lake with no motorized vehicles within 20 meters.
After completing background noise readings, we will enter the water and via snorkeling, we will record a series of nest-guarding behaviors exhibited by the black crappie for approximately 10 minutes. Each unique nest-guarding behavior will have a unique label associated with it that will be recorded along with the duration of the observed behavior in seconds. All nest-guarding behaviors will be categorized as guarding or non-guarding and will be noted as occurring inside or outside the nest. An underwater camera will be placed at the first identified active black crappie nest to continuously record nesting behaviors. Throughout the process of observing nesting behaviors and setting up the camera, we will be careful not to disturb or approach the nests.