Video Surveillance of Spawning Fish: Real-Time Peeps into Nesting Behavior

We designed a digital underwater video camera system to monitor nesting centrarchid behavior in the Tallapoosa River, Alabama, 20 km below a peaking hydropower dam with a highly variable flow regime.  Major components of the system include a digital video recorder, multiple underwater cameras, and specially fabricated substrate stakes.  The innovative design of the substrate stakes allowed us to effectively observe nesting redbreast sunfish Lepomis auritus in a highly regulated river.  Substrates stakes were constructed for the specific substrata complex (i.e., sand, gravel, and cobble) identified at our study site, were able to withstand discharge ~300 m³/s, and allowed us to simultaneously record 10 active nests before and during water releases from the dam.  Video of nesting behavior indicated that male redbreast sunfish primarily exhibited the defend and leave behavior during ‘baseflow’ (e.g., low flow conditions) observations. During higher discharge events (i.e., one-unit or turbine; ~ 200cms) spawning behaviors (e.g., milt and court) ceased and the defend behavior decreased; whereas, the leave and the clean behaviors increased. Behavior observations indicated that increased flow caused disruption of spawning and nest abandonment. Behavior during two-unit discharge events was only minimally observed because of drought conditions; however, data indicated detrimental effects of two-unit discharge on nests (i.e., destruction).  Our technique was effective for monitoring specific nesting behaviors in a highly disturbed river and could be easily modified for behavioral analysis of most species in other habitat types.