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AUTHORS: Jeremy Hammen, Emily Pherigo, Josey Ridgway, Jason Goeckler, Wyatt Doyle - U.S. Fish & Wildlife Service, Columbia Fish & Wildlife Conservation Office; Ron Brooks, Jessica Morris - Kentucky Department of Fish and Wildlife Resources
ABSTRACT: Fish species will occupy a diverse array of positions within the water column depending on season and time of day. These behaviors influence whether an individual fish is vulnerable to capture when managers assess a population. Silver Carp, an invasive species, are notoriously difficult to capture making it problematic to assess. Recent evidence has shown that Asian carp will move to the top of the water column after sunset possibly increasing their vulnerability to gears targeting this area. The USFWS Columbia Fish and Wildlife Conservation Office wanted to determine when the greatest likelihood to capture a Silver Carp would occur over a diel cycle and season. Sampling occurred in two reservoirs (Kentucky Lake and Lake Barkley, Kentucky) and a large backwater area (Hanson Material Services, Marseilles Pool, Illinois River, Illinois) in spring, summer, and fall of 2017. Randomized transects were sampled continuously through the evening starting two hours pre-sunset and ending five hours post-sunset. Preliminary data has shown that Silver Carp catch rates increase throughout the evening and peak 2-4 hours after sunset in both a reservoir and backwater habitats. Plateaus in Silver Carp catch rates sustained for 2-3 hours and then began to decrease into the morning. Catch rates were 2-3 times greater during these peak times compared to the 2 hours prior to sunset. Additionally, it appeared that the greatest catch rates occurred during spring and fall months in large reservoirs. Current management strategies for Asian Carp revolve around daytime sampling efforts. Evidence here suggests that Silver Carp catch rates could be significantly improved if management actions were to occur after sunset and during the spring or fall seasons.
