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AUTHORS: Jordan M. Kukal, U.S. Geological Survey, Columbia Environmental Research Center; Patrick M. Kocovsky, U.S. Geological Survey, Lake Erie Biological Field Station; Duane C. Chapman, U.S. Geological Survey, Columbia Environmental Research Center
ABSTRACT: Grass carp (Ctenopharyngodon idella) is an invasive species that management agencies in the US and Canada want to control or eradicate. Assessing the behavior of this species’ larval life stage could improve our understanding of which spawning events result in recruitment. Quatrefoil light traps are a widely used method for early life history assessments of many fish species. Previous research suggested catch per unit effort (CPUE) varied with light color for some species. We tested the hypothesis that CPUE of grass carp varied with light color. Two cohorts of approximately 30,000 larval grass carp each were stocked in two ponds at the USGS Columbia Environmental Research Center (CERC). The first cohort was stocked on the first sampling day, and the second cohort was stocked 23 days later. We used a Latin Square design for the fixed trap placement that accounts for potential environmental gradients. Each pond was sampled 10 times, while monitoring turbidity and ambient light during sampling as potential co-variates. The pond that exhibited a higher turbidity yielded a lower CPUE than the pond with a lower turbidity. A “column” effect was observed with CPUE in columns 1 and 4, which were closer to the pond edges. However, after accounting for turbidity, light intensity, and other effects, there were no significant differences in CPUE by light color. Future studies will examine additional variables and means of grass carp larval attractants. These may include different light sources (e.g. LEDs), field trials that assess multiple species, and determination of grass carp larval size in relation to the susceptibility of trap capture.