AUTHORS: Alexandria Keiler-Klein, University of Nebraska at Kearney; Melissa Wuellner, University of Nebraska at Kearney; Keith Koupal, Nebraska Game and Parks Commission and University of Nebraska at Kearney
ABSTRACT: Nuisance and invasive species can, directly and indirectly, affect sport fisheries, but few agencies target these fishes in annual standard surveys. Understanding when and how to sample nuisance and invasive species is important to understanding their abundance and size structures. Determining optimal assessment techniques can provide management insight into interventions to address the impacts of nuisance and invasive fish abundance on salmonid species. The objective of this study was to determine which gear and time of year could be used to assess populations of invasive (Common Carp Cyprinus carpio) and/or nuisance (White sucker Catostomus commersonii) species in one Nebraska reservoir. Experimental gill nets, modified fyke nets, and nighttime boat electrofishing were employed at nine locations across Lake Ogallala monthly from April through September 2023. All individuals of the two species were enumerated and measured for total length (mm). This information was used to calculate catch per unit effort (CPUE), the coefficient of variation around CPUE, and a measure of length variability (Shannon-Weiner diversity based on 10-mm length bins) for each gear, month, and species. Additionally, we calculated the measurement of operational effort. Measurements were ranked across gears for each month and summed. The smallest ranks were used to identify the best gear and month for sampling each species. Preliminary results indicate electrofishing captures the best length diversity and operational effort for Common Carp and White Sucker in June and May respectively. CPUE for White Suckers and Common Carp was highest in April and July fyke netting respectively. Lastly, variability in CPUE was lowest with Common Carp July electrofishing and White Suckers May gill netting. The results from this study can be used by other states and provinces addressing similar and other nuisance and invasive species assessments to allow for more proactive, rather than reactive, management interventions to support salmonid fisheries.
