Midwest Fish & Wildlife Conference 2016

AUTHORS: Nathan J. Lederman*, Minnesota State University, Mankato; Shannon J. Fisher Minnesota State University, Mankato

ABSTRACT: The Minnesota River is under increasing scrutiny, as commercial and recreational use increases, and threat of exotic species invasion heightens. Larval fish are extremely sensitive to environmental changes and therefore, maybe indicators of system functionally. Larval fish, however, are challenging to capture in riverine systems due to spatial and temporal distribution and clustering. To further understand larval sampling in riverine systems, light traps and a modified slednet was assessed. Collectively, 106 larvae and 8 eggs were captured during the 2014 sample season (representing 8 families and 19 genera). In 2014, the slednet captured a total of 87 larvae, and light traps captured a total of 27 larvae. Slednets captured 6 families representing 16 genera with a CPUE of 0.02/m3 (SE = 0.48). Light traps captured 3 families representing 9 genera with a CPUE of 0.3125/trap night (SE = 0.11). Light traps captured 2 unique taxon, whereas, sled nets captured 14. The slednet also captured more taxa during the earlier sampling periods (mid-May to mid-June), while light traps captured more during later periods (July and August). Additional data were collected during the 2015 field season in a differing hydrologic regime and using both modified versions of previously used gears and non-modified versions were employed. Initial recommendation is both gears should be utilized to secure a better data set than each would achieve individually however, gear selection should be objective orientated.