Effects of Sampling Time, Intraspecific Density, and Environmental Variables on Electrofishing Catch per Effort of Largemouth Bass in Minnesota Lakes

Abstract

Effects of sampling time (day or night and fall or spring), target fish density, water clarity, water temperature, water conductivity, and lake morphometry on electrofishing catch per effort (CPUE) of largemouth bass Micropterus salmoides 200 mm total length (TL) and longer were determined. Electrofishing catch per hour (CPH) and catch per kilometer (CPK) were also compared to determine if each expression provided similar trends in CPUE. Correlations between day CPH and day CPK (r = 0.99; P < 0.0001) and night CPH and night CPK (r = 0.97; P < 0.0001) suggested that both measures provided similar trends in CPUE. Night CPH significantly exceeded day CPH, and spring CPH significantly exceeded fall CPH. Catchability (q) decreased with increasing density; therefore, CPH increased nonlinearly with density. Day CPH in fall decreased with increasing Secchi depth and water temperature but was unrelated to largemouth bass density. Day CPH in spring decreased with increasing Secchi depth and water temperature and increased with increasing density of largemouth bass and water conductivity. Night CPH in fall increased with increasing density and decreased with decreasing water conductivity, and night CPH in spring increased with increasing density and decreasing percent littoral area (percent of lake with depth less than 4.6 m) among lakes. These variables explained 44% of day CPH in fall, 75% of day CPH in spring, 28% of night CPH in fall, and 59% of night CPH in spring. Effects of density on q must be determined and environmental conditions must be similar before CPUE can be a useful index of largemouth bass density.

Effect of Block Net Use and Time of Sampling on Backpack Electrofishing Catches in Three Kansas Reservoirs

“…were significantly greater than day catch rates is contrary to other study findings on age-0 centrarchid catch rates using boom-mounted electrofishing units (Gilliland 1987;Dumont and Dennis 1997) but concurs with boat electrofishing studies focused on harvestable centrarchids (Ն251 mm; Malvestuto and Sonski 1990;McInerny and Cross 2000;Pierce et al 2001). Gilliland (1987) found that catch rates of largemouth bass in two Oklahoma reservoirs were significantly higher for all ages combined at night than during daylight, but age-0 catch rates were higher during daylight.…”

“…have used boom-mounted electrodes to target harvestable-sized fish (Gilliland 1987;Maceina et al 1995;Dumont and Dennis 1997;McInerny and Cross 2000). Past studies have investigated differences between day and night sampling and have found varying results.…”

Establishment patterns of non-native fishes: Lessons from the Duluth–Superior harbor and lower St. Louis River, an invasion-prone Great Lakes coastal ecosystem

“…Brook silverside, a midwater species, was captured well by the seine, but so were the benthic tubenose goby and threespine stickleback. Shoreline electrofishing is sufficiently effective for fish population analysis (McInerny and Cross, 2000), but CPUE and occurrence rates were generally lower compared to other gear in this study. In general, nocturnal sampling can increase richness and CPUE (Portt et al, 2006) but was not done in this study, with the exception of fyke nets, which were set overnight.…”

Comparison of Day and Night Fyke Netting, Electrofishing and Snorkelling for Monitoring a Population of the Threatened Golden Galaxias (Galaxias auratus)

“…Night electrofishing has been reported to more efficient than day electrofishing for fish in riverine (Paragamian, 1989) and lake (McInerny & Cross, 2000) habitats. Electrofishing is biased towards larger size fish (Zalewski, 1983) and it is also more effective in shallower water where avoidance of the electric field is more difficult (Reynolds, 1996).…”