Efficiency of Rotenone Sampling with Large and Small Block Nets in Vegetated and Open-Water Habitats

Abstract

The sampling effectiveness of rotenone applied within large (0.41 hectare) and small (0.08 hectare) blocknetted areas was compared at open-water and vegetated sites in Orange Lake, Florida. Eighteen fish species were collected within the large nets and 21 species within the small nets; 16 species were common to both nets. Total fish biomass (kg/hectare) and abundance (number/hectare) estimates did not differ significantly (P ≤ 0.10) between areas in either open-water or vegetated habitats; abundance estimates (number/hectare) did not differ between large and small open-water areas. Significantly higher abundance estimates were obtained in the smaller nets in vegetated habitats due to more efficient pickup of small fish. For larger size game fish, total abundance, biomass, and individual species estimates were not significantly different between sample areas in either habitat. The smaller experimental nets provided inventories of fish populations that were as accurate as those from large-area samples, with much lower labor and equipment requirements.