Environmental Biology of Fishes

, Volume 81, Issue 3, pp 313–319

Comparison of visual survey and seining methods for estimating abundance of an endangered, benthic stream fish

Authors

    • Department of Biological SciencesLoyola University New Orleans
  • Howard L. Jelks
    • US Geological SurveyFlorida Integrated Science Center
  • Stephen A. Bortone
    • Minnesota Sea Grant College Program
  • Robert M. Dorazio
    • US Geological Survey, Florida Integrated Science Center, Department of StatisticsUniversity of Florida
Full Paper

DOI: 10.1007/s10641-007-9202-0

Cite this article as:
Jordan, F., Jelks, H.L., Bortone, S.A. et al. Environ Biol Fish (2008) 81: 313. doi:10.1007/s10641-007-9202-0

Abstract

We compared visual survey and seining methods for estimating abundance of endangered Okaloosa darters, Etheostoma okaloosae, in 12 replicate stream reaches during August 2001. For each 20-m stream reach, two divers systematically located and marked the position of darters and then a second crew of three to five people came through with a small-mesh seine and exhaustively sampled the same area. Visual surveys required little extra time to complete. Visual counts (24.2 ± 12.0; mean ± one SD) considerably exceeded seine captures (7.4 ± 4.8), and counts from the two methods were uncorrelated. Visual surveys, but not seines, detected the presence of Okaloosa darters at one site with low population densities. In 2003, we performed a depletion removal study in 10 replicate stream reaches to assess the accuracy of the visual survey method. Visual surveys detected 59% of Okaloosa darters present, and visual counts and removal estimates were positively correlated. Taken together, our comparisons indicate that visual surveys more accurately and precisely estimate abundance of Okaloosa darters than seining and more reliably detect presence at low population densities. We recommend evaluation of visual survey methods when designing programs to monitor abundance of benthic fishes in clear streams, especially for threatened and endangered species that may be sensitive to handling and habitat disturbance.

Keywords

ConservationCountsDetectionEndangered speciesRemovalSampling

Copyright information

© Springer Science+Business Media, Inc. 2007