The effectiveness of two common sampling methods for assessing imperilled freshwater fishes

Abstract

This study tested the hypothesis that the most common gear type used to sample fishes in wadeable systems, electrofishing, was more effective than another commonly used gear type, seining, for sampling fish species at risk. Five predictions were tested. At sites where species at risk were detected, (1) the probability of detecting the species at risk, (2) the probability of only one gear type detecting the species at risk and (3) the estimated catch per unit effort of the species at risk, was as high as, or higher, when using electrofishing than when using a seine. (4) The number of sample sites required to detect a species at risk within a watershed and (5) the number of subsections required to detect a species at risk within a site, were as low as, or lower, using electrofishing than the number required using a seine. Based on analyses of these measurements, electrofishing was a more effective gear type than seining for sampling fish species at risk, irrespective of the unit (presence or absence or catch per unit effort) or scale of measurement (watershed or site level). Dissolved oxygen, turbidity, specific conductivity and nitrate concentrations were measured at each site and did not account for the between gear differences. Selection of sampling gear can be a fundamental consideration for the assessment of fish species at risk, where, unlike common species, they may be particularly influenced by small population sizes, restricted geographic ranges and narrow habitat preferences. Resource managers must weigh differences in the risks of injury of fish species at risk against differences in the effectiveness of each gear type when deciding between gear types and the utility of the assessments they represent.

Dependence of beach seine net efficiency on net length and diel period

“…The simple ratio of the mean efficiency estimates is biased and we did not have information about its real distribution. We therefore used an unbiased resampling method according to Manly (1997) and Poos et al (2007). This resampling method was based on the sampling with replacement of the measured data following calculation of the ratio from these sampled values.…”

Secondary invasion of the round goby into high diversity Great Lakes tributaries and species at risk hotspots: potential new concerns for endangered freshwater species

“…Fish species that may be impacted from the secondary invasion of round goby were selected from a recent database of fish distributions in the Great Lakes (Mandrak and Crossman 1992;Hubbs and Lagler 2004;Mandrak unpublished data) and updated using recent surveys conducted on these systems (Cudmore et al 2004;Poos et al 2007;Poos et al 2008; A. J. Dextrase (Ontario Ministry of Natural Resources, unpublished data); N.E. Mandrak (Fisheries and Oceans Canada, unpublished data).…”

Evaluating Two Observational Sampling Techniques for Determining the Distribution and Detection Probability of Age‐0 Smallmouth Bass in Clear, Warmwater Streams

“…Our preliminary sampling indicated that electrofishing was inadequate (very few age-0 fish were captured after several days of effort), similar to the findings of McClendon and Rabeni (1988), who sampled very few juvenile smallmouth bass by use of electrofishing in the same river system. Likewise, we found that seining was ineffective, as many fish avoided the seine, which is generally considered to be less effective than electrofishing (Wiley and Tsai 1983;Poos et al 2007). We therefore proceeded with a combination of two observational techniques: snorkeling and AW observation.…”