Notes Comparison of Two Escapement Designs for Western Painted Turtles Captured in Modified Fyke Nets Tyrel S. Moos,* Brian G. Blackwell South Dakota Department of Game, Fish and Parks, 603 East 8th Avenue, Webster, South Dakota 57274 Abstract Altering sampling methods to reduce bycatch during fish population sampling can introduce biases that affect the capture of target species. Therefore, understanding bycatch reduction devices and how they affect fish sampling is important. Our goal was to test two potential escapement designs intended to reduce bycatch of western painted turtles Chrysemys picta bellii during freshwater-fish population assessments with modified fyke nets. Design A tested an escapement flap on the interior of the modified fyke net and design B tested an escapement throat on the exterior of the modified fyke net. We completed 4-h and 24-h trials for turtle escapement to determine the effectiveness of each design for reducing turtle bycatch. We also simulated fish population assessments to determine the escapement of fish and turtles from each design. Turtles escaped from each design with mean escapement rates during the 4-h and 24-h trials of 71.1% and 63.8% from design A and 55.6% and 50.0% from design B, respectively. In the fish population assessment simulation we observed a mean escapement rate of 49% for turtles from design A, but a mean escapement rate of only 11% from design B. Species-specific escapement rates were observed for fish in both designs. Significant differences in the size structure of some species were observed. Escapement rates from design A were likely underestimated for most species captured due to movement of fish and turtles from the holding pen back into the fyke net. Based on our results, we do not recommend either design to reduce bycatch of turtles during fish community sampling without substantial refinement of the designs. Further research is needed to identify alternative methods for reducing turtle bycatch mortality. Keywords: bycatch reduction device (BRD); escapement; fish population assessments; modified fyke net; sampling bias; turtles Received: November 4, 2016; Accepted: November 9, 2017; Published Online Early: December 2017; Published: June 2018 Citation: Moos TS, Blackwell BG. 2018. Comparison of two escapement designs for western painted turtles captured in modified fyke nets. Journal of Fish and Wildlife Management 9(1):228–237; e1944-687X. doi:10.3996/112016-JFWM-082 Copyright: All material appearing in the Journal of Fish and Wildlife Management is in the public domain and may be reproduced or copied without permission unless specifically noted with the copyright symbol &. Citation of the source, as given above, is requested. The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service. * Corresponding authors: Tyrel.Moos@state.sd.us Introduction Many reptile species are imperiled. B ¨ ohm et al. (2013) noted nearly 1 in 5 species, of the 1,500 studied, are threatened with extinction; and freshwater environ- ments, tropical regions, and oceanic islands had the highest proportion of threatened reptile species. The primary threats to reptiles are habitat degradation, pollution, overexploitation, introduction of invasive species, and disease (Wilcove et al. 1998; Gibbons et al. 2000). An often overlooked threat to aquatic reptiles is bycatch mortality. Bycatch has been extensively studied in marine systems but is poorly understood in freshwater environments. Raby et al. (2011) noted only 37 of 1,152 papers on bycatch were devoted to freshwater systems. In freshwater environments, high rates of bycatch mortality have been observed in a variety of passive fishing gears (Barko et al. 2004), in commercial fisheries (Larocque et al. 2012a) and in fisheries management sampling (Moos and Blackwell 2017). However, studies on freshwater turtles have indicated that population declines can occur with only a slight increase in adult Journal of Fish and Wildlife Management | www.fwspubs.org June 2018 | Volume 9 | Issue 1 | 228 Downloaded from http://meridian.allenpress.com/jfwm/article-pdf/9/1/228/2336381/112016-jfwm-082.pdf by guest on 31 August 2023