Seasonal patterns in bycatch composition and mortality associated with a freshwater hoop net fishery S. M. Larocque 1,2 , A. H. Colotelo 1 , S. J. Cooke 1,3 , G. Blouin-Demers 2 , T. Haxton 4 & K. E. Smokorowski 5 1 Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, ON, Canada 2 Department of Biology, University of Ottawa, Ottawa, ON, Canada 3 Institute of Environmental Science, Carleton University, Ottawa, ON, Canada 4 Ontario Ministry of Natural Resources, Southern Science & Information Section, Peterborough, ON, Canada 5 Fisheries and Oceans Canada, Great Lakes Laboratory for Fisheries and Aquatic Sciences, Sault Ste. Marie, ON, Canada Keywords turtles; species at risk; gamefish; commercial fisheries; temporal restrictions. Correspondence Sarah M. Larocque, Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada. Email: slarocque9@gmail.com Editor: Matthew Gompper Associate Editor: Trevor Branch Received 13 April 2011; accepted 12 July 2011 doi:10.1111/j.1469-1795.2011.00487.x Abstract Although bycatch is well known and well studied in marine fisheries, compara- tively little is known about bycatch in freshwater fisheries. Even basic informa- tion on bycatch composition and mortality in freshwater is unavailable, given that few inland jurisdictions require reporting of bycatch. A small-scale inland hoop net fishery that targets pan fish (e.g. sunfish, Lepomis spp.) and operates primarily in the spring and fall was simulated in two lakes in south-eastern Ontario to characterize both bycatch composition and mortality. We fished one lake in both spring and fall to compare catch rates, while in the other lake we set nets for 2 or 6 days during the spring to assess fish mortality associated with different net tending frequencies. In both lakes, bycatch consisted of gamefish, turtles (including several species at risk), and mammals. For fish, there was no difference in spring and fall catches. Turtles, however, were captured more often in spring. Fish mortality of both target and non-target species increased from 0.3–0.9% to 3.0–3.7% (4–10 times) when set net duration increased from 2 to 6 days. Despite the provision of an air breathing space in our nets, we docu- mented severe turtle mortality (33% in one lake) and all mammals died, sug- gesting that provision of air spaces is not always effective. Although all bycatch mortality is a concern, turtles are prone to population declines even with low levels of non-natural mortality. As such, regulators may consider limiting com- mercial fishing to the fall in this region to reduce turtle captures. Seasonal restrictions on fishing or use of frequent net tending (e.g. < 2 days) will not prevent all turtle bycatch and therefore gear modifications should be investigated to further reduce turtle captures and mortality associated with hoop nets. Introduction Bycatch, the incidental capture of non-targeted organisms in commercial fisheries, is a growing concern and an impor- tant conservation issue (Alverson et al., 1994; Hall & Main- prize, 2005; Harrington, Myers & Rosenberg, 2005; Kelleher, 2005). Fisheries are now not only concerned with the sustainability of targeted organisms, but also beginning to consider whether catches of non-targeted fauna are at sustainable levels (Hall, Alverson & Metuzals, 2000). Reflecting this concern, the number of studies examining bycatch issues has increased exponentially in recent decades (Soykan et al., 2008). These studies, however, focus prima- rily on marine systems, leaving freshwater bycatch issues relatively unstudied (Raby et al., 2011). This is disconcert- ing given that biodiversity in highly diverse freshwater eco- systems is declining, with overexploitation identified as one of the leading causes (Dudgeon et al., 2006). As bycatch has contributed to the degradation of marine ecosystems (Crowder & Murawski, 1998; Hall et al., 2000; Lewison et al., 2004), bycatch likely has had similar impacts on fresh- water ecosystems. Therefore, there is a need to determine the extent and consequences of bycatch in freshwater com- mercial fisheries. In freshwater commercial fisheries, hoop or fyke nets are commonly used. In south-eastern Ontario, a commercial hoop net fishery operates on several lakes and large river systems. This fishery targets a variety of species such as sunfish (Lepomis spp.), bullheads (Ameiurus spp.), yellow perch (Perca flavescens), rock bass (Ambloplites rupestris) Animal Conservation. Print ISSN 1367-9430 Animal Conservation 15 (2012) 53–60 © 2011 The Authors. Animal Conservation © 2011 The Zoological Society of London 53