A breath of fresh air: avoiding anoxia and mortality of freshwater turtles in fyke nets by the use of floats

Authors

  • Sarah M. Larocque,

    Corresponding author
    1. Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, ON, Canada
    • Herpetology Laboratory, Department of Biology, University of Ottawa, Ottawa, ON, Canada
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  • Steven J. Cooke,

    1. Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, ON, Canada
    2. Institute of Environmental Science, Carleton University, Ottawa, ON, Canada
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  • Gabriel Blouin-Demers

    1. Herpetology Laboratory, Department of Biology, University of Ottawa, Ottawa, ON, Canada
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S. M. Larocque, Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, 1125 Colonel By Dr., Ottawa, ON K1S 5B6 Canada. E-mail: slarocque9@gmail.com

ABSTRACT

  1. Freshwater turtles are susceptible to drowning in commercial fishing nets and this is a major conservation concern. Methods to mitigate turtle bycatch mortality typically involve reducing the capture of bycatch using gear modifications. Another method to reduce mortality is to keep bycatch alive following capture.
  2. Using physiological measures of anoxia, this study determined whether providing air spaces using floats within fyke nets could prevent turtles from drowning. In a controlled setting, blood lactate and pH of painted turtles (Chrysemys picta) experimentally introduced into submerged nets, nets with floats, and nets that breached the surface were compared. While emulating commercial fishing practices – where turtles and fish voluntarily entered nets – catch rates and compositions as well as blood lactate in turtles captured were compared in submerged nets with and without floats.
  3. Painted turtles in submerged nets exhibited elevated blood lactate and pronounced acidosis compared with turtles from nets with floats and surfaced nets.
  4. Catch rates and compositions from emulated fishing were statistically similar in nets with and without floats; however, total fish catches were roughly one-third less in nets with floats. The same pattern of physiological disturbance was observed with turtles captured in submerged nets with and without floats as in the controlled experiment.
  5. Overall, blood physiology indicated that anoxia occurred in turtles in submerged nets while nets with floats reduced physiological disturbance. However, variation in blood lactate levels when fishing fyke nets with floats suggests that turtles were experiencing slight anoxia and so the size of air spaces may be important in allowing access to air. Creating air spaces in fyke nets using floats is a simple and cost-effective method to avoid the drowning of turtles.

Copyright © 2012 John Wiley & Sons, Ltd.

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