Study

Mitigating bycatch of freshwater turtles in passively fished fyke nets through the use of exclusion and escape modifications

  • Published source details Larocque S.M., Cooke S.J. & Blouin-Demers G. (2012) Mitigating bycatch of freshwater turtles in passively fished fyke nets through the use of exclusion and escape modifications. Fisheries Research, 125, 149-155.

Actions

This study is summarised as evidence for the following.

Action Category

Install escape devices on fishing gear: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation

Install exclusion devices on fishing gear: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation
  1. Install escape devices on fishing gear: Tortoises, terrapins, side-necked & softshell turtles

    A replicated, randomized, paired, controlled study in 2010–2011 in a freshwater lake in eastern Ontario, Canada (Larocque et al. 2012) found that adding an escape chimney to fyke nets increased the escape rate of painted turtles Chrysemys picta and reduced the escape rate of fish compared to modifying nets with a large hole. More painted turtles escaped from fyke nets modified with escape chimneys (10 of 10 turtles escaped) compared to fyke nets modified with a large hole (12 of 20 turtles escaped). The proportion of fish escaping was reduced in escape-chimney nets (0.13 fish/24 hr) compared to large-hole nets (0.77 fish/24 hr). Escape rates of turtles and fishes were tested in modified commercial seven-hooped fyke nets set in a shallow warmwater lake (788 ha, nets set to 1.5 m depths) in April–June 2010–2011. Two nets were modified with either an open-topped chimney (a mesh tube 15 cm wide, 28 cm long and 28 cm tall) attached to the net between the 6th and 7th hoop (see original paper for details), or a large hole in the top (15 cm x 28 cm, typical of damage that occurs through normal fishing). Individual male painted turtles or fish Lepomis spp. were placed in the cod-end of a closed net for four hours (turtles) or 24 hours (fish) and escapes counted (turtles: 10 chimney trials and 20 large hole trials; fish: 10 chimney trials and 10 large hole trials).

    (Summarised by: Maggie Watson, Katie Sainsbury)

  2. Install exclusion devices on fishing gear: Tortoises, terrapins, side-necked & softshell turtles

    A replicated, randomized, paired, controlled study in 2010 in a shallow freshwater lake in Ontario, Canada (Larocque et al. 2012, same experimental location as Cairns et al. 2013) found that adding exclusion bars to fyke nets (a ‘bycatch reduction device’) reduced turtle bycatch but that adding exclusion rectangles did not. Fyke nets modified with exclusion bars captured fewer turtles (0.03 turtles/hour) compared to unmodified nets (0.1 turtles/hour). In separate trials, nets modified with an exclusion rectangle captured similar numbers of turtles (0.02 turtles/hour) compared to unmodified nets (0.04 turtles/hour). Catch rates of target fish species were similar in exclusion bar nets (2.9 fish/hour), exclusion rectangle nets (2.6 fish/hour) and unmodified nets (2.9 fish/hour). Standard commercial hooped fyke nets (see original paper for details) were set in a shallow freshwater lake (788 ha) in April–June and September–October 2010 in pairs of modified and unmodified nets. Nets were either modified with exclusion bars made of wooden dowels (8 x 1.3 cm spaced 8 cm apart; set at 30 sites in April–June) or an exclusion rectangle made by attaching a hose clamp at the first funnel of the fyke net (18 x 7.5 cm rectangle; set at 15 sites in September–October). Tandem modified and unmodified nets were set fully submerged within 15 m of each other for 8–48 hours at a time.

    (Summarised by: Maggie Watson, Katie Sainsbury)

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