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

Published source details Larocque S.M., Cooke S.J. & Blouin-Demers G. (2012) A breath of fresh air: avoiding anoxia and mortality of freshwater turtles in fyke nets by the use of floats. Aquatic Conservation: Marine and Freshwater Ecosystems, 22, 198-205.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

	Action	Category
	Deploy fishing gear at different depths Action Link

Deploy fishing gear at different depths

A replicated, randomized, paired study in 2009–2010 in a freshwater lake in Ontario, Canada (Larocque et al. 2012) found that using floated nets did not reduce levels of unwanted catch but did reduce drowning risk (measured using blood lactate levels) and mortality in turtles caught in fyke nets. Turtle catch rates and species composition were similar between floated (0.06 turtles/hour, 35 individuals) and submerged nets (0.10 turtles/hour, 48 individuals). Blood lactate levels (a measure of drowning risk) were reduced in turtles tested in floated nets (1.3–3.5 mmol/L) compared to submerged nets (13.2–16.4 mmol/L). Turtle mortality only occurred in submerged nets (3 individuals, no statistical tests were carried out). Species composition was similar between net types (data presented as statistical model outputs). Turtle species caught included painted turtles Chrysemys picta, eastern musk turtles Sternotherus odoratus, northern map turtles Graptemys geographica, and common snapping turtle Chelydra serpentina. Target fish catch rates were similar between floated (2.5 fish/hour) and submerged nets (3.1 fish/hour). In August 2009, experimental tests of blood lactate and pH levels of turtles placed in submerged, floated and semi-submerged nets were carried out initially to test whether turtles used air spaces provided by elevating nets in the water (9–10 trials/net, see original paper for details). In April–June 2010, submerged nets (without floats) and nets with floats were deployed in pairs (two submerged nets deployed within 15 m of two floated nets) for 8–48 hours in 30 locations (1–2 m deep). Blood samples were taken from all turtles and the number caught (including mortalities) was recorded.

(Summarised by: Katie Sainsbury)