Biologgers reveal post‐release behavioural impairments of freshwater turtles following interactions with fishing nets

• Published in: Animal conservation 2017-08, Vol.20 (4), p.350-359
• Main Authors: Gutowsky, L. F. G., Stoot, L. J., Cairns, N. A., Thiem, J. D., Brownscombe, J. W., Danylchuk, A. J., Blouin‐Demers, G., Cooke, S. J.
• Format: Article
• Language: English
• Subjects: Acceleration; accelerometer; behavioural effects; Bycatch; Chrysemys picta; depth; Distribution; Entrapment; Fisheries; Fishing; Fishing nets; Freshwater; Freshwater tortoises; Inland water environment; Interactions; Lethal effects; Locomotor activity; Man-induced effects; Mortality; Mortality causes; Nets; overall dynamic body acceleration; Populations; Sensors; Sternotherus odoratus; Stress concentration; Submergence; sub‐lethal; Temperature; Temperature effects; Temperature sensors; Turtles; Vertical distribution
• ISSN: 1367-9430; 1469-1795
• DOI: 10.1111/acv.12323

Bycatch, the incidental capture of non‐target organisms, occurs in most commercial fisheries. Although immediate bycatch mortality is frequently documented in fisheries, detrimental sub‐lethal effects and potential post‐release mortality remain largely unknown despite the potential population‐level consequences. Turtles are captured as bycatch and their populations are vulnerable to slight increases in adult mortality. In eastern Ontario, turtles are frequently captured as bycatch in a small‐scale freshwater commercial fyke‐net fishery and, currently, the fate of discarded turtles is unknown. We wished to determine the effect of fyke‐net capture on post‐release survival and behaviour in eastern musk turtles Sternotherus odoratus and painted turtles Chrysemys picta. We used biologgers equipped with tri‐axial acceleration, depth and temperature sensors to document locomotor activity, vertical distribution, and temperature use of entrapped (exposed to forced submergence for 4 h) and control turtles upon release. Overall dynamic body acceleration was used as a measure of post‐release activity for the first hour, first 6 h, and first 48 h. Post‐release mortality was not detected. Turtles subjected to entrapment exhibited lower activity during the first 6 h following release, and their vertical distribution and temperature use differed in the first 2 h following release, but these effects disappeared after 48 h, suggesting turtles have the ability to recover. Quantifying the post‐release mortality and sub‐lethal effects of entrapment is important for estimating the population effects associated with bycatch. Bycatch, the incidental capture and discard of non‐target organisms, occurs in most commercial fisheries. Although immediate bycatch mortality is frequently documented in fisheries, detrimental sub‐lethal effects and potential post‐release mortality remain largely unknown despite the potential population‐level consequences. In eastern Ontario, turtles are frequently captured as bycatch in a small‐scale freshwater commercial fyke‐net fishery and, currently, the fate of discarded turtles is unknown. Musk and painted turtles subjected to simulated bycatch exhibit lower activity during the first 6 h following release, and their vertical distribution and temperature use differ in the first 2 h following release, but these effects disappeared after 48 h, suggesting turtles have the ability to recover.