Abstract
Decompression sickness (DCS) was first diagnosed in marine turtles in 2014. After capture in net fisheries, animals typically start showing clinical evidence of DCS hours after being hauled on-board, often dying if untreated. These turtles are normally immediately released without any understanding of subsequent clinical problems or outcome. The objectives of this study were to describe early occurrence and severity of gaseous embolism (GE) and DCS in marine turtles after incidental capture in trawl gear, and to provide estimates of on-board and post-release mortality. Twenty-eight marine turtles were examined on-board fishing vessels. All 20 turtles assessed by ultrasound and/or post-mortem examination developed GE, independent of season, depth and duration of trawl and ascent speed. Gas emboli were obvious by ultrasound within 15 minutes after surfacing and worsened over the course of 2 hours. Blood data were consistent with extreme lactic acidosis, reduced glomerular filtration, and stress. Twelve of 28 (43%) animals died on-board, and 3 of 15 (20%) active turtles released with satellite tags died within 6 days. This is the first empirically-based estimate of on-board and post-release mortality of bycaught marine turtles that has until now been unaccounted for in trawl fisheries not equipped with turtle excluder devices.
Highlights
Bycatch of marine turtles is a well-documented threat to populations worldwide and, depending on types of fishing gear and nature of interaction, can be associated with high mortality rates1,2
In 2014, gas embolism (GE) and consequent decompression sickness (DCS) were first diagnosed in marine turtles captured in trawl and gillnet fisheries in Spain13
These novel findings challenged our previous assumptions about marine turtle physiological adaptations to diving14–16 and opened a new area of interest regarding the effects of subsurface incidental capture and delayed mortality
Summary
Bycatch of marine turtles is a well-documented threat to populations worldwide and, depending on types of fishing gear and nature of interaction, can be associated with high mortality rates. There has been limited study of post-release mortality of marine turtles following capture by trawl fisheries. There has been limited study of post-release mortality of marine turtles following capture by trawl fisheries11,12 This presents a critical knowledge gap, since such knowledge is essential in informing policy makers to refine sustainable fisheries management practices. In 2014, gas embolism (GE) and consequent decompression sickness (DCS) were first diagnosed in marine turtles captured in trawl and gillnet fisheries in Spain. In 2014, gas embolism (GE) and consequent decompression sickness (DCS) were first diagnosed in marine turtles captured in trawl and gillnet fisheries in Spain13 These novel findings challenged our previous assumptions about marine turtle physiological adaptations to diving and opened a new area of interest regarding the effects of subsurface incidental capture and delayed mortality. Studies at the Oceanogràfic Sea Turtle Rescue Centre (Valencia, Spain) have shown a prevalence of GE in 52–80% of admitted loggerhead turtles (Caretta caretta) bycaught in local trawl and gillnet fisheries, with an estimated 20% of by-caught turtles developing severe GE that likely leads to death by DCS over the course of hours or days if untreated
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call