On-board study of gas embolism in marine turtles caught in bottom trawl fisheries in the Atlantic Ocean

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.

Gas Embolism Assessment in Sea Turtles: Predictors of Mortality for the Deadliest Pathology related to Trawling

“…We did not nd a correlation between mortality and duration and depth of shing nets, animal size, sex, weight, body temperature, respiratory rate and peripheral edema. Unlike what has been reported recently 20 where PCV was signi cantly lower in turtles that died from GE, we found no statistically signi cant PCV alteration in the turtles that died. However, in about one third turtles analyzed (71/204) we found that PCV was slightly above normal ranges, without any statistical correlations with mortality.…”

“…These turtles died during hospitalization in a time comparable to that observed in our study. In a recent study 20 12 of 28 (43%) animals died onboard shing vessels and 3 of 15 (20%) turtles released with satellite tags died within 6 days. About 90% turtles with GE alive upon arrival at STC recovered from the disease in a time ranging from 1 and 13 days without any supportive drug therapy.…”

“…Delayed mortality of bycaught turtles due to sequelae of near-drowning, metabolic disturbance, and gas embolism upon release 17 is suspected to be high. To date, relatively few studies with small sample sizes have been conducted on GE in trawled sea turtles 17,20,21 . The present study provides the largest data set to date for sea turtles affected by GE, including a diverse collection of variables and clinical data.…”

“…These effects are believed to disrupt the normal, protective vagal diving re ex that minimizes blood ow through air-lled pressurized lungs during diving 17 . Lactic acidosis and evidence of decreased renal function and cellular injury have been reported in GE-affected turtles 20 . To date, reported mortality rates due to GE in bycaught sea turtles range from 30-53% 17,20,21 .…”

“…To date, reported mortality rates due to GE in bycaught sea turtles range from 30-53% 17,20,21 . In the only study to assess survival of immediately released turtles affected by GE 20 , 12 of 28 (43%) animals died on-board prior to release, and 3 of 15 (20%) active turtles released with satellite tags died within 6 days.…”