Analysis of risk factors associated with gas embolism and evaluation of predictors of mortality in 482 loggerhead sea turtles

Abstract

Sea turtles that are entrapped in static and towed nets may develop gas embolism which can lead to severe organ injury and death. Trawling characteristics, physical and physiologic factors associated with gas-embolism and predictors of mortality were analysed from 482 bycaught loggerheads. We found 204 turtles affected by gas-embolism and significant positive correlations between the presence of gas-embolism and duration, depth, ascent rate of trawl, turtle size and temperature, and between mortality and ascent time, neurological deficits, significant acidosis and involvement of > 12 cardiovascular sites and the left atrium and sinus venosus-right atrium. About 90% turtles with GE alive upon arrival at Sea Turtle Clinic recovered from the disease without any supportive drug therapy. Results of this study may be useful in clinical evaluation, prognostication, and management for turtles affected by gas-embolism, but bycatch reduction must become a priority for major international organizations. According to the results of the present study the measures to be considered to reduce the catches or mortality of sea turtles for trawling are to be found in the modification of fishing nets or fishing operations and in greater awareness and education of fishermen.

Figure 1

Flowchart of the outcome and clinical findings for 482 loggerhead turtles after being accidentally captured by trawling.

Figure 2

Clinical findings in turtles with GE. (A) Eyelid and conjunctival oedema and external foam coming from ramphotheca and nostrils in a Loggerhead turtle (Caretta caretta) with GE and drowning; (B) prominent oedema of the eyelid and neck; (C) prolapse of the cloaca in Caretta caretta.

Figure 3

(A) Hind limbs flexed under the carapace in a turtle with GE; (B) turtle with blood coming from the oral cavity arising from the larynx that died 6 h after arriving at the STC (11 h after trawling).

Figure 4

Dorsoventral radiograph of 3 Loggerhead turtles (Caretta caretta) with GE of mild (A), medium (B) and severe (C) radiographic degree.

Figure 5

(A) Dorsoventral radiograph of a Loggerhead turtle (Caretta caretta) with severe GE. Gas is evident in the sinus venosus/right atrium (sv/ra), left atrium (LA), pulmonary vessels (PV), vessels of the brachiocephalic trunk (bct), hepatic vessels (H), gastric vessels (G), postcava vein (PsC), superior mesenteric artery (SM) and marginocostal vessels (MC); (B,C) dorsoventral radiograph of two Loggerhead turtles (Caretta caretta) with GE of medium to severe degree. Precava (PrC) and postcava vein (PsC), vessels of the brachiocephalic trunk (bct), hepatic vessels (H), gastric vessels (G), superior mesenteric artery (SM), abdominal vein (AV) and transverse abdominal vein (AT); (D) dorsoventral radiograph of a Loggerhead turtle (Caretta caretta) with severe GE. Gas fills the sinus venosus (SV), left atrium (LA), precava (PrC) and postcava vein (PsC), hepatic vessels (H), gastric vessels (G) and marginocostal vessels (MC); (E) dorsoventral radiograph of a Loggerhead turtle (Caretta caretta) with GE of mild degree. Gas is present in renal portal vessels (RP) and external iliac vessels (EI); (F) dorsoventral radiograph of a Loggerhead turtle (Caretta caretta) with GE of medium degree. Gas is present in postcava vein (PsC), hepatic vessels (H), gastric vessels (G), abdominal vein (AV), transverse abdominal vein (AT) and renal portal vessels (RP).