Modify vessels to reduce or prevent injuries to reptiles from collisions
Overall effectiveness category Awaiting assessment
Number of studies: 2
Background information and definitions
Many sorts of propeller guards or design changes have been suggested to prevent human injuries, ranging from polypropylene to stainless-steel cages or baffles on outboard motors and these may also help prevent or limit injuries to aquatic reptiles.
Supporting evidence from individual studies
A controlled study in 2009 in a sand quarry in Georgia, USA (Work et al. 2010) found that using propeller guards did not reduce catastrophic injuries to artificial loggerhead turtle Caretta caretta shells compared to an unmodified propeller. Results were not statistically tested. At 7 km/hr, a cage propeller guard caused none of five artificial loggerhead turtle shells catastrophic damage, whereas a horizontal-fin propeller guard or no guard caused one of five shells to be catastrophically damaged. At 40 km/hr, vessels with both types of guard, or no propeller guard caused catastrophic injuries to all shells in all trials (horizontal-fin: five of five shells damaged; cage guard: four of four; no guard: five of five). The authors reported that the types of injuries sustained were different when guards were used (see paper for details). A 90 hp, 4-stroke outboard motor with a three-bladed stainless steel propeller was mounted on a 5.8 m flat-bottomed skiff and driven at 7 and 40 km/h over propeller-depth (48 cm) fibre-glass model loggerhead turtle shells using either one of two propeller guards: a horizontal-fin mounted below the propeller (Hydroshield®; 5 trials each at 7 and 40 km/h), or a stainless-steel cage surrounding the propeller (Prop Buddy® 5 trials at 7 km/h and 4 trials at 40 km/h), or no guard at all (5 trials/speed). Injuries to the artificial shell were classified as catastrophic if they would have killed a real sea turtle.Study and other actions tested
A controlled study in 2009 in a sand quarry in Georgia, USA (Work et al. 2010) found that using a jet drive outboard motor on a skiff reduced catastrophic injuries to artificial loggerhead turtle Caretta caretta shells compared to a standard outboard motor. Artificial loggerhead turtle shells hit by a skiff with a jet drive outboard motor received fewer catastrophic injuries regardless of speed or turtle depth in the water (0 catastrophic injuries in 20 trials) compared to shells hit by a skiff with a standard outboard motor (14 catastrophic injuries in 20 trials). A 5.8 m flat-bottomed vessel was fitted with either a 90 hp, 4-stroke outboard motor with a three-bladed stainless-steel propeller or an 80 hp, jet drive outboard motor and driven at 7 and 40 km/h over fibre-glass model loggerhead turtle shells (see original paper for details). Shells were placed on the surface or floating 48 cm below the surface. Five trials were carried out for each motor type at each speed and each turtle depth (40 total trials). Injuries to the artificial shell were classified as catastrophic if they would have killed a real sea turtle.Study and other actions tested