Study

Influence of small vessel operation and propulsion system on loggerhead sea turtle injuries

  • Published source details Work P.A., Sapp A.L., Scott D.W. & Dodd M.G. (2010) Influence of small vessel operation and propulsion system on loggerhead sea turtle injuries. Journal of Experimental Marine Biology and Ecology, 393, 168-175.

Actions

This study is summarised as evidence for the following.

Action Category

Modify vessels to reduce or prevent injuries to reptiles from collisions

Action Link
Reptile Conservation

Modify vessels to reduce or prevent injuries to reptiles from collisions

Action Link
Reptile Conservation

Limit vessel speeds

Action Link
Reptile Conservation
  1. Modify vessels to reduce or prevent injuries to reptiles from collisions

    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.

    (Summarised by: Maggie Watson, Katie Sainsbury)

  2. Modify vessels to reduce or prevent injuries to reptiles from collisions

    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.

    (Summarised by: Maggie Watson, Katie Sainsbury)

  3. Limit vessel speeds

    A replicated study in 2009 in an abandoned sand quarry in Georgia, USA (Work et al. 2010) found that lower vessel speeds reduced catastrophic injuries to artificial loggerhead turtle Caretta caretta shells. Catastrophic injuries to artificial turtle shells occurred less frequently at lower speeds than higher speeds on unmodified vessels (7 km/hr: four of 10 turtles; 40 km/hr: 10 of 10 turtles) and vessels with propeller guards (7 km/hr: one of 10; 40 km/hr:  nine of nine). With a jet outbound motor or an inboard jet motor (on a jet ski) none of 40 turtles were damaged at 7 or 40 km/hr. Injury rates were similar regardless of the position of the artificial shell in the water. A 90 hp, 4-stroke outboard motor with a three-bladed stainless-steel propeller was mounted on a 5.8 m skiff and driven at 7 or 40 km/h over surface level or propeller-depth (48 cm) fibreglass model loggerhead turtle shells (5 trials/speed/turtle depth). One of two propeller guard designs were then added to the same skiff: a horizontal-fin (Hydroshield®), or a stainless-steel cage (Prop Buddy®) and driven over propeller-depth artificial turtle shells (7 km/h: 5 trials/guard; 40 km/h: 4–5 trials/guard). A personal watercraft (jet ski) with an inboard jet motor and the 5.8 m skiff modified with an 80 hp, jet-drive outboard motor were also both driven at 7 and 40 km/h over surface-level or propeller-depth artificial loggerhead turtle shells (5 trials/speed/vessel/turtle depth). Injuries to artificial shells were classified as catastrophic if they would have killed a real sea turtle.

    (Summarised by: Maggie Watson, Katie Sainsbury)

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