Modify vessels to reduce or prevent injuries to reptiles from collisions

Overall effectiveness category Awaiting assessment
Number of studies: 2
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not assessed
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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.

Study locations

Key messages

Two studies evaluated the effects on reptile populations of modifying vessels to reduce or prevent injuries to reptiles from collisions. Both studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Survival (2 studies): One controlled study found that using a horizontal-fin propeller guard or a cage propeller guard did not reduce catastrophic injuries to artificial loggerhead turtle shells compared to using no guard, but that the types of injuries sustained were different. One controlled study found that using a jet drive outboard motor reduced catastrophic injuries to artificial loggerhead turtle shells compared to using a standard outboard motor.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

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
Referenced paper
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.
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
Referenced paper
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.

Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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This Action forms part of the Action Synopsis:

Reptile Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Modify vessels to reduce or prevent injuries to reptiles from collisions Action Link	Awaiting assessment	2	Synopsis Link
Use visual or acoustic deterrents to discourage reptiles from approaching vessels Action Link	No evidence found (no assessment)	0	Synopsis Link
Limit vessel numbers Action Link	No evidence found (no assessment)	0	Synopsis Link