No abstract

Vessel collisions contribute to the anthropogenic mortality of several threatened marine species including turtles, manatees, dugongs and whales, but scant data exist to inform the design of optimal mitigation measures. We conducted a field experiment to evaluate behavioural responses of green turtles Chelonia mydas to a research vessel approaching at slow, moderate or fast speed (4, 11 and 19 km h -1 , respectively). Data were recorded for 1890 encounters with turtles sighted within 10 m of the research vessel's track. The proportion of turtles that fled to avoid the vessel decreased significantly as vessel speed increased, and turtles that fled from moderate and fast approaches did so at significantly shorter distances from the vessel than turtles that fled from slow approaches. Our results imply that vessel operators cannot rely on turtles to actively avoid being struck by the vessel if it exceeds 4 km h -1. As most vessels travel much faster than 4 km h -1 in open waters, we infer that mandatory speed restrictions will be necessary to reduce the cumulative risk of vessel strike to green turtles in key habitats subject to frequent vessel traffic.

Incomplete knowledge about local foraging ecology of green turtles hampers their conservation management in Japan, where stocks have only partially recovered from heavy exploitation in previous centuries. We used stable isotope ratios of δ 13 C and δ 15

No abstract

Identification of threats is a standard component of conservation planning and the ability to rank threats may improve the allocation of scarce resources in threat-mitigation programs. For vulnerable and endangered sea turtles in Australia, vessel strike is recognised as an important threat but its severity relative to other threats remains speculative. Documented evidence for this problem is available only in stranding records collected by the Queensland Environment Protection Authority. With the authority's support we assessed the scope and quality of the data and analysed vessel-related records. We found adequate evidence that during the period 1999-2002 at least 65 turtles were killed annually as a result of collisions with vessels on the Queensland east coast. This level of mortality appears broadly comparable to that recorded in the Queensland East Coast Trawl Fishery before the introduction of mandatory turtle-exclusion devices in that fishery. Green turtles (Chelonia mydas) comprised the majority of vessel-related records, followed by loggerhead turtles (Caretta caretta), and 72% of cases concerned adult or subadult turtles. The majority of vessel-related records came from the greater Moreton Bay area, followed by Hervey Bay and Cleveland Bay. The waters of all three areas are subject to variable levels of commercial and recreational vessel traffic, and their shores are both populated and unpopulated.