Limpus, 2008:

"Changes in the size of the annual loggerhead turtle nesting populations over the last three decades or more at the multiple index beaches in eastern Australia are summarised in Figures 4-6. Since the mid 1970s and up until 2000, the populations nesting on the Great Barrier Reef islands (all National Parks) declined to a greater extent than the populations nesting on the mainland where only Mon Repos was a protected beach. The response of the Woongarra coast loggerhead turtle nesting population to changes in management of coastal prawn trawl fisheries is illustrated in Figure 7. This summary illustrates the benefits of reducing anthropogenic mortality in both the inter-nesting habitat adjacent to the rookeries and in the distant foraging areas. Changes in Queensland and Australian fisheries regulations in 2000 introduced the compulsory use of Turtle Exclusion Devices (TEDs) in the Queensland East Coast Prawn Trawl Fisheries and the Northern Prawn Trawl Fishery. Since that date, the long term decline in nesting turtle numbers has changed to a trend for increasing numbers at all eastern Australian loggerhead turtle index beaches (Figures 4-6). These data provide strong support for the regulated use of TEDs in trawl fisheries being effective for reducing mortality of adult and large immature loggerhead turtles in coastal foraging areas in eastern and northern Australia. Because coastal trawl fisheries can only interact with adults & large immature loggerhead turtles – the size range that lives in our coastal water, changes in trawl bycatch mortality can be detected through changes in the size of nesting populations within a few years of the management changes in the fisheries. However, changes in oceanic long-line and purse seine fisheries bycatch mortality will not be detectable at the nesting population for more than 13 years after the change impacts on the pelagic oceanic post-hatchling life history phase. Similarly changes in egg mortality and associated hatchling production at the nesting beaches will not be detectable in the next generation of nesting turtles for some 25 to 30 years.

There has been a declining recruitment of new immature loggerhead turtles into eastern Australian coastal waters across at least 15 years. These data provide a warning signal with regards to future population dynamics of eastern Australian loggerhead turtles. This parameter warrants validation among loggerhead turtles foraging at other coastal areas in eastern Australia. With a long term decline in immature recruitment to the coastal foraging populations, there can be expected, after about a 13 yr lag time, a decline in recruitment into the adult breeding population. The cumulative impact of pelagic fisheries bycatch and ingestion of synthetic marine debris are flagged as having the potential for causing excessive mortality of post-hatchling loggerhead turtles in the South Pacific Ocean.

Two significant management actions have continued since the late 1980s that have substantially increased hatchling production from the mainland rookeries. The increased numbers of hatchlings produced through these projects have a strong female sex ratio bias because these are brown sand beaches that have nest temperatures that are generally warmer than the pivotal temperature for this population (Limpus et al. 1983,1985; Maloney et al. 1990; Reed, 1980). ? The reduction on fox predation of loggerhead turtle eggs on the mainland beaches including the Wreck Rock beaches from approximately 90% loss of eggs during the late 1970s – early 1980s to less than 5% egg loss since the late 1980s (Limpus, in press). These activities are continuing. EPA staff in collaboration with DNRW staff and Queensland Turtle Conservation Volunteers maintain annual baiting for foxes (Fox-off 1080 baits) along mainland beaches of the Woongarra Coast , Skyringville, Moore Park, and Wreck Rock beaches. Queensland Turtle Conservation Volunteers are also placing plastic fox excluder devices (plastic mesh) over loggerhead turtle nests along the Sunshine Coast and North Stradbroke Island beaches. Rescuing of doomed eggs on the Woongarra Coast to increase hatchling production (Pfaller, et al. 2008). This project increases loggerhead turtle hatchling production with some 40-50 thousand extra hatchlings being produced along the Woongarra Coast annually. Queensland Turtle Conservation volunteers are rescuing doomed eggs from small numbers of clutches laid along the Sunshine Coast and North Stradbroke Island. The increased hatchling production from these two projects is expected to produce increased adult recruitment into the eastern Australian loggerhead turtle nesting population by about 2020, given the expected age at first breeding for the species. While the increased hatchling production from these two actions will not yet be evident in the current adult nesting population, the increased hatchling production since the late 1980s should have been detectable as increased recruitment from the oceanic pelagic-foraging life history phase into the coastal foraging populations of eastern Australia by about 2005.

The expanding coastal development along the Woongarra Coast has created a brightly illuminated salt spray dome over the Bargara township at night. This illuminated sky is now clearly visible from the entire Mon Repos beach. This illuminated sky over Bargara is so bright that it now masks the capacity for hatchling turtles to clearly distinguish the natural horizons over the sea that they need to see for successfully dispersing from the beach to the open ocean. The illuminated night sky along the Woongarra Coast is a major threat to the maintenance of sustainable turtle nesting and hatchling populations on this coast." 

---

Citation and/or URL

Limpus, C.J. 2008. Status of the eastern Australian loggerhead turtle, Caretta caretta, population, November 2008: unpublished report to the Great Barrier Reef Marine Park Authority.  

Spatial Coverage

Eastern coast of Australia, primarily Queensland

Temporal Coverage

Late 1960s to the mid - 2000s 

Update Frequency

Not applicable 

Other Information

None