The challenge of ‘Keeping It Great’ for marine wildlife

The Great Barrier Reef – more than coral ……… Recognised in World Heritage listing as a globally important refuge for marine wildlife

6 species of sea turtles globally important nesting & feeding grounds for 4 species

2 million seabirds of 22 species 55 significant seabird islands

Significant breeding ground for humpback whales and habitat for dwarf minke whales

Important feeding and breeding area for coastal dolphins and dugongs

The challenges of ‘keeping it great’ for marine wildlife Most species require specialist habitats subject to human impacts Most species are long-lived and slow breeding Some species are already seriously depleted Human impacts are complex and difficult to disaggregate from each other and from natural change Many species move across jurisdictions within GBR and between GBR and other areas

The challenges of ‘keeping it great’ for marine wildlife Most species require specialist habitats subject to human impacts Most species are long-lived and slow breeding Some species are already seriously depleted Human impacts are complex and difficult to disaggregate from each other and from natural change Many species move across jurisdictions within GBR and between GBR and other areas

The challenges of ‘keeping it great’ for marine wildlife Most species require specialist habitats subject to human impacts Most species are long-lived and slow breeding Some species are already seriously depleted Human impacts are complex and difficult to disaggregate from each other and from natural change Many species move across jurisdictions within GBR and between GBR and other areas

The challenges of ‘keeping it great’ for marine wildlife Most species require specialist habitats subject to human impacts Most species are long-lived and slow breeding Some species are already seriously depleted Human impacts are complex and difficult to disaggregate from each other and from natural change Many species move across jurisdictions within GBR and between GBR and other areas

The challenges of ‘keeping it great’ for marine wildlife Most species are long-lived and slow breeding Most species require specialist habitats subject to human impacts Some species are already seriously depleted Human impacts are complex and difficult to disaggregate from each other and from natural change Many species move across jurisdictions within GBR and between GBR and other areas This talk illustrates these points using the dugong as a case study

Dugong threatened species of cultural value to Indigenous Australians seagrass specialist

Long-lived, slow breeding Lifespan < 70 yr Age first breeding 6-17yr Gestation period mth Calving interval yr Lactation ~ 1.5 yr Adult survival >95% p.a. Sustainable harvest ~2% Dugong tusk with growth layers

Conclusions To be effective dugong management must address the issues of: –Conserving the quality of critical habitats and –Minimising dugong mortality

Seagrass - restricted coastal habitat subject to large-scale diebacks e.g km 2 of seagrass habitat were lost in Hervey Bay adjacent to GBRWHA after two floods and a cyclone. Similar diebacks recorded in pristine and remote areas in Qld and WA

Impact of dugong habitat loss in Hervey Bay adjacent to GBRWHA 1992 When their habitat is lost dugongs: stop breeding and move or starve and die Locations of dugong carcasses Date Dugong numbers

Change in dugong numbers along urban coast of GBR since 1960s From 1962, Queensland Shark Control Program to reduce shark numbers at popular beaches Nets used to catch sharks also catch dugongs Analysed changes in the dugong catch per beach from as index of dugong abundance

Location of shark meshing contract areas

Assumptions Netting practice did not change  Dugongs did not learn to avoid nets ?  Dugongs were not alienated from netted beaches by human use ???

The dugong by-catch in the shark nets declined at 8.7% p.a.

If assumptions are correct, dugongs numbers on the urban coast of Qld in the local regions of the shark nets have declined to about 3% of their 1960 value Conclusion

Boat traffic? Net entanglements ? Habitat loss from terrestrial runoff ? But what caused the decline? Hunting ?

Impacts of Boats Disturbance interruption of normal daily behaviour (cumulative effects) displacement stress Two Potential Impacts: Boat strikes injury death

Results: Dugongs respond slowly - may be run over Dugongs usually move up to m away and resume their original activity Greatest danger from boats is mortality not displacement Glow-slow zones + education and enforcement

Movements –>60 animals satellite tracked –most movements local –several animals made long-distance movements –longest movement ~600 km in few days

Movements of satellite- tracked dugongs –3 animals covered >80% of coast –1/3 moved >80km –1/6 moved >150km 1500km 400km Shoalwater  Bay Cooktown  Townsville 

Dugongs spend: >8 hours day feeding 72% of their time in less than 3m Dugong diving behaviour : 15 dugongs & 40,000 dives

Conclusions from studying dugong movements and diving Dugongs spend most of their time in shallow water –including intertidal region outside the GBRMP Dugongs move across jurisdictions within GBRWHA and between GBRWHA and adjacent areas Cross-jurisdictional initiatives essential

Basis for estimating sustainable human-induced mortality Maximum number of animals that may be removed sustainably from population = n min * 0.5 r max * recovery factor recovery factor= 0.5 for population of unknown status

Best estimate of current catch ~ 1000 dugong p.a Absolute population estimate= s.e in December 2001 N min = Sustainable annual catch for Torres Strait Estimated for range of values for rate of increase

Conclusions The dugong harvest in Torres Strait is too high – same dugong stock as GBR Similar situation likely in some GBR dugong hunting communities Indigenous leaders support these conclusions and want greater and more meaningful involvement in management

How to address problem of over-harvest? Regulation of hunting at three levels: Indigenous communities GBR region across jurisdictions in northern Australia

Effects of GBRMP rezoning for dugongs Improves protection from – drowning in gill nets –physical disturbance to habitat especially from trawling

But….. Also need: –complementary zoning in adjacent intertidal areas –speed limits for boat traffic in ***** dugong habitats –protection of seagrass habitats from increased water turbidity and chemical pollution –regulation of hunting

Rezoning of GBRMPA very significant advance but additional initiatives essential, especially across jurisdictions Initiatives must reduce mortality and protect critical habitats Lessons for other marine wildlife

Thanks Funding AFMA ARC CRC Reef Research GBRMPA JCU Pew Foundation SWRRFI Contributions to the Research Amanda Hodgson Donna Kwan Ivan Lawler Tony Preen