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 13-15 mth• Calving interval 2.5 -7yr• 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. 1000 km2 of seagrass habitatwere lost in Hervey Bay adjacent to GBRWHAafter 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

DateDu

go

ng

nu

mb

ers

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 1962-99 as index of dugong abundance

Location of shark meshingcontract areas

Assumptions•Netting practice did not change

•Dugongs did not learn to avoid nets ?

•Dugongs were not alienated from netted beaches by human use ???

••

•

•

•••

•

•

••

•••••

•••

•

••••••••

••••••••••

1970 1980 1990 2000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1960

Dug

ongs

ca

ught

per

mon

th /

beac

h

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 300-400 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 =

nmin * 0.5 r max* recovery factor

recovery factor= 0.5 for population of unknown status

Best estimate of current catch ~ 1000 dugong p.a.

 

31 61 92 123 154

Absolute population

estimate= 14100 + s.e. 2150

in December 2001

Nmin = 12300

Sustainable annual catch for Torres Strait

307

305 213

306

312

212

304

211210209208207206205204203202201

315

401

303

302

314

405

404

403

402

311

310

308

309

224223222221220219218217216215214

101

103

313

102

105104106

107108109

128

301

110

146

407

406

111

130

134

132

138

112

140

126

144

136

142

124

114

122

10

116

505

409408

120

501

410504

225

118

503502

4115041412

3061

3051

3

4

0

2A

1B

2B

1A

5

Estimated for range of values for rate of increase

ConclusionsThe 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