The global status of dugongs

Conservation significance of dugongs Only member of family Dugongidae Only strictly marine herbivorous mammal Largest population size (>100,000) and range of extant Sirenians

Methods Evaluation based on published information and expert opinions of about 100 scientists and managers regarding 37 countries in dugong’s range Informants contacted during process leading to development of global status and action plan Information reviewed by 60 in-country experts.

Dugongs are seagrass specialists

Dugong life history Lifespan < 70+ yr Age first breeding 6-17yr Gestation period mth Calving interval > 2.5 yr Lactation ~ 1.5 yr Adult survivorship >95% Max rate of increase < 5% Sustainable harvest ~2%

Conclusions Rate of change in dugong numbers is very sensitive to changes in adult survivorship Impact of mortality (drowning in nets, boat strikes, hunting) on dugongs is serious When dugongs don’t have enough to eat because of habitat loss, they delay breeding or move - this reduces the level of mortality that is sustainable Dugong conservation MUST address the issues of habitat conservation AND mortality reduction

Preliminary information on genetics of female dugongs Genetic types of female dugongs from Southeast Asia (Indonesia, Thailand, Philippines generally distinct from those from Australia) - overlap at Ashmore Reef between Australia and Timor Two maternal lineages in Australian coastal waters - overlap in Torres Strait between Australia and Papua New Guinea One Australian lineage also recorded from East Africa and the Arabian Gulf

Movements Dugong –>60 animals satellite tracked –most movements local –several animals made long-distance movements –longest movement ~800 km in few days –recent Aldabra sighting confirms capacity to cross ocean trenches

Dugong Movements >10-20>20-40>40-80 > > > >640 Maximum movement Frequency Dugongs have movement capacity to colonise areas of their range where they have been extirpated but probably do so rarely

Threats to dugongs- overview from 37 countries

Dugongs tangle in mesh nets and accidentally drown in many countries

Habitat loss, especially due to extreme weather events 1000 km 2 of seagrass habitat were lost in Hervey Bay Queensland after two floods and a cyclone

Hunting and poaching kill dugongs in many countries

Evidence for dugong decline- 37 countries Anecdotal evidence suggests that dugong numbers have declined in at least 21 countries and that dugongs are extinct in 3 island groups No evidence of reduction in extent of range - reduction of area of occupancy within range Quantitative evidence of decline available only for Queensland, Australia

The dugong by-catch declined at 8.7% p.a. for 40 years Urban coast of Queensland Australia - dugong CPUE in shark nets.

High risk of extinction  Populations apparently small and fragmented  Pressure from gill-netting, shark meshing and habitat destruction  Few effective conservation initiatives

 Likely that region supports significant numbers of dugongs  Human population density and coastal impacts low on Saudi coast Reasonable prospects for survival

 Second largest dugong population in the world (7307+ s.e. 1302)  Habitat threatened by coastal development and oil spill  Few effective conservation initiatives Uncertain prospects for survival

High risk of extinction  Populations apparently small, fragmented and isolated  Pressure from gill-netting, dynamite fishing, habitat destruction and hunting likely to increase  Few effective conservation initiatives

Uncertain: likely extinction in Japan  Populations apparently small and fragmented. but cover vast areas with potential for recruitment from other areas  Japanese population extremely small and isolated and subject to habitat loss and fishing impacts  Pressure from gill-netting, dynamite fishing, habitat destruction, boat impacts and hunting likely to increase  Few effective conservation initiatives

Uncertain: likely extinction in Palau  Populations apparently small and fragmented.  Potential for recruitment from other areas uncertain  Palau population extremely small and isolated  Pressure from gill-netting, dynamite fishing, habitat destruction and hunting likely to increase  Few conservation initiatives

Secure except for urban coast of Qld  Region supports large numbers of dugongs (estimated population 85,000)  Human population density and coastal impacts low except on urban coast of Queensland  Population changes confounded by large-scale movements  Active conservation initiatives, including dugong-specific actions along east coast of Queensland.

Suggested approaches to dugong conservation Identify areas that still support significant numbers of dugongs Consider with extensive local involvement how dugong mortality can be minimised and their habitat protected If possible, protect dugongs in the context of comprehensive plans for coastal zone management using the dugong as a flagship species