Threats to coastal dolphins

Coastal development, gillnet fishing, pollution and climate change are all threats that converge on our coasts and could jeopardise the survival of Australia’s unique coastal dolphins, the Australian snubfin and recently described Australian humpback dolphins.

Coastal development

Coastal development, including large-scale liquefied natural gas projects, coal industry expansion, land reclamation, dredging, port development and the building of marinas in river mouths and embayments can all cause a direct loss of habitat. 

Increased human activity in these areas – from boat traffic and infrastructure construction – can create noise disturbances. Increased chemical pollution can have devastating indirect effects on dolphins and interfere with their mating and reproduction.

Pollution

The introduction of toxic waste, pesticides, nutrients and lethal bacteria into their habitat is making coastal dolphins vulnerable. Marine debris, such as plastic bags and discarded fishing gear also degrades the quality of coastal dolphin habitat and can contribute to population declines.

In particular, declining water quality not only impacts directly on coastal dolphin health but also threatens the productivity of the ecosystems upon which they depend.

Boat strike and entanglement in fishing gear
Globally, fishing is the major immediate threat to coastal dolphins. A number of species are now endangered as a result, such as the Māui dolphin from New Zealand.

In Australia, inshore nets, entanglement in shark nets, capture in gillnets, hooks, lines and boat strikes all pose an ongoing threat to snubfin and humpback dolphins, along with other marine species like turtles, dugongs and whales.

In Roebuck Bay, in Western Australia, many dolphins assessed by researchers bore scars indicative of vessel strikes and entanglement in fishing nets and lines. This high injury rate highlights a potential issue that needs further investigation.

Click here to read more about WWF’s research into snubfin dolphins in Roebuck Bay.
Hector's dolphin calf killed in gillnet. Banks Peninsula, New Zealand. / ©: Stephen Dawson / WWF
Hector's dolphin calf killed in gillnet. Banks Peninsula, New Zealand.
© Stephen Dawson / WWF
A Maui's dolphin or popoto (Cephalorhynchus hectori maui) above water. Having distinctive grey, ... / ©: Silvia Scali / WWF-New Zealand
A Maui's dolphin or popoto (Cephalorhynchus hectori maui) above water. Having distinctive grey, white and black markings and a short snout, Maui's dolphins are most easily recognized by their round dorsal fin.
© Silvia Scali / WWF-New Zealand
 / ©: MUCRU / WWF-Aus
Map: Dolphin sightings and transect lines for 2013 and 2014 sampling periods combined, illustrating group sizes for snubfin (yellow circles), bottlenose (blue circles) and humpback (red circles) dolphins. Depth contours are Lowest Astronomical Tide. Source: Brown, A.M., Bejder, L., Pollock, K.H. & Allen, S.J. (2014). Abundance of coastal dolphins in Roebuck Bay, Western Australia: Updated results from 2013 and 2014 sampling periods.
© MUCRU / WWF-Aus
Dolphin sightings and transect lines for 2013 and 2014 sampling periods combined, illustrating group sizes for snubfin (yellow circles), bottlenose (blue circles) and humpback (red circles) dolphins. Depth contours are Lowest Astronomical Tide.

Source: Brown, A.M., Bejder, L., Pollock, K.H. & Allen, S.J. (2014). Abundance of coastal dolphins in Roebuck Bay, Western Australia: Updated results from 2013 and 2014 sampling periods.

 
Overfishing

The overfishing of marine species for human consumption poses a growing problem for coastal dolphins around the world.

Most of the Australian fish catch is taken close to the coast, in waters less than 50 metres deep, and commercial fisheries are at or near full exploitation.

Some prey species of inshore dolphins are targeted by trawl and inshore fisheries in Queensland, such as the East Coast Inshore Fin Fishery. If not managed appropriately, prey species could become so depleted as to impact on inshore dolphin feeding.

Click here to read more about overfishing.

Climate change

The impact of climate change on coastal dolphins is difficult to ascertain, however predicted sea level rise, and increases in water temperature and acidification could have disastrous consequences for the species themselves and the ecosystems upon which they depend.