This dolphin is vulnerable to set net (gill net) and trawl fishing, marine pollution and debris, boat strikes, genetic bottleneck, mining, acoustic disturbance and coastal development.
Scientists estimate that over 95% of unnatural Māui deaths are caused by entanglement and drowning in gillnet or trawl fishing. In fact, just more than one human-induced death every seven years seriously threatens the chances of population recovery.
Since March 2001, seven dead Māui dolphins have been found. Five of these deaths were due to fishing, one was impossible to determine and one was because of natural causes.
A slow breeding rate and small population size have made of dolphin a Critically Endangered sub-species.
The Scientific Committee of the International Whaling Commission (IWC) acknowledged in its 2013 report, that Māui dolphins will decline to just 10 adult breeding females in six years and become functionally extinct in less than 20 years—unless their full range is protected from gillnetting and trawling.
Fishing with nets has pushed Māui dolphins to the brink of extinction. The dolphins get entangled in set nets and trawl nets and drown. Dolphins do not seem able to detect the fine nylon nets with echolocation and swim into them.
An expert panel convened by the NZ government in 2012 estimated that around 5 Māui are killed each year in fishing nets, a rate 75.5 times what the population can withstand.
They cannot swim backwards, so are unable to free themselves from the net. Since they cannot reach the surface to breathe, they drown within a couple of minutes. A set net ban is in place in part of the dolphin's range. The ban at this stage does not fully include harbours yet, even though dolphins have been sighted there.
In the South Island, Hector's dolphins have drowned in coastal trawl nets. It appears there is a risk to the Māui dolphin where there is overlap between dolphin habitat and trawl operations. Trawlers are still operating beyond of 1 nautical mile of the coast where dolphins continue to be vulnerable to bycatch.
We can save Māui dolphins if the NZ government extends the ban on set netting and traditional trawling fishing to cover all of their known range.
Marine pollution and debris
Dolphins like Māui which inhabit shallow coastal waters are vulnerable to the pollutants which humans allow into the sea. Chemicals from industrial waste, storm water and agricultural runoff like PCBs, DDT, dioxins and metals have been found in the blubber of Hector's and Māui dolphins. These pollutants bio-accumulate, which means they increase in potency as they move up the food chain. Māui dolphins are near the top of their food chain and these pollutants can be passed on to young dolphins through their mother's milk. High levels of exposure can cause loss of fertility and compromise immune systems in marine mammals. Another form of pollution which threatens Māui dolphins is solid rubbish such as plastic shopping bags which can be mistaken for squid and ingested, killing the dolphin.
The propellers of motor boats pose a risk to Māui dolphins. Dolphin can suffer skin surface cuts to severe injuries from propellers. For example, in Akaroa Harbour, South Island, a Hector's dolphin calf died due to the direct impact of a boat strike.
Oil and Gas Exploration
Oil and gas exploration and activity in Māui habitat also poses a growing threat, with the New Zealand Government granting an increasing number of permits inside the dolphin's known range.
The genetic diversity of Māui dolphin has declined significantly over the last 100 years, raising concerns about a "genetic bottleneck". Their genetic diversity has been reduced from at least three lineages to one, making them susceptible to extinction from environmental and demographic change.