Maui's Dolphins Under Threat
By zteve t evans
Maui’s dolphins are the smallest dolphin in the world and one of the rarest. The only place in the world they are found is off the west coast of New Zealand’s North Island. Under the New Zealand Threat Classification System they are classified as Nationally Critical which is the highest risk rating. The International Union for Conservation of Nature (IUCN) classifies them as Critically Endangered. This highlights the reality that Maui’s dolphins could soon become extinct.
Just One Death
The plight of Maui's dolphins is increased by having a small population and slow rate of breeding leaving their population finely balanced. All it would take is just more than one death caused by humans every seven years to seriously threaten the recovery of their numbers. Their main hazards to survival are from gill net, trawl fishing, marine pollution, boat strikes and declining genetic diversity.
Just One Death
The plight of Maui's dolphins is increased by having a small population and slow rate of breeding leaving their population finely balanced. All it would take is just more than one death caused by humans every seven years to seriously threaten the recovery of their numbers. Their main hazards to survival are from gill net, trawl fishing, marine pollution, boat strikes and declining genetic diversity.
Falling Victim To Fine Nylon Nets
Seven dead Maui's dolphins were found in March 2001. It was determined that 5 of these were attributed to fishing. Of the two remaining, one was due to natural causes and the reason for the death of the other one could not be determined.
The greatest danger to Maui's dolphins come from gill, or set fishing. It seems the dolphin's echolocation does not identify these fine nylon nets and they swim into them unawares. When they try to swim out, or backwards, to escape they become entangled in the fine nylon mesh. Consequently they cannot swim to the surface to breathe air and drown within a few minutes. Although there is a ban on these types of nets in a part of the Maui's range harbours are not included despite them having been observed in such places.
Trawl nets around New Zealand's South Island have claimed the lives of many Hector's dolphins and there is a risk for Maui's dolphins where there range overlaps areas where trawl fishing takes place. Trawlers sometimes still work further than 1 nautical mile from the shore so Maui's dolphins are still in danger of bycatch.
Seven dead Maui's dolphins were found in March 2001. It was determined that 5 of these were attributed to fishing. Of the two remaining, one was due to natural causes and the reason for the death of the other one could not be determined.
The greatest danger to Maui's dolphins come from gill, or set fishing. It seems the dolphin's echolocation does not identify these fine nylon nets and they swim into them unawares. When they try to swim out, or backwards, to escape they become entangled in the fine nylon mesh. Consequently they cannot swim to the surface to breathe air and drown within a few minutes. Although there is a ban on these types of nets in a part of the Maui's range harbours are not included despite them having been observed in such places.
Trawl nets around New Zealand's South Island have claimed the lives of many Hector's dolphins and there is a risk for Maui's dolphins where there range overlaps areas where trawl fishing takes place. Trawlers sometimes still work further than 1 nautical mile from the shore so Maui's dolphins are still in danger of bycatch.
Marine Polution and Debris
Like other marine animals Maui's dolphins are at risk from pollutants contaminating the sea from human activity. Industrial waste, storm water and run off from agricultural land contaminate the sea with chemicals such as PCBs, dioxins, DDT and metals which have been found in the blubber of Maui's and Hector's dolphins.
These contaminants bio-accumulate as they are ingested by other creatures in the food chain of Maui's dolphins finally reaching their calves through their mother's milk. This can result in the weakening of immune systems and a lowering of their fertility which is already low. Floating debris such as plastic bags are an increasing problem with the dolphins mistaking them for squid and eating them and being killed.
Boat Strikes
Motor boats are also a risk for Maui's dolphins. Direct collisions with motor boats can kill and the propellers can cause cuts and other injuries.
Declining Genetic Diversity
Another problem for Maui's dolphins is that over the last century their genetic diversity has declined reducing from at least three lineages to one. This increases vulnerability for survival from demographic change and environmental factors.
Can Maui’s dolphin be saved?
The WWF New Zealand is pressing for the closure of fisheries and promotes education in the community and in schools to increase awareness of the plight of Maui's dolphins. There is also a network that the public can use to report sightings and ongoing research, genetic studies and population surveys to help create a clearer understanding of the situation. It is uncertain how effective these measures will prove to be but there is a lot of determination to help them.
Copyright 10/09/2014 zteve t evans
Like other marine animals Maui's dolphins are at risk from pollutants contaminating the sea from human activity. Industrial waste, storm water and run off from agricultural land contaminate the sea with chemicals such as PCBs, dioxins, DDT and metals which have been found in the blubber of Maui's and Hector's dolphins.
These contaminants bio-accumulate as they are ingested by other creatures in the food chain of Maui's dolphins finally reaching their calves through their mother's milk. This can result in the weakening of immune systems and a lowering of their fertility which is already low. Floating debris such as plastic bags are an increasing problem with the dolphins mistaking them for squid and eating them and being killed.
Boat Strikes
Motor boats are also a risk for Maui's dolphins. Direct collisions with motor boats can kill and the propellers can cause cuts and other injuries.
Declining Genetic Diversity
Another problem for Maui's dolphins is that over the last century their genetic diversity has declined reducing from at least three lineages to one. This increases vulnerability for survival from demographic change and environmental factors.
Can Maui’s dolphin be saved?
The WWF New Zealand is pressing for the closure of fisheries and promotes education in the community and in schools to increase awareness of the plight of Maui's dolphins. There is also a network that the public can use to report sightings and ongoing research, genetic studies and population surveys to help create a clearer understanding of the situation. It is uncertain how effective these measures will prove to be but there is a lot of determination to help them.
Copyright 10/09/2014 zteve t evans
References and Attributions
Copyright 10th September 2014 zteve t evans
Copyright 10th September 2014 zteve t evans
- File:Two Maui's dolphins.jpg From Wikimedia Commons - Two Maui's dolphins (Cephalorhynchus hectori maui).- Author ©Department of Conservation, New Zealand - Creative Commons Attribution-Share Alike 3.0 New Zealand licence
- WWF - Maui's dolphin Threats -
- Hector's and Maui's Dolphin SOS
- MPI - Fisheries | Environmental | Maui's and Hector's Dolphins
- Maui's dolphin: Marine mammals