Marine sanctuary helps Māui dolphins access food

New Zealand’s Māui dolphin is the world’s most endangered marine dolphin. New research shows that the species changed its diet during the past 30 years. 

For the study, scientists checked tiny skin samples collected between 1993 and 2020 to analyze microchemical markers that are associated with diet.

The results showed the dolphins’ meals became less diverse from 2008. During this time, a marine sanctuary restricted fishing in their habitat, which stretches along 40 kilometres of Tamaki Makaurau’s west coast.

The Marine Mammal Sanctuary was established on the west coast of the North Island in 2008, and expanded in 2020.

“We think that the sanctuary increased the amount of food available to the dolphins,” said study lead author Courtney Ogilvy, a PhD student at Waipapa Taumata Rau, University of Auckland. “That meant they were able to get more of their preferred prey, and not work so hard to get many different types of food.”

Māui dolphins typically eat fish smaller than 10 centimetres in length, dining on species such as ahuru, red cod and sprats. A temporary change in diet also occurred during the El Niño weather event in 2015 and 2016.

“Dramatic climate events like El Niño can change water temperatures and currents, meaning that fish from different regions can move into the dolphins’ habitat,” explained study co-author Professor Rochelle Constantine. “As you really are what you eat, this change is reflected in the microchemical markers in the dolphin’s skin.”

The researchers consider these findings good news for the Māui dolphin as they adapt to changing conditions and are able to find preferred prey. In the future, the researchers plan to investigate how climate change will alter the dolphins’ habitat.

“We know they are likely to be at their maximum thermal limit, so increasing ocean temperatures may eventually shift the distribution of the dolphins and their preferred prey,” said Professor Constantine. 

Located only in Aotearoa, the number of Māui dolphins aged a year or older may be as few as 54, according to the latest estimate.  

The study is published in the journal Royal Society Open Science.

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By Katherine Bucko, Earth.com Staff Writer