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Dolphin protection plan – Expert Reaction

The Government has proposed plans to expand protection for Māui and Hector's dolphins.

A discussion document, released today, includes proposals to extend the boundaries of two marine mammal sanctuaries and identifies threats to the dolphins including toxoplasmosis spread by cats.

The SMC asked experts to comment on the plan, feel free to use these comments in your reporting.

Associate Professor Karen Stockin, Massey University, comments:

"It is great to see the New Zealand Government release this much needed Threat Management Plan for the Hector’s and Māui dolphins. It has been a huge body of work for which many people have contributed.

"Despite the recent downgrading in threat status of the Hector's dolphins to nationally vulnerable, it is apparent there is still much to do to ensure successful conservation efforts for this and the nationally critical subspecies, Māui dolphins.

"In my opinion, the acknowledgement and discussion of broader threats beyond just fisheries bycatch is welcome as a much-needed step forward for successful management of this genus.

"Disease has historically been overlooked in the wider assessment of impacts likely affecting all New Zealand marine mammals. Undoubtedly, the recent discovery of toxoplasmosis is an important finding which I hope the government will not only explore further, but broader in the context of disease screening.

"One thing pleasing to see stated in the Threat Management Plan is the need for multi-disciplinary agreement on toxoplasmosis mitigation. As part of this, I am hopeful the government will conduct further assessment of toxoplasmosis in a wider context to what appears in the Threat Management Plan presently. For example, in many mammalian species including marine mammals and humans, we know that toxoplasmosis is often a secondary disease, present within organisms (sometimes without consequence) until such a time when a primary disease and/or elevated or cumulative contaminant burden suppresses immunity.

"As such, as part of this Threat Management Plan, I would encourage the government to support a broader disease surveillance programme (above and beyond just toxoplasmosis) and that factors likely to suppress immunity, such as persistent contaminants, are fully evaluated and within a cumulative framework. For example, only a handful of legacy contaminants have been examined in isolation for New Zealand marine mammals. However, in the context of current disease concerns, we need to look towards assessing cumulative impacts and notably, including emerging contaminants in our evaluations."

Conflict of interest statement: Speaking in my capacity as a New Zealand researcher of marine mammals - NOT in any International Whaling Commission capacity.

Professor Steve Dawson and Professor Liz Slooten, University of Otago, comment:

"Plans for protecting Hector’s and Māui dolphins, released this morning, are based on flawed science and the protection plans are piecemeal.

"The plan states that disease is a much bigger problem than bycatch, despite no robust evidence this is so, and against advice from an invited team of experts. With current data, there is no scientifically valid way to estimate the number of dolphin deaths from disease.

"The Expert Panel report includes a long list of other problems with the MPI model and its conclusions. Essentially, the MPI approach failed this peer review.

"MPI have almost certainly under-estimated how many dolphins are dying in fishing nets, due to very low observer coverage (2-3%) and problems with estimating the overlap between dolphins and fishing. The MPI approach is complex, and a one-off. It has not been published in a peer-reviewed journal and is very sensitive to the many assumptions made.

"Recently reported dolphin deaths, which include three and five dolphins caught in the same net, are inconsistent with MPI’s estimates.

"The simple solution is to use only dolphin-safe fishing methods (no gillnets or trawling), in all waters less than 100 metres deep throughout the range of Hector’s and Māui dolphins."

No conflicts of interest.

Associate Professor Rochelle Constantine, University of Auckland, comments:

"The consultation document for the Threat Management Plan clearly lays out the known threats to our endemic Hector's and Māui dolphins and provides options to mitigate the risk of dolphin deaths alongside the economic impacts where changes to fisheries are suggested.

"This is the most comprehensive assessment of the status of Hector's and Māui dolphins with toxoplasmosis, transmitted by cat faeces, and fisheries entanglement the main known causes of death. Setnets are the fishing gear that poses the greatest risk to dolphins, this is without a full assessment of the recreational setnet deaths so the number is likely higher. It is important to note that this is not a 'one size fits all' plan. The risks of death are not the same throughout the dolphins' range therefore, the options account for different management actions in different regions.

"The threat from toxoplasmosis, which is spread from cat faeces, is one of our greatest challenges as there are gaps in knowledge about this disease, but cat owners play an important role in minimising spread of toxoplasmosis. The initiatives by councils, pest controllers and Predator Free New Zealand to control feral cats are very important to manage those threats.

"It is encouraging to see sub-lethal threats considered including mining, tourism, and seismic surveys as these non-direct impacts are likely to be amplified for populations that are isolated, very small and/or under stress. The effects on ecosystem function from habitat disturbance, prey availability and climate change impacts are increasingly of concern in our oceans."

Conflict of interest statement: Principal investigator on Maui and Hector's dolphin research; Member of the scientific advisory group for the Hector's and Maui Dolphin Threat Management Plan; Member of the New Zealand Threat Classification System for Marine Mammals.


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