Maui’s Dolphin Population Status: giving facts a helping hand – a Guest post by Hasile


GFBF’s guest poster Hasile is very interested in the plight of the New Zealand Maui’s dolphin, of which there are an estimated 55 individuals left.

For some the jury is still out on whether Maui’s dolphins constitute a new species, a sub-species, or simply an extant population isolated from the other more common South Island Hector’s dolphins. For others whether or not the Maui’s population constitutes a distinct species is an irrelevant consideration… It is accepted by all that the population is distinct, and it is critically endangered to the point where extinction is imminent if something drastic is not done.

According to the New Zealand Department of Conservation (DOC):

Maui’s dolphin (Cephalorhynchus hectori mauiis the world’s smallest dolphin and is found only on the west coast of the North Island of New Zealand and nowhere else in the world. It is New Zealand’s rarest dolphin […]

In 2012 a DOC-commissioned study estimated the Maui’s dolphin population to consist of 55 with a 95% confidence interval of between 48 to 69. The estimate is for individuals aged more than 1 year (i.e. this excludes calves of under a year). This small population of dolphins is thought to have been isolated from their more-numerous relatives, South Island Hector’s dolphin, for thousands of years. Maui’s dolphin used to be known as North Island Hector’s dolphin. But research showed the North and South Island dolphins are separate sub-species that are physically and genetically distinct from each other.”

However like so many critical situations the search consensus on a way forward with respect to saving the Maui’s dolphin has been hindered, by politics, finger-pointing, and mistrust. I highlighted in a previous post in April last year (Maui’s Dolphins: Swimming in a sea of all sorts of mischief?) that the plight of the Maui’s dolphin has seen

“...sustained pressure on the Government by eNGOs,the Media, the public and of course opposition politicians who are  using the campaign as leverage to garner political points at the expense of the Government. This pressure has been squarely placed on the Commercial Fishing Industry, who beset on all sides by sectors pointing accusatory fingers, protest their perceived culpability.”

Often the campaign has been theatrical… There was even a funeral march in 2012… where protestors marched through the Auckland Electorate of  Kumeu-Huapai to New Zealand Prime Minister John Key’s electorate office in Helensville demanding urgent action to save the Maui’s dolphin. The Rodney Times reported that the “mourners” included Rodney Labour candidate and former Rodney and Auckland Regional Council representative Christine Rose of Huapai who has long used the issue of protection of the critically endangered dolphin as political leverage.

According to Hasile central figures have manipulated scientific data for the purpose of controlling the debate. In an Article (below) sent to GFBF in December 2012 Hasile charters the statistical drift of the Maui’s dolphin scientific information.

A visual education tool about the state of the critically endangered Maui’s Dolphin and fishing-related threat management options currently under review by the NZ Ministry of Primary Resources.  Source:

A visual education tool about the state of the critically endangered Maui’s Dolphin and fishing-related threat management options currently under review by the NZ Ministry of Primary Resources. CLICK TO VIEW EDUCATION TOOL. Source:

A Case of Giving Facts on Maui’s Dolphin a Helping Hand (by Hasile)

Cephalorhynchus hectori. Photograph by James Shook. Source: Wiki Commons

Cephalorhynchus hectori. Photograph by James Shook.
Source: Wiki Commons

Increasingly, as technology becomes more sophisticated, reliable and adaptable, the terms of access to natural resources should be ideally based on robust and coherent science on the effects of that extraction. 

Unfortunately, there is an apparent trend, based variously on academic niche and security, international scientific status, ideological attitudes to humanity’s place on the planet, the need to simplify and generalise for popular opinion and a central belief that commercial use of any and every resource inevitably leads to its overexploitation and environmental degradation.

This trend can lead to scientific literature which is less reliable than it ought to be.

The Background of Otago University’s Liz Slooten

Dr. Liz Slooten, an Otago University professor of Zoology, called for greater supervision aboard trawling boats. “The numbers of observers on the boats are far too low.” Source: See

An article in Endangered Species Research by Elisabeth Slooten could be a case where factors have led to a mismatch of the empirical data with the conclusions reached.  Dr Slooten argues that data shows what is unquestionably a severely endangered animal sub-species is not only under threat from fishing activities, but that threat has increased over the years, rather than diminished.

Dr Slooten has devoted most of her professional life to the study of Hector’s dolphins.  It is no exaggeration that she was traumatised seeing the effects on the Hector’s dolphins of the introduction of monofilament nets some decades ago.

The 1 August 2012 issue of Life and Leisure retells, in almost folk lore terms, how she spent half of 1984 on a VW Kombi van tour of the South Island coast in search of Hector’s dolphins with Steve Dawson.  She is quoted at her first sight of a Hector’s as, “A sort of ‘Dr Livingstone I presume’ moment.”

Dr Slooten is an Associate Professor in the Zoology Department at Otago University and is described by the University as ‘the foremost authority’ on Hector’s (Cephalorhynchus hectori) and Maui’s subspecies (C. hectori maui).’ She teaches ecology, statistics, risk analysis and a MSc course on marine mammals. She and Dr Dawson have supervised several MSc and PhD projects on the species. They have published more than 100 peer-reviewed scientific publications.

In 1992, Drs Slooten and Dawson launched the New Zealand Whale and Dolphin Trust for research and conservation. In 2004, they were awarded the Royal Society’s Sir Charles Fleming Award for their contribution to conservation science.

The University of Otago website states Dr Slooten ‘represents New Zealand at the Scientific Committee of the International Whaling Commission’ and that she, and Dr Dawson, are ‘members of the IUCN Cetacean Specialist Group and regularly advise government.’

Dr Slooten predicts an international trade boycott of New Zealand seafood products, if the restrictions on fishing in what she claims are Maui’s dolphin sub-species habitats, are not increased.  In the Taranaki Daily News on 17th July 2012 she said,

Logically it doesn’t make sense for people to boycott hoki, for instance, because dolphins aren’t being killed in the hoki industry but that is the next step.  Do we want to be seen as dolphin killers overseas?

She also told BBCNews on 10th June 2013;

If Maui’s dolphins went extinct that would be very bad in terms of our international reputation.  Obviously New Zealand is known as a clean green country and that reputation is very important to exports, to tourism and in general to our international reputation.

Dr Slooten has written and expressed views on sea mammals other than dolphins. The Final Advice Paper on New Zealand Sea Lions by DOC and MPI in 2012, was critical of Dr Slooten’s suggestions for measuring the frequency of sea lion captures in Sea Lion Escape Devices by blocking their escape, stating;

 The Ministry does not support the proposal advanced by Elisabeth Slooten to cover the escape hole of SLEDs. This would need to be conducted over several years to get a robust estimate of strike rate and would result in deliberate drowning of sea lions.

In April 2013, Otago University Press published Drs Slooten and Dawson’s book, Dolphins Down Under: Understanding the New Zealand DolphinThis book is a dolphin watcher’s handbook, complete with photos of Hector’s Dolphins at Banks Peninsular, which she named ‘Zorro’, Huffer’, Biggus Nickus’ and ‘Rooster’.

In December 2013 Dr Slooten chaired the Organising Committee of the 20th Biennial Conference on the Biology of Marine Mammals, which was hosted by Otago University.  These conferences are rarely held outside North America. Dr Dawson chaired the Scientific Programme Committee and Dr Slooten was also on that committee. Dr. Slooten and Dawson delivered a keynote presentation on the conference opening morning, ‘A flagship of NZ conservation is foundering’.

Dolphin Reproduction Research

Cover of Raewyn Peart's 2013 book 'The Dolphins of Aotearoa' Source:

Cover of Raewyn Peart’s 2013 book ‘The Dolphins of Aotearoa’

The Otago University promotion of ‘Dolphins Down Under: Understanding the New Zealand Dolphin’ stated that Dr Slooten ‘researches and publishes on reproductive and population biology…’

A review of Dr Slooten’s papers on Hector’s type dolphins, as listed by Otago University on its website, nonetheless does not reveal publications exhibiting this expertise in any but a most limited sense.  This work, listed as published since 2006, is confined to various forms of observation which avoids actual or protracted contact with the dolphins.

The limits to what is acceptable and relevant science on Hector’s dolphin in New Zealand appear to have thus been set by its most prominent researcher.  For example, in ‘Dolphins Down Under’ (page 63) Dr Slooten objects to satellite tagging Hector’s type dolphins, on the basis that such attaching such tags would alter their behaviour and also would endanger the dolphins. She added that such tagging was unnecessary anyway, given that that she knows and can recognise all of the Hector’s dolphins around Banks Peninsular.

In Raewyn Peart’s 2013 book ‘Dolphins of Aotearoa’ she writes (page 254) that Drs Slooten and Dawson in 2003 opposed the use of satellite tags on Maui’s since it was ‘intrusive’.

The only exception to non-intrusive observation research currently into the Hector’s species in New Zealand is laboratory analysis of the DNA composition of individuals of the species, with skin samples being darted off the dolphins.  The lure of producing interesting pie graphs in learned papers on genetic variation among the Hectors and Maui’s, was obviously too much, even for Dr Slooten to prevent.

The DNA work by itself has some interest in establishing; individual identification, whether Hector’s and Maui’s breed, population spread or whether there is sufficient genetic diversity to prevent inbreeding depression.  The work though is largely of academic interest and has, at best, a marginal utility of actually being used to protect the species from decline or extinction.

Investigations into the nature, identification and duration of Hector’s dolphin oestrus for example, which would be a vital precursor to assisted reproduction of Maui’s dolphins, have not been carried out. The viewpoint of New Zealand’s announced foremost expert on such dolphins, is that such research is neither necessary nor acceptable.

Indeed Dr Barbara Maas, the London based Head of International Species for NABU International, mocked the idea of assisted reproduction in her presentation on Hector’s type dolphins at the Marine Mammal Conference in Dunedin, though she provided neither reasons nor basis for her derision.

DNA Evidence of Distribution

In the Taranaki Daily News on 20th July 2012, Liz Slooten, wrote that the southernmost confirmed sighting of a Maui’s dolphin was one from which a biopsy sample was taken in Wellington Harbour.

Ten days later, on 30th July, Scott Gallacher, Deputy Director-General of the Ministry for Primary Industries, replied in the same publication, writing  that there were claims made by ‘some commentators’,  about Maui’s dolphins that were ‘misleading or incorrect’. He referred to the Wellington biopsy sample and pointed out,

The only biopsy sample taken from a dolphin in Wellington Harbour was that of a Hector’s, and that happened in 2009.”

Indeed Dr Slooten is justified in acknowledging the existence of such biopsy samples – there is even a Maui’s sample taken in Wellington which may have been collected  back in 1873.

Fishing and Dolphins

Fishing Vessels docked at the Tauranga Waterfront, New Zealand. Source QFSE Media, Wiki Commons

Fishing Vessels docked at the Tauranga Waterfront, New Zealand. Source QFSE Media, Wiki Commons

In the Endangered Species Research article Dr Slooten analyses the efficacy of restrictions on fishing on the three populations of Hector’s dolphins Cephalorhynchus hectori in South Island waters and that of the Maui’s subspecies C. hectori maui which inhabits an indeterminate range (albeit with a well-known core) in the waters off the west coast of the North Island.

Dr Slooten refers to the Maui’s habitat as WCNI (West Coast North Island).  Four of South Island originating Hector’s, two alive and two dead, have been identified in recent years within the Maui’s population in West Coast North Island (WCNI).  Thus Cephalorhynchus found off the West Coast of the North Island are not all Maui’s.

Marine Mammal Sanctuaries. The marine mammal sanctuaries layer has been updated to include the marine mammal sanctuaries (as they were legislated in October 2008).

Marine Mammal Sanctuaries. The marine mammal sanctuaries layer has been updated to include the marine mammal sanctuaries (as they were legislated in October 2008).

Dr Slooten’s position is clear.  She states that she believes that “bycatch in fisheries is the most serious threat to both species, (sic) …

However her views on the efficacy of banning fishing, to save Maui’s from extinction, are ambivalent.  She was cited, 30, April 2012, as stating,

…natural processes could take them away. If we stopped catching them in fishing nets tomorrow we would still hold our breath … so we really need to pull out all the stops or soon we’ll go past the point of no return.”

She details the introduction of various targeted fishing area restriction measures in the years since 1988 and finds favour with the results.  But she still asserts that the overall New Zealand Cephalorhynchus population is in decline. In relation to by catch of Hector’s species in the period since 2008, she states,

Formal and informal reports from the fishing industry include NZ dolphin deaths on the SCSI and WCNI”.

This implies a plural culpability in both areas.

According to the New Zealand Department of Conservation (DOC) Hector’s dolphin incident database; in which any formal report would be displayed, there have been five Hector’s type dolphins found and examined in the period since 2008 on the West Coast of the North Island (WCNI).  The post mortems for four of the dolphins describe no indications of fishing being the cause of death.  There is only one fatality attributed to fishing recorded – that of the Hector’s type taken by fisherman Ian McDougall off Cape Egmont in January 2012.

So the Slooten statement, based on one capture, is technically correct.  There has been one formal report of a Hector’s type dolphin killed by fishing in the WCNI since 2008.

In ‘Dolphins Down Under: Understanding the New Zealand Dolphin’ (page 70) Dr Slooten’s inclination to expand a singular event into a whole series of occurrences can be seen when she states that there have been recent ‘sightings and deaths in gillnets off the Taranaki coastline’.  There certainly have been many sightings along this coast, and other coasts.  DOC encourages these reports.

But [one fact remains], other than the one in 2012, there have been no mortalities which could be [directly] attributed to fishing recorded in Taranaki waters for nearly a quarter of a century.

Use of DoC Data on Fishing Induced Mortality Maui’s Dolphins

Maui's dolphin extinction scenario - Under current protection levels, Maui’s dolphins will become practically extinct by 2030 as a result of fishing. Green bars: Historic population status, orange bars: prognosis at an annual decline of 9% due to fishing. Source:

Maui’s dolphin extinction scenario – Under current protection levels, Maui’s dolphins will become practically extinct by 2030 as a result of fishing. Green bars: Historic population status, orange bars: prognosis at an annual decline of 9% due to fishing.

In Endangered Species Research (Page 126), Dr Slooten, explains (under the subtitle of ‘Strandings and reported bycatch’) that she is using information from ‘the DOC’s database (database) of strandings and bycatch’, mainatining that the value of the information on the database as ‘at best, a qualitative (i.e. theoretical) indication of dolphin mortality’.  This is a sound reservation.

However at page 127, she refers to the same ‘qualitative’ information:

“In the far north and far south, bycatch increased slightly over time. For WCNI, there was 1.00 dolphin death (sic) yr from 1970 to 2008 and 1.33 dolphin deaths yr from 2009 to 2012.  The protected area off the WCNI was originally put in place in 2003.  Therefore it is useful to compare the periods before and after 2003.  Again, an average of 1.00 dolphin deaths yr from 1970 to 2002, increases slightly to 1.11 yr from 2003 to 2012.”

This paragraph is problematic.  Either Dr Slooten is misrepresenting the figures of deaths attributed to fishing by DOC in its database;  or, she is, without clearly stating this, assuming and conveying that all reported Maui’s dolphin mortality through the years is attributable to fishing activity.

First, lets look at the empirical evidence of Maui’s dolphin fishing caused mortality. The DOC database has reported up to quarterly in detail since 1st July 2008.  It reports by possible cause of death, but not by date, for the period 1921 – 19th March 2008. It reports five WCNI mortalities since 1 July 2008, and 40 in the period 1921 – 19th March 2008. Furthermore of these five dolphin mortalities since 1st July 2008, only one, the Ian McDougall capture in January 2012, is attributed as a fishing caused mortality. Of the other four, two were Hector’s and two were Maui’s.

Of course, it is not only possible, but likely in earlier instances, that there was some fishing mortality which was not attributed.  Thus, quite correctly, Dr Slooten acknowledges her analysis to be qualitive only.

Conversely it should also be noted that the mortalities listed as attributed to fishing, may in fact not be due to fishing at all, since DOC describes some as these as ‘fishing’ being only the ‘possible’ cause.

Of the total of 40, in the period 1921 – 2008, only five mortalities in WCNI are described as showing signs of fishing being the cause of death. They are variously listed as; ‘net marks – not determinate’, ‘possible entanglement’ (2X), ‘probable entanglement’ and ‘known entanglement’.

The DOC/MPI Sept 2012 Consultation Paper (Paper) states six such mortalities, with three stated as ‘known entanglements’ including the Ian McDougall capture in 2012.

The Paper’s total of 46 mortalities 1921 – 2012 is inconsistent with the database which also lists 46 mortalities, but database includes one beachcast off Dargaville in 2013 and so not on the Paper list.

Neither the database nor the Paper break down the 1921 – 2008 tally by years, only possible causes of mortality, and so, from either the online DOC incident database or Consultation Paper, any sub periods of 1921 to 2008 cannot be compared directly with the year groupings of Dr Slooten’s figures.

In contrast any figures Dr Slooten uses between 2008 and 2013 can be directly compared with the public DOC site database.

However the information is even more confused with DOC providing to some parties a more detailed list (list) of the pre 1st July 2008 mortality, including the dates of mortalities against possible causes of death.  The list allows for a direct comparison of Dr Slooten’s figures prior to 2008 with those DOC has. The additional list discloses, for instance, that the first possibly fishing attributed mortality was in 1997, a ‘possible entanglement’. Presumably Dr Slooten has this list.  She would need it, or a similar source, to be able to identify breakdowns by different year groups prior to 2008, though she makes no mention of doing do.

The data from all three DOC sources is adopted in the table below, with the list derived data used for groups of years to provide the comparison with the Slooten figures.  Prior to 1970 there were four mortalities reported on the list.  For the period 2003 – 2008, where the list contains six entries, there are no fishing related deaths.

However the list, while detailed, is complicated. It includes an auxiliary  tally, citing 44 mortalities 1921 – 2012, against the on-line database list of 45 (plus one in 2013) and the Paper’s 46 for the same 1921 – 2012 period. These discrepancies in these data from DOC, have nothing but a marginal bearing on the inaccuracy or otherwise of the use of any or all DOC data by Dr Slooten.  She has only stated one source of her figures, that which is, ironically, the lowest of the three DOC totals.

Dr Slooten has set out various periods between 1970 and 2012.  This removes four of the pre 1970 deaths listed on the DOC list.

WCNI Hector’s type dolphin mortality, and mortality attributed to fishing; by DOC and by Slooten 1970 - 2012

WCNI Hector’s type dolphin mortality, and mortality attributed to fishing; by DOC and by Slooten 1970 – 2012

Apart from the matter of how the total of a 43 year period could include a decimal point, let alone two, the Slooten figures for the two time breakdowns closely agree; at 44.3 apparently fishing related deaths from 1970 to 2012 when divided at 2002-03, and 44.32 when the tally is divided at 2008-09.

They nonetheless exceed all of DOC’s on line database register estimations, the additional more detailed list and the discussion paper tally, whether counting total deaths, or the ones Dr Slooten may be attributing to fishing.

All three DOC sources produce a tally of potentially fishing related mortality since 1970 as six.  Dr Slooten appears to state the tally is 33.

The DOC data describes 10 Hector’s type dolphin deaths on WCNI in the ten years 2003 – 2012 from all causes.  Of these, DOC attributes only one mortality to fishing and that one was well outside the restricted fishing zone and by MPI’s admission was ‘about as likely as not’ to have been a Hector’s in the Discussion Paper.

It is possible that Dr Slooten relies on the ‘open’ diagnosis in the post mortems as displayed on the database for two Hector’s type, (November 2010 and October 2011) as suspect fishing mortalities.  However the post mortems as specific as to the lack of fishing by-catch injury and are open in their conclusions simply over disease analysis which has now been carried out though not entered in to the incident database.

In contrast, to this DOC figure of one, Dr Slooten appears to claim 11.1 deaths of Hector’s type from fishing in the ten year period 2003 – 2012.

A proposition that Dr Slooten is trying to cite by-catch deaths, and not all reported deaths, is therefore completely unsubstantiated by the data.

Astonishing as it is, this is the clear interpretation put upon Dr Slooten’s paper by Dr Barbara Maas, in her submission to the Scientific Committee of the International Whaling Commission, ‘Science-based management of New Zealand’s Maui’s dolphins – Scientific paper for IWC’, SC/65a/SMO6′.

Dr Maas states, at page 4 of the report,

“Since the 2008 protection measures were introduced, the number of stranded and reported bycatch cases has increased slightly (Slooten 2013). Between 1970 and 2008 an average of 1.00 entangled Maui’s dolphin was recorded per year. This figure increased marginally to 1.33 dolphin deaths per annum between 2009 and 2012.”

Accordingly, a maximum of six Maui’s deaths since 1970, for which evidence held by DOC exists, that the dolphin is both Maui’s and fishing might be responsible for its death, is now reported by Dr Maas to the IWC as a total of at least 52 Maui’s deaths confirmed as caused by fishing in the same period.

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One thought on “Maui’s Dolphin Population Status: giving facts a helping hand – a Guest post by Hasile

  1. Pingback: Maui’s Dolphins: Rather than pointing fingers, let’s negotiate the polemic and point the way forward | Green Fish Blue Fish

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