IWC Report of the Scientific Committee Annual Meeting 2013 Held on Jeju Island, Republic of Korea from 3-15 June 2013
Extract regarding New Zealand:
14.3.2 Hector's dolphin
SC/65a/SM7 reported on efforts to improve estimates of abundance for local populations of Hector's dolphins using capture-recapture (CR) methods based on genotyping and photo-identification. The authors presented three consistent abundance population estimates: (1) a genotype CR (Lincoln-Petersen estimator with Chapman Correction); (2) a photo-identification CR; and (3) a single-sample, linkage disequilibrium method, giving the effective number of breeding individuals in the parental generation. All details are given in Annex L, section 8.1.
22.214.171.124 MAUI'S DOLPHIN
Maui's dolphin is the North Island (New Zealand) coastal endemic sub-species of Hector's dolphin. The Committee was informed that the management measures it recommended last year were incorrectly attributed to a proposal by the New Zealand Government. The Committee acknowledges and regrets this mistake.
SC/65a/SM06 presented an update on the status of Maui's dolphins. The population has declined significantly with the latest genetic mark-recapture analysis in 2010/11 estimating a population size of 55 individuals one year and older (Hamner et al., 2012). The author suggested that unless their full range out to the 100m depth contour (including harbours) is protected against gillnetting and trawling (95.5% of human-caused mortality; Currey et al., 2012), Maui's dolphins will decline to 10 adult females in six years and become functionally extinct (<3 breeding females) in less than 20 years, even under maximum population growth (0.018 according to Slooten and Lad, 1991). Additional threats to Maui's dolphins (besides bycatch) include seismic survey work in or near their habitat and a plan to begin development of the world's largest marine iron sand mining operation.
SC/65a/SM22 reviewed the response of the New Zealand Government to the 2012 recommendations of the Committee for urgent action. Although some measures were taken to limit bycatch, the author considered that they were insufficient because they did not cover the entire range. The paper stated that the protected area should be expanded, all gillnetting and trawling should be banned within it (including harbours), and restrictions should be placed on oil and gas development and on other potentially harmful activities where the dolphins are found, including a buffer zone.
Currey et al. (2012) described the risk assessment undertaken in June 2012 to inform the Maui's Dolphin Threat Management Plan. The risk assessment identified 23 activities or processes that pose a threat to the sub-species, with bycatch in commercial set net, commercial trawl, and recreational/customary set net fisheries assessed as likely to have the greatest impacts. The risk posed by the cumulative impact of all threats was assessed as significant, resulting in a high likelihood of, and a potentially rapid rate of, population decline. The spatial overlap between dolphin distribution and commercial fishing effort helped to identify specific areas where risk posed by commercial fishing activities remained given management measures already in place. There was a reported capture of a dolphin in the south end of the Maui's range in January 2012 but no specimen was available to determine whether it was a Maui's dolphin or a specimen of the other Hector's dolphin subspecies. In response, interim measures were put in place in July 2012 that either restrict fisheries activities or require 100% observer coverage in the set net fishery in much of the area where the risk assessment indicated a continuing risk to Maui's dolphins from commercial fisheries.
Maas stated that the 100m depth contour is used to define the offshore limit of the range for Maui's dolphins; this ranges from 4 to 39 n.miles. However, Currey noted that the risk assessment expert panel estimated the offshore distribution as out to 7 n.miles based modelling, public sightings, strandings and historical information on the dolphins' alongshore range. The fishery restrictions are based on distance from shore and vary between 2 to 7 n.miles.
New Zealand has a limited observer programme for Maui's dolphins in the trawl fisheries and the limited data suggests some risk of bycatch in trawl gear. The great uncertainty surrounding aspects of Maui's dolphin ecology and distribution makes evaluation of the efficacy of management very difficult.
REPORT OF THE IWC SCIENTIFIC COMMITTEE, 2013
Emergency measures could be triggered by further bycatch.
The Committee agrees that management measures must be precautionary. If any fisheries with the potential for bycatch were to remain active within the range of Maui's dolphins, 100% observer coverage would maximise the chance of identifying any bycatch and providing information that might trigger immediate further area closures.
In conclusion, the Committee reiterates its extreme concern about the survival of Maui's dolphin given the evidence of population decline, contraction of range and low current abundance. The Committee agrees that the human-caused death of even one dolphin in such a small population would increase the extinction risk for this subspecies.
The Committee therefore recommends that rather than seeking further scientific evidence, the highest priority should be given to immediate management actions that will lead to the elimination of bycatch of Maui's dolphins. This includes full closures of any fisheries within the range of Maui's dolphins that are known to pose a risk of bycatch of small cetaceans.
The Committee commends the New Zealand Government on its initial and interim measures to protect Maui's dolphins. However, the Committee emphasises that the critically endangered status of this sub-species and the inherent and irresolvable uncertainty surrounding information on small populations require the immediate implementation of precautionary measures. Ensuring full protection of Maui's dolphins in all areas throughout their habitat, together with an ample buffer zone, will minimise the risk of bycatch and maximise the chances of population increase.