A risk assessment of threats to Maui's dolphins

Biological Conservation, 2006

Hector's dolphin Cephalorhynchus hectori is found only in New Zealand waters. We carried out a population survey of the North Island subspecies Cephalorhychus hectori maui, also known as Maui's dolphin. The total population size estimate is 111 individuals (95% confidence interval = 48-252). The small population size confirms its critically endangered IUCN status. A sustainable level of human-caused mortality for this population would be 0.16 (one dolphin every 6.4 years). This essentially means that fisheries bycatch, and where possible other human impacts, need to be eliminated to allow population recovery. A protected area has been created to reduce the threat from entanglement in fishing gear. Gillnet fishing is prohibited along a 210 nautical mile stretch of coastline. The main concerns are that gillnet fishing is still allowed inside harbours and trawling continues inside the protected area.

Endangered Species Research, 2014

The New Zealand endemic Maui's dolphin Cephalorhynchus hectori maui is characterized by several life history traits thought to be important predictors of extinction risk in marine mammals, including a slow rate of reproduction, small geographic range, small group size, and coastal distribution. We continued the genetic monitoring of the remnant population of Maui's dolphins using DNA profiles to identify 39 individuals from 73 skin biopsy samples collected during dedicated boat surveys in the austral summers of 2010 and 2011. Using a 2-sample, closed-population model with the genotype recapture records, we estimated the current abundance to be N = 55 individuals approximately age 1+ (95% confidence limits = 48, 69; coefficient of variation = 0.15). The endangered species potential biological removal that would permit the recovery of the Maui's dolphin was calculated to be 1 dolphin every 10 to 23 yr. Despite this, the Maui's dolphin is not necessarily doomed to extinction. It appears to be maintaining an equal sex ratio and connectivity within its remnant range and has the potential for rescue by interbreeding with Hector's dolphin C. h. hectori migrants.

Hector’s dolphins (Cephalorhynchus hectori hectori) and their close relative the Maui’s dolphin (Cephalorhynchus hectori maui) live only in New Zealand and are the smallest and rarest marine dolphins on earth. Hector’s dolphins have declined from an estimated 29,000 in the 1970s to just over 7,000 today as a result of fishing. Maui’s dolphins have been affected even more severely. Gillnetting and trawling have decimated them from almost 2,000 to around 50 individuals in 40 years. Despite such low numbers, the New Zealand government is failing to implement effective protection measures. Both sub-species are in decline. Maui’s dolphins have become so rare that the population can sustain only one human induced death every 10-23 years (0.044 – 0.1/year, Currey et al. 2012). Fisheries bycatch alone however amounts to 3-4 Maui's per year – still more than 54 times the sustainable level (PBR). Under these conditions optimistic projections predict the functional extinction (< 3 breeding females) of Maui’s dolphins in 16-20 years. The Scientific Committee of the International Whaling Commission has sharply criticized New Zealand over three consecutive years over its failure to address the dolphins’ decline by banning gillnet and trawl fisheries across their habitat. The IUCN, the Society for Marine Mammalogy (SMM) and the New Zealand Marine Sciences Society have issued similar recommendations. The New Zealand government has entirely ignored this advice. Other threats, including large scale marine mining, seismic air gun blasts and oil and gas production also threaten the survival of Maui’s and Hector’s dolphins.

Biological Conservation, 1999

Hector's dolphin (Cephalorhynchus hectori) is an uncommon endemic of New Zealand which is suspected to be in decline due to entanglement mortality. However, uncertainty in available data has led to a dispute between the New Zealand Ministry of Fisheries and the New Zealand Department of Conservation over the status of this species. We use a density-dependent deterministic model to predict the future abundance and geographic distribution of Hector's dolphin under dierent scenarios of ®sheries management. We then examine the sensitivity of this model to a number of parameters for which few or no data are available. We ®nd that two populations of Hector's dolphins are predicted to decline in the future even when the most optimistic parameter estimates are used. The status of the third population is dependent upon the estimate of maximum annual population growth rate. Because of the dependence of ®nal abundance estimates on the estimates of entanglement mortality rates and maximum population growth rate, research eorts should be concentrated on estimating these parameters. # 0006-3207/99/$ -see front matter # 1999 Published by Elsevier Science Ltd. All rights reserved. P I I : S 0 0 0 6 -3 2 0 7 ( 9 9 ) 0 0 0 2 0 -8 Biological Conservation 90 (1999) 183±191 www.elsevier.com/locate/biocon

Open Conservation Biology Journal, 2008

Hector's dolphin is endemic to New Zealand, and listed as endangered on the IUCN Red List and equivalent New Zealand list of threatened species. The main threat to the species is entanglement in fishing gear, in particular gillnets. The Potential Biological Removal (PBR) method developed by the US National Marine Fisheries Service is a commonly used standard for determining a level of bycatch for marine mammal populations which, if exceeded, is likely to cause population decline. For Hector's dolphin, PBRs are less than one individual per year for most populations and the total for the whole species is less than 10 per year. Current estimated bycatch is on the order of 10-35 times higher than these PBRs. This is consistent with several Population Viability Analyses indicating that under current management Hector's dolphin populations are declining rapidly.

Biological Conservation, 2009

Numerous globally abundant species are exposed to human impacts that threaten the viability of regional populations. Assessing and characterising the risks faced by these populations can have significant implications for biodiversity conservation, given the ecological importance of many such species. To address these risks, the IUCN is starting to conduct assessments of regional populations in addition to species-level assessments of conservation status. Here, we demonstrate a threat assessment process that is robust to uncertainty, applying the IUCN criteria to a regional population of bottlenose dolphins in Fiordland, New Zealand. We compiled available population-specific information to assess the population under the five Red List criteria. We estimated there were 205 Fiordland bottlenose dolphins (CV = 3.5%), using current estimates of abundance for two sub-populations and stochastic modelling of an earlier estimate for the third sub-population. Population trajectory and extinction risk were assessed using stochastic age-structured Leslie matrix population models. The majority of model runs met the criteria for classification as critically endangered (C1: 67.6% of runs) given the number of mature individuals (123; CV = 6.7%) and the predicted rate of population decline (average decline: 31.4% over one generation). The evidence of isolation of the population confirms this was an appropriate regional classification. This approach provided an assessment that was robust to uncertainty.

PLOS ONE

Estimation of visibility bias is critical to accurately compute abundance of wild populations. The franciscana, Pontoporia blainvillei, is considered the most threatened small cetacean in the southwestern Atlantic Ocean. Aerial surveys are considered the most effective method to estimate abundance of this species, but many existing estimates have been considered unreliable because they lack proper estimation of correction factors for visibility bias. In this study, helicopter surveys were conducted to determine surfacing-diving intervals of franciscanas and to estimate availability for aerial platforms. Fifteen hours were flown and 101 groups of 1 to 7 franciscanas were monitored, resulting in a sample of 248 surface-dive cycles. The mean surfacing interval and diving interval times were 16.10 seconds (SE = 9.74) and 39.77 seconds (SE = 29.06), respectively. Availability was estimated at 0.39 (SE = 0.01), a value 16-46% greater than estimates computed from diving parameters obtained from boats or from land. Generalized mixed-effects models were used to investigate the influence of biological and environmental predictors on the proportion of time franciscana groups are visually available to be seen from an aerial platform. These models revealed that group size was the main factor influencing the proportion at surface. The use of negatively biased estimates of availability results in overestimation of abundance, leads to overly optimistic assessments of extinction probabilities and to potentially ineffective management actions. This study demonstrates that estimates of availability must be computed from suitable platforms to ensure proper conservation decisions are implemented to protect threatened species such as the franciscana.

2005

Since 1997, a conservation biology research project focusing on cetaceans in the Central and Southern Mediterranean Sea around the Maltese Islands has managed to increase accurate information of the various species inhabiting these waters (Vella, 1998; 2000a; 2000b). Among the species studied, this paper focuses upon the common dolphin, Delphinus delphis in the Mediterranean. This species/subpopulation rated as endangered in the Mediterranean (EN A2abc -IUCN 2003 -) necessitates particular conservation assessment, monitoring and management planning in this region (IUCN, 2003;. This ongoing longterm research therefore also aims at contributing valuable information (Vella, 2000b) required in relation to the Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS). Although Mediterranean cetaceans are legally protected by Maltese law, through specific legal notices, this field conservation research is, to date, the only scientific effort around the Maltese Islands that may furnish the required details for local conservation measures to be implemented. Common dolphin distribution, abundance, habitat preference, behaviour, and associations with fisheries that are exploited in the same area are among the parameters studied. Marine habitat degradation and resource over-exploitation are considerations that need to be addressed since both may affect cetacean survival in the region. Part of the study area, closer to the Maltese Islands is shown in Fig. , and includes most of the fishing area utilised by Maltese fishermen.