A new abundance estimate for Maui’s dolphin: What does it mean for managing this critically endangered species?

Slooten, Elisabeth; Dawson, Stephen M.; Rayment, William; Childerhouse, Simon

doi:10.1016/j.biocon.2005.10.013

Cited by 66 publications

(71 citation statements)

References 19 publications

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“…For example, the areas linking North Island and South Island (Areas 4, 5 and 9) have relatively high levels of fishing effort and low dolphin numbers. Likewise, fishing impacts may explain the , 2006a. However, relative levels of fishing activity in different parts of this species' range also appear to have a strong influence on the distribution of Hector's dolphins.…”

Section: Discussionmentioning

confidence: 97%

“…A similar method of back-calculation is described in Smith & Polachek (1979), Barlow & Hanan (1995) and Martien et al (1999). The distribution for population size was based on the most recent population estimate for each area (see Slooten et al 2004Slooten et al , 2006a.…”

Section: Methodsmentioning

confidence: 99%

“…Small populations are found around the South Island (7270 individuals, CV 0.16; Slooten et al 2004) and off the North Island west coast (111 individuals, CV 0.44; Slooten et al 2006a). Since the early 1970s, Hector's dolphins have been caught in commercial gillnet fisheries (Taylor 1992, Baird & Bradford 2000.…”

Section: Introductionmentioning

confidence: 99%

“…The present paper presents a population viability analysis for Hector's dolphin populations around New Zealand, based on recent estimates of dolphin abundance , 2006a, estimates of catch rate from the commercial gillnet fishery (Baird & Bradford 2000) and fishing effort data from the Ministry of Fisheries. This analysis indicates negative effects of fisheries mortality, at the local level, on regional populations and on the overall spatial distribution of the species.…”

Section: Introductionmentioning

confidence: 99%

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Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch

Slooten

2007

Endang. Species Res.

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New Zealand's endemic Hector's dolphins Cephalorhynchus hectori overlap with gillnet and trawl fisheries throughout their geographic range. The catch rate in commercial gillnets has been estimated using independent observers. No quantitative estimates are available for bycatch in recreational gillnets or trawl fisheries. The catch rate (per dolphin, per km of gillnet, per year) in commercial gillnets was used in a population viability analysis to estimate past and future population sizes. Total population size today (7873, coefficient of variation [CV] 0.16) was estimated at 27% of population size in 1970 (29316, CV 0.16), before a major expansion of commercial gillnetting. The species matches IUCN criteria for 'endangered'. The North Island subspecies matches criteria for 'critically endangered'. Current management, which includes 2 protected areas, is not sufficient to halt population declines. Hector's dolphin populations are predicted to continue declining to 5475 (CV 0.20) by 2050. Creating 4 strategically placed protected areas would allow population recovery towards 1970 levels, with an estimated 47% probability of reaching 50% of 1970 population size by 2050 (proportion of 5000 model runs in which final population size was at or above this reference level). Reducing fisheries mortality to levels approaching zero shows the strongest promise of meeting national and international guidelines for managing dolphin bycatch, with a 59% probability of reaching 50% of 1970 population size by 2050.

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Section: Discussionmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch

Slooten

2007

Endang. Species Res.

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“…In aerial surveys of similar design, the furthest offshore sightings were 4 nautical miles off the North Island west coast, 6 nautical miles off the South Island west coast, and at least 15 nautical miles off Banks Peninsula (Rayment et al 2003;Slooten et al 2005Slooten et al , 2006. The common denominator appears to be water depth, with all sightings made in less than 90 m of water.…”

Section: Discussionmentioning

confidence: 99%

Offshore distribution of Hector's dolphins at Banks Peninsula, New Zealand: Is the Banks Peninsula Marine Mammal sanctuary large enough?

Slooten¹,

Rayment

Dawson

2006

New Zealand Journal of Marine and Freshwater Research

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Aerial surveys of Hector's dolphins were carried out to evaluate the effectiveness of the Banks Peninsula Marine Mammal Sanctuary. In summer, the proportion of sightings inside the 4 nautical mile offshore boundary of the sanctuary was 79%. This dropped to just over 35% in winter. These estimates were used in a population viability analysis to determine whether the sanctuary needs to be extended to reduce dolphin bycatch to sustainable levels. We followed the standard procedure for setting limits on marine mammal bycatch in the United States to calculate a bycatch limit of 1.6 or 2.8 dolphins per year (depending on whether the sanctuary population is included). If the offshore boundary was extended to 15 nautical miles, the sanctuary would need to be extended alongshore north and south by more than 30 nautical miles to reduce bycatch to 2.8, or north and south by 60 nautical miles to reduce bycatch to 1.6 dolphins per year.

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Seasonal changes in distribution of Hector's dolphin at Banks Peninsula, New Zealand: implications for protected area design

Rayment

Dawson

Slooten

2009

Aquatic Conservation

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ABSTRACT1. The efficacy of protected areas for wildlife management is largely dependent on appropriate design. It is therefore crucial that the distribution of target species is well understood.2. The Banks Peninsula Marine Mammal Sanctuary (BPMMS) was designed to protect Hector's dolphins from bycatch in gillnets. However, the Banks Peninsula dolphin population is likely to be still declining, partly due to continued bycatch outside the boundaries of the BPMMS.3. A three year series of aerial line-transect surveys around Banks Peninsula was carried out to investigate seasonal changes in distribution of Hector's dolphins out to 20 nautical miles (37 km) from the coast.4. Dolphin sightings were concentrated close to shore in shallow water in summer, but were more evenly distributed throughout the study area in winter. A greater proportion of dolphins were sighted outside the 4 nautical miles (7.4 km) offshore boundary of the BPMMS in winter (mean 5 56%) than in summer (mean 5 19%) (G 5 88.25, df 5 1, Po0.001).5. Partial Mantel tests revealed the effects of distance offshore and depth on dolphin occurrence while controlling for spatial autocorrelation and multicollinearity within the data. Distance offshore had the strongest and most consistent effect on dolphin presence, while depth had a strong effect in summer only.6. It is proposed that restrictions on gillnetting around Banks Peninsula must be extended in order to reduce bycatch of Hector's dolphins to a sustainable level, and that a new offshore boundary of the BPMMS would be best defined by distance from the coast.

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A new abundance estimate for Maui’s dolphin: What does it mean for managing this critically endangered species?

Cited by 66 publications

References 19 publications

Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch

Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch

Offshore distribution of Hector's dolphins at Banks Peninsula, New Zealand: Is the Banks Peninsula Marine Mammal sanctuary large enough?

Seasonal changes in distribution of Hector's dolphin at Banks Peninsula, New Zealand: implications for protected area design

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A new abundance estimate for Maui’s dolphin: What does it mean for managing this critically endangered species?

Cited by 66 publications

References 19 publications

Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch

Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch

Offshore distribution of Hector's dolphins at Banks Peninsula, New Zealand: Is the Banks Peninsula Marine Mammal sanctuary large enough?

Seasonal changes in distribution of Hector's dolphin at Banks Peninsula, New Zealand: implications for protected area design

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Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch

Conservation management in the face of uncertainty: effectiveness of four options for managing Hectors dolphin bycatch