Near‐shore distribution and abundance of dolphins along the West Coast of the South Island, New Zealand

Department of Marine Science, University of Otago, Taieri, Otago, New Zealand
New Zealand Journal of Marine and Freshwater Research (Impact Factor: 0.8). 03/1998; 32(1):105-112. DOI: 10.1080/00288330.1998.9516809


Compared to other stretches of the New Zealand coast, very little is known about the cetacean fauna off the West Coast of the South Island. The purpose of this paper is to describe the near‐shore distribution and abundance of dolphins in that area by summarising the results of two major studies. Between February 1995 and February 1997, 97 day trips were undertaken from Westport, Greymouth, and Jackson Bay in a small boat to survey the near‐shore distribution of dolphins. Between July 1994 and February 1997, 283 field days were spent on the water in Doubtful Sound studying the local bottlenose dolphin (Tursiops truncatus) population of c. 63 individuals. At the same time, three longer surveys were undertaken into other fiords of Fiordland which indicated the presence of further populations. Altogether, five delphinid species were recorded in various abundances. Small‐medium‐sized groups of Hector's dolphins (Cephalorhynchus hectori) with 1–60 individuals were observed in almost all areas of Westland in winter as well as in summer. Maximum densities peaked at 5–18 individuals per nautical mile of coastline between Cape Foulwind and Hokitika. Dusky and common dolphins (Lagenorhynchus obscurus and Delphinus delphis) occurred almost exclusively in summer in groups of 2–150 individuals, often with calves, especially at Cape Foulwind and Jackson Head. Bottlenose dolphins (Tursiops truncatus) and killer whales (Orcinus orca) were observed rarely off Westland, but occurred more frequently in Fiordland.

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Available from: Stefan Bräger
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    • "The Fiordland bottlenose dolphins (Tursiops truncatus) comprise a regional population (sensu IUCN, 2003) located at the southern limit of the species' worldwide range, apparently isolated from other coastal New Zealand populations (Tezanos-Pinto et al., 2008). The population is subdivided into three sub-populations (sensu IUCN, 2003): two sub-populations are found within the complexes formed by Doubtful and Thompson Sounds, and Dusky and Breaksea Sounds while one sub-population ranges along the Northern Fiordland coast (Bräger and Schneider, 1998; Lusseau and Slooten, 2002) (Fig. 1). One sub-population (Doubtful/Thompson ) has declined by at least 34% over 12 years (Currey et al., 2007). "
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    ABSTRACT: 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.
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    • "The bottlenose dolphins of Fiordland (Tursiops truncatus) are thought to be the world's southern-most resident groups of bottlenose dolphins (Bräger & Schneider 1998). The population inhabiting the Doubtful/Patea-Thompson Sound complex (referred to as Doubtful Sound) is experiencing a decline in abundance and survival, threatening the long-term viability of the population (Lusseau et al 2006, Currey et al 2007, Currey et al in press). "
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    ABSTRACT: 1. The bottlenose dolphin population in Doubtful Sound/Patea, New Zealand is declining and subject to potential impacts from tourism and habitat modification via freshwater discharge from the Manapouri hydroelectric power station. The bottlenose dolphin population in neighbouring Dusky Sound is exposed to much lower levels of tourism and the fiord receives only natural freshwater run-off. 2. We used dorsal fin identification photographs from the both populations to compare levels of epidermal disease. Further, we used laser photogrammetry to measure the dorsal fin base length of calves (< one year old) to assess differences in calf size and birth seasonality between the populations. 3. Epidermal lesions were common in both populations (affecting > 95% of individuals), but lesion severity (recorded as percentage cover) was four times higher in Doubtful Sound. Within Doubtful Sound, lesion severity was higher for females than males. No such differences were observed in Dusky Sound. Calves were larger and were born over a wider period in Dusky Sound. 4. The freshwater discharge into Doubtful Sound alters temperature and salinity regimes in the fiord, which may exacerbate naturally occurring epidermal disease. The increased incidence of disease in females and the smaller size of calves in Doubtful Sound may help to account for the low survival of calves in the population. The narrow calving season in Doubtful Sound may be an adaptation to localised temperature conditions. 5. In order to tease apart the effects of water temperature on calving season, and examine the potential influence of the freshwater discharge into Doubtful Sound, comparative studies of calving seasonality, calf survival, calf size, and sea-surface temperature will be needed in both Dusky and Doubtful Sounds.
    Full-text · Book · Jan 2009
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    • "To date, there is no estimate for Marlborough Sounds; but a photo-identification catalog (Merriman et al. 2005) suggests a population of at least several hundreds. Comparison of individual identification photographs between Northland, Marlborough Sounds, and Fiordland suggests no exchange of individuals among populations (Bräger and Schneider 1998; Schneider 1999; Constantine 2002). Here, we describe the population structure and genetic diversity of coastal bottlenose dolphins in New Zealand waters based on mtDNA control region sequences. "
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    ABSTRACT: Bottlenose dolphins (Tursiops truncatus) occupy a wide range of coastal and pelagic habitats throughout tropical and temperate waters worldwide. In some regions, "inshore" and "offshore" forms or ecotypes differ genetically and morphologically, despite no obvious boundaries to interchange. Around New Zealand, bottlenose dolphins inhabit 3 coastal regions: Northland, Marlborough Sounds, and Fiordland. Previous demographic studies showed no interchange of individuals among these populations. Here, we describe the genetic structure and diversity of these populations using skin samples collected with a remote biopsy dart. Analysis of the molecular variance from mitochondrial DNA (mtDNA) control region sequences (n = 193) showed considerable differentiation among populations (F(ST) = 0.17, Phi(ST) = 0.21, P < 0.001) suggesting little or no female gene flow or interchange. All 3 populations showed higher mtDNA diversity than expected given their small population sizes and isolation. To explain the source of this variation, 22 control region haplotypes from New Zealand were compared with 108 haplotypes worldwide representing 586 individuals from 19 populations and including both inshore and offshore ecotypes as described in the Western North Atlantic. All haplotypes found in the Pacific, regardless of population habitat use (i.e., coastal or pelagic), are more divergent from populations described as inshore ecotype in the Western North Atlantic than from populations described as offshore ecotype. Analysis of gene flow indicated long-distance dispersal among coastal and pelagic populations worldwide (except for those haplotypes described as inshore ecotype in the Western North Atlantic), suggesting that these populations are interconnected on an evolutionary timescale. This finding suggests that habitat specialization has occurred independently in different ocean basins, perhaps with Tursiops aduncus filling the ecological niche of the inshore ecotype in some coastal regions of the Indian and Western Pacific Oceans.
    Full-text · Article · May 2008 · The Journal of heredity
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