Stephen M. Dawson

Stephen M. Dawson
University of Otago · Department of Marine Science

PhD
Emeritus Professor, Marine Science Dept, University of Otago. Retired from teaching and admin, but continuing research

About

182
Publications
50,638
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
7,402
Citations
Citations since 2016
46 Research Items
3433 Citations
20162017201820192020202120220100200300400500
20162017201820192020202120220100200300400500
20162017201820192020202120220100200300400500
20162017201820192020202120220100200300400500
Introduction
I don't actively maintain this site. I encourage anyone interested in what I do to check out my page on Google Scholar
Additional affiliations
January 2004 - present
University of Otago
January 1986 - February 1990
University of Canterbury
Description
  • PhD studies

Publications

Publications (182)
Article
Before the 2020 COVID‐19 pandemic, cruise ship tourism had been one of the fastest growing segments of global tourism, presenting a range of potential impacts. At Akaroa Harbour, Aotearoa New Zealand, the number of annual cruise ship visits more than quadrupled following earthquake damage to Ōtautahi Christchurch's Lyttelton Port in 2011. Akaroa Ha...
Article
Culture, a pillar of the remarkable ecological success of humans, is increasingly recognized as a powerful force structuring nonhuman animal populations. A key gap between these two types of culture is quantitative evidence of symbolic markers—seemingly arbitrary traits that function as reliable indicators of cultural group membership to conspecifi...
Article
Full-text available
After near extirpation by nineteenth century whaling, New Zealand's southern right whales (Eubalaena australis) are recovering strongly, calving almost exclusively at the subantarctic Auckland Islands. Right whales are capital breeders; body condition is an important driver of their breeding success. Here we use unmanned aerial vehicles to characte...
Article
Kaikōura, New Zealand, is one of the few places worldwide where sperm whales can be routinely found close to the coast. Although whales are present nearly all year round, no individuals are truly resident. In this study, we analyzed photo‐identification data collected over 27 years to investigate long‐term trends in inshore abundance. We contrasted...
Article
The broadnose sevengill shark (Notorynchus cepedianus) is a large marine predator found in temperate coastal marine habitats. Despite being commonly encountered, details of its ecology are limited. To partially address this, we quantified the size and sex structure of N. cepedianus in Paterson Inlet, Stewart Island, New Zealand. A stereo-camera bai...
Article
Knowledge of the spatial distribution and habitat preferences of marine top‐predators is essential for monitoring their populations. The summertime abundance of male sperm whales (parāoa, Physeter macrocephalus) at the Kaikōura Canyon (New Zealand) has almost halved over the last three decades, possibly reflecting a shift in distribution away from...
Article
Measurements of body length play an important role in the assessment of size and population structure of whales, allowing estimation of population parameters such as age at sexual and physical maturity. Uniquely, sperm whales can be measured from the interpulse interval (IPI) of their echolocation clicks, which contain information on the length of...
Article
Full-text available
Hector’s dolphin is a small, endangered dolphin species found exclusively in the inshore coastal waters of New Zealand. We draw on 36 years of involvement in research on Hector’s dolphin, and its subspecies Māui dolphin, to provide an overview of the species’ conservation biology, and summarize the incremental progress towards sustainable managemen...
Article
Full-text available
Cetacean tourism in Aotearoa New Zealand is now over 30 years old and has experienced substantial growth in visitor numbers and operations. The industry is remarkably diverse, targeting several dolphin and whale species, and encompassing varied habitats in coastal waters, fiords and submarine canyons. The knowledge and experience collected over the...
Article
Species distribution models (SDMs) often rely on abiotic variables as proxies for biotic relationships. This means that important biotic relationships may be missed, creating ambiguity in our understanding of the drivers of habitat use. These problems are especially relevant for populations of predators, as their habitat use is likely to be strongl...
Article
• A small population of approximately 68 bottlenose dolphins, Tursiops truncatus, resident in Doubtful Sound, New Zealand, is subject to physiologically challenging conditions, and is exposed to anthropogenic pressure from tourism. • A voluntary Code of Management incorporating dolphin protection zones (DPZs), in which tour boat access is limited,...
Article
Mark rate, or the proportion of the population with unique, identifiable marks, must be determined in order to estimate population size from photographic identification data. In this study we address field sampling protocols and estimation methods for robust estimation of mark rate and its uncertainty in cetacean populations. We present two alterna...
Article
The broadnose sevengill shark (Notorynchus cepedianus) is a common high trophic level predator around coastal New Zealand. Data on the ecology of the species in New Zealand are severely lacking and anthropogenic impacts are unquantified. To partially address this, we undertook a study of the demographics of a population at Stewart Island. Sampling...
Preprint
Full-text available
The New Zealand Ministry for Primary Industries (MPI) developed a risk analysis for Hectors and Maui dolphins, in order to inform protection options being considered by the Ministers of Fisheries and Conservation. Unfortunately, the MPI risk analysis combines several estimates that are biased, and the biases consistently act together to underestima...
Article
Full-text available
The North Atlantic right whale Eubalaena glacialis (NARW), currently numbering <410 individuals, is on a trajectory to extinction. Although direct mortality from ship strikes and fishing gear entanglements remain the major threats to the population, reproductive failure, resulting from poor body condition and sublethal chronic entanglement stress,...
Preprint
Full-text available
EXECUTIVE SUMMARY Updated population viability analyses, incorporating the latest abundance and bycatch data indicate that: The estimated population decline for Maui dolphin is 2% per year There is a 68% probability that the population is continuing to decline After 30 years (6 more surveys) statistical power of detecting this rate of decline would...
Article
Studying inter-individual variation in foraging by top predators is key for understanding the ecology of their populations, while knowledge of seasonal variability in foraging helps explain temporal changes in habitat use and ecological role. We investigated the inter-individual and seasonal differences in stable isotope ratios of sperm whales Phys...
Article
Many species of marine predators display defined hotspots in their distribution, although the reasons why this happens are not well understood in some species. Understanding whether hotspots are used for certain behaviours provides insights into the importance of these areas for the predators’ ecology and population viability. In this study, we inv...
Article
Earthquakes can significantly impact ecosystem function and survivability of marine organisms, however their effect on marine predators remains unknown. In November 2016, a 7.8 magnitude earthquake triggered a ‘canyon flushing’ event in the submarine canyon of Kaikōura (New Zealand), a year-round foraging ground for sperm whales (Physeter macroceph...
Article
Full-text available
Quantifying the distribution of prey greatly improves models of habitat use by marine predators and can assist in determining threats to both predators and prey. Small epipelagic fishes are important prey for many predators yet their distribution is difficult to quantify due to extreme patchiness. This study explores the use of recreational grade e...
Article
Several dolphin species occur close inshore and in harbours, where underwater noise generated by pile-driving used in wharf construction may constitute an important impact. Such impacts are likely to be greatest on species such as the endangered Hector's dolphin (Cephalorhynchus hectori), which has small home ranges and uses this habitat type routi...
Article
Full-text available
Autonomous recorders are frequently used for examining vocal behaviour of animals, and are particularly effective in remote habitats. Southern right whales are known to have an extensive acoustic repertoire. A recorder was moored at the isolated sub-Antarctic Auckland Islands for a year to examine whether the acoustic behaviour of southern right wh...
Article
Impact pile-driving generates loud underwater anthropogenic sounds, and is routinely conducted in harbours around the world. Surprisingly few studies of these sounds and their propagation are published in the primary literature. To partially redress this we studied pile-driving sounds in Lyttelton Harbour, New Zealand, during wharf reconstruction a...
Article
Marine mammal populations often have “hotspots” of distribution. Understanding what drives these is important for understanding relationships with habitat and evaluating exposure to threats. Few studies investigate the stability of hotspots, yet this information is vital in assessing their importance. In this study, over 9,000 sightings made during...
Article
Full-text available
Humpback whales (Megaptera novaeangliae) congregate to breed during the austral winter near tropical islands of the South Pacific (Oceania). It has long been assumed that humpback whales from Oceania migrate primarily to Antarctic feeding grounds directly south (International Whaling Commission Management Areas V and VI); however, there are few rec...
Article
Full-text available
Passive acoustic detectors are widely used for monitoring distribution of cetaceans. Autonomous visual methods are less frequently employed; they are limited to detections during daylight and good weather, but offer potential advantages due to certainty of species’ identification and longevity of deployment. To compare performance of acoustic and v...
Article
Full-text available
Southern right whales (Eubalaena australis) were widespread in New Zealand waters before commercial whaling in the nineteenth century caused drastic declines in their abundance and distribution. Following the cessation of whaling, the population has been recovering and is now slowly recolonising its former range. Estimates of population demographic...
Article
Full-text available
We describe a simple system enabling accurate measurement of swimming marine mammals and other large vertebrates from low-altitude single-frame photogrammetry via inexpensive modifications to a “prosumer” unmanned aerial vehicle (UAV) equipped with gimballed micro4/3 camera and 25 mm lens. Image scale is established via an independently powered LID...
Article
Photo-identification is an invaluable method for documenting associations. Based on the assumption that individuals photographed close together in time are physically close in space, the metadata associated with digital photography offers an opportunity to base association analyses on time between images. This was tested via analysis of association...
Article
Full-text available
As awareness of the effects of anthropogenic noise on marine mammals has grown, research has broadened from evaluating physiological responses, including injury and mortality, to considering effects on behavior and acoustic communication. Most mitigation efforts attempt to minimize injury by enabling animals to move away as noise levels are increas...
Article
Full-text available
Quantitatively describing the acoustic repertoire of a species is important for establishing effective passive acoustic monitoring programs and developing automated call detectors. This process is particularly important when the study site is remote and visual surveys are not cost effective. Little is known about the vocal behavior of southern righ...
Article
Full-text available
A central question to any understanding of ecology is how animals use their habitat, and how habitat use is influenced by temporally changing features of the environment. Previous research on Hector's dolphins at Akaroa Harbour, New Zealand suggested that dolphins leave inshore, harbour environments during or after rough weather. To test this hypot...
Chapter
Monitoring echolocation using SAMs—static acoustic monitors—such as T-PODs or, more recently, C-PODs—has provided a wealth of information on the fine-scale distribution and activity of dolphins, porpoises and other toothed whales. Effects of marine construction noise on these animals have been identified at much longer ranges than expected. Strong...
Article
Full-text available
ABSTRACT: For threatened species or populations, variation in reproductive success among females may be explicitly linked with vulnerability to extinction. Thus an understanding of factors that may cause variability in reproductive success is important. The population of bottlenose dolphins in Doubtful Sound, New Zealand, has a recent history of ra...
Article
Full-text available
Climate change is likely to result in continued warming of the oceans and an in - crease in the frequency and intensity of storms. To gain some insight into how such changes might affect little penguins, we studied how variation in sea surface temperature, chlorophyll a concentrations and the occurrence of severe storms affected little penguin Eudy...
Article
Full-text available
Declines in the abundance of bottlenose dolphins in the Bay of Islands and in Doubtful Sound have contributed to the species being classified as Nationally Endangered in New Zealand waters. Updated information on distribution and abundance nationwide is therefore a high priority. This study presents data from the first photo-identification surveys...
Article
Full-text available
AimTo develop and validate a model for fine-scale distribution of southern right whales (Eubalaena australis) on their calving grounds, accounting for breeding status.LocationPort Ross, a harbour at the northern end of the sub-Antarctic Auckland Islands, approximately 450 km south of mainland New Zealand.Methods Species–habitat surveys were conduct...
Article
Full-text available
Understanding the reproductive parameters of very small or declining populations is of clear importance to conservation. From 1995 to 2011 we recorded calf production (n = 71) and calf survival for 27 breeding females in the bottlenose dolphin (Tursiops truncatus) population in Doubtful Sound, New Zealand; a population with a recent history of decl...
Article
Full-text available
Coastal cetaceans are increasingly being exposed to boats and noise as nature tourism grows. Such activity has a wide range of detrimental effects on the surface behaviour of cetaceans, but effects on their acoustic behaviour are poorly understood. We quantified the effects of tour boats and of the observing research boat on the group structure and...
Article
Full-text available
Collecting enough data to obtain reasonable abundance estimates of whales is often difficult, particularly when studying rare species. Passive acoustics can be used to detect whale sounds and are increasingly used to estimate whale abundance. Much of the existing effort centres on the use of acoustics to estimate abundance directly, e.g. analysing...
Conference Paper
Full-text available
Southern right whales (SRWs) were decimated by whaling in the 1800s and are currently making a comeback around New Zealand. The sub-Antarctic Auckland Islands particularly Port Ross, a sheltered inlet, represents their stronghold and primary calving grounds in New Zealand waters. Due to the remote location of these islands little is known about SRW...
Article
Full-text available
Observations are presented of the vocal behavior and three dimensional (3D) underwater movements of sperm whales measured with a passive acoustic array off the coast of Kaikoura, New Zealand. Visual observations and vocal behaviors of whales were used to divide dive tracks into different phases, and depths and movements of whales are reported for e...
Article
Full-text available
A non-invasive acoustic method for measuring the growth of sperm whales was developed based on estimating the length of individuals by measuring the inter-pulse interval (IPI) of their clicks. Most prior knowledge of growth in male sperm whales has come from from fitting growth curves to length data gained from whaling. Recordings made at Kaikoura,...
Article
Full-text available
Data-logging devices are commonly used to study the foraging behaviour of individual seabirds. Such studies need to examine the potential effects of using devices on instrumented individuals, not only for ethical reasons but also to ensure the validity of data gathered. We studied the effects of two types of device (time-depth recorder and global p...
Article
Full-text available
We studied habitat use by Hector's dolphins Cephalorhynchus hectori in order to quantify the influences of location, season, time and tide, and to determine how frequently dolphins use inner Akaroa Harbour where unattended gillnetting is allowed for 6 mo of the year (1 April to 30 September). T-POD acoustic dataloggers were moored in outer, mid- an...
Article
Full-text available
Data on the distribution and abundance of Hector's dolphins (Cephalorhynchus hectori) along the Otago coastline, between Taieri Mouth and Ōamaru (approximately 130 km alongshore), were collected in 2010–2011. Alongshore surveys were conducted in small boats, travelling approximately 400 m from shore, at speeds of 10 to 15 knots. Photographic identi...
Article
Full-text available
Patterns of habitat use by wide-ranging animals may change in response to perturbations within their environment. In 2009, a group of 15 bottlenose dolphins, known to be part of the population in Doubtful Sound, New Zealand, were seen in another nearby fiord. This popula- tion has been closely monitored since 1990, and this was the first time that...
Article
Full-text available
The harbour porpoise Phocoena phocoena is one of the small cetacean species most frequently caught in gillnets. Understanding how this occurs is important to devising effective mitigation strategies. To assess the distance at which harbour porpoises can detect and avoid gillnets, Nielsen et al. (2012; Mar Ecol Prog Ser 453:241-248) quantified the m...
Article
Full-text available
Active sound emitters ('pingers') are used in several gillnet fisheries to reduce bycatch of small cetaceans, and/or to reduce depredation by dolphins. Here, we review studies conducted to determine how effective these devices may be as management tools. Significant reductions in bycatch of harbour porpoise Phocoena phocoena, franciscana Pontoporia...
Chapter
Full-text available
This species is considered to be Endangered A4d due to an ongoing and projected decline of greater than 50% over 3 generations (approx. 39 years, Slooten et al. 2000) considering both the past and the future. It is also important to consider that although its extent of occurrence and area of occupancy likely exceed the thresholds for criteria B1, B...
Article
Full-text available
Southern right whales (Eubalaena australis) were virtually extirpated from New Zealand by commercial whaling, but are now recovering. Previous research at the Auckland Islands has suggested that Port Ross, a sheltered embayment at the northern end of the islands, is the primary calving ground for right whales in New Zealand. However, an abundance o...
Article
Full-text available
Stomach contents of 63 Hector's dolphins (Cephalorhynchus hectori) were collected between 1984 and 2006 from throughout New Zealand to provide the first quantitative assessment of prey composition. Twenty-nine taxa were identified. Those most commonly consumed were red cod (Pseudophycis bachus), ahuru (Auchenoceros punctatus), arrow squid (Nototoda...
Article
1. Marine protected areas (MPAs) have been advocated for the protection of threatened marine mammals, but there is no empirical evidence that they are effective. In 1988, the Banks Peninsula Marine Mammal Sanctuary was established to reduce gillnet mortalities of Hector’s dolphin Cephalorhynchus hectori, an endangered dolphin species endemic to New...
Article
Full-text available
Wellington, New ZealandDOC Science Internal Series is a published record of scientific research carried out, or advice given, by Department of Conservation staff, or external contractors funded by DOC. It comprises progress reports and short communications that are generally peer-reviewed within DOC, but not always externally refereed. Fully refere...
Article
Full-text available
1. Mark–recapture studies are often used to estimate adult survival probability , which is an important demographic parameter for long-lived species, as it can have a large impact on the population growth rate. We consider the impact of variation in capture probability among individuals (capture heterogeneity) on the estimation of ϕ from a mark–rec...
Article
Full-text available
Passive acoustic methods are increasingly used to study cetacean habitat use and behaviour. The Timing Porpoise Detector (T-POD; www.chelonia.co.uk) is a self-contained acoustic data logger, which records echolocation by cetaceans. This study used nine T-PODs to document habitat use by bottlenose dolphins in Doubtful Sound, New Zealand, over a 12-m...
Conference Paper
Full-text available
In New Zealand, the Southern right whale (SRW) is recovering from near extinction due to commercial whaling. The Auckland Islands (AI), particularly Port Ross, represent the stronghold for SRWs in NZ waters, and are likely their primary calving grounds. Although well-studied in some right whale populations, acoustic behaviour of SRWs has received l...
Article
We applied temporal symmetry capture–recapture (TSCR) models to assess the strength of evidence for factors potentially responsible for population decline in bottlenose dolphins (Tursiops truncatus) in Doubtful Sound, New Zealand from 1995 to 2008. Model selection was conducted to estimate recruitment and population growth rates. There were similar...
Article
Full-text available
Passive acoustic surveys have potential for detecting trends in abundance and habitat use by rare cetaceans. We deployed commercially available acoustic data loggers (T-PODs) in 4 harbours on the west coast of New Zealand's North Island between 2005 and 2008 to investigate the distribution of Maui's dolphin Cephalorhynchus hectori maui and assess w...