Otago Peninsula Research Articles

Drivers of neritic water intrusions at the subtropical front along a narrow shelf

The near-ubiquitous presence of freshwater over the inner to mid-continental shelf off of the Otago Peninsula in southeast Aotearoa/New Zealand has been previously identified in long-term cross-shelf transects. Occasional influxes of this silicate-rich neritic water past the shelf break and beyond the Subtropical Front have been observed, potentially supporting elevated chlorophyll-a concentrations in SubAntarctic waters. Nearshore salinity variability has been connected to flow rates of the Clutha River, Aotearoa’s largest river by discharge, however, other physical mechanisms influencing the structure of freshwater along this coast have not been explicitly explored. A numerical model of Aotearoa’s southeast continental shelf forced with realistic discharge from the Clutha River is used to assess the drivers of river plume variability and identify conditions associated with the transport of neritic water beyond the shelf break. Event scale, lagged correlation, EOF, and composite analysis of a model passive dye tracer revealed three generalised plume structures that are dependent on river discharge, along-front wind stress, and shelf current velocities. Downfront wind stress suppresses bulge formation at the river mouth and constrains the river plume against the coast, whereas upfront wind stress causes the river plume to move offshore over the shelf and spread across the upper water column. Rarely, upfront wind stress generates a nearshore current reversal over the shelf, causing the plume to deflect straight off-shelf and across the shelf edge before meeting the frontal current and advecting to the northeast. Future observational work is required to validate the mechanisms described and address the biological implications of these findings.

Episodic Summer Chlorophyll‐a Blooms Driven by Along‐Front Winds at Aotearoa's Southeast Shelf Break Front

AbstractThis study investigates the influence of along‐front wind forcing on chlorophyll‐a (Chl‐a) at the Otago Shelf Break (OSB) in southeast Aotearoa/New Zealand using remotely‐sensed and in situ data. Summer wind stress over the OSB was shelf‐aligned, oscillating between upfront and downfront. Surface Chl‐a concentrations along the OSB were shown to increase episodically (≤10 days duration) following upfront wind stress. This response occurred over most of the 350 km long shelf break, and was most intense north of the Otago Peninsula. Peak Chl‐a enhancement at the shelf break occurred following periods of upfront winds, exhibiting a lagged response of approximately 5 days. Moored thermistor data indicated that upfront wind events were followed by increased thermal stratification over the mid‐shelf, whereas downfront wind events were followed by a well‐mixed water column. In situ temperature, salinity, and nutrient measurements suggested an offshore movement of the surface expression of the front following upfront winds, and a reduction in nitrate over the shelf break. From these observations a model of Ekman restratification driven by upfront winds is proposed for this system, wherein off‐shelf Ekman transport converts strong horizontal isopycnal gradients at the shelf break front into vertical stratification. This stratification holds phytoplankton in the upper water column, allowing increased access to light, which is marked by the increased drawdown of nitrate at the shelf break. Downfront winds break down this stratification, move the shelf break front onshore, and mix phytoplankton through the water column, reducing the surface expression of chlorophyll.

Inorganic geochemistry of saline substrates associated with coastal turf, Otago Peninsula, New Zealand

ABSTRACT Halophytic plant communities have developed on exposed coastal landforms to form low-stature turf in several locations around New Zealand. We quantify the inorganic geochemistry, mineralogy and simulated ephemeral surface water composition of saline soil-free bare ground at a well-preserved site at Maori Head on Otago Peninsula, where halophytes have colonised from adjacent coastal turf. The community at this site is dominated by Leptinella dioica, Samolus repens, Disphyma australe and Selliera radicans. Maori Head substrates are dominated by clay-altered basalt colluvium and show a general trend from high electrical conductivity (EC > 10 mS/cm) and weakly acid pH (< 6) on bare ground to low EC (< 1 mS cm−1) and higher pH (> 7) in turf and adjacent pasture soils. High salinities on dry substrates and in simulated ephemeral surface waters result from surface evaporation of airborne sea spray and contain halite (NaCl) with some gypsum (CaSO4.2H2O). Chemical interactions with the substrate are minor. The high surface salinities were maintained despite a major winter rain event with strong onshore winds. However, surface salinity is frequently leached by rain and shallow groundwater, whereas inland saline sites (pH 8–11) have substantial salt accumulations driven by lower rainfall, high evaporation and chemical interaction with Otago Schist-derived substrates.

Staying close to home: Marine habitat selection by foraging yellow-eyed penguins using spatial distribution models

Endangered yellow-eyed penguins (Megadyptes antipodes) are central-place, benthic-diving foragers that search for prey in the productive marine areas off the coast of the South Island, New Zealand. Like other seabirds, they target specific, reliable areas of high prey abundance, which are often associated with oceanographic characteristics such as bathymetry, seafloor sediment type, and sea surface temperature. Employing GPS tracking data collected between 2003 and 2021, we created species distribution models using maximum entropy modelling (Maxent) to determine foraging space use and habitat suitability for yellow-eyed penguins across their entire South Island range and within five distinct subpopulations: Banks Peninsula, North Otago, Otago Peninsula, the Catlins, and Stewart Island. We quantified the importance of environmental variables for predicting foraging site selection during and outside the breeding season. Significant regional variation existed in predicted probability of penguin presence, and proximity to the nearest breeding area was a key predictor of suitable foraging habitat. When distance was not included in the models, dissolved oxygen concentration was the most important predictor in the overall South Island model and the North Otago, Otago Peninsula, and the Catlins subpopulation models, whereas water current speed and mean monthly turbidity were most important in Banks Peninsula and Stewart Island subpopulation models, respectively. Dynamic variables related to prey availability were often the most important variables in model predictions of the habitat selection of yellow-eyed penguins. Visualisations and findings from this study, particularly of the observed interactions between penguins and their marine habitat, can be used to direct conservation and resources during marine spatial planning and species management.

‘It’s not like any survey I’ve ever seen before’: Discrete Choice Experiments as a Valuation Technology

This paper unpacks what happened when members of the local community were invited to design and test a valuation tool – specifically a discrete choice experiment – to find a valuation for New Zealand’s Otago Peninsula. We argue that the assumptions that lie within a discrete choice experiment are revealed when we look closely at how community participants react to the discrete choice experiment survey they have helped design. These assumptions, usually unnoticed, include the necessity of making trade-offs; what actions are possible; the ‘reality’ of one’s preference structures; the need for abstraction; and the importance of big picture patterns. We also argue that how these assumptions are negotiated in practice depends on complex power relationships between researchers, participants, and the technology itself. While we might seek to ‘empower’ the community with knowledge of economic processes and valuation practices, this might not be the empowerment they seek. Participants find ways to be active negotiators in the face of valuation technologies.

The Face of Nature: An Environmental History of the Otago Peninsula.

It is a tricky thing when one is asked to review a book on something that pervades your existence, your work and your whānau. Jonathan West’s book writes an environmental history of the Otago Peninsula. I have grown up at Ōtākou, the small village at the eastern edge of the Peninsula. I grew up looking across from the east to the west, I close my eyes and could draw an outline of the hills that embrace Aramoana and Port Chalmers. I have been told that Jonathan grew up at Port Chalmers, alternatively looking across from the west to the east, to the Otago Peninsula. This is perhaps where his connections to this piece of land sprung from. His book illustrates his passion for the Otago Peninsula and its interaction with all inhabitants from time immorial.

WASTING AWAY IN THE INTERTIDAL: THE FATE OF CHITON VALVES IN AN ACIDIFYING OCEAN

Chitons are locally common in New Zealand, and several studies have suggested that their valves are resistant to dissolution, so it seems contradictory that they are under-represented in the sediment and fossil records of New Zealand. Indeed, special resistance to dissolution seems counterintuitive since the valves are primarily made of aragonite. Here we examine the resistance of chiton skeletal material to dissolution in order to expand our understanding of how taphonomic forces affect chitons and to provide insight into the preservation potential of chiton valves. Live individuals of eight species of chitons were collected from Otago Peninsula, South Island, New Zealand. The valves were subjected to one of two pH treatments: ambient pH of 8.10 and reduced pH of 7.70. Notoplax violacea, Sypharochiton pelliserpentis, and S. sinclairi were the most resistant to dissolution while Acanthochitona zelandica, Chiton glaucus, Onithochiton neglectus, and Ischnochiton maorianus were more vulnerable to dissolution. Leptochiton inquinatus lost the most mass in both treatments, but did not show a significant difference between them. SEM images of the dorsal and ventral surfaces on each valve revealed low-pH damage to crystal structures in the articulamentum, while the tegmentum showed no significant damage. Chiton skeletal material in general does not appear to resist dissolution any better than other examined mollusks, but the resistant tegmentum confers considerable resilience to lowered pH. Chiton valves can last up to an estimated 45 years before becoming unrecognizable, which is much shorter than the normal temperate shallow-water exposure time of hundreds to thousands of years.

Environmental change, resilience, and adaptation in nature-based tourism: conceptualizing the social-ecological resilience of birdwatching tour operations

Resilience theory has emerged as a holistic concept well suited to analyzing tourism systems and which promises important insights into the sustainability of tourism destinations in the face of accelerating global environmental change (GEC). This article presents empirical research into the social-ecological resilience of tour operators using the case study destination of the Otago Peninsula, Dunedin, New Zealand. It addresses the following research question: How do birdwatching tour operators build resilience to drivers of environmental change, including climatic drivers, into their operations? Qualitative interviews with providers of a specific nature tourism sector activity – birdwatching – were conducted with stakeholders including tour operators, conservation organizations, and local government members. The findings highlight current and possible future challenges to birdwatching tourism on the Otago Peninsula. The paper introduces a conceptual framework which highlights the tour operators’ main coping strategies in response to key perceived social-ecological system (SES) drivers of change. Overall, tour operators perceived their main social-ecological resilience to be the diversity of the species of the Otago Peninsula, their business experience, and the strength of their local stakeholder network to respond to SES crises.

Isotopic signatures in Mytilus galloprovincialis and Ulva latuca as bioindicators for assessing discharged sewage effluent in coastal waters along Otago Peninsula, New Zealand

ABSTRACTSewage, waste organic matter from domestic and municipal wastewater, causes increased secondary productivity, eutrophication and trace metal contamination, reduced oxygen levels, and biodiversity which can lead to ecological disturbances in the natural aquatic ecosystem. The impact of sewage-derived organic matter (SDOM) on the nearshore marine ecosystem of the Otago Coast was assessed before, and 15 years after upgrade of the Dunedin sewage treatment plant. Carbon and nitrogen isotopic ratios in the tissues of sentinel organisms were used as bioindicators to elucidate the primary sources of nutrition the coastal environment. Mytilus galloprovincialis, a marine bivalve, exhibited a strong influence of SDOM from two sites in 2001. In 2015, M. galloprovincialis had a trophic enrichment factor of 3‰ (δ15N) and 1‰ (δ13C) when compared to the marine particulate organic matter (POM), suggestive of a dietary change away from the SDOM. Suspended POM collected from riverine and estuarine sources revealed other possible nitrogen sources from human-driven activities such as pastoral farming, application of organic manure and inorganic fertilisers, nitrification of ammonium from semi-urban septic tanks, and animal organic waste residues.

Abrasion provides clues on a chiton taphonomic conundrum

Chitons are common marine invertebrates found worldwide that use aragonite to form their shell and are rare in the sedimentary and fossil records. Their rarity in the fossil record is interesting due to how abundant live chitons are. Previous work suggests that chitons resist dissolution, which appears inconsistent with their rarity in the sediment and fossil records and aragonite composition. This result warrants examination of other taphonomic processes on chiton skeletal material since other taphonomic processes may play a larger role in removal than previously thought. As many chitons are intertidal, mechanical abrasion of chiton valves is likely to occur; its extent is largely unknown and yet necessary to provide insight to the taphonomy of chiton material. Eight species of chitons were collected from the Otago Peninsula, South Island, New Zealand. A total of 129 valves were isolated, cleaned, weighed, and tumbled in a Lortone 3A rock tumbler for 96 h. The valves from each species lost an average of between 9 and 44% of their weight; damage varied among species. Leptochiton inquinatus (the sole lepidopleuran) lost the most material while the acanthochitonids (Acanthochitona zelandica, and Notoplax violacea) and the chitonids (Chiton glaucus, Onithochiton neglectus, Sypharochiton pelliserpentis, and S. sinclairi) were more resistant to abrasion. The dorsal layer of the valves (the tegmentum), which is penetrated by aesthete tissue and has a granular crystal microstructure, was the most damaged by abrasion in all species. The ventral layer (the articulamentum), which has a highly-organised crystal structure with fewer organic components than the tegmentum, showed the least signs of abrasion. Since abrasion reduces the tegmentum and changes the valve shape, it is likely that abraded chiton material is present but unrecognisable in the fossil record. The valves are estimated to last about seven years when in the intertidal zone when enduring abrasion alone, which is much less than the hundreds to thousands of years material is exposed.

Mate choice explains high genetic diversity in a small founding population of the New Zealand sea lion (Phocarctos hookeri)

Founder populations are susceptible to reduced genetic diversity, which can hinder successful population establishment. A new genetic lineage of the New Zealand sea lion (Phocarctos hookeri) has recently colonised the historical range of the New Zealand mainland (Otago Peninsula). Despite a small founding population, previous research indicated that nuclear genetic diversity in the Otago Peninsula population is similar to that of the larger source population (Sandy Bay, Auckland Islands). Our research aimed to identify whether mechanisms of female mate choice could help to explain the unexpectedly high level of genetic diversity in the founder population. We used genetic data at 12 microsatellite loci for mother–pup pairs from both populations, and the software COLONY to identify putative paternal genotypes inferred from allele sharing between known mother–pup pairs. We found that mating pairs were, on average, more related at the Otago Peninsula location. However, Sandy Bay females were mating with males more related to themselves than expected by chance, while the Otago Peninsula females were not. These findings suggest that female choice in this otariid species appears important, although may be constrained in some situations. Our findings also help to explain how the recently founded population is able to maintain a viable, growing population.

Understanding Aotearoa’s past through the recovery and conservation of a 15th-century canoe and its fibrework from Papanui Inlet, Otago Peninsula

When Tasman and Cook arrived in New Zealand in 1642 and 1769 respectively they both sighted double-hulled canoes ('waka') on New Zealand's coast. However, over the next 100 or so years these canoes disappeared. Fortuitously the recent rescue and conservation of a waterlogged 'waka' and fibrework assemblage on the shores of Papanui Inlet has allowed rare insight into the lives of its inhabitants nearly 550 years ago, when New Zealand's seminal migrants established themselves in the remote south of New Zealand. These discoveries reinforce traditional stories around early Maori occupation of Te Waipounamu and offer additional clarification of 'iwi' 'tribal' activities in their local environment many generations ago. Conservation of these 'taoka' 'treasures' on Otakou Marae has provided easy, continuous access for descendants of the 'waka' to their 'taoka' throughout the process and aided the development of constructive relationships for 'iwi' and conservation and archaeological agencies. Here we discuss recent fieldwork with an emphasis on conservation, cross-cultural engagement and the assemblage recovered to date, followed by comparison of the waka reported here with another discovered within the Te Runanga o Otakou 'rohe' 'territory' over 120 years ago by Elsdon Best. Imminent investigations to excavate cultural material from Papanui Inlet's actively degrading coastline are scheduled for January 2018, and the resulting environmental and archaeological information from this research will be discussed fully elsewhere.

Unique and isolated: population structure has implications for management of the endangered New Zealand sea lion

Female otariids (eared seals) frequently display strong levels of philopatry, a behaviour that has the potential to influence population structure, particularly at the mitochondrial level. Conversely, male otariids often move between breeding colonies, likely facilitating nuclear gene flow between colonies. Such gender-specific movements have the potential to influence species population structure. Here we investigate the genetic population structure of the endangered New Zealand (NZ) sea lion, using nuclear (microsatellite) and mitochondrial molecular markers, with the intention to better inform conservation through identification of management units for the species. The strong levels of female philopatry in this species have potential to lead to population structure at the mitochondrial loci. In contrast, weak or no population structure is expected across nuclear loci. NZ sea lions were sampled from the main breeding areas across the species’ current distribution (three Auckland Islands sites, two Campbell Island sites, one Stewart Island site and one Otago Peninsula site). Individuals were screened for microsatellite (n = 271; 16 loci) and mitochondrial (n = 56; 1027 bp D-loop and 1189 bp cytb). Despite a small (c. 9880 individuals) population size, moderate levels of microsatellite variation are observed in the NZ sea lions, in contrast to low levels of mitochondrial genetic variation. Results from mitochondrial DNA analyses revealed no population structure, suggesting that the strong level of female philopatry in NZ sea lions alone is not sufficient to maintain genetic population structure. Due to the frequent male movements between breeding colonies, no population structure was detected across the nuclear loci either. The absence of genetic structure suggests that, from a genetic perspective, NZ sea lions can be considered to be a single population. Despite this, the differing impacts of threats (e.g. fisheries by-catch) to each individual breeding colony must also be taken into consideration when defining management units for this endangered species.

Investigation of a mortality cluster in wild adult yellow-eyed penguins (Megadyptes antipodes) at Otago Peninsula, New Zealand

ABSTRACTWe investigated an epidemic mortality cluster of yellow-eyed penguins (Megadyptes antipodes) that involved 67 moribund or dead birds found on various beaches of the Otago Peninsula, New Zealand, between 21 January and 20 March 2013. Twenty-four carcases were examined post-mortem. Histological lesions of pulmonary, hepatic and splenic erythrophagocytosis and haemosiderosis were found in 23 of 24 birds. Fifteen birds also had haemoglobin-like protein droplets within renal tubular epithelial cells. Despite consistent histological lesions, a cause of death could not be established. Virology, bacteriology and molecular tests for avian influenza, avian paramyxovirus-1, avipoxvirus, Chlamydia psittaci, Plasmodium spp., Babesia spp., Leucocytozoon spp. and Toxoplasma gondii were negative. Tissue concentrations of a range of heavy metals (n = 4 birds) were consistent with low level exposure, while examination of proventricular contents and mucus failed to detect any marine biotoxins or Clostridium botulinum toxin. Hepatic concentrations of total polycyclic aromatic hydrocarbons (PAHs) (n = 5 birds) were similar to background concentrations of polycyclic aromatic hydrocarbons previously found in yellow-eyed penguins from the South Island of New Zealand, but there were significantly higher concentrations of 1-methylnapthelene and 2-methylnapthelene in the birds found dead in this mortality cluster. The biological significance of this finding is unclear. A temporal investigation of the epidemic did not indicate either a common source or propagative epidemic pattern. Although our investigation did not definitively implicate a toxic or infectious agent, we could not rule out causes such as toxic marine organisms or mycoplasmosis. Further investigations should therefore by carried out in the event of future mortality clusters.

Investigator disturbance does not reduce annual breeding success or lifetime reproductive success in a vulnerable long-lived species, the yellow-eyed penguin

Well-studied, long-lived species, such as seabirds, can be exposed to decades of investigator interventions, and if the species is of conservation concern, intensive monitoring and management as well. Most evaluations of impacts of investigator disturbance have been relatively short-term. We evaluated both short- and long-term impacts of investigator disturbance on the yellow-eyed penguin (Megadyptes antipodes) by focusing on both the breeding season during which the impact occurred and lifetime reproductive success (LRS). In long-lived species, reproductive decisions are often trade-offs between current and future reproductive success, and lifetime reproductive success (LRS) can be influenced by many life- history and environmental parameters, including investigator disturbance. Yellow-eyed penguins, a long-lived seabird that has been intensively studied on the Otago Peninsula of South Island, New Zealand for three decades, are known to be vulnerable to human intrusion. Research and monitoring has required banding and band maintenance, handling, blood sampling, stomach flushing, and device deployment. We found no negative effects associated with any investigator disturbance type on breeding success or LRS. Monitoring disturbances (egg, chick and adult handling, band maintenance) that occurred during the egg and chick phases showed a positive association with breeding success and LRS, probably because the longer a nest survived the more likely eggs, chicks, or adults would be handled. There appeared to be a core of resilient individuals with long lifespans and high LRS that may buffer the population despite being exposed to many investigator disturbance events.

Valve microstructure and phylomineralogy of New Zealand chitons.

The microstructure and mineralogy of chiton valves has been largely ignored in the literature and only described in 29 species to date. Eight species: Acanthochitona zelandica, Notoplax violacea (Family Acanthochitonidae, Suborder Acanthochitonina, Order Chitonida), Chiton glaucus, Onithochiton neglectus, Sypharochiton spelliserpentis, Sypharochiton sinclairi (Family Chitonidae, Suborder, Chitonina, Order Chitonida), Ischnochiton maorianus (Family Ischnochitonidae, Suborder Chitonina, Order Chitonida), and Leptochiton inquinatus (Family Leptochitonidae, Suborder Lepidopleurina, Order Lepidopleurida) were collected from the Otago Peninsula, South Island, New Zealand. The valves of these chitons were analysed with X-ray diffractometry, Raman spectrometry, and Scanning Electron Micrography (SEM) to determine their mineralogy and microstructure. Both the XRD and Raman data show that the valves consisted solely of aragonite. The observed microstructures of the valves were complex, typically composed of four to seven sublayers, and varied among species. The dorsal layer, the tegmentum, of each species was granular and the ventral layer, the articulamentum, was predominately composed of a spherulitic sublayer, a crossed lamellar sublayer, and an acicular sublayer. The chitonids Sypharochiton pelliserpentis and S. sinclairi had the most complex microstructure layering with three crossed lamellar, two spherulitic sublayers, and a ventral acicular sublayer while the acanthochitonids Acanthochitona zelandica and Notoplax violacea as well as the ischnochitonid Ischnochiton maorianus had the simplest structure with one spherulitic, one crossed lamellar sublayer, and a ventral acicular sublayer. Terminal valves were less complex than intermediate valves and tended to be dominated by the crossed lamellar structure. The leptochitonid Leptochiton inquinatus generated a unique crossed lamellar sublayer different from the other analysed chitonids. Acanthochitona zelandica is the only analysed chitonid that utilizes two different crossed lamellar structures. Clearly, many of these properties do not reflect the currently recognized polyplacophoran phylogeny.

Seabird guano enhances phytoplankton production in the Southern Ocean

Six incubation experiments were carried out to investigate the phytoplankton biomass response to seabird guano-enrichment under different nutrient regimes. Study locations included Antarctic waters of the Ross Sea and sub-Antarctic waters offshore of the Otago Peninsula, both being characterized by iron limitation of phytoplankton productivity in summer, the Sub-Tropical Frontal Zone offshore of the Snares Islands, which is generally micronutrient-replete, and the island wake waters of the Snares Islands, which have a high nutrient supply from land. In all of the experiments the increase of phytoplankton biomass was higher in the treatments with guano addition compared to the controls. Guano additions were compared to Fe and macronutrients treatments (both added in quantities similar to those in the guano treatment) to shed light on which constituent(s) of guano are responsible for the observed increases in phytoplankton biomass. Macronutrients increased the phytoplankton biomass in the Sub-Tropical Frontal Zone, however, the response was less prominent than in the Guano treatment, suggesting synergetic effects of nutrients in seabird guano on phytoplankton production. It was also found that the pattern of response varied between the water masses with 6–10days lag phase in the Sub-Antarctic water mass and no lag phase in Sub-Tropical Frontal Zone. The calculations presented here suggest that micro- and macronutrients delivered from seabird colonies on some of the sub-Antarctic islands may provide a significant amount of limiting nutrients to the nutrient budget of the surrounding coastal waters, potentially sufficient to sustain a local phytoplankton bloom. Findings of the present study indicate that biological recycling of nutrients by seabirds likely supports marine primary production and enhances productivity of associated food webs in the vicinity of islands.

GIS-based multi-criteria analysis of breeding habitats for recolonising species: New Zealand sea lions

The New Zealand sea lion (Phocarctos hookeri) is a threatened endemic species, with only three breeding colonies in the sub-Antarctic islands. Since 1993, there has been evidence for recolonisation of mainland New Zealand. Yet the coast that the sea lion has returned to only has fragmented and unevenly distributed potential habitats due to coastal urbanisation and development. Therefore, the need to identify and protect potential breeding habitats for recolonisation is a priority for management.A GIS-based multi-criteria analysis was used to identify potential suitable habitats for a 1600 km length of the NZ South Island coast based on distance to anthropogenic disturbance (urban areas, roads), distance to desirable environmental features (beaches, estuaries) and presence of suitable habitat/land access. From this model, we identified preliminary suitable habitat for breeding sites on the Otago Peninsula (east coast) and Catlins Coast (south). We independently detected some of the current dominant areas used by recolonising sea lions as well as identifying some promising new sites.We discuss the limitation of the results of this case study and the need for further data to be added to the model in the face of limited data availability. Overcoming this data limitation will meet an increasing need for a New Zealand-wide study for determining potential habitat for NZ sea lions. The results of such a study would identify areas to allow real-world management (protection or restoration) of the limited potential breeding sites for New Zealand sea lions. This new method could also be used for other recolonising species and encourage management of areas most likely to be recolonized by them.

Seroprevalence of Toxoplasma gondii in mainland and sub-Antarctic New Zealand sea lion (Phocarctos hookeri) populations

AIMS: To investigate the seroprevalence of antibodies to Toxoplasma gondii in New Zealand sea lions (Phocarctos hookeri), as a potential contributor to reproductive failure.METHODS: Archived sera were sourced from New Zealand sea lions from two recolonising mainland populations in the Otago Peninsula (n=15) and Stewart Island (n=12), as well as a declining population at Enderby Island (n=28) in the New Zealand sub-Antarctic. Sera were tested for antibodies to T. gondii using a commercially available ELISA (with samples considered positive if the sample to positive ratio was >30%), and latex agglutination test (LAT; with titres ≥1:32 considered positive). Western blot analysis was used to validate the results of a subset of 14 samples.RESULTS: Five samples from sea lions in mainland locations were confirmed positive for antibodies to T. gondii. Two adult females exhibited high LAT antibody titres (min 1:2048, max 1:4096) on both occasions when sampled 1 and 2 years apart, respectively. No animals from Enderby Island were seropositive.CONCLUSIONS: Toxoplasma gondii infection is unlikely to be a major contributor to poor reproductive success in New Zealand sea lions. However, continued surveillance is pertinent to assess subclinical and clinical impacts of the parasite on these threatened populations. The commercial tests evaluated here, with further species-specific threshold refinement could provide a fast, inexpensive and reliable indicator of T. gondii exposure in New Zealand sea lions.

Investigation of an outbreak of craniofacial deformity in yellow-eyed penguin (Megadyptes antipodes) chicks

AIM: To investigate an outbreak of severe craniofacial deformity in yellow-eyed penguin (Megadyptes antipodes, hōiho) chicks at a single breeding site on the Otago Peninsula in the South Island of New Zealand.METHODS: Morbidity and mortality of yellow-eyed penguins breeding on the coastal regions of Otago was monitored from November 2008 to March 2009. Dead chicks and unhatched eggs were recovered and examined. Between October and December 2008 32 eggs were recorded at 17 nests in the Okia Reserve. Eleven chicks survived to about 90 days of age, of which eight were found to have moderate to severe craniofacial deformity. The six most severe chicks were subject to euthanasia and examined in detail at necropsy, and the remaining two affected chicks were released to the wild after a period of care in a rehabilitation centre. Post-mortem samples were analysed for inorganic and organic toxins.RESULTS: The six deformed chicks all had severe shortening of the mandible and maxilla by 20−50 mm. The rostral and caudal regions of the skull were approximately 40 and 80% of normal length, respectively. Other, more variable lesions included crossbill deformity, malformed bill keratin, microphthalmia with misshapen scleral ossicles and oral soft tissue excess thought to be secondary to bony malformations. During the same year, mild sporadic bill deformities were also reported in 10 unrelated chicks from >167 chicks at other breeding sites on the southern Otago coast. Concentrations of organic toxins and heavy metals in body tissues from affected chicks were apparently similar to those in unaffected chicks on other beaches.CONCLUSIONS: No cause of this outbreak of craniofacial deformity could be established although the high prevalence at a single site suggests that it was due to an unidentified local teratogen.