Hauraki Gulf Research Articles

Influences on recovery of seabirds on islands where invasive predators have been eradicated, with a focus on Procellariiformes

AbstractProtecting seabirds is a global conservation priority given that 29% of seabird species are threatened with extinction. One of the most acute threats to seabirds is the presence of introduced predators, which depredate seabirds at all life stages, from eggs to adults. Consequently, eradication of invasive predators has been identified as an effective and commonly used approach to seabird conservation. Seabird recovery following the eradication of predators is influenced by complex and interacting environmental and demographic factors, and there are gaps in our understanding of species-specific responses. We reflect on the recovery of seabirds on islands cleared of predators, drawing on the equilibrium theory of island biogeography, and synthesize key influences on recovery reported in the literature. We present a regionally specific case study on the recovery of seabird colonies (n = 98) in the Hauraki Gulf, New Zealand, which is a hotspot of seabird diversity (27 species), with a long history of eradications of invasive predators. We found that on islands cleared of predators seabirds recover over time, and such islands have more diverse seabird assemblages than islands that never had predators. Recovery appears to be influenced by a suite of site- and species-specific factors. Managers may assume that given enough time following eradication of predators, seabirds will recolonize an island. Although time is a factor, proximity to source populations and human activities has a significant effect on recolonization by seabirds, as do demographic traits, colonizing ability and habitat suitability. Therefore, integrating expected site and species-specific recovery responses in the planning of eradications should help guide post-eradication management actions.

Waiheke Island: An island paradise facing an uncertain future

Waiheke Island in Auckland's Hauraki Gulf shares similarities with once isolated coastal areas on the periphery of large cities. Now a commuter suburb and popular tourist destination only a 35‐min ferry ride from downtown Auckland, it is under increasing development pressure. However, it remains differentiated from other urban fringe settings by dimensions of its islandness: weak infrastructure, restricted transportation networks and robust community politics. The resulting pressure on infrastructure and services is now being compounded by debates related to the Auckland housing crisis. This report, based on interviews with permanent and part‐time residents, explores competing imaginaries of the island's futures.

Rotoroa Island: building a designed ecosystem for conservation education, training and visitor engagement

Wildlife populations around the world are declining and becoming increasingly fragmented, and management efforts to support them have become more intensive. This means that the delineation between extensive wildlife‐management systems (e.g. in national parks or large wildlife reserves) and intensive systems (e.g. zoos and aquariums) is becoming increasingly blurred. Furthermore, attitudes about how people fit into a traditional conservation or ecosystem‐restoration framework are being challenged. In partnership with the Rotoroa Island Trust, Auckland Zoo in New Zealand is delivering a project on Rotoroa Island, which is located in the Hauraki Gulf. The aim of this project is to contribute to the conservation of wildlife, through education, training and visitor‐engagement activities. To this end, Auckland Zoo has translocated seven native species to the Island, all selected to demonstrate a range of techniques across the spectrum of intensive and extensive wildlife‐management systems. The creation of a designed ecosystem, primarily directed towards servicing education and training programmes, is unique in New Zealand. This project also aims to demonstrate an ecosystem where human intervention is integral to enabling higher levels of biodiversity in the available area than would otherwise be possible. At the time of writing the Rotoroa Wildlife Management and Translocation Plan 2013–2038 is being used to work towards the translocation of an additional 13 species to Rotoroa Island, which would expand the number of techniques and management systems that could be demonstrated to visitors.

The Rotoroa Island and Auckland Zoo partnership: Connecting heterotopic spaces

In partnership, Rotoroa Island and Auckland Zoo in the Hauraki Gulf have established a conservation sanctuary that has linked a literal sea‐bound island with an urban and metaphorical island. Each entity (Rotoroa and the Zoo) has a presence in each other's space. Ideas of archipelago as well as Foucault's heterotopia assist our interpretation of these developments as expressed in the observed landscape, policy documents and media sources. We conclude that an interpenetration of influences is enabling a diverse set of experiences within the controlled bounds of two intensely managed and insular spaces.

Distribution and relative density of cetaceans in the Hauraki Gulf, New Zealand

ABSTRACTUnderstanding species distributions, and how they change in space and time, is vital when prioritising conservation or management initiatives. We assessed the distribution and density patterns of common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus) and Bryde’s whales (Balaenoptera edeni) in the Hauraki Gulf, New Zealand. Dedicated boat-based surveys were conducted in the inner Hauraki Gulf (IHG) and off Great Barrier Island (GBI) during 2010–2012. Generalised linear models were used to investigate temporal changes in relative densities and kernel density estimation was implemented to examine spatial trends. Common dolphins were widely distributed during all seasons, with higher densities observed during winter and spring in the IHG but during autumn off GBI. There was inter-annual variation in Bryde’s whale distribution, with high densities recorded off GBI in 2011. Bottlenose dolphins were infrequently sighted in the IHG but regularly encountered off GBI, with the highest densities during spring and summer.

Bridging the temporal gap: Continuous and cost-effective monitoring of dynamic recreational fisheries by web cameras and creel surveys

We describe a cost effective method of continuously monitoring relative trends in recreational effort and harvest, based on web camera imagery and interview data provided by a concurrent low intensity creel survey. The number of boats returning to three boat ramps in separate regions on the north eastern coast of New Zealand’s North Island fluctuated over a ten year period between 2004–05 and 2013–14. The most pronounced change occurred in the Hauraki Gulf, where most recreational fishing occurs. Web camera monitoring detected a 34% decline in the number of boats returning to one of the busiest ramps in the Hauraki Gulf over a three year period between 2011–12 and 2013–14, which was mirrored by a 58% decline in snapper catch rates over the same period. The combined result was a 71% decline in the weight of snapper landed annually at the monitored ramp over this three year period, which was far more rapid than anticipated given differences seen between harvest estimates provided by infrequent large scale surveys in the past. Trends in effort and harvest derived from data collected at a small number of ramps will only have utility, however, if they reflect trends in the wider fishery. The relative difference in snapper harvest estimates provided by aerial-access surveys of the entire Hauraki Gulf fishery in 2004–05 and 2011–12, closely matched the difference in the harvest landed at the high traffic ramp that was monitored in the Gulf during these years. This independent confirmation of relative trends inferred from combined web camera and creel survey monitoring at a small number of sites has further highlighted the need to continuously monitor recreational fisheries, which are potentially far more dynamic than previously thought. We discuss strategies that we have progressively developed to minimise the cost of monitoring these recreational fisheries and how they could be applied to continuously monitor recreational fisheries elsewhere.

Perceptions of practitioners: Managing marine protected areas for climate change resilience

Climate change is impacting upon global marine ecosystems and ocean wide changes in ecosystem properties are expected to continue. Marine Protected Areas (MPAs) have been implemented as a conservation tool throughout the world, primarily as a measure to reduce local impacts, but their usefulness and effectiveness is strongly related to climate change. MPAs may have a role in mitigation through effects on carbon sequestration, affect interactions between climatic effects and other drivers and be affected themselves as the distributions of protected species change over time. However, to date, few MPA programmes have directly considered climate change in the design, management or monitoring of an MPA network. This paper presents a series of international case studies from four locations: British Columbia, Canada; central California, USA; the Great Barrier Reef, Australia and the Hauraki Gulf, New Zealand; to review perceptions of how climate change has been considered in the design, implementation, management and monitoring of MPAs. The results indicate that some MPA processes have already incorporated design criteria or principles for adaptive management, which address some of the potential impacts of climate change on MPAs. Key lessons include: i) Strictly protected marine reserves are considered essential for climate change resilience and will be necessary as scientific reference sites to understand climate change effects ii) Adaptive management of MPA networks is important but hard to implement iii) Strictly protected reserves managed as ecosystems are the best option for an uncertain future. Although the case studies addressed aspects of considering climate change within MPA networks and provided key lessons for the practical inclusion of these considerations, there are some significant challenges remaining. This paper provides new insights into the policy and practical challenges MPA managers face under climate change scenarios.

The potential for vessel noise to mask biologically important sounds within ecologically significant embayments

With underwater sound levels rising due to increasing vessel activity, there is a pressing need to better understand the potential distances for which masking impacts on acoustically sensitive marine life may occur, especially in embayments with shipping activity. Given the known detrimental noise impacts on the marine environment, managing underwater noise pollution has been identified as a pressing conservation issue. Therefore, baseline underwater noise measurements from a range of vessels in the Hauraki Gulf Marine Park, a large and ecologically significant embayment (1.2 M Ha) in New Zealand, were undertaken and used to estimate detection distances for which potential auditory masking in dolphins, fish and crustaceans is expected. Sound pressure measurements and octave analyses of recorded vessel noise revealed considerable energy below 5 kHz at source levels of approximately 30 dB above the highest threshold in dolphins and fish. Measureable increases to background sound levels below 5 kHz of at least 54 ± 5.8 dB (mean ± SD) at the source were estimated to have a masking effect inside a minimum 90 m within the busy inner Gulf and 1240 m within the quieter outer Gulf. Impact zones increased considerably for dolphins with assumed detection thresholds equal to ambient sound pressures. These findings show that the sound emanating from both recreational and commercial vessels within the Hauraki Gulf will be significantly raising background sound levels and is likely to have a wide-ranging masking impact on marine life. These findings have significance for embayments worldwide for which vessel activity is a common feature.

Loved to pieces: Toward the sustainable management of the Waitematā Harbour and Hauraki Gulf

The Waitematā Harbour is a drowned river valley in the south-west of the Hauraki Gulf, on the north east of New Zealand’s North Island. The central business district for the city of Auckland is situated on the southern shore of the central Waitematā Harbour and is New Zealand’s largest and fastest growing city. The Waitematā Harbour hosts a major international port, New Zealand’s primary naval base and international cruise terminal, as well as a large and committed community of recreational users. In comparison with the marine ecosystems surrounding many of the world’s coastal cities, the Waitematā Harbour and the Hauraki Gulf have experienced a relatively short period of human occupation. Nonetheless, rapid and widespread changes have occurred within these ecosystems. Habitat loss and declines in biodiversity as well as impacts on human activities such as safe swimming and recreational harvesting have motivated several conservation and restoration initiatives. Here, we review the natural and social context of the Waitematā Harbour and Hauraki Gulf, and summarise some of the pressures the region faces. Last, we present three case studies highlighting current participatory initiatives aimed at ensuring more sustainable management of the region’s marine ecosystems. The Waitematā Harbour and Hauraki Gulf have provided considerable ecological, social and economic wealth for the people of Auckland; accordingly, conserving these ecosystems and preserving future prosperity should be a collective priority for all sectors of society.

Treasure Islands: biosecurity in the Hauraki Gulf Marine Park

Treasure Islands: biosecurity in the Hauraki Gulf Marine Park

Limitations of biophysical habitats as biodiversity surrogates in the Hauraki Gulf Marine Park

The Hauraki Gulf Marine Park (HGMP) is recognised for its diverse natural environment and associated biodiversity, as well as the extensive social, cultural and economic values derived therein. Here, we evaluate the current level of biodiversity protection provided by existing Marine Protected Areas (MPAs) within the HGMP. We use abiotic datasets to develop a habitat classification system to identify the suite of biophysical habitats found in the Marine Park, and their relative protection within existing MPAs (both no-take marine reserves and Cable Protection Zones). Our analysis demonstrated that half of the biophysical habitats identified in the HGMP are not currently afforded protection within MPAs, and that biophysical classifications poorly differentiate across subtidal, soft-sediment habitats using available data layers. We then evaluated representation of these environmental surrogates within a biodiversity prioritisation analysis based on distribution models for demersal fish species. Biophysical habitat surrogates showed poor representation across habitats within highest-priority areas based on prioritisations of demersal fish biodiversity. This suggests the need for further development of biophysical habitat surrogates that are more strongly correlated with biodiversity, if they are to be used to inform biodiversity protection in the HGMP.

Variation in morphology and life-history strategy of an exploited sparid fish

Defining appropriate management units to balance productivity and yield of exploited species is fundamental to effective resource management. Anecdotal and tag–recapture information related to morphology, movement behaviour and life-history strategy suggest that separate groups of snapper (Chrysophrys auratus) exist in the Hauraki Gulf, New Zealand. To address the existence of discrete groups, we examined morphology, meristics and otolith chemistry from snapper collected throughout the Hauraki Gulf. We also used tag–recapture information, stable isotope analysis and interpreted functional aspects of morphology and meristics data to understand potential life-history strategy differences. Snapper from rocky reef habitats did not display morphology and meristic features distinct from snapper from soft sediment habitats and differences in otolith chemistry and stable isotope ratios could respectively be explained by a locational influence and predominance of kelp in rocky reef food webs. Conversely, snapper collected from a known spawning area had distinct morphological and meristic features consistent with semi–pelagic sparids and stable isotope analysis also indicated a potentially more pelagic and higher trophic-level diet. Maintenance of population complexity such as this is generally beneficial to fish populations, and can be achieved by revisiting the spatial units used for fishery management.

Using miniaturized radiotelemetry to discover the breeding grounds of the endangered New Zealand Storm Petrel Fregetta maoriana

Identification of breeding sites remains a critical step in species conservation, particularly in procellariiform seabirds whose threat status is of global concern. We designed and conducted an integrative radiotelemetry approach to uncover the breeding grounds of the critically endangered New Zealand Storm Petrel Fregetta maoriana (NZSP), a species considered extinct before its rediscovery in 2003. Solar‐powered automated radio receivers and hand‐held telemetry were used to detect the presence of birds on three island groups in the Hauraki Gulf near Auckland, New Zealand. At least 11 NZSP captured and radiotagged at sea were detected at night near Te Hauturu‐o‐Toi/Little Barrier Island with the detection of an incubating bird leading to the discovery of the first known breeding site for this species. In total, four NZSP breeding burrows were detected under mature forest canopy and three adult NZSP and two NZSP chicks were ringed. Telemetry data indicated NZSP showed strong moonlight avoidance behaviour over the breeding site, had incubation shifts of approximately 5 days and had a breeding season extending from February to June/July, a different season from other Procellariiformes in the region. Radiotelemetry, in combination with rigorously collected field data on species distribution, offers a valuable technique for locating breeding grounds of procellariiform seabirds and gaining insights into breeding biology while minimizing disturbance to sensitive species or damage to fragile habitat. Our study suggests an avenue for other breeding ground searches in one of the most threatened avian Orders, and highlights the general need for information on the location of breeding sites and understanding the breeding biology in data‐deficient birds.

A GIS‐based decision‐making approach for prioritizing seabird management following predator eradication

Given that 29% of seabird species are threatened with extinction, protecting seabird colonies on offshore islands is a global conservation priority. Seabirds are vulnerable to non‐native predator invasions, which reduce or eliminate colonies. Accordingly, conservation efforts have focused on predator eradication. However, affected populations are often left to passively recover following eradications. Although seabirds are highly mobile, their life history traits such as philopatry can limit passive recolonization of newly predator‐free habitat. In such cases, seabird colonies can potentially be re‐instated with active restoration via chick translocations or social attraction methods, which can be risky and expensive. We used biogeographic and species‐specific behavioral data in the Hauraki Gulf, New Zealand, a global hotspot of seabird diversity and predator eradications, to illustrate the use of geographic information systems multi‐criteria decision analysis to prioritize islands for active seabird restoration. We identified nine islands with low observed passive recovery of seabirds posteradication over a 50‐year timeframe, and classified these as sites where active seabird management could be prioritized. Such spatially explicit tools are flexible, allowing for managers to choose case‐specific criteria such as time, funding, and goals constrained for their conservation needs. Furthermore, this flexibility can also be applied to threatened species management by customizing the decision criteria for individual species' capacity to passively recolonize islands. On islands with complex restoration challenges, decision tools that help island restoration practitioners decide whether active seabird management should be paired with eradication can optimize restoration outcomes and ecosystem recovery.

Investigation of mortalities associated with Salmonella spp. infection in wildlife on Tiritiri Matangi Island in the Hauraki Gulf of New Zealand

CASE HISTORY: Salmonellosis was suspected as the cause of death in eight wild animals on Tiritiri Matangi Island, in the Hauraki Gulf of New Zealand, between November and September 2011, including three hihi (Notiomystis cincta), a tuatara (Sphenodon punctatus), a masked lapwing (Vanellus miles novaehollandiae), and a saddleback (Philesturnus carunculatus). An outbreak investigation to identify the source and distribution of infection was undertaken over the summer of 2011–2012. CLINICAL AND LABORATORY FINDINGS: Surveillance of five species of forest bird (n=165) in December 2011 returned a single positive result for Salmonella spp. Environmental sampling of 35 key water sources and hihi supplementary feeding stations conducted in December 2011 and March 2012 returned isolates of S. enterica subspecies houtenae and S. enterica serovar Saintpaul from a stream, a dam and a supplementary feeding station. The same serotypes were identified in tissue samples collected from post mortem specimens of the affected birds, and their similarity was confirmed by pulsed-field gel electrophoresis. DIAGNOSIS: Mortality in wildlife associated with infection with S. enterica subspecies houtenae and S. enterica serovar Saintpaul. CLINICAL RELEVANCE: This is the first detection of these Salmonella spp. from wild birds in New Zealand. Our study highlights how active surveillance in response to observed disease emergence (here mortalities) can provide important insight for risk assessment and management within populations of endangered species and inform risk assessment in translocation planning.

Differences in population connectivity of a benthic marine invertebrate Evechinus chloroticus (Echinodermata: Echinoidea) across large and small spatial scales

Marine organisms with a planktonic larval stage have the potential to be transported substantial distances, with the distance travelled depending on factors such as pelagic larval duration (PLD) and physical factors such as ocean currents and geographical barriers. The endemic New Zealand sea urchin, Evechinus chloroticus, is found throughout the North and South Islands, and with a PLD of approximately 30 days, is expected to show strong connectivity among all populations. Population connectivity and genetic differentiation were examined over both a geographically broad scale, throughout New Zealand, and on a fine scale (within the Hauraki Gulf on the North Island). Significant genetic differentiation was revealed through analysis of mitochondrial COI sequences (FST = 0.096 p < 0.01) and six microsatellite loci (FST = 0.0120 p < 0.008). This was consistent with a division between northern and southern regions located to the south of Cook Strait, at a phylogeographic barrier previously reported in other New Zealand benthic marine invertebrates. Fine-scale population differentiation was evident between the inner and outer Hauraki Gulf populations, and between the most northern populations and the remainder of the North Island. Together, this study suggests that strong coastal currents, upwelling in the Cook Strait region, and geographic distance (approximately 2000 km north to south) may all be acting to restrict gene flow and contribute to genetic divergence among populations of E. chloroticus.

Mitigation of vessel-strike mortality of endangered Bryde’s whales in the Hauraki Gulf, New Zealand

Collisions between traffic and wildlife can have population-level consequences and carry economic costs. Vessel-strike may threaten the viability of whale populations especially where habitat overlaps with frequent vessel traffic; as seen in the Hauraki Gulf, New Zealand, which is the entrance to the busy Ports of Auckland and holds a year-round population of endangered Bryde’s whales (Balaenoptera edeni). Here, we identify a serious threat: out of 44 Bryde’s whale-deaths, 17 of 20 (85%), with known cause of mortality, sustained injuries consistent with vessel-strike; a mortality rate that is likely to be unsustainable. This information started a social forum with stakeholders engaged in science-based discussion of mitigation measures to reduce lethal vessel-strikes in this region. To determine the viability of different mitigation actions we studied Bryde’s whale behavior with suction-cup attached tags. Tagged whales (n=7, 62.5h) spent 91% of their time at depths within the maximum draft of vessels transiting the Gulf, increasing the probability of vessel-strike. Whales are broadly distributed throughout the Gulf so re-routing traffic would not lessen the threat of vessel-strike. Monitoring whales visually is difficult and not applicable at night, when whales rested closer to the surface than during the day. Passive acoustic monitoring is unreliable due to the whales’ low vocal activity and because low frequency calls are susceptible to masking from vessel noise. These findings resulted in a Transit Protocol for Shipping including voluntary speed restrictions and a monitoring plan, highlighting the value of scientific and social stakeholders working together for conservation.

Using non-systematic surveys to investigate effects of regional climate variability on Australasian gannets in the Hauraki Gulf, New Zealand

Few studies have investigated regional and natural climate variability on seabird populations using ocean reanalysis datasets (e.g. Simple Ocean Data Assimilation (SODA)) that integrate atmospheric information to supplement ocean observations and provide improved estimates of ocean conditions. Herein we use a non-systematic dataset on Australasian gannets (Morus serrator) from 2001 to 2009 to identify potential connections between Gannet Sightings Per Unit Effort (GSPUE) and climate and oceanographic variability in a region of known importance for breeding seabirds, the Hauraki Gulf (HG), New Zealand. While no statistically significant relationships between GSPUE and global climate indices were determined, there was a significant correlation between GSPUE and regional SST anomaly for HG. Also, there appears to be a strong link between global climate indices and regional climate in the HG. Further, based on cross-correlation function coefficients and lagged multiple regression models, we identified potential leading and lagging climate variables, and climate variables but with limited predictive capacity in forecasting future GSPUE. Despite significant inter-annual variability and marginally cooler SSTs since 2001, gannet sightings appear to be increasing. We hypothesize that at present underlying physical changes in the marine ecosystem may be insufficient to affect supply of preferred gannet main prey (pilchard Sardinops spp.), which tolerate a wide thermal range. Our study showcases the potential scientific value of lengthy non-systematic data streams and when designed properly (i.e., contain abundance, flock size, and spatial data), can yield useful information in climate impact studies on seabirds and other marine fauna. Such information can be invaluable for enhancing conservation measures for protected species in fiscally constrained research environments.

Application of sociometric methods to collaborative coastal management

Collaborative models for environmental management are emerging in New Zealand. At the forefront are processes for coastal and freshwater environments. It is proposed that application of sociometric methods and skilled facilitation can produce leadership from local communities, creating more enduring solutions than occur from central and regional government initiatives. This paper presents examples of how this approach has been adopted in situations at local and regional scales. Three case studies of integrated management initiatives are analysed in a sociometric framework at stages of development from pre-initiation research to completed legislation and implementation, in the context of a national legal framework. The full development of a community led programme is demonstrated using the Kaikoura integrated coastal management programme. An analysis of the Top of the South Marine Biosecurity Partnership shows how scope reduction can aid successful collaboration. Finally, the Hauraki Gulf Sea Change project is used to describe how the approach is being adapted and scaled to a more complex situation in the area of highest population density in New Zealand. These three case studies are compared and contrasted to draw out commonalities, lessons learned, and the potential for these approaches to be applied elsewhere. Systemic, sociometric and structural analyses are used to define the elements needed for consensus to emerge at the local level and to be translated into regional and national administrative systems. Collaborative processes are found to be useful for complex issues involving multiple parties with overlapping interests, making these approaches suitable for integrated coastal management.

Year-round maturity of the chaetognath Aidanosagitta regularis in the Hauraki Gulf, New Zealand

The reproductive biology of planktonic chaetognaths is poorly known, particularly with regard to the importance of seasonal factors such as daylength, temperature and lunar phase. We undertook semilunar plankton sampling (March 2013–March 2014) in the Hauraki Gulf, New Zealand, to survey sexual maturity of the abundant chaetognath Aidanosagitta regularis (the only chaetognath species present in sufficient numbers for reproductive study). Contrary to our expectations, breeding of A. regularis appeared unconstrained by seasonal factors, as reproductively mature individuals were available year-round. This finding has implications for embryological study of the chaetognaths.