Shaun Ogilvie

Phytoplankton biomass associated with mussel farms in Beatrix Bay, New Zealand

The spatial and temporal variability in phytoplankton abundance is a major factor determining the productivity of mussel (Perna canaliculus) farms. During periods of low phytoplankton abundance, food depletion may be a significant factor in the productivity of mussel farms. Measurements of phytoplankton abundance (as chlorophyll a) were made over the entire depth of the water column both inside and outside four mussel farm sites in Beatrix Bay, over a 13-month period. Ambient (outside) concentrations of dissolved inorganic nitrogen (NO3–N and NH4–N) and dissolved reactive phosphorus (DRP) were also measured. The highest ambient chlorophyll a concentrations in the surface waters occurred during autumn–winter, with peak levels of around 5 μg l−1. At this time, all farms had a significant reducing impact on phytoplankton biomass (P<0.05 in all cases). The lowest ambient chlorophyll a concentrations of <0.5 μg l−1 were recorded in the summer, coinciding with low nitrogen concentrations. In November, there was significantly more phytoplankton inside all the farms (P<0.05 in all cases). It was hypothesised that this increase occurred because mussels are net producers of dissolved inorganic nitrogen. In five out of the 7 months when farms were surveyed, the highest chlorophyll concentrations were in the deeper water, associated with a pycnocline. Two management options to increase mussel productivity are presented: (1) Deployment of mussel dropper ropes to deeper waters to take advantage of chlorophyll maxima in summer; (2) Artificially increasing nitrogen inside farms during spring and summer to increase phytoplankton supply.

Innovative developments for long‐term mammalian pest control

BACKGROUND Invasive mammalian pests have inflicted substantial environmental and economic damage on a worldwide scale. RESULTS Over the last 30 years there has been minimal innovation in the development of new control tools. The development of new vertebrate pesticides, for example, has been largely restricted due to the costly and time-consuming processes associated with testing and registration. CONCLUSION In this article we discuss recent progress and trends in a number of areas of research aimed to achieve long-term population suppression or eradication of mammalian pest species. The examples discussed here are emerging from research being conducted in New Zealand, where invasive mammalian pests are one of the greatest threats facing the national environment and economy.

In situ enclosure experiments on the influence of cultured mussels (Perna canaliculus) on phytoplankton at times of high and low ambient nitrogen

Abstract The influence of the cultured mussel Perna canaliculus (Gmelin 1791) on the abundance of phytoplankton was investigated in Pelorus Sound, New Zealand. Four in situ enclosure experiments were undertaken, two in summer when ambient nitrogen was low, and two in winter when it was high. Each experiment had four manipulation types: added mussels; added nitrogen; both mussels and nitrogen added; and control (no additions). In summer, there was a significant increase of chlorophyll a in response to added nitrogen, indicating that the phytoplankton were nitrogen-limited. At this time, mussels caused an increase (11–17%) in phytoplankton biomass, possibly by converting particulate nitrogen to ammonium, making the nitrogen available for phytoplankton utilisation. The highest ambient chlorophyll a concentrations coincided with high ambient nitrogen in the winter. At this time, mussel grazing caused a significant decrease (5–14%) in phytoplankton concentration, indicating that within-farm depletion of phytoplankton is most likely to occur in winter. On an annual time scale, the mussels had a stabilising influence on phytoplankton biomass, reducing high ambient levels in winter and slightly increasing low levels in summer.

Bridging Disciplines, Knowledge Systems and Cultures in Pest Management

The success of research in integrated environmental and natural resource management relies on the participation and involvement of different disciplines and stakeholders. This can be difficult to achieve in practice because many initiatives fail to address the underlying social processes required for successful engagement and social learning. We used an action research approach to support a research-based group with a range of disciplinary and stakeholder expertise to critically reflect on their engagement practice and identify lessons around how to collaborate more effectively. This approach is provided here as a guide that can be used to support reflective research practice for engagement in other integration-based initiatives. This paper is set in the context of an integrated wildlife management research case study in New Zealand. We illustrate how multi-, inter- and trans-disciplinary approaches can provide a framework for considering the different conversations that need to occur in an integrated research program. We then outline rubrics that list the criteria required in inter- and trans-disciplinary collaborations, along with examples of effective engagement processes that directly support integration through such efforts. Finally, we discuss the implications of these experiences for other researchers and managers seeking to improve engagement and collaboration in integrated science, management and policy initiatives. Our experiences reaffirm the need for those involved in integrative initiatives to attend to the processes of engagement in both formal and informal settings, to provide opportunities for critical reflective practice, and to look for measures of success that acknowledge the importance of effective social process.

Low-dose cholecalciferol bait for possum and rodent control

Abstract A new low-concentration formulation of Feracol® paste containing 0.4% concentration cholecalciferol was tested for efficacy against possums in cage trials, and against possums and rodents in a single unreplicated field trial. A new low-concentration 0.4% cholecalciferol cereal pellet was also tested in the field against possums and rodents. 20 wild-caught possums, held in individual cages, were presented with 15 g of 0.4% cholecalciferol paste. Possum body weight, amount of paste eaten and days until death were recorded. The field trial occurred on Banks Peninsula, Canterbury, from September to November 2009, using a treatment site of c. 100 ha and a non-treatment site of c. 200 ha. The treatment site was divided into two even blocks, one for paste and one for pellets. Pre- and post-monitoring were carried out using leg-hold traps for possums, and tracking tunnels for rodents. Of the 20 caged possums, a kill rate of 89.5% with an average time to death of 7.0 days±0.41 SEM was achieved, similar to earlier work on cholecalciferol using a higher concentration. In the field trial pellet treatment block, possum numbers were reduced by 94±11%, mice numbers by 100±0% and rat numbers by 89±12%. In the paste treatment block, possum numbers were reduced by 93±16%, mice numbers by 75±29% and rat numbers by 100±0%. Under the current study conditions, the effectiveness of the new Feracol® paste and pellets containing 0.4% concentration cholecalciferol was comparable to the currently registered 0.8% concentration cholecalciferol Feracol® paste formula, and was effective in controlling multiple pest species while reducing the poisoning risk to non-target species. Replication of this field trial using the new bait matrices is necessary to increase confidence under similar and differing conditions, to ensure that the efficacy seen here is not arbitrary.

Vertebrate pesticide risk assessment by indigenous communities in New Zealand.

In New Zealand, the vertebrate pesticide sodium fluoroacetate (Compound 1080) is aerially applied in baits for control of the brush-tailed possum Trichosurus vulpecula (Kerr, 1792). Maori, the indigenous people of New Zealand, have raised concerns about 1080 impacts on culturally-important species. Here, we outline two steps taken to help Maori assess 1080 risk. First, field research was undertaken to determine if naturally-occurring plants utilized by a Maori community for food and medicine would take up 1080 from baits. Single baits were placed at the base of individual plants of two species, pikopiko (Asplenium bulbiferum) and karamuramu (Coprosma robusta). Plants were sampled at various times up to 56 days, and samples were analyzed for 1080 content. No 1080 was detected in any of the pikopiko samples, whereas 1080 was detected in karamuramu, at a maximum concentration of 5 ppb after seven days, and 2.5 ppb after 14 days. This concentration decreased to 0 at 28 days, indicating that 1080 was not persistent. The results of the present study suggest there is negligible risk of humans being poisoned by consuming plants that have taken up 1080 from baits. To allay community concerns that minute concentrations of 1080 might influence the medicinal properties of plants, it is suggested that a withholding period of 30 days after 1080 control operations could be adopted. Second, after further consultation we undertook a review of the scientific literature relating to 1080 impacts on additional non-target species of cultural importance to Maori. The information was presented on an interactive foodweb database that allowed the collection and presentation of a large volume of complex information about 1080 in a holistic and pictorial fashion. This database was presented to many Maori communities throughout New Zealand, and feedback was overwhelmingly positive. The database is likely to play a key role in informing these communities about 1080, and is seen as an important new tool to help these communities make their own risk assessments.

Erratum to: The Use of Rubrics to Improve Integration and Engagement Between Biosecurity Agencies and Their Key Partners and Stakeholders: A Surveillance Example

New Zealand’s forest conservation estate and primary production sectors are increasingly at risk from exotic plant pests (insects and pathogens). A growing challenge for biosecurity managers is to step beyond a narrow operational focus that deals with individual technical aspects, and engage more meaningfully with a range of partners and key stakeholders through improved communication and engagement activities. However, there are a lack of methodologies and tools to guide agencies in helping the different stakeholder groups involved to increase awareness and to see where they can best contribute. We use a participatory action research approach to the development of rubrics as a design and assessment approach to improve surveillance systems and illustrate how this can support a more integrated and collaborative approach to key biosecurity activities.

Estimating feral cat (Felis catus) density in a rural to urban gradient using camera trapping

ABSTRACT Control or eradication of feral cats (Felis cattus) is necessary for a number of reasons, including controlling zoonotic diseases and protecting native species in New Zealand. Estimating feral cat density provides vital information about location and logistical effort required for control operations but current methods used to estimate feral cat densities are often labour intensive and invasive, and may not provide appropriate baseline data. We determined the effectiveness of using camera traps to estimate a feral cat population compared with live-capture trapping in a semi-rural park. Camera trapping, with capture–recapture statistical modelling, was used to estimate population density of feral cats as between 1.06 and 1.19 cats/km2 with an individual detection probability of 5.3% per camera/night. Camera trapping (seven individual feral cats identified) was a valuable addition to live trapping of feral cats (four cats live trapped) and provided a cost-effective, non-invasive and potentially more accurate tool for wildlife managers and researchers to measure feral cat densities.