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Clevedon, New Zealand

Bulmer R.,University of Auckland | Kelly S.,Coast and Catchment Ltd | Jeffs A.G.,University of Auckland
Aquaculture Environment Interactions | Year: 2012

Hanging baskets are rapidly being adopted in many parts of the world to grow shellfish, especially oysters. The adoption of this method is opening up new areas for aquaculture development. However, expansion into areas that have previously been unusable has been controversial, due to concerns about farms being established in areas with particularly high ecological values and sensitivity. This study investigated the impact of establishing a hanging basket oyster farm in the Kaipara Harbour in northern New Zealand on seagrass. Aerial photographs were analysed with a geographical imaging software in combination with field sampling to detect potential impacts. The hanging basket oyster farm technology was found to have no significant overall impact on seagrass beneath the farm. However, field sampling found a narrow band directly beneath the oyster farm growout lines of less than 5% of the farm area that had lower seagrass densities and abundance compared to adjacent control zones sampled within the farm. This area was obscured in aerial photographs by farm structures. This highly localised impact is likely due to shading or scour caused by farm structures. Overall, the results indicate that hanging basket technology for shellfish aquaculture has minimal environmental impact on underlying seagrass, representing an improvement over traditional culture technologies. Furthermore, the results confirm that remote sensing methods are useful tools for examining aquaculture impacts on seagrass communities, but only when combined with field sampling. © Inter-Research 2012.

Bulmer R.H.,University of Auckland | Kelly S.,Coast and Catchment Ltd | Jeffs A.G.,University of Auckland
New Zealand Journal of Marine and Freshwater Research | Year: 2016

The Kaipara Harbour in New Zealand is one of the largest estuarine systems in the world, containing significant areas of subtidal seagrass habitat (Zostera muelleri). Light availability at the maximum depth limit for Z. muelleri was measured at 2.10 (0.19 SEM) and 4.91 (0.53 SEM) mol photons m−2 d−1 during the winter and summer monitoring periods, respectively. The primary drivers of benthic light availability were found to be surface light availability, the timing of the low tide and water clarity. Core sampling analysis suggested that biomass of seagrass growing at the maximum depth limit was low, indicative of light limitation. The results of this study suggest that the subtidal distribution of seagrass in the Kaipara Harbour is light-limited and that reductions in water clarity due to changes in land use are likely to result in significant reductions in the extent and productivity of subtidal seagrass habitat. © 2016 The Royal Society of New Zealand

Freeman D.J.,University of Auckland | MacDiarmid A.B.,NIWA - National Institute of Water and Atmospheric Research | Taylor R.B.,University of Auckland | Davidson R.J.,Davidson Environmental Ltd | And 4 more authors.
Environmental Conservation | Year: 2012

Monitoring species' response in marine protected areas is important for informing both the management of those areas and the establishment of additional protected areas. Populations of spiny lobsters Jasus edwardsii were monitored in eight New Zealand marine reserves for up to 34 years. The populations displayed highly variable responses to protection. While a few showed rapid (within 1-2 years of protection) increases in abundance, others showed little response even after a decade of protection. Some reserves displayed little initial recovery, then a sudden increase following several years of protection, while others displayed significant declines in abundance following initial recovery. Marine reserves located in areas with initially high densities of juveniles tended to have rapid recovery, but aspects of reserve design had no significant influence on the recovery rate. Variability among recovery trajectories also suggests that supply-side dynamics may be a key driver of lobster recovery. Densities of legal-sized lobsters were positively correlated with reserve age, but the abundance of juvenile lobsters increased in all but one reserve, indicating enhanced recruitment, survival and/or movement of juvenile lobsters into reserves. It is important to consider the placement of reserves, with respect to potential levels of larval supply, when establishing marine reserves for either conservation or fisheries management purposes and for evaluating their effectiveness. © Copyright Foundation for Environmental Conservation 2012.

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