Abstract
Hanging baskets are rapidly being adopted in many parts of the world to grow shell- fish, 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 con- troversial, due to concerns about farms being established in areas with particularly high ecologi- cal values and sensitivity. This study investigated the impact of establishing a hanging basket oys- ter 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.
Highlights
The recent development of plastic hanging basket technology for the aquaculture of oysters is rapidly replacing more traditional techniques, such as rack and rail technology, which is widely used in many oyster-growing regions of the world, including France, Australia and New Zealand
In the present study we have addressed this problem by directly measuring the distribution of seagrass Zostera muelleri directly beneath oyster farm structures by field sampling in addition to analysing aerial photographs to determine the impact of hanging basket oyster aquaculture technology on seagrass
In the 2008 photograph immediately prior to the oyster farm construction, seagrass occupied 610 m2 (3.1%) of the total area of the oyster farm zone, and in the 2010 photograph after the farm had been in operation for over a year, seagrass had expanded to occupy a total of 2537 m2 (12.8%) of the zone
Summary
The recent development of plastic hanging basket technology for the aquaculture of oysters is rapidly replacing more traditional techniques, such as rack and rail technology, which is widely used in many oyster-growing regions of the world, including France, Australia and New Zealand. Rack and rail technology usually consists of a pair of parallel wooden rails suspended in the intertidal zone by posts driven into the seabed at regular intervals, usually in shallow and sheltered areas of the coast. The racks are laid across the rails, and most often consist of wooden or plastic sticks on which the cultivated oysters are attached. The racks can be used to support large mesh trays or flat bags of loose oysters, especially where single-seed oysters from a hatchery are cultivated. The hanging basket technology consists of horizontal wires stretched between posts driven into the seabed; a series of small mesh baskets containing oysters are suspended from the wires. One of the advantages of this farming method is that it allows oyster aquaculture in deeper, more exposed areas, often further from the shore, that were previously unavailable for this activity using the rack and rail aquaculture technology
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
