“Plastic pollution in our marine environment is a growing problem,” Olivia said. While the bags have done well overall, our team believe switching to gabions will help the lagoon by encouraging more oysters to grow on the projects, removing plastics from the waterway, protecting marine life from the potential harm of entanglement and micro-plastics and providing a material that will hold up better in active lagoon areas. “Gabions provide a plastic-free way of doing this and may hold up better than plastic mesh bags.” “Containing the shell also allows more time for live oysters and reef structure to form and hold shell together before wave action erodes or flattens how the shell is built up,” Olivia said. The greater water flow could also increase food availability, leading to faster growth rates of the oysters.
On average, the gabions at this site naturally recruited almost three times as many live oysters as the bags and the oysters were much larger! We believe the gabion’s height and larger holes allow for better water flow and less sedimentation, increasing the potential for oyster spawn to attach to the shells inside. This is a test site for different restoration methods with a side-by-side comparison between oyster bags and gabions. Recently, we joined our partners from UCF to monitor an oyster project built in March 2021 in Melbourne Beach. However, protective mesh bags may foul quickly and, to maximise retention and spat growth, weekly replacement of mesh bags should be undertaken.Restore Our Shores team is seeing some promising early results from a plastic-free material in its oyster restoration projects called gabions.įor about a year, we’ve been using gabions, or galvanized metal cages, on select oyster reef builds.
The results show that the presence of a mesh bag around spat culture units may improve retention of spat by between 18–41%. Weights than those from the REPLACE treatment. Mean wet weight of the mesh bags at the end of the experiment differed between treatments with bags from the WASH and NO WASH treatments having significantly greater mean wet Grading of the spat from each treatment at the end of the experiment showed that the REPLACE treatment had the highest number of spat in large and medium size classes with mean (± SE) dorso-ventral height of 23.9 ± 0.5 mm and 17.4 ± 0.5 mm, respectively. Culture units in the REPLACE treatment had the greatest number of spat at the end of the experiment and 41% more spat than in the REMOVE treatment.
It assessed spat retention and growth in culture units without mesh bags (REMOVE) and in those where mesh bags were replaced weekly (REPLACE), washed weekly (WASH) or left unwashed (NO WASH) for the duration of the six-week experiment. This study examined the effectiveness of mesh bag covers on culture units for spat of the blacklip pearl oyster, Pinctada margaritifera. Hatchery produced pearl oyster spat are generally transferred to the ocean on spat collectors which may, or may not, be covered with fine mesh to prevent spat loss.
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