Biosecurity Pathway: Habitat and Species Restoration
Oyster Biosecurity Fieldwork
Marine habitat restoration is taking place throughout the Solent to create new seagrass beds, saltmarsh and oyster reefs. Such restoration and enhancement projects can pose invasive spread risk due to the movement of people, plants, substrate, vessels and seawater. For example, the translocation of whole seagrass plants or plant structures may represent a risk as they are often colonised with epiflora and fauna which could include hard-to-detect species or juvenile life stages. These risks are amplified if seagrass plants are translocated with associated sediment and seawater. The slipper limpet that is found in the Solent can stop seagrass from re-establishing in areas as dead shells prevent propagule growth. If we consider saltmarsh restoration using beneficial dredgings, we need to think about whether the dredging arisings can spread marine invasives onto the habitat being recharged.
Habitat restoration can mitigate the impacts of invasive species by restoring natural habitats to promote the recovery of native species. Combining eradication efforts with habitat restoration, that promotes native species colonisation, enhances the success of invasive species management initiatives and reduces the likelihood of future invasions. It is also thought (there is limited evidence) that using eco enhancement methods on hard infrastructure helps to increase species diversity and reduce the risk of long term marine invasive colonisation.
Habitat restoration activities will require a Marine Licence and it is likely that there will be a licence condition for a biosecurity plan. Habitat restoration handbooks recommend using the Check Clean Dry protocol for project equipment such as vans, boats and field kit.
Case Study: Blue Marine Foundation's Oyster Restoration Biosecurity Decision Chart
- Oysters placed into static holding tanks in perforated trays or bushels (baskets) - in most cases algal paste is added and left overnight to feed the oysters if shipped throughout the day.
- Trays of oysters moved into the laboratory, excess water from trays allowed to drip into the static holding tanks as much as possible.
- Oysters transferred from holding trays into unperforated trays. Oysters are assessed for other living species and to ensure that they are Ostrea edulis and not Crassostrea (Magallan) gigas.
- Adult or larger juvenile oysters scrubbed manually to remove excess sediment and colonising species. Forceps or oyster shucking knives used to remove encrusting species.
- Juvenile species sorted and encrusting species removed.
- Shell material of deceased oysters removed into separate trays to be cleaned and used as cultch in the future.
- Any other species present are sorted into separate buckets and disposed of in general waste.
- Live oysters sorted from unperforated trays back into perforated trays and counted, if possible, at this point.
- Any water from the unperforated trays is emptied down the laboratory sinks that enter the wastewater system and is flushed through with fresh water.
- Trays of sorted oysters are then submerged in bleach or chlorine solution for approx. 20minutes.
- Sorted, cleaned and bleached/chlorinated - therefore biosecure - oysters washed/rinsed in a 5000L seawater tank (or similar) before being placed into flow-through holding tanks.
- Oysters can then be deposited onto the seabed at this point. They are often left at least overnight to reduce stress.
- Once static holding tanks are emptied of oysters, concentrated bleach solution or chlorine tablets are added, and the tanks are left to sit for at least a few days. Tanks are then assessed for surviving organisms, if present they are removed, and further solution added. If nothing persists, then move to step 9.
- Water from these tanks is then further diluted with fresh seawater discharged slowly at high tide into the harbour with a sieve placed on the discharge point to collect any deceased organisms and prevent them entering the harbour.
- All trays and cleaning equipment thoroughly cleaned in bleach or chlorine solution after the process is complete.
- Laboratory benches and floor are cleaned and wiped down with cleaning solution.
- All outside tanks are cleaned with a pressure washer prior to the next biosecurity event taking place.
Please refer to our Biosecurity Action Plans for measures that you can take regarding habitat and species restoration.
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