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Around 50 people volunteered to shovel tonnes of mussels into the sea early this month in a ground-breaking initiative to clean up the Mahurangi Harbour.
The project is being undertaken by Revive Our Gulf – a group of scientists, planners and environmental advocates, who hope to improve water quality and increase the abundance and diversity of marine life in the harbour.
Project manager and marine biologist Dr Carina Sim-Smith says mussels are renowned for their capabilities as “filter feeders” where they feed on sediment and other impurities in the water, and improve its purity and clarity.
At the same time, mussel beds provide the perfect habitat for young fish.
“Not only are you cleaning the water, you are increasing the biodiversity and growth of your marine environment hugely by building new mussel beds,” Dr Sim-Smith says.
About 30 tonnes of mussels have been tossed overboard from barges in the outer harbour area in recent weeks, which follows a deposit of about 50 tonnes, made around the same time last year.
Dr Sim-Smith says once back in the water, the mussels are quite mobile and will crawl together, then attach to one another and to stones and bits of shell on the sea floor, forming their own beds.
Revive Our Gulf believes the Hauraki Gulf is the first area in the world where attempts have been made to recreate mussel beds in this way.
About 80 years ago, mussel beds were found extensively throughout the Gulf, but commercial dredging operations virtually eliminated them with devastating consequences for the environment.
Dr Sim-Smith says the long-term goal is for the mussels to begin regenerating themselves, but scientists are still uncertain how extensive beds need to be for this to start to happen. Getting them to sufficient size could take time.
“It’s probably likely to be years to be honest. The scale of the mussel beds in the Hauraki Gulf in the 1940s was huge and we have just started in terms of the whole process of restoration,” she says.
Dr Sim-Smith says currently, Revive Our Gulf deposits mussels on an ad hoc basis when resources and mussel donations allow.
But it’s hoped that as the project gathers steam, it will gain more support and Revive will be able to form a more cohesive plan for the entire Gulf.
This would enable it to set goals for mussel restoration in the next 10, 20 and 50 years.
Dr Sim-Smith is unconcerned that commercial operations might again savage the restored mussel beds as mussel farms now deliver better mussels at greater volume.
Revive Our Gulf keeps the precise location of the beds secret to deter recreational fishermen, but even then the risk of disrupting the restored beds is considered to be minimal. Accessing the mussels would be difficult and they can be bought relatively cheaply at the supermarket.
Dr Sim-Smith says she was delighted by the number of volunteers who turned up to shovel mussels into the sea.
“The community spirit in getting behind an event like this has just been amazing,” she says.
