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Shedding light on the effects of oyster farming

On the eastern coast of Canada, eelgrass is a habitat for many fish, providing them shelter and good feeding and rearing grounds. Scientists at Fisheries and Oceans Canada discovered that oyster aquaculture can contribute to the overall health and productivity of eelgrass on a larger bay scale, and now they’re investigating why. Learn about the science behind this interesting study.

Transcript

Narrator: Fisheries and Oceans Canada is working with the aquaculture Industry with the goal of helping it operate in a sustainable and responsible way.

In Prince Edward Island and New Brunswick, areas like Cocagne have experienced a major decline in native wild oyster populations over the past century - due to a combination of factors including overfishing, disease outbreaks in the 1950s, and other land-based human activities like forestry, agriculture, and wastes.

Oysters are an important part of the ecosystem acting as natural filters for the water.

This team of researchers is studying what effect the growth of commercial oyster aquaculture will have on the natural environment.

M. Thomas Landry, section head, Aquatic Ecosystems, DFO, Gulf Fisheries Centre: We are presently sitting with about 5% to 10% of the natural population, so we have to rebuild these populations to a level that used to exist in order to have the same function that we used to have in these ecosystems.

Along with oysters there are other species that play a significant role to the health and productivity of these systems, and one of them is the eelgrass.

So we are trying to understand how the development of aquaculture, the re-establishment of the oyster population is going to interact with the eelgrass population.

Guy Robichaud, team leader, Fisheries Protection Program, DFO, Canada Gulf Fisheries Centre: Eelgrass has for estuaries, especially along the eastern Canada coast, is a good habitat for a lot of fish, and it provides shelter, feeding grounds, rearing grounds. We want to make sure that at the end of the day that eelgrass is protected.

Narrator: In a natural setting, oysters can improve water quality and clarity for eelgrass.

Monique Niles, aquatic science biologist, DFO, Gulf Fisheries Centre: Oysters are filter feeders, and by filtering the water, clear the water column, and permit the sun to reach the bottom, and that's how you can improve the environment for the eelgrass growth.

Narrator: But the addition of commercial shellfish aquaculture structures adds an extra dimension.

Marc Ouellette, aquatic science biologist, DFO, Gulf Fisheries Centre: There are different ways that the shellfish aquaculture interacts with the ecosystem.

And because we are focusing specifically with interactions with aquatic vegetation, light is very important.

Narrator: On a local scale, there are some concerns about shading effects from oyster and mussel aquaculture sites on sensitive eelgrass directly beneath them, however these researchers are looking at what kind of impact shellfish aquaculture might have on a larger, bay scale.

Monique Niles, aquatic science biologist, DFO, Gulf Fisheries Centre: We noticed that there is a positive relationship, the more there was oyster aquaculture in the bays, the more there was eelgrass.

That was just a mathematical relationship.

So, this project that we are doing now is to explore why there is a positive relationship.

M. Thomas Landry, section head, Aquatic Ecosystems, DFO, Gulf Fisheries Centre: If we know that the addition of oysters in an ecosystem is contributing to the productivity and the health of eelgrass, then it's a question of how to maximize, or optimize those two components.

Narrator: The research is multifaceted.

The team uses remote sensing data that is collected by airplane using LIDAR, (Bathymetric LIDAR uses lasers to penetrate the water column and reflect the seabed).

This technology is paired with high resolution photography to produce detailed maps that are seamless from the land into the nearshore - providing them with a picture of the bottom of the bay to see where and how much eelgrass there is.

This data is then cross-referenced with data that the team collects in the bay to ensure its' accuracy.

The team begins by measuring water transparency.

This secchi disk lets them measure how deep the light can penetrate the water.

They also use an underwater camera to take actual photos of the seabed - looking at the health and presence of the eelgrass.

They then use a sonde to record the salinity and amount of oxygen in the water.

And finally they collect water samples which they take back to the lab.

In the lab, the team is able to measure the types and quantities of particles that are suspended in the water, which affects its clarity.

The oysters are also being studies to establish how well and how fast they filter the water.

All of the data that they collect is then used to build a computer model that allows the team to forecast what effects this type of aquaculture might have when deployed on different scales and in different locations.

Thomas Guyondet, research scientist, DFO, Gulf Fisheries Centre: What the model does is you reproduce a simplified form of that system.

You can increase the stock, the numbers of oysters in cultivation in the bay, and see how the different variables react to that increase.

Narrator: Not all locations are suitable for aquaculture sites, so these scenarios help with decisions about future sites in a strategic way that will protect and enhance interactions with eelgrass.

M. Thomas Landry, section head, Aquatic Ecosystems, DFO, Gulf Fisheries Centre: We're trying to make sure that we're gaining the function of filtering animals back into these coastal ecosystems, and aquaculture is definitely bringing that back... at a profit.

Narrator: As part of the Program for Aquaculture Regulatory Research this project is providing critical information to regulators that will allow them to make decisions that will ensure that growth of the industry is done in a responsible and sustainable manner, and in this case could in fact help to restore ecosystem health in some areas - providing benefits for the industry, the environment, and coastal communities.

Charles Maillet, oyster grower, Charles Maillet Oysters, Cocagne, New Brunswick: We hope that with time that we will be able to maybe we can get some more square footage on the water, to try to become a little bit bigger and create some more jobs, that's where we're heading.

That's a nice oyster, this is number one grade... cream of the crop.

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