Is Oyster Aquaculture Preventing Wild Oysters From Returning?

I’ve been interested in shellfish aquaculture for years, and lately the industry has grown exponentially in both size and popularity. Most people tout all the benefits that the farms provide. Shellfish get all their food by filtering it out of the water, so you can grow shellfish without having to feed them anything. As filter feeders, they also clean the water while growing. This is very different from finfish aquaculture, which introduces excess food and fish waste into the environment. A shellfish farm seems like a totally positive thing; it provides food while also removing nutrients from the water.

This nutrient removal is especially important in places like Long Island Sound, which borders my home state of Connecticut. Long Island Sound is New England’s drainage basin, collecting all the excess nutrients and concentrating them in the western part of the Sound. The nutrients cause algae blooms, and when the algae die and decompose the process consumes the oxygen in the water. This can create oxygen-deficient “dead zones” in the Sound.

I appreciated all the benefits of shellfish aquaculture, and a few years ago I looked at starting my own shellfish farm. I learned that you need about a year or so to grow oysters to market size. Having little in savings and a full time job, I didn’t want to wait that long to see if I’d make money. I decided to look for a commercial fishing license to hold me over while I waited for my oysters to grow. I figured I could catch some wild shellfish to pay the bills while my farmed shellfish were growing.

After a few emails to the Bureau of Aquaculture, I learned that Connecticut’s policy on shellfish management is to lease the bottom for aquaculture and let the industry regulate the shellfisheries in the state. There is no commercial wild harvest shellfish industry in the state.

Something seemed wrong with this arrangement. I can’t think of too many natural resources that are 100% left to private industry to regulate. It’s not the worst way to regulate—aquatic farmers have an obvious interest in preserving shellfish habitat and water quality—but it seems a bit short-sighted that there is little or no concern for wild stocks. The only provision I found in the lease permitting process is that you can’t lease grounds that have a substantial wild population already on them.

But, if the bottom is already leased, how would wild populations ever recover? The initial reason people started cultivating oysters was because the natural population was depleted, and the current regulatory structure ensures that aquaculture will continue indefinitely as the main conservation measure for oysters. This is when I started to think that oyster aquaculture might not be a good long term solution for our nation’s coastlines. Seeing how fast the industry is growing lately makes me think I’m part of a small minority.

What’s wrong with the current regulatory system?

Private industry is trusted to create a population of oysters. This artificial system results in an environment that doesn’t allow oysters to reclaim habitat. For instance, what would happen if the wild oyster populations were healthy enough to expand substantially? Traditional growers tow dredges and constantly disturb the bottom. This muddy bottom creates an unsuitable environment for natural oyster reefs to form. Even if wild oysters settled in someone’s leased area, there would be no easy way to tell the wild ones from the farmers’ oysters.

Welfleet, MA- a place with a healthy aquaculture and wild harvest fishery.
Welfleet, MA

The current regulatory system in Connecticut creates an environment that discourages reestablishment of wild oyster reefs. The parts of Long Island Sound that are most suitable for oyster growth are already in private hands. The rapid growth of the oyster aquaculture industry along the rest of the coast may create similar circumstances.

How can we change this? How will wild stocks ever reemerge if the shellfish are managed like this? Does it matter? I think so. I’d love to see wild oyster reefs and all their benefits, and think small time oystermen plying the sound’s waters would be a welcome addition to the coastal area. Coastal towns would benefit from the storm protection that oyster reefs can provide, and summer tourists would appreciate the cleaner, clearer water.

The ocean is a public resource, and any management plan should encourage wild fisheries, not private “ownership” of the bottom.

So why aren’t there thriving oyster populations in places like the Sound? You would think that if the waters are good for oyster farming then they would be good for wild oysters. However, water quality isn’t the only condition needed for a thriving population. The growth of oyster populations seems to depend on the presence of numerous already established oysters, and when the natural populations were depleted, they weren’t able to rebuild themselves. This eventually led to the end of wild oyster harvests, and the subsequent rise of aquaculture.

Really basic oyster life cycle

Oysters reproduce by sending millions of free swimming larvae into open water. There, they mix with the plankton in the ocean to drift wherever the currents take them. When they find a suitable home, they settle down for their sedentary life as the oyster that we know. Oysters in the free-swimming larval stage of their lives are fond of settling down with other oysters; they are somehow attracted to oyster shells and attach themselves to the adults. That’s why you find clumps of oysters that, over time, eventually form large oyster reefs.

The problem is that oyster larvae could drift anywhere—the open ocean, the intakes of power plants, the mouths of filter feeders. That’s why you need a lot of them; and when oyster reefs are gone, they are really hard to rebuild. Without large oyster reefs stabilizing the bottom, silt and sediment move around much more and smother any small groups of oysters, eventually killing them. Picture erosion on a hillside that has been cleared of growth. That’s what the bottom of a bay is like when there aren’t oyster reefs to stabilize things. Oysters anchor the sediments by covering them up and also take the brunt of wave action during storms. They provide the clean water and stable seafloor necessary for eelgrass and other plants to grow which further stabilize things.

When oyster populations shrank, there were not enough larvae in the area to build oyster reefs robust enough to withstand the silting that occurs. Traditional aquaculture doesn’t provide the population density needed to rebuild the oyster reefs. Traditional aquaculture also requires the use of dredges, which further destabilizes the bottom and definitely doesn’t foster oyster reef growth.

How can we re-establish wild oysters?

I read Paul Greenberg’s book “American Catch” and learned a lot about the history of oysters in our region. In it he writes about how prolific oysters used to be in Long Island Sound and around New York City. There used to be millions of oysters in the Sound—a staple of the diet of Connecticut and New York residents. It’s a great book. I recommend it to anyone who cares about our countries’ fishing industries.

In his book, he writes about restoration projects in areas with poor water quality. While that seems like a good idea, I think it needs to be done in healthy areas first; a place where the project might have a better chance of success because of optimal water conditions. I also think it needs to be a large scale long term project with significant government funding. Most projects I read about are smaller scale projects carried out by non-profit groups or universities.

I’d try to find an area that can support a healthy population and have some sort of natural containment for the free swimming larvae. A small estuary in eastern Long Island Sound with good water quality might be a good place to start. You could heavily seed the area and attempt to stabilize it with some eel grass. The area would have to naturally retain an above average number of the free swimming larvae within the basin and build the reef up. Once healthy the reef would sustain itself (because it was an area that had good water quality to begin with) and could be used to help build other reefs in similar areas. Once these reefs take hold it might be easier to restore reefs in nearby areas that may have poorer water quality.

Can things change?

A major hurdle in Connecticut is the legal structure of the bottom leasing system. How would you encourage restoration in a leased area? No farmer wants to willingly create a situation that could put them out of business. Most of the grounds that have good water quality are leased already, so you’d have to take land away from farmers to make this work. Trying to develop a wild stock creates a threat to farmers. They may not be able to renew their leases or expand their farms if wild stocks take over their area. I can’t see anyone agreeing to a restoration project with those potential consequences.

So, you have no real way to tell if wild stocks are infiltrating a leased area, no restoration projects in healthy areas, and a legislative structure that encourages private ownership of what should be a public resource. Combine these conflicts with the growing popularity of aquaculture and you have a serious challenge to restoring wild oysters in large numbers.

We have seen what agriculture has done to the land—we need to consider more than just the positive benefits of shellfish aquaculture. We need to think about the long term effects of privatizing the coastal waters—our last (mostly) public resource. I don’t think aquaculture should take precedent over restoring wild populations—once our coastlines are fully industrialized with private farms, it may be very difficult to turn back from.

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