What’s behind the decline in O.B.’s shellfish population?

Second in a series of columns by Friends of the Bay.

For several years now, Friends of the Bay has been sounding the alarm that our bay is at a critical juncture.

Shellfish populations, in decline for centuries, are now so stressed that they may be reaching the point of ecological collapse. Clams have become increasingly scarce, and oysters are all but nonexistent in Oyster Bay and Cold Spring Harbor. Independent baymen have a harder time making a living. Perhaps the most telling indicator of the decline is that the bay is no longer capable of supplying the oysters we celebrate during the Oyster Festival. This was once unimaginable.

Several years ago, Frank M. Flower & Sons closed its shellfish hatchery in Bayville, but have continued to use hydraulic dredging to strip all marketable shellfish from nearly 2,000 acres of leased bay bottom. This will leave barren what were once the most productive grounds in the bay.

What we are facing is more than the potential collapse of the commercial shellfish industry in a bay that once produced up to 90 percent of the oysters and 40 percent of the clams harvested in New York state. What we are facing is the potential collapse of an entire ecosystem.

Clams and oysters are “keystone species.” They are the basis for an entire ecosystem that would not exist, or would be fundamentally changed, without them. They provide food and habitat for numerous species, protect shorelines from erosion and storm damage and, as filter feeders, improve water quality. They also provide the offspring to seed other areas of the bay and beyond.

A healthy ecosystem needs to be able to grow and develop without interruption. Shellfish, and particularly oysters, are ecosystem engineers. As they grow, mature, spawn and die, they leave behind their shells, which accumulate and build reefs. These reefs historically grew to considerable size, attracting a wide range of other species and acting as a nursery for their young. Preserving the size and density of oyster reefs is crucial to keeping the species viable.

Once this scale and density is lost, the entire system begins to break down.

Shellfish spawn by simultaneously ejecting sperm and eggs into the water column. For this process to be successful, it is necessary to have large numbers of individuals packed tightly together to ensure that the sperm and eggs make contact. Once the eggs are fertilized, they become free-floating larvae that are carried by the tide and currents until they settle to the bottom. To survive at this stage, they must settle on bottom material that is suitable. In the case of oysters, the material most conducive to survival is oyster shell. Soft mud or silt will most likely result in the death of the larvae.

This entire process, as well as the growth phase that follows, must also take place in water that is clean enough to support it. Since large quantities of shellfish contribute to clean water, sparse populations will result in compromised water quality, further hindering the likelihood of successful reproduction. Loss of scale and density also make the population more susceptible to disease and predators.

Loss of scale and density, declining water quality, silt and contaminants entering the bay though stormwater, disease, predators, climate change and unsustainable harvesting are all contributors to system collapse. As more and more shellfish are lost, there is a snowball effect. Ecological collapse happens when all of these factors combine to a point at which the remaining shellfish can no longer replace and increase their numbers.

Once our bays get to this point, huge investments of time, effort, money and political will be necessary to restore them — if they can be restored at all. If we are not already at that point, we are surely close.

Bill Bleyer is president of Friends of the Bay.

The next installment in this series will be “How do we fix this?” For more information, go to www.friendsofthebay.org.