Oyster Pond is home to several important fish species including alewife herring (Alosa pseudoharengus), American eels (Anguilla rostrata), white perch (Morone americana) and at one time, yellow perch (Perca flavescens). It was the dramatic decline of white and yellow perch in the mid-1980s that signaled to the residents of the Oyster Pond that something was amiss about the pond and spurred the formation of OPET.
River herring played an important role in the history and coastal heritage of Cape Cod. They are a keystone species in a coastal ecosystem as food source for other fish and other animals (see the wildlife videos of the variety of animals that show up at the weir to catch herring during the spring run).
Oyster Pond is the third largest herring run in Falmouth. OPET plays a crucial role in ensuring this run remains viable. The Town of Falmouth Herring Warden, Chuck Martinsen, relies on OPET to maintain safe passage for the adult herring during the annual spring migration. We monitor Trunk River daily during the spring migration season since high tides and spring storms can create sand plugs that block the river channel.
Many long-term residents of Cape Cod tell stories about herring runs so large and so dense that they were “a fire hose of fish”– you could scoop as much as you wanted and they still kept coming. Unfortunately, those days are long gone. Herring populations declined precipitously along the Atlantic seaboard in the 2000s. Some herring run numbers dropped by 90%, prompting the Massachusetts Marine Fisheries Advisory Commission to put a moratorium on the harvest, possession and sale of river herring in 2006 that continues to this day. This prompted OPET to take a closer look at our own herring population and realize what an important role preserving and improving this population can play for the species as a whole. Since 2009, Lou Turner has organized volunteers to count the incoming herring for about an hour in the evening once a week. Volunteers start at dusk as the herring like to move under the cover of darkness. Though these numbers are not robust statistically, since herring that move later in the night are missed, they do give us a snap shot.
Herring are an anadromous fish, meaning they spawn in fresh water and then spend the rest of their adult life in the ocean. They return three to four years later to spawn in their natal, fresh water pond. They can live up to eight years and will continue to return each spring to spawn. Alewives begin returning in mid-March, depending on the weather. The fish usually wait until the water temperature is about 50 degrees F before they start their “run” that lasts from 6 to 8 weeks.
After spawning, the adults return to the sea over a period of several weeks. Their young exit the pond beginning in June and continue until December. The fry often school at the Oyster Pond weir for several days before they exit. It is a sight to see this massive ball of young herring waiting for a signal to begin their journey to the sea, known only to them. Usually a large rain storm will prompt them to leave.
American Eels – Oyster Pond’s Other Important Resident
Much of the focus for the pond’s wildlife has centered on alewife herring, but there is another resident that makes Oyster Pond its home that is just as important – the American eel. Unfortunately like the herring, eel populations are dropping. Dams and other river obstructions, hydropower plants and overfishing are contributing to their population drop. Fortunately, Oyster Pond is home to a very healthy eel population.
Less is known about our eel population due to their more elusive live style. One herring counter did see hundreds of tiny eels, known as glass eels, migrate into Oyster Pond a few years ago.
Eels have an opposite life cycle from herring. While adult herring are entering Trunk River to migrate up to Oyster Pond in the spring to spawn, young eels or elvers are entering the pond to grow into adults. They were hatched in the far-off Sargasso Sea, an area of becalmed ocean between Bermuda and the Bahamas in the middle of the Atlantic. Unlike herring, elvers do not migrate back to a particular estuary or river. Rather, millions of small eels a few inches long drift along ocean currents migrating to where luck will take them to any fresh or marine waters.
They can spend up to 30 years in the juvenile yellow eel stage eating fish, crustaceans, insects, worms and frogs. In turn eels are meals for striped bass and other fish, gulls, ospreys and other fish-eating birds. When they reach adulthood they turn silver for the long migration back to the Sargasso Sea.
White Perch Fish stories from 2007
In the late 1980s the white perch disappeared – the pond essentially crashed because of the influx of salt water that was coming into the pond via the much larger new culvert the town installed. The salt water sank to the bottom and the fresh water from the north end of the pond remained on top; hence the bottom became anoxic – there was insufficient oxygen to support fish. When it was realized what was going on, the weir was installed at the entrance of the pond to keep the pond sufficiently fresh and increase oxygen at the bottom. The fish returned and today the pond is as healthy as far as white perch are concerned as it was in the early 80s.
Unfortunately, yellow perch have not fared as well. Few if any yellow perch have been seen in recent years.
Lou Turner helped John Dowling catch white perch for John’s annual research on the health of the white perch population in the Pond. For a number of years John used white perch from Oyster Pond for research on retinal neurons at Harvard University.
In one hour in 2007, they caught about 40 white perch. The smallest was about 5 inches and largest about 11 inches. They all looked very healthy. They were all returned. John used worms and Lou a small white lure with a spinner. Being the fisherman that he is, Lou reports that the fish did not prefer one type of bait over the other.