Habitat

American Eel - Anguilla rostrata

The American Eel on Cape Cod from Association to Preserve Cape Cod on Vimeo.

The American eel is a pretty amazing creature. For starters, it’s the only freshwater eel in North America and the only catadromous fish in North America. And yes, despite its body shape, it is a fish. The eel is an ancient species that survived the glacial periods. It has a fascinating life story and we don’t even know the entire story. It’s all a bit of a mystery. But what we do know is that on Cape Cod, American eels can be found in freshwater ponds and streams. This is where they live their adult life, but they began their life thousands of miles away in the Sargasso Sea.

Identification. An eel is not a particularly beautiful creature because of its snake-like physique. They can vary in color, but have a dorsal fin and An eel lives its adult life in freshwater ponds where the males can grow up to 3 feet in length and the females can reach up to 5 feet, weighing up to 16lbs.

Habitat. They hide in shaded areas of ponds and prey on small fish, worms and other invertebrates. Some freshwater mussels depend on the eels to complete their life cycle.

Life Cycle. This migratory behavior is the opposite of the anadromous river herring Cape Codders know well that spend their adult life in the sea and journey upstream to freshwater ponds to spawn. The catadromous eel, when a mature adult will leave its freshwater habitat for the sea. And not just anywhere in the ocean. These eels will swim thousands of miles to the sea within the Atlantic Ocean the Sargasso Sea whose boundaries are created by ocean currents. The Sargasso Sea is named for the floating Sargassum seaweed that provides a safe haven nursery for many marine creatures and a rich ecosystem of food and shelter. Here, eels meet up with other eels and spawn, each female releasing tens of thousands of eggs.

There are many details of the eel life cycle which remain mysterious. What we know amounts to just an outline of understanding. We believe the spawning adults to be at least 5 years old, but some are believed to live to be 15 years or more. After spawning in the Sargasso Sea, the adults are thought to die. However, hundreds of millions of eggs hatch, and over the next year, the eel larvae drift in the Gulf Stream as they transform into a transparent form called the “glass eel”.

Somehow, these worm-sized larvae gravitate toward the shore in search of freshwater. Researchers have found that baby eels have crystals of magnetite in their brain, which is typical of other migrating species that provides sensitivity to the earth’s magnetic fields for navigation. As soon as springtime temperatures warm the water, the baby eels swim into estuaries to reach the freshwater ponds. In the estuaries, they begin to gain pigment and are referred to as elvers at about 2.5inches in length. At this stage, their sex is still undetermined. In the ponds they will mature to adults and live for many years before they return to the Sargasso Sea to create the next generation. A remarkable life history.

Ecological Value. Like herring, the eel is a keystone species that supports a wide variety of other animals as a food source in all its life stages. Even the life cycle of certain freshwater mussels depends on the eel.

The Problem. Eel populations are threatened due to degraded habitat from pollution and loss of the natural water connections between the ocean and freshwater ponds due to construction of dams and roadways, and from overfishing the species.

The Solution. To help recover the species, the harvesting of the baby eels as they re-enter fish runs has been prohibited in Massachusetts. Harvesting is still allowed in Maine and South Carolina where the small glass eels, about the size of large earthworms, are sold to Japan where they are grown out into adults for consumption. Some eels will return back to New England, but as a food item at your favorite sushi restaurant!

For more information: https://www.pbs.org/video/nature-mystery-eels/ ; https://www.mass.gov/service-details/learn-about-the-american-eel

River Herring - Alosa pseudoharengus and Alosa aestivalis
River Herring on Cape Cod from Association to Preserve Cape Cod on Vimeo.

River Herring. The river herring of the northeast US include the alewife (Alosa pseudoharengus) and the blueback herring (Alosa aestivalis). Herring are anadromous fish, which means they spend their adult life in the ocean and spawn in freshwater.

In the ocean, herring also fill an important niche. They are a food source for larger fish like striped bass and bluefish, dolphins and whales, and numerous other sea creatures. They are called a keystone species which is a species whose health and well-being reflects the overall state of the coastal ecosystem and can be an indicator of water quality problems.

Identification. Herring are small, streamlined, laterally compressed silvery fish in the family Clupeidae. The more than 200 species in this family share several distinguishing characteristics such as a single dorsal fin, no lateral line, and a protruding, bulldog-like lower jaw. Unlike many other fish, herring have soft fins that lack spines.

Life Cycle. As adults, river herring live in marine waters most of the year. They arrive to the Cape as early as mid-March, swimming through estuaries to where the freshwater meets the salt. There is some speculation that they return to the freshwater pond in which they were born and it is here they will spawn the next generation.

This is a harrowing trek as they swim the gauntlet of predators that over the millennia have cued into their arrival. The herring arrive when the gulls, osprey and herons are seeking nourishment for themselves and food for their young. Terrestrial predators include racoons and river otters. River herring are a crucial link in the food chain.

In general, spawning is initiated for alewives when the water temperature reaches 51 F (10.6 C). Alewives generally spawn in ponds. During spawning, the eggs settle and stick to gravel, stones, logs, or other objects. Unlike Pacific salmon that die after spawning, herring typically survive and move back to the ocean after spawning. Toward the end of summer and early fall, the young fish will head out of the ponds down the streams and into the estuaries when they are about 1-1/2 to 2-1/2 inches long and will eventually move to the open ocean to live their adult life.

Food. They are plankton-feeding (planktivores), typically traveling in large schools.

Historic Perspective. River herring have an important role in the history and coastal heritage of Cape Cod as well as other coastal communities from the Mid-Atlantic region up through New England. Towns with herring runs depended on the annual spring herring migration to harvest fish for food and sale, and herring contributed to the local economy. Native Americans also harvested herring for food. The Wampanoag culture and the herring are intertwined.

Less than a lifetime ago, the streams and rivers of Cape Cod were thick with river herring in spring. But river herring populations have been declining in the mid-Atlantic and Northeast coastal regions for several decades. For example, in the 1920s there were a million fish in the Coonamessett River which in recent years became less than 30,000. By the 1990s, the MA Department of Marine Fisheries knew there was something wrong with the herring population and in 2005 declared a moratorium on taking or catching any river herring in Massachusetts.

Habitat. River herring need a variety of habitats for spawning, rearing, and transitioning to and from saltwater. They are not selective of pond bottom which can include gravel, detritus, and submerged aquatic vegetation.

Threats. The decline in river herring is symptomatic of environmental problems that are impacting other fish, wildlife and whole ecosystems. Reasons for their decline include development that has introduced barriers to fish passage, like roadways that obstruct natural water flow and alterations dues to historic agricultural activities that closed off the natural flowing water connection from fresh to salt water.

Water withdrawals and diversion change stream paths, depth of water and flow. Warm temperatures stress fish and sometimes result in mortality. Improper management of water control during low stream flows can result in higher water temperatures than normal and result in less freshwater input to estuaries which are important nursery areas for young herring as they make their way out to sea.

Habitat loss due to development degradation of estuarine systems and quiescent ponds from alteration, excess nutrients and pollution. Water quality is declining due to pollution from septic systems, stormwater runoff and fertilizer use, causing acceleration of phytoplankton growth and when it dies, the bacteria that decomposes the microalgae consumes oxygen. This results in reduced dissolved oxygen, stressing fish and even resulting in fish kills.

Predation by wildlife, while a natural part of the food web, can be thrown off balance by land use activities that favor species, either intentionally or not. Poaching by humans despite the moratorium on taking herring is an annual occurrence. Only the Wampanoags through their tribal rights are permitted harvest herring in keeping with their cultural traditions.

A potential cause of the significant decrease in herring returning to spawn has been the overfishing and bycatch at sea. There was an effort by the Cape Cod Commercial Fishermen’s Alliance to advocate for a buffer zone for mid-water trawling that they feel is contributing to the reduction in river herring populations. As of February 2019, the National Marine Fisheries placed a reduced quota on the amount of Atlantic herring that can be caught, however this does not address river herring lost to bycatch.

The impacts of climate change include changes in precipitation and increased water temperature that changes the ecological balance of the pond and streams will also impact future generations of herring.

The Solution. Protect herring populations by

  • Insuring healthy estuaries, streams and ponds, and address nutrient overload from septic systems, stormwater runoff and fertilizers
  • Using best practices when recreating on ponds and for land use around ponds and within their watersheds
  • Support monitoring efforts and volunteer to count herring as they make their way to spawning grounds
  • Mitigating impact of groundwater withdrawals
  • Managing outflows from ponds during critical periods with this fish species in mind
    Removing barriers to fish passage like dams and restore natural water flow where possible
  • Be concerned about chemicals of emerging concern (CEC’s) entering our groundwater and surface waters through wastewater, particularly endocrine disruptors
  • Be mindful of the threats of climate change impacts
  • Advocate for appropriate fishery management policies to reduce bycatch

For more information on herring:

A Guide to Viewing River Herring in Coastal Massachusetts
Fish Restoration Fact Sheet

Sea Run Brook Trout

Sea Run Brook Trout

Sea Run Brook Trout. This is the Cape’s only native trout. Cape Codders refer to them as “Salters”. They are an anadromous form of brook trout, which means they live part of their lives in marine waters, thus the nickname Salters.

Identification. Technically sea run brookies are not a true trout. They are a char which is a subgroup of the salmon family. They are distinguished from other trout and salmon by the absence of teeth in the roof of the mouth and other physical attributes. They are beautifully colored, speckled with lighter colored spots of orange. It is the silver sheen of a brook trout’s skin that indicates it has spent time in salt water. It has been out to sea or at very least the estuary where it was enticed by the abundance of food available in the estuarine system.

Habitat. As sea level rose after the glaciers retreated, long fingers of cold water streams carved valleys as they flowed to the ocean. These cold groundwater-fed streams became excellent habitat for brook trout. Brook trout on Cape Cod are at the most southern part of their range as they require cold water where 50 degree water temperature is optimum.
Forested stream edges that include a jumble of tree roots and overhanging vegetation is critical to brook trout. The shade of vegetation helps moderate the temperature of the water. As temperatures go up, the fish get stressed and at 67 degrees they stop growing. There is much we do not know about the sea run brook trout, but we do know that 78 degrees will kill them.

Food. They are opportunists and will eat small aquatic and terrestrial invertebrates such as caddisflies, mayfly and damselfly larvae, flying insects, water beetles, snails, worms, whatever they can get their mouths on. In fast running streams, fallen logs and stream debris provide excellent feeding areas as well as cover from predators.

Life Expectancy. At a year of age, they are about 4 inches long. A 9 inch fish has been growing for at least three years. Brook trout are more plentiful in the streams in the western part of MA, but here on the Cape populations are slim due to many factors affecting their habitat. On Cape Cod, brook trout are a short-lived species and may live to only about 3-4yrs. Trout are mainly predated upon by osprey, herons and river otters.

Reproduction. Typically spawning in late October to early November. The female scours out a nest in the gravelling bottom, depositing her eggs that incubate in the gravel over the winter and hatch in late Jan to Feb. The spawning areas are very specific, where the edge of the bank meets the river and where there is upwelling spring water, substrate of sand and gravel. After hatching, they seek the marginal areas where water velocity is low.

Historic Accounts. Oral legends of the Wampanoag document abundant populations of the fish. Written historic accounts from John Rowe in the 1700s also speak to the plentiful fish and their much larger size. He documented catching several trout 18 inches in length, a size which is unheard of today.

Threats. Streams have been lost due to our development of the land. For example, two streams, the Monument River that originally flowed into Buzzards Bay and the Scussett River, would have been prime habitat for salters. These were both lost with the construction of the Cape Cod canal.

  • Other development, like dams and mills, created impediments to the movement and passage of sea run brook trout.
  • Road crossings often restrict the natural water flow.
  • Withdrawals of groundwater can reduce stream flow.
  • Removal of woody debris in the stream removes critically important protective cover for the trout. Logs and overhanging vegetation create cold pockets where fish can hold up in warmer days and hide from predators.
  • Good intentions of increasing habitat for ospreys has had unintended consequences for the brookies, giving these predators from above an unfair advantage.
  • Water quality impacts from wastewater, stormwater and fertilizers. Excess nutrients have changed the balance of natural systems from aquatic vegetation dominated ponds to one dominated by algae and cyanobacteria. Pollution has consequences yet to be fully understood.
  • The disruption of our climate is causing increased summer temperatures and warming of the waters.

The Solution. Protect existing trout populations by

  • Leaving and/or restoring the woody vegetation along both sides of streams and enhancing these riparian zones
  • Insure healthy estuaries and eel grass beds that provide valuable feeding areas
  • Mitigate impact of groundwater withdrawals
  • Monitor temperatures and flows to gain understanding of what is happening
  • Manage outflows from ponds during critical periods with these cold water fish species in mind
  • Remove barriers to fish passage like dams and restore natural water flow where possible
  • Be concerned about chemicals of emerging concern (CEC’s) entering our groundwater and surface waters through wastewater, particularly endocrine disruptors
    Be mindful of the threats of climate change impacts

Sea Run Brook Trout need

  • Woody debris
  • Vegetated banks
  • Overhanging vegetation
  • Shaded waters
  • Coldwater refugia – cold pockets of upwelling freshwater
  • Unobstructed water connections
  • Properly controlled water management with their needs in mind

For more information on Sea Run Brook Trout:

Sea Run Brook Trout Coalition
Fish Run Restoration Fact Sheet
Wild Brook Trout Mapping Tools