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Bay Blog: migration


Photo of the Week: Migrating river herring face upstream struggle

A school of alewife spawn in the calm shallows where Deer Creek meets the Susquehanna River in Susquehanna State Park in Havre de Grace, Maryland, on April 16, 2015.

Alewife (Alosa pseudoharengus) and their close relative blueback herring (Alosa aestivalis) are collectively known as "river herring." The two can be difficult to distinguish from one another—both are thin, silver-sided fish, each with a single dark spot located behind its head. Alewife, however, can be distinguished by their bronze-green backs, whereas the aptly named blueback has a blue-colored back.

River herring are anadromous: they spend their adult lives at sea, returning to freshwater areas only to spawn in the spring. The small fish serve as important prey for larger predators like striped bass and bluefish. They also once served as one of the largest fisheries in the Chesapeake Bay; in 1931, over 25 million pounds of river herring were harvested from the estuary.

But the destruction of spawning habitat, the constructions of dams restricting migration and increased fishing pressure led to a major decline in river herring abundance. In 2006, commercial catch of river herring for the entire Atlantic coast totaled just 823,000 pounds. By 2012, Maryland, Virginia and the Potomac River had harvest moratoriums for river herring in place, as did many other states along the East Coast.

To restore herring to the Chesapeake Bay, experts like the Chesapeake Bay Program’s Fish Passage Workgroup are helping to remove barriers such as dams and culverts where they block waterways and prevent river herring from migrating. Where structures are unable to be removed, fish ladders and lifts help fish get over or around larger barriers.

Learn more about alewife, or learn about the Chesapeake Bay Program’s work to open the region’s streams to the migration of fish.

Image by Will Parson

Stephanie Smith's avatar
About Stephanie Smith - Stephanie is the Web Content Manager at the Chesapeake Bay Program. A native of the Midwest, she received her Bachelor’s in Professional Writing from Purdue University and Master of Science degree from the University of Michigan. Stephanie’s lifelong love of nature motivates her to explore solutions to environmental problems and teach others what they can do to help.


Photo of the Week: In winter, the Bay can be paradise for both bird and bird-watcher

A group of tundra swans gathers at Beverly-Triton Beach Park in Edgewater, Maryland. Tundra swans breed during the summer in the tundra of northern Canada, but migrate to the Chesapeake Bay region in the fall and stay here throughout the winter.

Tundra swans aren’t the only birds that migrate to or through the Chesapeake Bay region in winter. The Bay sits on the Atlantic Flyway, a broad range covering the East Coast of the United States and eastern Canada that many birds follow on their annual migration. The Chesapeake Bay is an ideal resting point for many species of songbirds, shorebirds and raptors as they fly south, but also serves as the final destination for about 1 million swans, geese and ducks. Some of those birds come from as far north as the Arctic while others migrate as far south as South America.

Due to its location on the Atlantic Flyway, the Chesapeake Bay region is full of great places for birding. But if you want to be able to enjoy birds from the comfort of your home, there are many things you can do to make your home bird-friendly, even in winter. For example, you can provide a source of food for birds by planting species such as Virginia creeper or winterberry holly that have berries in the winter. If you don’t have yard, you can hang a bird feeder or set out a shallow dish filled with seeds. After attracting birds to your home, the next step is to identify them!

Learn more about how you can begin birding this winter.

Image by Will Parson

Joan Smedinghoff's avatar
About Joan Smedinghoff - Joan is the Communications Office Staffer at the Chesapeake Bay Program. Originally from Chicago, she was introduced to the Chesapeake Bay region through the streams of central Pennsylvania. She received her Bachelor's in Environmental Studies from Dickinson College in Carlisle, Pa., where she first discovered her passion for storytelling.


Photo of the Week: Monarchs prepare for a remarkable journey

A monarch butterfly (Danaus plexippus) alights on a flower to forage for nectar. The insect’s distinctive orange and black wings signal to predators that the species is poisonous. Milkweed, the preferred food source for monarch caterpillars and adults, produces toxic chemicals that accumulate in the insect’s body.

The bright, delicate flutter of a monarch is a common sight throughout the Chesapeake Bay watershed—but in the fall, when the butterflies begin their migration south, the view becomes spectacular. From early September through late October, millions of monarchs in central and eastern North America make their way to the Gulf States and Mexico (while monarchs in the west migrate to southern California).

To avoid crossing large bodies of water as they migrate, monarchs are naturally drawn to peninsulas. This makes the Delmarva Peninsula a major player in the insect’s migration—but peninsulas on both the eastern and western shores of the Bay are opportune spots to sight the migrating butterflies.

Learn more about the monarch butterfly, or check this migration map to see where monarchs have been spotted near you.


Image by Will Parson

Stephanie Smith's avatar
About Stephanie Smith - Stephanie is the Web Content Manager at the Chesapeake Bay Program. A native of the Midwest, she received her Bachelor’s in Professional Writing from Purdue University and Master of Science degree from the University of Michigan. Stephanie’s lifelong love of nature motivates her to explore solutions to environmental problems and teach others what they can do to help.


By the Numbers: 33

Each spring, migratory fish use the rivers and streams of the Chesapeake Bay watershed to move between fresh water and the saltier ocean. Anadromous species—like American shad, hickory shad and blueback herring—return from the ocean to lay their eggs in fresh water, while catadromous species—like the American eel—move from streams to the ocean to spawn. While dams and culverts can block the movement of these fish, dam removal and fish passage construction projects have reopened thousands of area stream miles to fish migration.

In 2005, the U.S. Fish and Wildlife Service, the Maryland Department of Natural Resources and other partners began the demolition of the Octoraro Creek Dam near Rising Sun, Maryland. Image courtesy U.S. Fish and Wildlife Service Headquarters/Flickr)

According to the Maryland Department of Natural Resources, 33 fish species have ascended a fish lift, ladder or other structure in the state. While this indicates the value of fish ladders, lifts and other structures that help move fish over dams, it’s important to note the shift that new research has brought to fish passage restoration.

“Our [fish passage] program has changed over the years,” said Nancy Butowski, who manages fish passage in Maryland and serves as a member of the Chesapeake Bay Program’s Fish Passage Workgroup. “In the 1990s, it was focused on providing fish passage through ladders. But…fish passages are not 100 percent efficient. Now, we prefer dam removal.”

A scientist holds an American eel in Buffalo Creek, Pennsylvania.

Dam removal can benefit a wider range of species—like the resident fish who also move up and downstream at different times of year—and the stream itself, Butowski said. Depending on the dam, its removal can even benefit human health: there have been several deaths at the Patapsco River’s Bloede Dam, which is slated for removal.

Maryland has worked with Pennsylvania, Virginia and the Nature Conservancy to develop a tool that will prioritize fish passage restoration projects. It takes close to 40 different characteristics into account, including how many miles a project would open, how much a project would cost and whether there are migratory fish currently using the waterway. Through the Chesapeake Bay Watershed Agreement, the Bay Program has committed to reopening 1,000 more stream miles to migratory fish by 2025. Learn more about our work to reopen fish passage.

Catherine Krikstan's avatar
About Catherine Krikstan - Catherine Krikstan is a web writer at the Chesapeake Bay Program. She began writing about the watershed as a reporter in Annapolis, Md., where she covered algae blooms and climate change and interviewed hog farmers and watermen. She lives in Washington, D.C.

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