America’s largest estuary and seafood buffet is starting to lose its crabs as its islands sink below the waves. Climate change is beginning to ravage the iconic Chesapeake Bay, right down stream from our nation’s capital.
Part 1: Decline of the “Beautiful Swimmers”
Measuring only four inches long and nine inches wide and encased in thick armor, the bottom-dwelling blue crab (Callinectes sapidus) seems like an unlikely candidate to anchor one of the ten most valuable fisheries in the U.S. The ten-legged crustacean, named for its two meaty, bright-blue front claws, is particularly integral to the region surrounding America’s largest estuary, the Chesapeake Bay, where a third of blue crabs are harvested. The blue crab harvest (about 55 million pounds per year between 2000 and 2009) underpins an estimated $3.39 billion seafood industry in Maryland and Virginia alone!
Worth billions and full of succulent flesh, it is no wonder that the blue crab has become a local icon around the Bay. It is Maryland’s state crustacean, adorning both t-shirts and the dinner table throughout the state. The seafood staple has became so beloved in the Chesapeake Bay region that most people refer to them as “Chesapeake blue crabs” even though they are found up and down the Atlantic Coast from Nova Scotia to Argentina. The crab’s scientific name even reflects the admiration that Marylanders have for them and their meat. It means “savory beautiful swimmer.”
A model female blue crab shows off her large claws at the National Museum of Natural History in Washington DC.
But over the last few years, the populations of these beautiful swimmers has alarmingly declined. According to the annual Blue Crab Advisory Report by the Chesapeake Bay Program, the overall population of blue crabs in the Chesapeake Bay fell by 18 percent between 2017 and 2018, from 455 to 372 million crabs. The diminished 2018 population had only 147 million adult female crabs, well below the Bay Program’s target of 215 million females.
The obvious culprit for the decline of the bay’s iconic shellfish would be overfishing. With blue crabs and other seafood worth billions to the states surrounding the bay, short-sighted over-harvesting seems likely. Yet, as with most environmental issues, the actual reasons for the decline are more nuanced.
Blue crab in watercolor.
Overfishing, or harvesting an animal faster than its population can reproduce, is a factor for the decline, but it is far from the only culprit. The eelgrass beds throughout the Chesapeake, that young crabs rely on for shelter, are being smothered by sediment and nutrient runoff from nearby agriculture. The excess nutrients in the water also cause bacteria populations to skyrocket, depleting large swaths of the bay of oxygen and killing off the crab’s prey in the resulting dead zones.
Although the crab’s population has dropped, the Chesapeake Bay Program still sees them as relatively healthy and has not adjusted blue crab management since the drop-off of 2018. NOAA (The National Oceanic and Atmospheric Administration) deems the crabs to not technically be overfished yet because the adult female crab population still exceeds the overfishing threshold of 70 million.
But the Chesapeake Bay is becoming increasingly impacted by human settlement. As these effects continue to increase and the Bay’s climate changes, will the incredibly valuable blue crab population continue to dwindle?
Maryland is famous for its steamed blue crabs lathered in Old Bay seasoning.
Part 2: A fragile bay and a changing climate
Blue crabs are a perfect window into the health of the Chesapeake’s overall ecosystem because their intricate life history transports them all over the bay. Blue crab eggs are released near the salty mouth of the Bay in egg masses that can contain up to 2 million crab eggs. The larvae is transported by currents into the ocean where they grow, molting their shells several times in the process. Eventually, the larvae move back into the brackish (a salt and freshwater mix) water of the Bay where they continue to molt, eventually become adult crabs a year to 18 months after they’re born. Adults move toward the upper bay and connecting rivers. Over their three-year lifespans, the blue crab will inhabit every habitat in the Bay, from the Atlantic Ocean at its mouth to the rivers that feed into the Bay.
A gray tree frog from Easton, Maryland. There are dozens of reptile and amphibian species that live in the Chesapeake region including Maryland’s state reptile the diamondback terrapin.
Over these stops, the crabs are vital to the function of the ecosystem. As versatile omnivores, the crabs voraciously eat anything smaller than them. Clams, oysters, mussels and even smaller blue crabs are all on the menu. The crabs also act as valuable recyclers of dead organic material in the Bay as they scavenge dead fish and other carrion.
In addition to being the Bay’s preeminent eaters of small and dead animals, blue crabs themselves are also important prey for young fish and birds, including the large, prehistoric-looking great blue herons that slot into the upper reaches of the Bay’s complex food chain. Sporting a 7-foot wingspan and a lethal stealth hunting approach, the great blue heron (or the dinosaur of the marsh) keeps the population of fish, crustaceans and amphibians in check.
A great blue heron grabs a fish from the water. Even though the bird has up to a seven foot wingspan, it has hollow bones, only weighing a couple of pounds!
Dozens of species of birds, like the great blue heron, live in the Bay year-round. Dozens more visit the Bay at different times of the year, such as the dive-bombing, fish-eating osprey and the majestic bald eagle. One million waterfowl visit the Chesapeake Bay region every winter during migration as an important stopover along the great Atlantic Flyway.
Above: Osprey are found everywhere except Australia and Antarctica, a testament to their success as species. Also known as sea hawks, they eat almost exclusively fish, with they hold on to with their sharp talons (picture 2).
In addition to the plethora of birds that pass through the Bay each year, the Chesapeake supports over 3,600 species of animals and plants. From forests to wetlands to the rivers that bring freshwater into the salty estuary, species as diverse as dragonflies and sea turtles thrive here. Over 300 species of fish call the estuary home, eating juvenile blue crabs before becoming heron food. What’s left over of the fish after the heron has had its fill is then recycled by blue crabs, an intricate food web where nothing is wasted. It is a machine that has hummed along since rising sea levels flooded the Susquehanna River valley 12,000 years ago, creating the Chesapeake Bay.
The ruby meadowhawk dragonfly is common in the northern United States
But the Bay’s climate is in a state of flux, drastically threatening its ecosystems.
Part 3: Swallowed by the Bay
The word Chesapeake comes from the Algonquian word Chesepiooc, first heard by European explorers traveling through one of the Bay’s many tributaries from the doomed Roanoke Colony in Virginia in the 1580s. The word may mean “great shellfish bay”.
Since then people have been using the Chesapeake Bay for recreation, sustenance and as a dumping ground for the undesirable leftovers from the many industries that line the Bay’s shores. After centuries of exploitation, the Chesapeake is starting to fight back.
The boatyard at Oxford, Maryland, a small town on the Bay’s Eastern Shore.
The Chesapeake Bay is uniquely vulnerable to sea level rise because of its low-lying topography. This threat is exacerbated as millions of people live along the bay’s coasts, putting themselves in the “flood-zone”. No where is this more painfully apparent than at historic Tangier Island. The tiny island, famous for its unparalleled catch of soft-shell crabs, has lost an average of eight acres per year since 1850. This island, in the middle of one of the Bay’s widest points, will be uninhabitable in 50 years.
Most of the 460 locals of Tangier Island believe the disappearance of their land to be due to erosion caused by the Bay’s powerful waves, but the island is experiencing many of the telltale signs of climate change-driven sea level rise. Water is coming up through the ground and the island’s marshes are drowning. On an interesting note, the island’s residents voted overwhelmingly for President Trump in 2016, causing a media-frenzy in 2017 and even a call from Trump himself, promising that the island would remain there for hundreds of years.
Dusk in the marsh.
Whatever the people on Tangier believe is causing the Chesapeake to swallow their island is up to them, but they are far from alone in facing this slippery predicament. Throughout the Bay, the combination of climate change-driven sea level rise and the natural sinking of soaked coastal lands have caused the water’s level to increase by a foot in many areas since 1900. At least 13 islands have disappeared from the Chesapeake, and estimates put the total water rise between 17 and 28 inches above 1990 levels by 2095.
The Chesapeake’s ecosystem has been broadcasting these troubles for decades. The disappearance of crabs and oysters has greatly altered the water-quality of the country’s largest estuary. Crabs no longer clean up the dead material, and the water that was once filtered out by oysters is full of harmful particulates in areas where the invertebrates have declined.
A retro oyster can-the Chesapeake’s oyster population has plummeted in recent years thanks to a combination of over-harvesting, disease and habitat loss.
The stark economic decline resulting from the coastal floods, the receding islands and the dwindling shellfish should be a call to action. Over the last 30 years, the decline in oysters has cost Maryland and Virginia more than $4 billion. Between 1998 and 2006, a similar decline in blue crab populations has cost Maryland and Virginia $640 million. The loss of Tangier Island to the residents would be incalculable.
Commercial fishing has been a staple industry in Maryland for over 300 years. The fish, crab and oysters of the Chesapeake Bay continue to provide the state with hundreds of millions of dollars each year.
The Chesapeake Bay is truly incredible because it not only offers refuge to over three thousand species of plants and animals, but it provides economic sustenance to the 17 million people that live around it. In order to continue to benefit from the Bay, we need to change the way we use it. The first step is to recognize and acknowledge that we are the ones who are sinking the Bay, and then to take the necessary actions to stop it.
Chesapeake dinner plate.
All photographs and art by Jack Tamisiea
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Sources:
https://www.cbf.org/issues/what-we-have-to-lose/economic-importance-of-the-bay/index.html
https://serc.si.edu/research/projects/blue-crab-and-fishery
https://chesapeakebay.noaa.gov/fish-facts/blue-crab
https://www.chesapeakebay.net/S=0/fieldguide/critter/blue_crab
https://www.nwf.org/Home/Educational-Resources/Wildlife-Guide/Wild-Places/Chesapeake-Bay
https://www.myeasternshoremd.com/kent_county_news/spotlight/blue-crab-population-declines-by-almost/article_e7d3b39d-dadb-5d2b-8dee-c3ece7d813f1.html
https://www.cbf.org/document-library/cbf-reports/CBF_BadWatersReport6d49.pdf
https://www.nationalgeographic.com/animals/invertebrates/b/blue-crab/
https://www.nationalgeographic.com/environment/2018/09/climate-change-rising-seas-tangier-island-chesapeake-book-talk/#/06_chesapeake_bay_book_talk_chesapeakerequiem_case.jpg
https://www.cbf.org/about-the-bay/chesapeake-bay-watershed-geography-and-facts.html