Every summer, the food web in Chesapeake Bay gets jostled around as two plankton-eating predators jockey for power: comb jellies and jellyfish. Most smaller species don’t have a stake in the battle—both predators eat zooplankton and fish eggs, after all. But for young oyster larvae, the victor could make the difference between being protected civilians or collateral damage.
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by Kristen Minogue
Every year, thousands of crab pots disappear, their lines snapped by violent storms or severed by the propellers of passing boats. Cut off from the buoys that once marked their presence, they become “ghost pots,” lost at the bottom of the Chesapeake.
But ghost pots aren’t dead pots. They’re still quite capable of trapping crabs, including mature females undergoing their spawning migration. And with no one to retrieve them, crabs too large to escape are condemned to a slow death by starvation. This often has the eerie effect of luring even more animals to their demise, says Laura Patrick, aquatic ecologist at the Smithsonian Environmental Research Center (SERC).
“The crabs are just going in and they’re dying,” Patrick says. “And one of the problems is that the dead animals that are in there can be bait for new crabs to come in. So it’s kind of a self-baiting pot.”
by Sarah Hansen
No one disputes that blue crab numbers in Chesapeake Bay are low. There is much discussion, however, about what to do to fix the problem. Smithsonian Environmental Research Center intern Julie Sepanik is working with SERC postdoctoral fellow Matt Ogburn to develop a computer model that will help improve our understanding of blue crab population dynamics in the Bay. The model works to identify where female crabs mature in the Bay and track their migration to lower Bay spawning areas. Ultimately, they hope the model will help inform decisions about preserving habitat and restoring the population.
by Kristen Minogue
The practice of selectively fishing male blue crabs in the Chesapeake—intended to give females a chance to reproduce—may have a hidden cost. A Bay without enough males could reduce the number of offspring females produce, ecologists at the Smithsonian Environmental Research Center found in a paper published in the July issue of Marine Ecology Progress Series.
Maryland and Virginia began reducing the harvest of female crabs by commercial and recreational watermen in 2008, the year officials declared the blue crab fishery a federal disaster. Since then, the crabs have shown signs of a shaky recovery. But a lasting comeback hinges on females producing enough offspring to sustain the population.
by Kristen Minogue
This summer and fall, biologists at the Smithsonian Environmental Research Center are looking to tag 10,000 blue crabs in Chesapeake Bay. They’re pursuing the project in spite of the two-year slump the crabs have suffered in the latest reports of the Chesapeake Bay Stock Assessment Committee. They’re hoping some of those crabs will help answer two unresolved questions on the path to recovery: the role of recreational crabbing, and the struggling population of adult females.
Every year watermen on Chesapeake Bay haul in between 40 and 110 million pounds of blue crabs on trotlines or in crab pots. The vast majority come from commercial watermen who rely on the crustaceans for their livelihoods. But recreational crabbers also take their share, and today no one knows exactly how large or small that share is.
“We really have very little idea how big the recreational fishery is now,” says Matt Ogburn, a postdoc at SERC’s Fish and Invertebrate Ecology Lab. Click to continue »
by Heather Soulen
With its motor located near the bow (front) of the boat, the modern-day mullet skiff could have been a character in Lewis Carroll’s novel “Alice’s Adventures in Wonderland.” Similar to the unpunctual rabbit, vanishing cat and hookah smoking caterpillar, it seems illogical…or does it?
In the early 1900s, the mullet skiff was originally designed for use in the commercial mullet fishery of the south. Popular for its simple construction, flat-bottom dory style hull with vee entry, and rounded stern (back) design, the mullet skiff was ideal for operating in shallow waters while carrying heavy loads of fish. However, during Prohibition, entrepreneurs souped up their mullet skiffs with straight-8 engines (precursor V8s) to run rum from the Bahamas and Cuba to the states. Since then, many mullet skiffs have undergone less scandalous modifications and have evolved to have an outboard motor in a well near the bow.
Why place a motor here? For three important reasons: 1) It places the motor higher in the water for maneuvering in shallow water, 2) it leaves the stern (back) open to work a net, and 3) it eliminates the risk of net entanglement in the propeller. So, with “the wrong end in front,” the mullet skiff was the perfect choice for the near-shore predator study our field crew conducted this summer throughout the Chesapeake Bay.
Predators of the Not-So-Deep
by Karen McDonald
Can’t get to water to fish up a blue crab? Want to teach about blue crabs and Smithsonian research but can’t make it to SERC or the Chesapeake Bay? Landlocked, but you want students to measure a crab’s carapace and learn about its life cycle? SERC has the answer: a virtual blue crab.
The blue crab is just part of the new Smithsonian X3D—a revolutionary way for visitors to interact with Smithsonian collections and research. In November 2013 the Smithsonian launched the Smithsonian X3D (beta) program, which allows visitors to flip, rotate and zoom in on digitized 3D images of objects from across the Institution. Right now they can explore more than 20 objects, including Amelia Earhart’s flight suit, the Wright brothers’ plane and a life mask of Lincoln.
How an invasive marsh plant could leave many fishes and invertebrates homeless, hungry and vulnerable to predatorsby Heather Soulen, SERC marine ecology lab technician
It’s no surprise that invasive species can dramatically alter an ecosystem. Often, invasive species outcompete native species and disturb ecosystems that have not evolved to handle the new intruder(s). One such invader is the introduced common reed (Phragmites australis australis). Introduced Phragmites alters native plant communities that native animals use. Over the past several decades, native marshes containing plants such as marsh elder, saltmeadow hay, black needlerush, sea lavender, cordgrasses, threesquares and bulrushes have fallen to introduced Phragmites in the Chesapeake Bay and throughout the Atlantic coast, turning once diverse marshes into a thick monoculture forest.
The Great Marsh Surface Uprising
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by Kristen Minogue
There are places in the U.S. so polluted, eating fish or crabs from their waters isn’t just unhealthy—it can be illegal. The Environmental Protection Agency calls sites like that “Superfund sites,” a label for abandoned or neglected sites that became dumping grounds for hazardous waste. Some of the highest levels of mercury contamination in the U.S. exist in Superfund sites. Cynthia Gilmour knows this first-hand. As a microbial ecologist at the Smithsonian Environmental Research Center, she has worked in several. But short of digging up the polluted sediments and dumping them elsewhere (an expensive and ecologically risky proposition), not many methods exist to get rid of the problem.
“If we use the traditional technologies of removing that and putting it in a landfill, we don’t have a wetland anymore,” says Upal Ghosh, an environmental engineer from the University of Maryland, Baltimore County, who works with Gilmour.
This fall, Gilmour and Ghosh explored a new technique: using charcoal to trap it in the soil.
by Brooke Weigel
Have you ever wondered how far a fish can swim in one day? Acoustic telemetry enables researchers to track the movement, migration and behavior of fish. Beginning this past summer, the Fish and Invertebrate Ecology Lab started using acoustic telemetry to study the movement patterns of invasive blue catfish in the Patuxent River, a tributary of Chesapeake Bay.
Native to the Mississippi River, blue catfish were introduced for sport fishing in Virginia in the 1970s. Since introduction, these non-native top predators have expanded their range into many of Maryland’s tributaries. Their voracious appetites affect native fish populations and disrupt the food webs in these rivers. Blue catfish are the largest and most migratory species of catfish in North America. In their native waters, blue catfish have been known to migrate up to 200 km between different habitats used for spawning, feeding and overwintering. But little is known about their movement patterns within the Chesapeake Bay watershed, which is our motivation for using acoustic telemetry to track the movements of individual blue catfish.
Similar to radio tracking used to locate animals over vast distances, acoustic telemetry is a two-part system: Each fish has a transmitting tag, which emits a unique series of underwater sounds or “pings” at a random interval every one to three minutes. Stationary receivers then detect and decode these pings whenever a fish swims within range of the receiver. These detection data are converted to digital data and stored until researchers download the data onto a computer.
Interning at SERC for the past six months has given me the opportunity to be involved in every step of the process—some of which were messier than others.