The Chesapeake Bay’s blue crab population has seen a modest rise, increasing 38 percent since the population was counted last winter. While an increase in blue crabs is an indicator of Bay health, the adult female crab population remains below its target, indicating the variability of the blue crab population and the complexities of managing the fishery.
Maryland and Virginia measure the Bay’s blue crab population through an annual winter dredge survey. Over the course of three and a half months, scientists visit 1,500 sites around the Bay, using metal dredges to pull up crabs over-wintering in the mud.
Results of the 2015 winter dredge survey show the Bay’s total blue crab population has increased from 297 million to 411 million since last winter. Results also show the number of spawning-age females has risen from a depleted 69 million to 101 million. The number of juvenile crabs has jumped from 199 million to 269 million, which is just above the long-term average.
According to the Maryland Department of Natural Resources (DNR), the cold winter and resulting low water temperatures contributed to a “substantial mortality” among blue crabs, killing an estimated 19 percent of adults.
“We are pleased that crab numbers increased despite the harsh winter temperatures,” said DNR Secretary Mark Belton in a media release.
The Chesapeake Bay Program tracks the adult female blue crab population as an indicator of Bay health. The Chesapeake Bay Stock Assessment Committee (CBSAC), which includes scientists and representatives from the federal government, state governments and academic institutions, will use this data to make recommendations on sustaining the blue crab population in its 2015 Blue Crab Advisory Report, expected to be released this summer.
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.
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.”
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.
A new voluntary education program aimed at increasing environmental literacy was introduced in Virginia on Wednesday.
The Virginia Environmental Literacy Challenge is intended to encourage educators to engage students with the natural world in new and creative ways, by highlighting those who excel in environmental literacy efforts. A series of lesson plans—from habitat construction to recycling projects—will accompany the challenge.
“We need to make sure that our students are graduating with the skills and knowledge they need to protect Virginia’s natural resources,” said Virginia Governor Terry McAuliffe in a release. Governor McAuliffe signed the executive order creating the program.
In supporting the outdoor education and sustainability efforts of teachers, administrators and schools, the program will help achieve the environmental literacy goals of the new Chesapeake Bay Watershed Agreement, signed last year by the Chesapeake Executive Council, the top-level leadership entity for the Chesapeake Bay Program that Governor McAuliffe now chairs.
“Environmental literacy is an important part of the Chesapeake Bay [Watershed] Agreement,” said Molly Ward, Virginia Secretary of Natural Resources and Chair of the Chesapeake Bay Program’s Principals’ Staff Committee. “A systemic approach to environmental literacy will ensure that future generations are prepared to protect and conserve our natural resources.”
Biodiversity—the variety of life on Earth—is key in supporting the complex processes that keep ecosystems healthy, stable and productive, according to a new study from an international team of researchers.
Conserving biodiversity has clear benefits for the plants and animals themselves, as well as the people that rely on these ecosystems and the services they provide. And many studies have found that biodiversity can boost a single function of an ecosystem, such as plant growth or nutrient filtering. But according to Jonathan Lefcheck, lead author of the study and post-doctoral research associate at the Virginia Institute of Marine Science (VIMS), this research is the first to look at how biodiversity supports the suite of complex, interconnected processes essential for a healthy and functioning ecosystem.
Researchers analyzed 94 experiments conducted around the world to examine the relationship between biodiversity and ecosystem health. Their findings show that greater species diversity can benefit multiple functions of an ecosystem. “In other words,” said Lefcheck in a release, “as you consider more aspects of an ecosystem, biodiversity becomes more important: one species cannot do it all.”
A key example of these relationships can be found close to home, in the underwater grass beds of Chesapeake Bay. “Seagrasses are home to a variety of small animals that perform different jobs,” said Lefcheck. “Some control algae that would smother seagrasses. Others keep out invasive species. Still others provide food for striped bass and blue crabs that are served on our dinner tables. By conserving this variety of animals, we can maximize the health of the grass bed, and the benefits to people.”
The study is available through the online journal Nature Communications.