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Bay Blog: land use

May
16
2017

Rockfish return to find a changing Chesapeake region

Each spring, as waters warm along the Atlantic coast and in the Chesapeake Bay, striped bass begin to migrate. Otherwise known as rockfish or stripers, striped bass are anadromous: they spend most of their adult lives in the ocean but travel back to the freshwater where they were born to spawn. As the fish make their return to the rivers of Maryland and Virginia, recreational fisherman celebrate with striped bass trophy season, hoping to catch and release the largest fish and spending time on the water with a tradition that spans generations.

Watermen Owen Clark, left, and Ashley Elbourn of Rock Hall, Md., catch striped bass with a roughly 1500-foot gill net for the spawning stock survey led by Maryland Department of Natural Resources in the northern Chesapeake Bay near Aberdeen Proving Ground last month. Surveys help inform fishery management decisions, track population size and measure spawning success. (Photo by Will Parson/Chesapeake Bay Program)

Rockfish have served as one of the most popular commercial and recreational fish in the Chesapeake Bay for hundreds of years. When Captain John Smith traveled the estuary in 1614, he wrote of seeing waters so full of “the Basse”—believed by many to mean striped bass—that a man might walk across their backs without getting his shoes wet.

For years, rockfish served as an iconic, ever-present Chesapeake species for both food and sport. But in the 1970s and 80s, the striped bass fishery collapsed. Between 1973 and 1983, commercial and recreational catches fell from a record-setting 14.7 million pounds to just 1.7 million pounds. By the late 1980s, states across the region had put moratoria in place in an attempt to help the species recover. After responding well to harvest restrictions, the population was considered fully restored in 1995. Today, active management and a Bay-wide quota for recreational and commercial striped bass fisheries have helped the species remain at a sustainable level.

The recovery of striped bass in the Bay is often seen as one of the estuary’s great success stories. But environmental pressures could put strain on habitats used by spawning adults and young striped bass, threatening the long-term health of the species. As the largest striped bass nursery area on the Atlantic coast, experts estimate that up to 90 percent of the Atlantic striped bass population uses the Bay and its tidal tributaries to spawn. Healthy habitats are key to the survival of young striped bass, a sustainable population and a robust commercial and recreational fishery in the Bay.

Researchers measure the length, determine the sex, and assess whether spawning has occurred or not during the annual striped bass spawning stock survey. Some fish also have scales removed for aging and some are fitted with tags.

From year to year, striped bass reproduction sees considerable natural variation. This means that the overall population relies on successful spawning years—which require suitable habitat—to compensate for below-average years. But threats like warming temperatures, for example, could disrupt the timing of migration and spawning and alter what areas are viable habitat for these life processes.

A less-discussed but equally significant threat to rockfish habitat, experts say, is land use—particularly development and urbanization. As the region’s human population grows, more farm and forest land is being converted into buildings, roads, parking lots and other paved surfaces. These impervious surfaces cause a surge in the amount and intensity of polluted runoff, which can erode streambanks, transport toxic contaminants and nutrient and sediment pollution into waterways and significantly alter the temperature of rivers and streams.

As the landscape is altered, these changes can turn previously suitable spawning and nursery areas into less productive habitat. Striped bass are sensitive to habitat changes because, when spawning and as larvae, they become concentrated in relatively small geographic areas. Any disturbances in those areas could potentially impact a large number of striped bass from across all life stages: from eggs to larvae to spawning adults.

Jeff Horne of Maryland Department of Natural Resources tags a striped bass. Fishermen who catch tagged fish can report them to DNR for a reward—sometimes as much as $125.

Horne releases a tagged striped bass. Information from reported tags helps determine striped bass migration rates, migration patterns, growth rates, and mortality rates.

When researchers overlaid a map of the Bay’s striped bass spawning areas with a map of projected development, the results showed all spawning habitat to be under moderate to very high development pressure. The Potomac and James Rivers, for example, are among the largest spawning areas in the Bay, and projections of growth show those areas could develop up to 10 percent impervious surface cover by 2020. Fisheries experts consider impervious surface cover at a level of five percent or below the target for a local region, but levels below 10 percent can still help keep the striped bass population stable.

Slight degradations in habitat can be offset by restoration efforts—although, once lost, there’s no guarantee habitat quality can be restored. By conserving farm fields, forests, wetlands and natural shorelines, land managers can help sustain healthy striped bass habitat. Concentrating the development that does occur in and around already-developed areas—a technique known as “smart growth”—can also help ease the effects of development, as can reducing the amount of runoff through green infrastructure like rain gardens, green roofs and permeable pavement.

Each year, researchers in Maryland and Virginia survey spawning and juvenile striped bass to inform fishery management decisions, track population size and measure spawning success. So far, the results of these surveys don’t have experts alarmed. Although results of Maryland’s 2016 juvenile striped bass survey were well below the long-term average, successful spawning years in 2011 and 2015 are expected to compensate for the below-average year. Meanwhile, experts continue to work to better understand how land use changes and other stressors may impact these numbers in the future, helping to ensure a robust rockfish population for years to come.

To view more photos, visit the Chesapeake Bay Program's Flickr page.

Photos 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.



Dec
06
2016

Groundbreaking land cover data to support Chesapeake Bay restoration efforts

The Chesapeake Bay Program today announced the completion of the Chesapeake Bay High Resolution Land Cover Project, a landmark initiative to improve information about the features of the Bay watershed landscape. The new high-resolution data on land cover—such as buildings, tree canopy and water—will support the Bay Program’s efforts to evaluate progress toward reducing the amount of pollution flowing into the Chesapeake Bay.

Aerial imagery featuring the U.S. Capitol in Washington, D.C., is overlayed with data from the Chesapeake Bay High Resolution Land Cover Project. The new dataset delivers 900 times more information as existing data covering the Chesapeake watershed.

Chesapeake Conservancy—an Annapolis, Maryland-based nonprofit—led a partnership with the University of Vermont and Worldview Solutions, Inc. to complete the project, which is one of the largest high resolution land cover datasets in the nation. A team of geospatial analysts worked for ten months to produce one-meter by one-meter resolution land cover data for nearly 100,000 square miles, spanning the entire Chesapeake Bay watershed and surrounding counties. Offering an unprecedented degree of accuracy, the new dataset provides 900 times the amount of information as the existing watershed-wide data.

Aerial imagery of Denton, Maryland, is overlayed with data from the Chespeake Bay High Resolution Land Cover Project. The new dataset offers high-resolution information on land cover for the entire Chesapeake Bay watershed, including tree canopy (represented in dark green), buildings (represented in red) and roads (represented in black).

“The power of data behind the Chesapeake Bay High Resolution Land Cover Project cannot be overstated,” said Nick DiPasquale, Director of the Chesapeake Bay Program. “This is a technological snapshot, the likes of which we’ve never had before, of exactly how the land is being used across the entire watershed. Now restoration and conservation decisions can be made that more closely and accurately reflect real-world conditions.”

Aerial imagery of the Chesapeake Bay watershed is overlayed with data from the Chespeake Bay High Resolution Land Cover Project, with the Captain John Smith Chesapeake National Historic Trail delineated in red. With the completion of the project, one-meter by one-meter resolution land cover data for the entire Chesapeake Bay watershed will be available at no cost to the public for the first time.

Available to the public at no cost, the high resolution land cover data will aid in the restoration and conservation work of federal, state and local government agencies, nonprofits, academic institutions and other organizations by allowing for better characterization and understanding of the landscape. In particular, the Bay Program will use the data to improve and refine its current suite of modeling tools, allowing for enhanced evaluation of progress in support of the 2017 Mid-Point Assessment of the Chesapeake Bay Total Maximum Daily Load (TMDL).



Nov
01
2016

County-by-county land use data available for review by local governments

Chesapeake Bay Program partners are welcoming the review of new high-resolution land use data for all 206 counties in the Chesapeake Bay watershed. The data will inform the partnership’s next generation of models used to estimate nutrient and sediment loads and to credit efforts to reduce those pollutants from draining into the nation’s largest estuary.

The high-resolution mapping of land use—such as residential areas, agricultural lands, streamside forests, parking lots and roads—is a critical component of the Bay Program’s Chesapeake Bay Watershed Model, used to inform restoration activities and support local, state and regional decision making across the region. The latest version of this model, Phase 6, is currently under development and review. To continually improve our understanding of the landscape, Bay Program partners have been working to incorporate the most accurate land use information available into this updated version.

Over the past two years, the Bay Program worked with local government partners in all the Chesapeake Bay watershed counties and major municipalities to ask for access to local land cover, land use, parcel and zoning data. Thanks to the commitment from our local partners, local land data were collected from over 80 percent of local jurisdictions. In parallel, Bay Program partners funded the development of new high-resolution data on land cover—such as impervious surfaces, tree cover and water—for the entire watershed. This unprecedented work, carried out by the Chesapeake Conservancy, the University of Vermont and World View Solutions, mapped out land cover across more than 80,000 square miles at a one-square-meter resolution. This land cover data was then combined with the information provided by numerous local governments to produce a detailed land use dataset for each county.

To ensure that local land use and parcel data has been correctly interpreted, Bay Program partners are seeking input on these final land use datasets. While open to all interested parties, this review process is especially intended for local governments to participate.

As datasets for each county become ready for review during the last week of October and the first week of November, they are being made available on the U.S. Geological Survey’s Phase 6 Land Use Review Application website. Reviewers will have four weeks to review once a dataset has been posted, but fatal flaw comments are due two weeks after data are made available. Once the data have been reviewed and finalized, the high resolution land cover and land use datasets will be made available free-of-charge to local governments and the public. In addition, Bay Program partners will be making available extensive data on past land cover and land use (from 1984 to 2013), as well as comprehensive geographic coverages of federal lands, sewer service areas, regulated stormwater areas and combined sewer overflow areas, all mapped at similar local scales within each county.

The current review is part of the Bay Program’s larger and long-term commitment to regular updated mapping of Chesapeake Bay watershed counties’ high resolution land cover and land use data to be repeated on a periodic basis. Local government representatives are encouraged to stay engaged in future efforts to continually improve data accuracy. All these future high resolution land cover and land use data sets will continue to be made available to local governments and the public free-of-charge.

Local governments will be able to use the full suite of high resolution land cover and land use data for their own purposes in making better, more well-informed decisions on where to carry out stream restoration projects, plant stream side forests, place easements and permanently conserve lands, as well as to inform comprehensive plans and future zoning and development decisions.

For additional information on the land use data and how to provide feedback, a pre-recorded webinar is available online. Questions and requests for further information can be directed to Lindsey Gordon at Gordon.Lindsey@epa.gov and (410) 295-1380.



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