Marine debris is any manmade solid material that is—directly or indirectly, intentionally or unintentionally—disposed of or abandoned into the marine environment. It may end up in the water or on the shoreline from people on boats or along the shoreline, or can be washed out to sea via rivers, streams, and storm drains. Because marine debris can hurt the ecosystem, NOAA is researching what those impacts are—and how to mitigate those negative effects.
Fishing equipment, such as nets, lines, crab and shrimp traps/pots that have been lost or abandoned in the water, is one type of marine debris. In the Chesapeake Bay, traps are the primary method of commercial harvest of blue crabs. These crab traps become derelict when their float line is severed by a propeller or chafed through due to wave action, or if the pot is moved into deeper water by strong current. Without a float to identify them, watermen are unable to find these “ghost traps,” which can continue to trap fish and animals, harm sensitive ecosystems and habitats, cause economic hardships for watermen and others, and form hazards to boating.
Through support from the NOAA Marine Debris Program, the NOAA Chesapeake Bay Office and its partner institutions—including the Center for Coastal Resources Management at the Virginia Institute of Marine Science (VIMS), as well as the states of Maryland and Virginia—are studying the effects of these “ghost traps” to determine how many derelict crab traps there are in the Bay, and whether they adversely affect blue crab and other resources.
The NOAA Chesapeake Bay Office Habitat Assessment Team used acoustic technology including side-scan sonar to identify derelict pots, and conducted field experiments simulating the effects of ghost fishing by derelict traps. In Maryland, surveys and analysis of 285 side-scan sonar transects conducted in 2007 showed that there are an estimated 84,567 derelict traps in the Maryland portion of the Bay. Based on the ghost fishing simulation study—which monitored experimental ghost pots for a year and a half—blue crab mortality from this type of marine debris is estimated to be 20 crabs per trap each year. In addition to blue crabs, the traps captured and killed by-catch species including white perch, pumpkinseed, oyster toadfish, and Atlantic croaker.
Surveys and analysis to determine a corresponding estimate of derelict traps for the Virginia portion of the Bay is still under way. At VIMS, researchers are conducting analogous sonar surveys and impact studies in the field and in the laboratory. When this work is complete, the NOAA Chesapeake Bay Office will develop an overarching report detailing the prevalence and impacts of derelict traps throughout the Chesapeake Bay. Once the overall impacts of derelict traps on the Bay’s living resources and habitats are fully known, management options can be considered to mitigate the impacts of ghost pots on living resources.
Management options under consideration include the incorporation of biodegradable components into crab trap design and construction, prevention of trap loss via improved marking and trap placement, and targeted removal of ghost fishing traps using sonar to identify and locate traps in areas of ecological significance. The Virginia Marine Resources Commission and VIMS conducted a pilot program employing watermen who would have worked in the 2008-09 winter dredge season (which was closed by the Virginia Marine Resources Commission) to instead retrieve derelict traps in a structured and environmentally sensitive manner.