Whether through deliberate abandonment or through accidental loss, derelict traps have significant negative effects on both the economic and ecological status of the Chesapeake Bay. A new report from NOAA, Ecological and Economic Effects of Derelict Fishing Gear in the Chesapeake Bay, estimates that 12% to 20% of blue crab pots deployed annually in Chesapeake Bay waters are lost or abandoned at any given time, and that that there are 145,000 derelict crab pots Bay-wide (non-depreciated replacement gear value between $3.6 and $5 million).
The crabbers removed more than 34,000 derelict pots during the six-year run of the program, paid for with $4.2 million in U.S. Commerce Department disaster-relief funds. The study, led by VIMS assistant professor Andrew Scheld, estimated that taking out all those pots generated $21.3 million worth of increased commercial catches – 27 percent more than otherwise would have been caught in the areas covered by the program.
As our local Eastern Shorekeepers have noted in the past, derelict pots capture and kill millions of blue crabs per year, amounting to nearly 5% of the commercial harvest. Inadvertent by-catch, such as white perch and Atlantic croaker are also affected.
Derelict gear may impose a variety of economic costs. The costs of decreased harvests due to ghost fishing can be further separated into those which are caused by stock reductions. In fisheries with large amounts of effort and gear loss, such as blue crab fisheries in the Chesapeake Bay, the economic costs of inefficient gear may be significant. The report notes that the 43,968 removals which occurred in Maryland and Virginia from 2008-2014 are thought to have resulted in an additional 38.17 million lbs of harvest valued at $33.5 million. In a nutshell, Chesapeake Bay waterman might obtain crab at a much lower cost, were it not for derelict gear.
The report notes that targeted derelict pot removal in high density areas, enforcement of the removal of abandoned pots, education of recreational boaters to minimize use-conflict, and pot modifications that include a biodegradable escape mechanism offset the adverse ecological and economic effects of ghost pots.
The report estimates that by removing just 10% of derelict pots from the five most heavily fished sites in each of Virginia and Maryland could increase blue crab harvest in the Chesapeake Bay by 22 million pounds or approximately 14%. Biodegradable escape panels in crab pots can reduce blue crab mortality in derelict pots from over 3.3 million to under 440,000 market crabs/year and reduce or eliminate mortality of other animals.
The report determined that key management actions which could effect derelict pot distribution are 1) Maryland regulations prohibit commercial crabbing in tributaries with pots, whereas this is allowed and practiced in Virginia; 2) a no-crabbing sanctuary (928 square miles) during the crab spawning season covering the mainstem and portions of the lower Chesapeake Bay to protect the spawning females; and 3) effort restrictions.
Blue crab fishery management actions are partially linked to the complex life cycle of the blue crab, which involves multiple horizontal and vertical migrations across state boundaries and dependencies on high salinity areas in the lower Chesapeake Bay, Virginia for spawning, larval development, and over-wintering.
Stock assessments have assumed that any crabs not taken in the fishery are lost to natural mortality. The report notes that if a portion of those crabs are actually lost through ghost pots, then through more management efforts, it gives agencies another tool to promote the sustainability of the blue crab population.