The recent results of the annual blue crab winter dredge survey have us worried. The population has dropped below the safe level for adult females, which means it has officially become "depleted," and increased conservation may be needed. However, crabbing pressure has been within sustainable levels in recent years, so other factors besides harvest are also involved.
As the Baltimore Sun recently stated: "It's clear something has fundamentally changed about the Maryland blue crab. Not the life cycle of the crab itself, of course, nor even the nature of the watermen who catch them, but the crab's habitat, which has been altered in a way that scientists are only now beginning to fully understand. The ability of crabs to bounce back from poor spawning years seems to have been greatly compromised by a less hospitable Chesapeake Bay."
Clearly one factor was the cold winter, which killed an estimated 28 percent of adult crabs in Maryland waters. Normally, the crab population would be resilient to such natural factors, but it is likely that the continued poor quality of the habitat for crabs and other species in the Bay has made the population more vulnerable. For example, underwater grasses—where crabs like to take refuge—cover about 20 percent of the Bay bottom they did historically. Also, dead zones, caused by excessive amounts of nitrogen and phosphorous in the water, reduce food for crabs by killing clams, worms, and other invertebrates, and crowd crabs into shallow water making them more vulnerable.
Poor habitat conditions emphasize the need to implement the Chesapeake Clean Water Blueprint in order to reduce pollution and improve water quality and habitat. Of course, habitat improvements will take years, so in the short term, the only controllable factor we have is the harvest. The scientific community has called for a "risk-averse" approach to the crab fishery, and in response, the jurisdictions that manage the Bay’s crab fishery (Maryland, Virginia, and the Potomac River Fisheries Commission) are planning to cut harvests by 10 percent in 2014. Exactly how they do that will depend on upcoming consultations with the crabbing industry.
Our viewpoint is as follows:
- The only prudent management response is to be conservative with harvest to maintain as much spawning potential as possible to rebuild the population. Therefore, we support the jurisdictions plan to work with the industry to cut back on harvest by 10 percent.
- A truly healthy crab population is not possible until water quality is improved and underwater grass bed habitat is restored. Improved habitat is essential to restoring resilience in the crab population. This underscores the urgent need to reduce pollution by implementing the Chesapeake Clean Water Blueprint.
- The science-based guidelines for the blue crab fishery (target crabbing rate and population levels) provide solid boundaries for management and should be maintained. However, it is evident from the recent, wide fluctuations of the stock that these targets alone cannot achieve the level of productivity and stability that we need to achieve our goals.
- We need to continue to improve harvest accountability and apply specific catch limits based on current population levels and allocate a portion to each jurisdiction.
- Ultimately, we need to find a way to reduce total effort in the crab fishery so crabs are not caught up as soon as they reach legal size. Allowing crabs to live longer and grow larger will help stabilize the population and the fishery--more reproductive capacity for crabs and better economic conditions for Bay watermen.
- With 25 years of data collected, the Chesapeake Bay winter dredge survey is a key tool in determining the health of the Bay’s blue crab population and provides the best information we have on the population of any Bay species.
—Bill Goldsborough, CBF's Director of Fisheries