The Chesapeake Blue Crab Fishery: A brief biological introduction.

The blue crab (Callinectes sapidus) is found from Nova Scotia through the East and Gulf coasts of the United States, and into the West Indies. Commercial and recreational fisheries for this species exist in many states, including New Jersey, Delaware, and the Carolinas. However, the largest active fishery for the blue crab, both today and historically, is on Chesapeake Bay, in the states of Maryland and Virginia.

Blue crabs live in a wide variety of coastal habitats, from shallow eelgrass beds during their juvenile stages and molting to deeper water on a variety of bottoms, and everything in between. Due to their wide variety of habitats and limiting methods of locomotion, they are opportunistic feeders, and will eat almost anything. Reproduction is based on eggs carried by the females which hatch into a series of planktonic stages. Ultimately these postlarvae settle out, and soon become small but functional crabs. During their relatively short life span, they are likely to migrate throughout the bay and its estuaries.

Because different stages of their life cycle are spent in different environments within the bay, they are exposed to a wide variety of adverse conditions. Young crabs depend on eelgrass beds for food and shelter early on- if these are lost, there is no viable nursery for these young crabs available, and they are subject to heavier predation than usual. In the estuaries where many adults and young live in the warmer months, they are exposed to agricultural runoff such as fertilizers and pesticides. They are also susceptible to abrupt salinity changes (in the estuaries)in times of heavy rain. At times, low oxygen conditions prevail in various parts of the bay- this is another significant environmental factor. Regardless of where they live in the bay, they are subject to at least one method of harvest used by the commercial and recreational crab fisheries throughout the year. This combination has ultimately led to the massive decline in the blue crab population of Chesapeake Bay.

For many years, the blue crab stock was relatively stable and seemed to be keeping up with the fishery, only showing cyclical declines and recoveries within the population. More recently however, the population has shown some warning signs, and its problems are indicated by its current low level. This decline has been blamed on various problems by different groups, including crabbers, researchers, regulators and others. Some believe that is due to the loss of eelgrass beds, others suggest that it is due to intense fishing pressure, another less plausible thought is that it is just another low in the population's cycle. So which is it? As of right now, only a relatively small amount of reliable data is available, and it is inconclusive as to the cause of the decline.

Undeniable evidence of this massive decline in the blue crab population is easily found. In 1991 91 million pounds of crab were harvested (Baywide), yet in 1992, the total harvest had dropped to only 54 millions pounds (Fincham, 1994). In recent years, a winter dredge survey (sponsored by NOAA) has been conducted by the University of Maryland's Chesapeake Biological Laboratory. This survey consists of dredging at1200 randomly chosen sites around the bay, using a fine-meshed dredge. The hope is that an accurate survey of the population can be obtained while there is less fishing pressure during the winter months, and the crabs lie dormant in the mud bottom. Suction techniques were also used by the Virginia Institute of Marine Science to sample eelgrass beds- findings of large numbers of juveniles confirm their (the beds) importance as a nursery (NOAA, 1995). As a result of this, researchers estimated that in 1988-89 the population consisted of 1.75 million, but in 1994, the estimate was only 664 million (Lipcius, 1995). In Maryland, the average annual pot catch dropped twenty pounds in ten years (1984-94). This decline was signalled by these findings and by the fact that crabbers were using more gear and working longer hours, to catch fewer crabs.

The decline of the blue crab fishery was brought on by a complex situation composed of many factors, and implementing the management necessary to save it will be even more complex and difficult. Part of the problem is that both Maryland and Virginia regulate the fishery independently, even though it is the same overall crab population. Within these regulations (or seeming lack thereof), there are both commercial and recreational crabbers who use a wide variety of equipment to harvest the crabs. Because of this, it is difficult to propose and enforce a set of laws that fairly manages all aspects of the fishery. At this time, crabs are harvested via dredges, trotlines, pots, and rings, depending on season and location within the bay.

As of now, both states are proposing various regulatory laws independently as well as starting to cooperate and manage the fishery as a whole (instead of two separate state fisheries). These efforts have taken a wide variety of forms. Soon even casual, recreational crabbing may require a license. At this time, this uncontrolled recreational harvest in Maryland alone may amount to 25%-50% of the commercial crab harvest. Commercial crabbers already face many seasonal restrictions, including catch limits, size limits, equipment restrictions, and area closures. In Maryland there is already a license for recreational crabbing- it allows people to use a limited amount of equipment, and take no more than two bushels of crabs per day. It has been suggested that this loose regulation provides ripe opportunity for a black market. Maryland legislators hope to obtain the right to limit (perhaps stop) the sale of commercial crab licenses, and therefore control the size of the fishery. It may even be necessary to cut the number of license holders to preserve the fishery. In addition to individual efforts, the two states have formed a panel in an attempt to develop "universal" management policies. Hopefully they will make progress in this endeavor, but it will be difficult and slow. Their decisions must take into account the views of many groups, including crabbers, researchers, and other concerned groups. The overall management problem is best summed up by Bill Goldsborough (of the Chesapeake Bay Foundation) "You have one blue crab population Baywide and two jurisdictions. It makes no sense to go about management independent of one another (Bay Journal, 1996)."

If progress is not made in these areas, it will be a sad day for the blue crab stocks and those who depend on them. Right now, the blue crab fishery is probably the largest fishery on the bay. Any further decline, or complete loss of the fishery would be disastrous. Many other Chesapeake fisheries (striped bass, shad, and oysters for example) have had similar problems due to habitat loss, overfishing, and adverse environmental conditions, and after significant declines have recovered slowly, or almost not at all. However, there are also success stories- not all that long ago, stripers were having these same problems- and are now a relatively viable fishery once more. Unfortunately, despite what people say, it will probably get worse before it gets better.

The Biological Perspective of fisheries management

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