The Chesapeake Bay’s declining bumper crab

As a Baltimore resident, it was only a matter of time before I talked about our most popular and ill-tempered local crustacean. The blue crab, Callinectes sapidus (savory beautiful swimmer), is a Portunid (swimming) crab found along the Western Atlantic coast, from Nova Scotia to Argentina. They have also been introduced to the Pacific coast of Central America, Europe, and Asia. They have a complex, migratory life-cycle that takes them between estuaries and the open ocean. Blue crabs are harvested for food in the US and play an integral part in coastal economies, especially within the Chesapeake Bay where they are somewhat of a cultural icon.

Unfortunately, the population and harvest of C. sapidus has been in sharp decline since the early 1990s due to over-fishing, development, and agricultural runoff. Pollution in the bay unbalances the ecosystem, resulting in harmful microorganism blooms, and stresses the crabs, making them more susceptible to bacterial and viral infections. Due to the economic impact of declining harvests, a variety of regulations and research directives have been employed in order to rejuvenate the blue crab population.

For instance, researchers at University of Maryland Biotechnology Institute, Center of Marine Biotechnology (UMBI, COMB) have been working on farm raising C. sapidus megalopae (the terminal larval stage) by the thousands. This complex process actually takes place in their impressive aquaculture facility in the inner harbor of downtown Baltimore. Recently, researchers have been releasing swarms of these megalopae in the southern Chesapeake in order to see if the farm raised juveniles survive to adulthood. If successful, farm-raising and releasing blue crabs could be used to supplement the natural population. This does not directly solve the underlying ecological problems, but it could be crucial “band-aid” to maintain the Bay crab population. Read more about the COMB blue crab initiative, here.

Another avenue of research into saving the blue crab involves identifying pollutants that directly affect the blue crab, and developing reliable metabolic bio-markers to assess pollutant stress in crabs. A new paper in Metabolomics reports the use of Nuclear Magnetic Resonance (NMR) for the detection of biochemical changes in response to impairment of the crab’s oxygen uptake processes. They showed that injection of bacteria (Vibrio campbellii) and chemical pollutants (DNP) caused oxygen uptake stress in blue crabs, detectable with NMR by changes in glucose and lactate metabolites, respectively. These bio-markers can now be used to accurately measure subtle, non-lethal metabolic stresses in crabs. In future experimentation this can allow researchers to determine specific chemicals and microbes the are harmful to the blue crab. Read more at Science Daily.

Once we have a better understanding of exactly which pollutants contribute significantly to stress is blue crabs, regulations can be enacted to limit the runoff of these chemicals into the Chesapeake Bay. Pollutants of all kinds need to be prevented from entering the Bay since, in addition to directly harming the crabs, they cause deadly micro-organism blooms that kill fish and, worse, the oysters that are irreplaceable for their incredible water-filtering capacities (COMB and other organizations are also working on bringing back oyster populations).

Cleaning up the Bay, more than any other initiative, is absolutely crucial to saving the beauteous savory swimmer.

Photo: USGS

References:

  • Schock, T. et al., 2010. Metabolomic analysis of Atlantic blue crab, Callinectes sapidus, hemolymph following oxidative stress. Metabolomics. Available at: http://dx.doi.org/10.1007/s11306-009-0194-y [Accessed January 29, 2010].
  • Millikin, M.R. and Williams, A.B. 1984. Synopsis of biological data on the blue crab, Callinectes sapidus (Rathbun). NOAA Technical Report NMFS, 1. U.S Department of Commerce. National Oceanic and Atmospheric Administration: Washington, DC (USA). 39 pp.

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4 Responses to “The Chesapeake Bay’s declining bumper crab”


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Michael Bok is a graduate student studying the visual system of mantis shrimp.

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