Sediment Runoff Main Cause of Blue Crab Decline

by: Matt McGrew, Alpha EMC Environmental Analyst

When most people think of the Chesapeake Bay their first thought is not Sediment Runoff. Instead, they relate it to the beautiful, natural environment..  Historically, along the Chesapeake Bay, the blue crab has been a source of income for watermen in the area, and brings people together for crab feasts every summer.  Whether you enjoy seafood or not, if you grew up in the area, you have been to a crab feast at some point in your life.  One of my earliest memories was my Dad instructing me how to eat, “pick,” a blue crab while watching a Redskins game on television.  This common popularity of the blue crab made it a Maryland icon.

Unfortunately, Virginia and Maryland wildlife managers report that the crab population has steadily declined by 65 percent since 1990. While over- harvesting the female crab may have contributed, the main cause of this decline is sediment runoff that environmental analysts combat on a daily basis. Over 10 million people live on and around the Chesapeake watershed, with more people moving to the area yearly. This population influx naturally led to more construction in areas where regulators were slow to protect the Bay.

When Sediment Runoff Moves Into Tributaries and Rivers

When sediment runoff moves into tributaries and rivers, it coats the natural habitats of species that live there. These areas can become “dead zones”. Dead zones are areas where wildlife does not thrive because of the lack of oxygen. Watermen, on the other hand, call this area “bad water”. Bad water is visible along the shoreline, and watermen can follow “shifts” along the water and track the crabs moving to a more shallow area that contain higher amounts of oxygen and nutrients. Blue crabs are not the only Bay wildlife that have been on a steady decline. Kriston Scott of the Washington Times reported recently that the oyster population today is at 1% of its previous population. However, due to increased sediment runoff creating more dead zones, oyster migration slowed tremendously. In the mid 1980’s, disease started to spread through the oyster beds and watermen quickly started over-harvesting the oysters in order to maintain their profits.

With the blue crab and oyster population decreasing and crabbing regulations in force, watermen have begun to seek other means of employment. Many sold their trolling boats for larger fishing vessels and began fishing charter businesses. Unfortunately, scientists report that the Bay’s popular Striped Bass and Rockfish populations are also dwindling.

For an Alpha Environmental Analyst such as myself, who grew up in a small town on the Bay, I see areas where sediment runoff leaks into the Bay, and it hits home. I have seen the result of sediment runoff change watermen’s historic way of life. This motivates me to make known and do what I can to prevent sediment runoff.  The blue crab, oyster, rockfish and striped bass are the Chesapeake Bay’s most cherished inhabitants, and if we are not careful, we may lose them forever. I cannot imagine what it would be like without summer crab feasts, stuffed Rockfish, and oyster cook offs.  I would like the opportunity to teach my children how to pick a blue crab the right way, all the while knowing that blue crab populations in the Chesapeake Bay are safe. 

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