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Blue Crabs Depend on Healthy Bay
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by Lauren Donelly | 2012

The blue crab is an iconic symbol of the Chesapeake Bay and of Maryland itself. Since 1990, the sheer number of both juvenile and harvestable crabs in the Chesapeake Bay drastically decreased from a population of 791 million to 260 million in 2007.

The blue crab is an iconic symbol of the Chesapeake Bay and of Maryland itself. Since 1990, the sheer number of both juvenile and harvestable crabs in the Chesapeake Bay drastically decreased from a population of 791 million to 260 million in 2007.

     There are two main reasons for the drastic decline in crabs—overfishing and pollution. This astonishing decline sparked a ban in both Maryland and Virginia in 2008 on the recreational catching and commercial harvest of female blue crabs in order to reduce harvests enough that the population could recover. Still the number of young crabs entering the population decreased from 345 million in 2010 to 207 million in 2011.

    The decline in 2011 was most likely due to the early and severe winter temperatures experienced last year, which killed many crabs before they were able to burrow for the winter. Other contributing factors include increased rainfall in the spring leading to runoff of pollution into waterways, and an increase in temperature, which decreases dissolved oxygen levels.

    Both the polluted run-off and higher temperatures are contributing factors to the persistent ‘dead zones’ in the Chesapeake Bay that make it difficult for crabs to survive. Despite these declines, scientists have recently been seeing an overarching trend of the crab population rebounding with respect to harvesting. The number of harvestable crabs in 2011 was still 254 million, which is well above the 1990-2010 average of 192 million. This however is not necessarily the case when looking at crabs of all ages, and NOAA scientists warn that it doesn’t mean we’re out of the woods yet. It will take a long time to remedy the decimation of the population. Continuing sustainable recreation and commercial fisheries as well as resource management of the crab populations are key to ensuring that we do not have a major decline in numbers again.

     An integral part of the restoration of the blue crab population is Maryland’s watershed implementation plan (WIP), into which the Sierra Club has invested great effort. It is essential that the WIP enforce a stringent reduction in the amount of pollution entering the Chesapeake Bay. If it does it will significantly benefit the blue crab population through a decrease in pollution which will significantly improve crab habitat and food sources. The process of Bay restoration and subsequent species recovery will be an ongoing process, but in the meantime, it is good news to those of us who look forward to crab season every year that we will not soon be disappointed by the absence of blue crabs.      n

 

Lauren Donelly is working on water resources as an intern with the Maryland Chapter.

 

 

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