- Last Updated on Wednesday, 25 September 2013 00:30
- Published on Wednesday, 25 September 2013 00:30
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Editor’s Note: This is Part 1 of a two part series about where all the crabs have gone, something people ask every time they go looking to supply crabs for their crab feast.
Flash back to the late winter and early spring of 2012 when the winter dredge survey showed that crab numbers were at a 19-year high. The governors of both Maryland and Virginia released statements proclaiming the conservation efforts of the blue crab as being successful. Things looked grand and the future looked bright for crabbers, anglers and for those that love to eat crabs.
Fast forward to the summer of 2013. Crabbing has been abysmal and watermen have taken the blow their bottom line that was unpredictable at best. Scientists and officials had implied just a year and a half earlier that the crabs were well on the road to recovery. What happened?
There are a few theories out there about the crab population taking a nose dive this past year. Many watermen are pointing fingers at the predators, mainly striped bass and red drum. Both species along with a host of other animals living in the Chesapeake Bay will consume crabs as a regular part of their diet. Some watermen were angry about the losses to their livelihood and that is completely understandable. Anyone would be upset if they were told how great the crab fishery was doing and then they took horrendous losses within a year.
The situation is a bit more complex than most might realize. After a good bit of research here is what the facts show.
The winter 2012 dredge survey of crabs showed a record high number of crabs in both Virginia and Maryland waters. However, the winter dredge survey of 2013 showed the worst level of juvenile crabs in 24 years according to John Bull of VMRC.
I followed up with a chat with Marty Gary of PRFC. You may have heard that Gary recently came from Maryland DNR to head up PRFC and has 27 years of fisheries experience under his belt.
He shared that he had a desk a few feet down from the biologists that handled the crab surveys and often discussed the ups and downs of the crab fishery with them. Those discussions focused on the facts that the crabs were there in the winter of 2012, and then again the summer trawl surveys of the Maryland waters of the bay showed them present in June of 2012 (juvenile crabs). However, from July of 2012 to September of 2012 their numbers fell right off the chart in a significant manner. By October of last year the crab’s numbers had dropped precipitously. This was followed by a record low winter dredge survey this past winter. Furthermore, environmental factors likely caused or at least heavily contributed to the scarcity of crabs this past summer.
Of all the theories out there about what happened to the crabs in that short amount of time many of them share a few solid angles that make sense. The two common variables that keep coming up among all parties include predation and habitat.
Let’s look at the habitat angle first as many people have not taken that portion of the equation into very serious consideration. If you look at any animal species whether it be fish, crabs, quail or ducks, you would have to admit that habitat has played a significant part in the demise or the restoration of a species.
We are having the toughest time with quail numbers and right now scientists are trying hard to figure it out. The two variables that keep coming up in that arena is the horrible loss of habitat due to development that wipes out farms, fields, old pasture and fragments what is left for cookie cutter subdivisions and clean farming that leaves no edge cover, briars and feed for the birds.
The same concern should be had for crabs. There has been limited submerged aquatic vegetation (SAV) in the bay for years. Imagine for a moment that you were a tiny crab about the size of a silver dollar. If you only had a few oyster shells, some old crab pots, a few sunken boats or parts of such or mud to hide in from all the various predators out there to include larger crabs (yes, crabs are very cannibalistic) how long do you think you would last?
Think about being a rabbit in a field that has been mowed completely down save a few clumps here and there or an overturned tree top for cover? Anytime you ventured anywhere you were totally exposed and a long way from cover.
Eel grass and other SAV plays a vital role in keeping small species alive. With documented losses of SAV over the past 20-30 years a connection can be made to the decline of the blue crab right with it. VIMS has the data on their website to prove that angle.
Marty Gary of PRFC made another interesting point. During the late summer of 2010 we had two tropical systems blow through the bay area. A lot of sediment was washed into the rivers and the bay. Guess what happens when sediment washes into the bay? It clouds the water and blocks sunlight. What do plants need to grow and survive? Yes, sunlight. Block the sunlight and you cut off plant growth. Less plants equal less filtration of sediment and more dirt in the water. It becomes a vicious cycle that gets worse and worse.
Back Bay near Virginia Beach used to be a world class bass fishery. It had great SAV until something happened to reverse the growth causing more dirty water and so on.
Chad Boyce of VDGIF has gotten grants and did a lot of hard work to reverse the cycle by installing curtains to filter out sediment. The short version of that anecdote is that the bass fishery is coming back in a big way now. The curtains allowed silt to be filtered out, more SAV grew and the fishery came back as a result and with a good bump from a supplemental stocking to boost it.
My point is that the loss of SAV has hurt the blue crabs and other organisms and species in the bay too. With nowhere to hide they are easy prey.
Part 2 next week will be: What about the predators.