Monday, October 28, 2013

2013 Connecticut Blue Crab Special Report #6

From Tim Visel at The Search For Megalops:
The Sound School – The ISSP and Capstone Project Proposal

     Building a Network of Citizen Monitors
The Connecticut Blue Crab Population
Habitat Study 2010-2015
 
  You Do Not Need To Be A Scientist To Report!
The Search for Megalops - The Sound School
Items of Interest to Blue Crabbers

The Search for Megalops Special Program Report #6
October 24, 2013
Young Blue Crabs Now Approaching Survival Size
 

With a little luck and warm fall, the Megalops set observed in eastern Connecticut is still growing. I would like to thank fishers, especially Gary Nolf of the Westbrook Shellfish Commission and Alison Varian of the Guilford Shellfish Commission for reports concerning “gut cavity analysis,” a term for describing the recent feeding experience of fish – in this case porgy(scup) (Stenotomus chrysops) and black sea bass (Centropristis striata) who earlier this fall were feasting on small blue crabs. Now it is black sea bass eating them in ninety feet of water.

“I was fishing for sea bass in 90 feet of water off Madison, the fish were spitting up thousands of small blue crabs, all just under 1/4 inch”. 

Much can be learned by checking what fish are feeding on the “match the hatch” concept of trout fishers. Checking stomach contents has helped fishery biologists describe predator/prey relationships for over a century. Fishers have also helped with their observations. It was striped bass fishers in 2011 who first reported stripers chasing “football crabs,” those swimming east and Stonington SCUBA divers who off of Napatree Point found “beds” of female crabs in 2010 and those blue crabs massing off Long Sand Shoal this spring and stripers feed on them-- that came from a conversation I had with striped bass fishers. I appreciate the help from fishers who provided information about blue crabs this season.

We can learn much from such gut cavity examinations and look perhaps for help (information) now that the tautog season is open in Connecticut.  Tautog like crabs a lot and can smash them with their “powerful jaws” (Native American name) the backs of large crabs from behind. I have seen them do this to lobsters and feel that the same may be true for blue crabs as well (although the bite-size green crabs worked best for me).  

The crabs are still moving down the Connecticut River, but the number of crabbers that now report releases indicates they prefer the bottom now to food, which could signal a reluctance to leave obscurity bottom cover (protection) with the arrival perhaps of new predators now tautog. The crabs are present and grab the bait but just let go. A new predator may now be in lower rivers, namely tautog. Some of the oyster tongers in Connecticut’s rivers would also set handlines for tautog– the oyster tonging operates itself. Churning of the tongs attracted stripe bass, flounder, but most prevalent in the 1930s and 1940s were the tautog and their favorite (bait) food then was crabs. Tongers would tell me that tautog would come in and surround the boat – alerted now by the sounds of the scratching of the metal tongs on the oysters and drift line of crushed crabs and occasional oysters down current. Of all the fish, oyster tongers told me that tautog would go up river as far as the tides would allow. Many oyster tongers in the East, West, and Hammonasset Rivers then handlined for fish and rarely came in without some tautog. Tautog gut content analysis might have some bearing on the next few weeks if these small blue crabs can make it to shore. So if you have a chance, check the stomachs while cleaning some tautog and drop me an email if you find they were feeding on blue crabs.  

In a study of the blue crab predation by juvenile red drum (Sciaenops ocellatus) in southern waters (Joseph J. Facendola, University of North Carolina, 2010) a daily ration based upon “gut fullness” and found that May to October the diet weight was roughly 50% of crustaceans, 15% which was blue crabs – but dropped nearly to zero by November. More recent studies in Chesapeake Bay have also looked at an increasing red drum population as impacting blue crab survival. It is an old story that which may seem to happen here – more prey, more predators. Nothing in the natural world seems to be wasted – but a perspective that we may not like.  For more information about fish feeding in or near natural oysters see Sound School adult education publication entitled, “A Review of Fisheries Histories For Natural Oyster Population in Tidal Rivers,” Dec 2007.

With porgy, black sea bass and striped bass known to eat blue crabs, tautog might be the most important species to benefit – they hang around and venture not that far from structure when they eat blue crabs. We could consider that to be significant local source in guts.

 As fall approaches, these small blue crabs need to get into the salt marshes, creeks and ponds especially. So reports of tautog eating blue crabs now would actually be a good sign; they made it to shore.

Email your blue crab reports to: tim.visel@new-haven.k12.ct.us
Every observation is valuable as we learn more about our blue crab population. 
The Search for Megalops is part of a Project Shellfish/Finfish Student/Citizen Monitoring Effort Supported by a 2005 grant to The Sound School from the National Fish and Wildlife Foundation grant #2005-0191-001.
Program reports are available upon request.
For more information about New Haven Environmental Monitoring Initiative or for reports please contact Susan Weber, Sound School Adult Education and Outreach Program Coordinator at susan.weber@new-haven.k12.ct.us
The Sound School is a Regional High School Agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.

 

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