Monday, July 15, 2013

Collecting Blue Crabs In Louisiana

Collecting Blue Crabs in Louisiana
By Matt Starr 2013

 


Since I've moved to Louisiana I haven't had a lot of time in the field.  Back in Panama, the lab would be out collecting snails at least once every few months but now if I need specimens I just order them and have them sent in the mail!  Last month, however, I was able to get back in the field and help new Neigel Lab doctoral student, Tim Sullivan, collecting blue crabs (Callinectes sapidus).

BLUE CRAB!

We were hoping to catch the crabs at a juvenile and adult stage. To catch them we used a combination of traps, hoop nets, and hand lines. The hoop nets were the best because you bait them with raw chicken and then all you do is wait for the crabs to come to you.


      


...and voilà!      Crabs in a bucket.

  



We were also hoping to collect the crabs at the megalopae stage.  The megalopae stage is a planktonic stage of the crab so they are still out swimming in the channel.  To catch them we set out traps made from a PVC pipe wrapped in a plastic air filter. The idea is that if a megalopae comes in contact with the filter it will think it is a great place to hide and grow so it will grab on to the filter. After the traps have been set for a few hours we lift them out and rinse them with fresh water to collect each megalopae.




Unfortunately we did not catch any megalopae this time...


After catching the crabs we measured them, politely took off one walking leg, and then placed the walking leg in alcohol.  Once we get back to the lab at the University of Louisiana at Lafayette Tim will extract the DNA for each crab we caught.

 
Measure....                                   Remove one walking leg....          Preserve the leg in alcohol

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