Michael Franklin Marine Field Methods 16 September 2008

I chose to use the Blue crab, Callinectus sapidus, for my experiment because it is abundant here in Barnegat Bay and it is relatively easy to catch.

 Callinectes sapidus is a swimming crab  Important to commercial soft-shell crabbers, both commercial and recreational (Jivoff 2008)  Main method of crabbing is basic crab trap

 Ghost traps occur when a trap is lost yet continues to catch organisms (Breen 1990)  John Wnek says there are easily 2,000 in Barnegat Bay  Since C. sapidus is so aggressive (Pollock 1998), what happens when they get stuck in cage with no food and what impact does this have?

If caught in a ghost trap, C. sapidus will have cannibalistic tendencies until the last one has died off from starvation.

 How do we duplicate a ghost trap in the lab?  Create ghost trap by closing of entrances with wire mesh and zip ties  Once specimen are loaded, close off top with zip ties Crab entrance closed off with wire mesh

 Crab Trap  Wire Mesh  Wire Cutters  Rope  Camera  Zip Ties

 How do we get crabs?  Trap some a few days early and starve them  Once ready to begin, collect new crabs from traps  Add directly to “ghost trap” with 2 from starved tank

 Six crabs total, one missing  Found small space to escape due; patched up with zip tie  Two crabs dead  One just has claws left  Other missing both paddles and one claw

 Four crabs alive and intact  Larger dead crab has no change  Smaller dead crab has only section of carapice left

 Last day of experiment  Took two samples  No change from second day in first sample  Second observation, larger carapice separated from rest of body/claw

Based on the results, I reject my null hypothesis that the crabs will simply “be” in the trap. The results show that they cannibalized two crabs in the trap, then, at least for the duration of my test, were satiated.

 Ghost traps do affect the organisms stuck in them, namely C. sapidus.  C. sapidus has no problem resorting to cannibalism when no other food source is available.  Cannot extrapolate my data over whole bay.

 Breen, P. A. A Review of Ghost Fishing by Traps and Gillnets. Ministry of Agriculture & Fisheries, Fisheries Research Center  Jivoff, Paul. “Blue Crabs.” Personal Communication. Rider University. 11 September  Pollock, L. W. A Practical Guide to Marine Animals of North America. Rutgers University Press. New Brunswick, NJ Pg 264  Wnek, John. “Barnegat Bay.” Personal Communication. Drexel University. 9 September 2008.

Fin