Michael FranklinMarine Field Methods16 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. 1990.

Jivoff, Paul. “Blue Crabs.” Personal Communication. Rider University. 11 September 2008.

Pollock, L. W. A Practical Guide to Marine Animals of North America. Rutgers University Press. New Brunswick, NJ. 1997. Pg 264

Wnek, John. “Barnegat Bay.” Personal Communication. Drexel University. 9 September 2008.

Fin