Testing the Effect of Ghost Traps on the Blue Crab, Callinectis Sapidus , in Barnegat Bay
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Transcript of Testing the Effect of Ghost Traps on the Blue Crab, Callinectis Sapidus , in Barnegat Bay
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 BaySince 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 tiesOnce specimen are loaded, close off top with zip ties
Crab entrance closed off with wire mesh
Crab TrapWire MeshWire CuttersRopeCameraZip Ties
How do we get crabs?Trap some a few days early and starve themOnce ready to begin, collect new crabs from trapsAdd directly to ghost trap with 2 from starved tank
Six crabs total, one missingFound small space to escape due; patched up with zip tieTwo crabs deadOne just has claws leftOther missing both paddles and one claw
Four crabs alive and intactLarger dead crab has no changeSmaller dead crab has only section of carapice left
Last day of experimentTook two samplesNo change from second day in first sampleSecond 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 264Wnek, John. Barnegat Bay. Personal Communication. Drexel University. 9 September 2008.