Cape Eleuthera Institute is excited to introduce a new project led by CEI Research Associate Dr. Travis Van Leeuwen and visiting scientist Dr. Iain “Crabman” McGaw from Memorial University, Canada. They are studying the effects of claw removal on stone crabs (Menippe mercenaria).
There is a large stone crab fishery in Florida which is classed as highly sustainable because the whole animal is not harvested during the fishing process. Instead, usually just one claw is removed and the crab is released. The crab will regrow its claw during the next moult, although it usually takes at least 2-3 moults before the regenerated claw reaches marketable size again. Because this is a highly valuable fishery, the effects of claw removal on survival, competition and growth of these crabs is an area of great interest.
Dr. Travis Van Leeuwen holds some of the crab claws harvested in North Eleuthera.
Last week, Travis and Iain headed up north to join John Cartwright aboard his crab boat. They left campus at 6.30am and were out on the water by 8.30am and started by hauling strings of pots, 10 pots per string and anywhere between 3-10 crabs per pot. The deck hands worked continually during the 11 hour work day, barely stopping for a break. They forgot to pack lunches so survived on a couple of bottles of coke and 4 bags of chips – it was a long but very interesting day!
The pots are opened and the catch inspected.
Once a pot is opened the crew inspect the catch and with a deft flick of the wrist, the crab autotomizes its claw. This is a natural process, just like a lizard dropping its tail, and causes minimal damage to the animal. 305 crabs were tagged with plastic Floy tags during this trip, some had both claws intact, others had one claw removed and a few had lost both claws.
A Floy tag is inserted in to a crab that had one claw removed.
Travis and Iain will return in a couple of weeks to fish again with John, when they can use these tags to identify recaptures and investigate the effects of claw removal on survival rates. In the coming months they will be tagging more crabs and hope to carry out studies in the CEI wetlab to determine the effect of claw removal on the behaviour and physiology of these animals.