The effect of claw removal methods and temperature on the post-release survival and critical thermal maximum of stone crab (Menippe mercenaria)

Florida stone crab (Menippe mercenaria) is an emerging commercial fishery in the Bahamas with its main export to the United States of America. This fishery capitalizes on the oversized claws of the crab, which are harvested, before the crab is returned to the sea where it can potentially regrow its claws. While it is often assumed that the crab will regrow its claws and re-enter the fishery, only 13% of harvested crabs in the fishery have regrown claws, and an estimated 2-81% of crabs survive post-claw removal and release. In addition, the Caribbean region is considered one of the most vulnerable areas with respect to climate change. Therefore, because most aquatic organisms cannot regulate their body temperature, they are directly influenced by environmental temperature stress, and when combined with the stress of claw removal may further decrease the capacity of the crab to survive warming temperatures.The purpose of my thesis was to: 1) determine a method of claw removal that maximizes survival for stone crab, 2) determine the effect of rapidly warming water temperatures on the reflex behavior of crabs post-release, and 3) determine the effect of claw removal on the critical thermal maximum (CTMax) of stone crab. In chapter 1, I used a controlled laboratory experiment to compare a new autotomy-inducing technique to the typical method of claw removal. For the two different claw removal methods, I compared the survival and start time for claw regeneration as a function of harvester experience and whether one claw or both claws were removed. Finally, the claws that were removed were inspected by independent observers to determine whether any differences using the two methods could be identified.Overall, I found that crabs with claws removed using the proposed induced autotomy method had significantly higher survival than crabs with claws removed using the typical method, while crabs with claws removed by inexperienced harvesters had the lowest. In Chapter 2, I conducted a series of laboratory experiments to measure nine reflex action mortality predictor reflexes of crabs and determine the critical thermal maximum (CTMax) for stone crab that had one or two claws removed using induced-autotomy. Of the nine reflexes used to develop an endpoint necessary for calculating CTMax, three were determined to be suitable (equilibrium, mouth closure and appendage turgor) and CTMax was 37.6 ℗ʻC, and independent of the number of claws removed using the proposed induced-autotomy method.Overall, the tool required to conduct the induced-autotomy method of claw removal is simple and easily purchased or constructed and can easily be taught to recreational and commercial harvesters as a way to improve survival and thus sustainability of this important fishery.