GILCHRIST, S.L.*; JOURDAN, M.C.; SANCHEZ, A.; New College of Florida; New College of Florida; New College of Florida: Impact of shell supply on population changes of Coenobita clypeatus on Bailey’s Cay, Roatan, Honduras

The land hermit crab (Coenobita clypeatus) population located on Bailey�s Cay has studied for the past 9 years. Gastropod shells (over 90, 000), commonly thought to be a limiting resource for hermit crab populations, have been added to the site to record the potential impact on population size and on size class distribution. Before release of shells every year, an extensive survey of shells on the cay was conducted. New shells were evenly distributed in three sampling areas each year; a vegetated site near fresh water, a vegetated site near shore, and a site near shore with sparse vegetation. For the first seven years, attention was given to increasing the availability of large, heavy shells on the cay. Over the past two years, small and lighter shells have been increased. Subsequent to first three years of shell additions, there was an apparent increase in crab population size, then there was a period where the population stabilized. Size classes of hermit crabs recovered showed stabilization of percentage of animals collected in each class as well. In 1998, Hurricane Mitch caused the cay to become inundated completely for several days. During summers of 1999 and 2000, few hermit crabs in the largest size classes were collected and numbers in the smaller classes decreased by an order of magnitude. The summers of 2001, 2002 and 2003 showed a large influx of the smallest size classes with an increasing number of larger crabs observed as well.