Post Hurricane Feeding Behavior and Preference of Strombus gigas in Greater Lamshur Bay, Saint John, U.S. Virgin Islands

Van Buren, Mary

ABSTRACT: Observations of feeding behavior and preference were conducted and compared to data taken before Hurricane Hugo to see if it had any effect on feeding habits. The hurricane had no noticeable effect on feeding preference but a change in feeding behavior is evident. Whether this change is hurricane related is unknown. INTRODUCTION: On September 17 and 18, 1989 Hurricane Hugo passed over the United States Virgin Islands. High winds of up to 130 miles per hour and turbulent waters caused extensive damage to both the marine and terrestrial environments. One of the marine ecosystems damaged was the seagrass beds, where large hurricane scars are found (Martino,1989 pers comm). These scars altered the sea grass beds which is the home of many marine organisms including the Queen conch, strombus gigas. Strombus gigas is a large herbivorous marine gastropod that lives on the sandy ocean floor of the Caribbean waters (Wormke and Abbot,1961 in Webb,1988). They can survive in depths up to 77 meters but are usually found in water 33 meters or shallower where light is abundant enough not to restrict the growth of seagrasses and microalgae (Randall, 1964 in Silin,1988). Conch use their extendable proboscis to graze on epiphytes which grow on vascular sea plants including Thalassia testudinum and Cymodocea filiforme and the macroalgeas, which include Halimeda, Penicillus, Udotea, and Avrainvillia(Young 1932 in Silin 1988). Epiphytes are also found growing on detritus and sand.(pers.obv.). Many epiphitic species including both brown and red algae can be found on the surface of seagrass species(Round, 1981). Earlier studies have been done on s. gigas feeding habits in Greater Lamshur Bay. In Hwang's 1987 report, queen conch were proven to move more and farther in sparser substrate, and dense substrate was their predominant habitat (p<.05). Later studies show that S. gigas juveniles have significant dlfference(p<.001) of feeding preference (Webb, 1988). In a study that extended Webb's, juveniles had a significant preference for T. testudinum when grass abundance was calculated (Silin, 1988). Adult conch clearly prefer macroalgaes(Baldwin, 1988). The purpose of this study is to compare the feeding preference of Strombus gigas pre hurricane to post hurricane. Using data obtained by (Silin 1988) and comparing with data taken within two months after the hurricane it will be determined if the hurricane caused a significant change in feeding preference of the Queen conch. The first null hypothesis states that there is no significant difference in the time spent by S. gigas in the consumption of plant epiphytes from time 1 (pre hurricane) to time 2 (post hurricane). Also data collected by Webb in 1988 will be compared with current data to distinguish between changes in feeding behavior. The second null hypothesis states that the hurricane had no effect on feeding behavior.