PARENT SESSION
Oral Session # 3: Fish Ecology.
Presiding: M Ford
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.
Influence of mutualism, competition, predation and habitat on shrimp goby population dynamics.
Thompson, Andrew*,1, 1 University of California, Santa Barbara, Santa Barbara, CA
ABSTRACT- Population dynamics of coral reef fish are influenced by a variety of biotic and abiotic factors. To determine how mutualism, predation, competition and habitat affect the population dynamics of the fierce shrimp goby (Ctenogobiops feroculus), I conducted field and laboratory experiments in Moorea, French Polynesia. Shrimp gobies interact mutualisticaly with snapping shrimp (Alpheus sp.) as follows: shrimp construct burrows in which both gobies and shrimp reside, and gobies warn shrimp of predators through touch-based signals. Surveys of 686 3 x 3m quadrats throughout the north shore of Moorea indicated that goby distributions were constrained by the presence of shrimp, whereas shrimp were confined to habitats with a mixture of rubble and sand. Even within appropriate habitats, however, goby densities were variable. Subsequent surveys demonstrated that recruitment explained 88% of the variability in adult goby density among locations with appropriate habitat. In locations with high recruitment, gobies competed intraspecifically for large shrimp, and large gobies were competitively dominant. A strong, negative correlation between predator and large goby densities indicated that predation also affected goby population structure. In addition, a positive correlation between the occurrence of small gobies residing with large shrimp and predators further suggested that predators impacted goby populations. A field experiment demonstrated that predators readily consumed large gobies, and that small individuals paired up with large shrimp when a shrimp became available due to the death of a large goby. These results indicate that shrimp availability, which is constrained by appropriate habitat, affects goby presence/absence; variable recruitment influences patterns of goby abundance; and predators influence goby size-structure and turnover rates.
Key words: shrimp-goby, mutualism, predation, competition