Shell Midden Surveys as Source of Information about Fished Queen Conch (Strombus gigas) Populations: A Case Study in Parque Nacional Del Este, Dominican Republic

Queen conch (Strombus gigas) populations are in decline throughout their range in the tropical western Atlantic, due to a combination of intense fishing, habitat loss and water quality degradation. The dramatic decline in abundance of queen conch has led to commercial extinction throughout much of its range. Life history features such as their slow movements, aggregational behavior, and dependence on shallow-water habitats make them vulnerable to over-exploitation by humans. A better understanding of how population dynamics have reacted to long-term fishing pressure is critical for future restoration and management efforts. From the beginning of conch fishing in the area, fishermen have left evidence of past fishing efforts in the form of shell middens. It is our objective to determine the characteristics of fished populations by surveying undisturbed middens that have been found on the shores of a marine lagoon in Parque Nacional del Este (PNE), Dominican Republic. Some of the middens date to pre-Columbian fishing times and provide a historical context for evaluating recent fishing intensity. Two conch shell middens were thoroughly surveyed by excavating a 2m x 2m area from top to ground level during March and April 2000. Nearly 10,000 queen conch shells were mapped within the middens and measured for shell length, shell width, spine length, and lip thickness when a flared lip was present. The type of opening used to extract the animal was also recorded. One of the middens dates approximately to 1400 plus or minus 70 years, suggested first by Taino artifacts found with the shells and later confirmed by carbon-14 isotopic analysis. The second midden was presumed to be modern based on anecdotal accounts, the pink coloration of shells, and the modern artifacts found at the base of the midden. Results from these excavations revealed that there is a long history of conch fishing in PNE. Shells from the older midden were found to be dominated by smaller shells than the modern midden (probably suggesting different fishing practices or target preferences by Tainos). As we excavated from the top to the bottom of the recent midden, a significant increase in mean shell length of queen conch shells was apparent. The further analysis and dating of these shell middens may help to reconstruct the history of S. gigas fishing and better understand how such activities have affected population dynamics in terms of size frequency distribution and shell morphology.