CONCH FRITTERS THROUGH TIME: HUMAN PREDATION AND POPULATION DEMOGRAPHICS OF STROMBUS GIGAS, SAN SALVADOR ISLAND, THE BAHAMAS

Strombus gigas is a culturally and nutritionally important component of Caribbean cuisine, however the over-fishing of juveniles has threatened the stability of wild conch populations. Current regulations require the possession of a thick and well-formed shell lip, typically>15 mm. The purpose of this study is to quantify temporal trends in population demographics of harvested S. gigas individuals from medieval (Pre-Columbus), modern (~10² years), and global (~10¹ years) aged middens and accumulations on San Salvador Island, the Bahamas (sensu Lotze et al., 2011). We hypothesize temporal increases in both body size and the proportion of adults harvested as a result of current fishing regulations. We collected 292 individuals from 11 localities and measured nine morphological variables. Individuals were assigned to temporal bins based upon information from the literature and shell interior color preservation. Among medieval specimens (n=34), 16 were adults, 15 were juveniles, and three were indeterminate. Modern specimens (n=158) comprised 63 adults and 95 juveniles. The global specimens (n=89) represent 22 adults and 67 juveniles. Contrary to our hypothesis, the proportion of adults harvested decreased through time. There was no discernible difference between medieval (47.1% adults) and modern (39.9% adults) samples (Fisher’s Exact p=0.238, α=0.05), though the difference between modern and global (24.7% adults) was statistically significant (Fisher’s Exact p=0.018). However, as predicted, median body size increased significantly through time (medieval=2.22, modern=2.24, global=2.30; Kruskal-Wallis p=4.26E-14). A temporal increase in preservational quality (Kruskal-Wallis p=3.059E-08) and a weak, but significant, correlation between size and taphonomic score (Spearman rho = 0.41, p=1.023E-12) suggest that size trends are partially explained by taphonomic bias. Nevertheless, these results demonstrate increasing stress on conch fisheries through time and highlight the need for continued regulation. Future analyses will include radiocarbon dating to further clarify our stratigraphic construct and measuring δ¹⁸O values of shell carbonate to quantify trends in seasonality of human activities.