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

Abstract

ABSTRACTLobatus gigas, the queen conch, is a central component of Caribbean cuisine but over-fishing of juveniles has threatened the stability of wild populations. Strombid gastropods, upon reaching sexual maturity, cease growing along the shell length axis and continue growing in width via a flared and thickened shell lip. This morphology serves as a useful indicator of an individual's sexual maturity. Here we examine temporal trends in population demographics, size, and morphology of harvested L. gigas individuals over the last ∼1 ky from San Salvador Island, the Bahamas to quantify the dynamics of human-induced stress on the local queen conch fishery. We collected 284 human-harvested individuals from shell middens at seven localities, measured seven morphological variables, and classified the specimens as either adult or juvenile. We randomly selected 64 of these shells for rapid AMS radiocarbon dating in order to establish three geochronological bins: Lucayan (Pre-European invasion, 1492 CE), Modern (∼102 y), and Global (∼101 y). The proportion of juveniles harvested increased significantly from 47% (Lucayan) to 61% (Modern) to 68% (Global) suggesting increasing pressure on the fishery through time. Patterns in body size and morphology diverge between adults and juveniles and are likely the result of an increase in the proportion of harvested juveniles, the selection of smaller juveniles through time, and possibly changes in fishing methods. This size selective predation did not result in the suppression of adult body size as found in other studies. Geohistorical data, such as these, are vital for providing long term ecological context for addressing anthropogenic ecological degradation and are central to the conservation paleobiology approach.