Abstract

Queen conch (Strombus gigas) are important epibenthic herbivores in soft-sediment communities, but have been intensively exploited in Parque Nacional del Este (PNDE) for approximately 30 years. Consistent, applied fishing pressure alters the population dynamics, growth rate, ecological role, and spatial abundance patterns of the population. The main focus of this study is to correlate queen conch abundance and size frequency distribution with benthic community types and sediment characteristics in order to detect ontogenetic habitat preferences using a systematic sampling methodology. A benthic community map for PNDE was delineated and ground-truthed; from this map five soft-sediment community types were surveyed using 50 x 5m strip transects during March 1996 and 1997. Results indicate that queen conch are more abundant in benthic communities with sediments that consist mostly of sand-mud instead of sand. Abundance estimates also indicate that queen conch are significantly more numerous in communities with sparse to moderate seagrass cover < 30%). Yearly surveys showed a marked decline in queen conch abundance; however, there was a corresponding increase in milk conch (Strombus costatus). Size frequency data suggest that juvenile queen conch use seagrass beds on the eastern margin of the park as a nursery area. Despite the vast seagrass plains found in PNDE, conch only occupied a small fraction of the available habitat and plankton tows for veligers conducted during August 1995 and 1996 yielded low strombid densities; this may indicate recruitment limitation. These findings have important implications for resource managers and conservationists who want to evaluate the likelihood of stock recovery. A closed fishing season during breeding months (if recruits are produced locally) and total closure (no-take) of nursery grounds can have a positive impact on the stock in PNDE.

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