Oyster biomass, abundance, and harvest in northern Chesapeake Bay: Trends and forecasts

摘要

We applied time series of fishery-dependent and fishery-independent data to develop indices of relative biomass and estimates of absolute abundance and biomass for the Maryland oyster population. The principal objectives for this work were to specify a baseline and determine trends relative to the Chesapeake Bay Program's goal to achieve a 10-fold increase in the standing stock of oysters in the Bay from a 1994 baseline. Population biomass varied by 3-fold from 1986-2001, with most of the variation caused by changes in the stock of market-sized oysters. There were also important spatial differences in population structure and trends over a gradient of salinity. Lagged correlations between small oyster biomass and either market-sized oyster biomass or landings were not statistically significant but suggested that most of the market-sized oysters and those harvested were four to five years old. The index of relative biomass for market-sized oysters proved to be a useful predictor of annual harvests in Maryland. We used this relationship to estimate absolute abundance and biomass of oysters for the time series. The latter estimates may be biased negatively with respect to true abundance and biomass because of biases in both the fishery and the fishery-independent monitoring program. The index of relative biomass will be a suitable measure of population status relative to the oyster restoration goal only so long as the population remains at relatively low levels. Because the index has a theoretical maximum of about 75% of the 10-fold goal, a quantitative estimator will be required for higher population levels.