Arriving at a Threshold
To help resource managers better protect Chesapeake blue crab stocks from overharvesting, researchers have calculated a two-part threshold regime, based on fisheries-independent monitoring (particularly the winter dredge survey) and levels of fishing effort. As this graph indicates, there would be a desired target to aim for each year - which would likely fall along the curved line that shows where researchers expect to find the equilibrium between fishing pressure and the stock size needed to sustain the population. Depending on the results of monitoring data, managers could adjust levels of fishing effort (e.g., numbers of pots) to approach that target. If the data indicates low stocks, fishing effort would be reduced to stay out of the "precautionary zone," an area that signals that the fishery could be in trouble. The low-stock threshold is marked by the 1968 level, the lowest observed by independent surveys. The 1999 level lies very close to that line.