Estimating Uncertainty in Stock Management Reference Points for Chesapeake Bay Blue Crabs

The Magnuson-Stevens Act (2006) requires management reference points to be established for managed species.  Moreover, managers must assess the uncertainty in these reference points so as to understand the amount of risk adopted by any specific level of harvest.  Due to the economic and ecological importance of the blue crab (Callinectes sapidus) in the Chesapeake Bay, estimating viable reference points is paramount in managing the fishery.   The latest stock assessment of the blue crab in Chesapeake Bay (Miller et al. 2011) presents a sex-specific catch, multiple survey model to estimate stock status and reference points.  However, the assessment does not provide estimates of the uncertainty associated with these reference points recommended.  Here we develop a stochastic, sex specific matrix model to explore the sensitivity of a reference point proxy, the intrinsic rate of population increase, to uncertainty and variability in several demographic parameters (i.e. fecundity and natural mortality) under varying degrees of instantaneous fishing mortality.   Preliminary results suggest stochastic models can produce estimations of uncertainty and that individual demography characteristics do not carry equal weight in overall reference point uncertainty.  By isolating the tolerance of parameter variation, we can then reassess which parameters require further research for more accurate estimations, which could culminate in greater reliability in reference point estimation.