Application of a Yield and Egg Production Model Based on Size to an Offshore American Lobster Population

We estimated size-specific growth, maturation, yield, and egg production per recruit for an offshore population of American lobster Homarus americanus. The yield and egg production model explicitly considered individual variability in growth. The model also incorporated the interaction between the growth and reproductive cycles of mature females and accommodated molt-related mortality for males and females. Growth rates of offshore American lobsters considerably exceeded estimates for inshore populations; yield and egg production per recruit were correspondingly higher. Simulations indicated that yield per recruit was maximized at low levels of fishing mortality for both males and females. Inclusion of molt-dependent mortality in these simulations resulted in lower levels of yield per recruit and less convex yield curves for both sexes. At high levels of fishing mortality, changes in the predicted mean size of the catch became small, indicating that detecting increases in mortality rates from size composition data would be difficult as fishing mortality increased.