Latitudinal variation of size-fecundity relationships in the Northwest Atlantic Lobster,Homarus americanus

Population parameters for lobsters are known to vary with latitudinal variation in environmental conditions, but a quantitative model, applicable throughout the species range has not been developed. To create such a model, fecundity estimates for American Lobster (Homarus americanus) were obtained from 11 different locations in the Northwest Atlantic (from the Strait of Belle Isle, Newfoundland to Buzzards Bay, Massachusetts). A two parameter power function (F=aCL^b) was used to describe the relationship between carapace length (CL) and fecundity (F). There was a well-defined north to south gradient in the allometric exponent b, with the largest values associated with the southern end of the species range. The relationship between the allometric exponent b and latitude was (b = -0.2015*Lat + 12.0015 with a sd of 0.0078 on the estimate of the slope). As a result, lobster stock assessments utilizing size data no longer need to rely on the spatially limited size-fecundity equations currently available. First approximations for fecundity estimates can now be made from power functions, where b is calculated from latitude.