The use of the convex hull estimation in data envelopment analysis (DEA) models is often characterized as a variable returns to scale model. However it is well known that standard microeconomic production theory posits a nonconvex S-shaped production frontier, i.e. a production technology that obeys the Regular Ultra Passum Law with a monotone decreasing scale elasticity along any expansion path. Recently for a homothetic production relation a nonparametric estimation approach that allows for a nonconvex S-shaped scaling law has been proposed. In this paper we use this approach to analyze and estimate scale characteristics of the US West Coast groundfish production for the period 2004–2007.