Assessment of the Stocks of the Western Rock Lobster Panulirus cygnus Using Surplus Yield Models

Abstract

Four different surplus yield models (namely Schaefer, GENPROD, PRODFIT and delayed recruitment) were applied to the data from the fishery for the western rock lobster. The four models all provided similar estimates of maximum yield and optimum effort. These estimates were 8.0-8.6 × 10⁶ kg at a level of effort of 5.6-5.9 × 10⁶ units. Variation in catches was shown to increase with increasing effort although this could not be attributed to increased variation in catch per unit of effort.

It was considered that while the four surplus yield models provided good descriptions of the relationship between total catch and equilibrium effort up to the level of effort so far encountered in the fishery, not as much confidence could be placed in their ability to predict catches at levels of effort outside the already observed range.