Julio Peña Torres

In the case of small pelagic fish, it seems reasonable to consider harvest functions depending nonlinearly on fishing effort and fish stock. Indeed, empirical evidence about these fish species suggests that marginal catch does not necessarily react in a linear way neither to changes in fishing effort nor in fish stock levels. This is in contradiction with traditional fishery economic models where catch‐to‐input marginal productivities are normally assumed to be constant. While allowing for nonlinearities in both catch‐to‐effort and catch‐to‐stock parameters, this paper extends the traditional single‐stock harvesting economic model by focusing on the dependence of the stationary solutions upon the nonlinear catch‐to‐stock parameter. Thus, we analyze equilibrium responses to changes in this parameter, which in turn may be triggered either by climatic or technological change. Given the focus in this study on the case of small pelagic fish, the analysis considers positive but small values for the catch‐to‐stock parameter.

This paper examines estimations of technical catch efficiency for a sample of 204 industrial vessels operating at the pelagic grounds of Southern-Central Chile during the 1985-95 period. We consider a Translog stochastic frontier model à-la Battese-Coelli (1995), which includes a vessel-specific inefficiency model. The vessel's age and scale of operation are found to be significant in explaining catch efficiency. Larger vessels tend to be the most efficient and those showing least variance in their efficiencies. Whereas smaller vessels, which on average are the oldest in the fleet, show greater dispersion and lower levels in their efficiencies. Explanatory variables aggregated at the ship-owner level, which aim at controlling for firm's operating scale, are also significant as a whole when explaining vessel-level efficiency. We find positive search externalities associated to the number of vessels under control of a given firm, as well as external diseconomies related to the use intensity given by each firm to its fleet. Yearly averages for vessel's catch efficiencies vary from 50% up to 86%. Whereas close to 90% of the residuals' total variance is associated with the inefficiency term, which suggests a significant disparity in vessels' catch performance at this fishery