Analysis of the process and observation error in recruitment estimates for the pacific sardine, Sardinops sagax caeruleus (Girard), off the southwest coast of the Baja California peninsula, Mexico

Abstract

This paper analyzed the dynamics of the stock-recruitment relationship for the Pacific sardine Sardinops sagax caeruleus (Girard) off the southwest coast of the Baja California peninsula, Mexico, from 1981 to 1993. A maximum likelihood estimator was used to estimate the parameters of the model assuming two hypotheses: (a) process error in the model and (b) observation error in the data. The results showed that the hypothesis of the process error was accepted. The parameter values and confidence intervals (CI) were as follows: α = 2.7 (CI = 2.0–3.6, P < 0.05) and ß = 0.04 (CI = 0.03–0.05, P < 0.05), with σ = 0.58; the maximum value of the objective function L(R_Est\α, ß) = 1.16 x 10^–5. In this paper, environmental variability is not interpreted as random variability (noise); the model was used to demonstrate and quantify effects of a statistical hypothesis on the possible stock-recruitment relationship, based on the error structure of the model and the stochastic effect on the parameters.