Modeling the Effect of Environmental Factors on the Ricker Stock-Recruitment Relationship for North Pacific Albacore Using Generalized Additive Models

Abstract

This study investigates how the inclusion of El Nino episodes affects the modeling of recruitment in North Pacific albacore. The relationship between spawning stock size and recruitment for the 1976 - 2004 period, including environmental variables (Southern Oscillation Index and sea surface temperature anomalies), was conducted by general linear and generalized additive models (GAM). The results indicate that the Southern Oscillation Index and the interaction between spawning stock size and sea surface temperature anomalies have significant effects on the recruitment of North Pacific albacore. GAM fit the original data better than general linear models, according to the Akaike information criterion. The recruitment declined when El Nino episodes occurred, but increased when La Nino episodes occurred. The recruitment also increased when the spawning stock size density was above 11.21 million tons with a -0.3°C sea surface temperature anomaly. El Nino was observed to have both long-period (above 10 - 15 years) and short-period (1 - 2 years) effects on North Pacific recruitment.