Relationship of precipitation, freshwater input, and sea level height with the abundance of the white shrimp (Litopenaeus occidentalis; Street, 1871) off Buenaventura, eastern tropical Pacific

Penaeid shrimp fisheries are an important source of income for the fishing communities that live in estuarine zones around the world. Off Buenaventura, the habitat of the western white shrimp (Litopenaeus occidentalis) is subject to high precipitation associated with the intertropical convergence zone, contributions from numerous short rivers descending from the Andes Mountains, and seasonal alternations in Trade Winds directions responsible for the upwelling in the Panama Bight. This work analyzes the relationship of precipitation, the San Juan River runoff, and sea level height with Litopenaeus occidentalis abundance in fishing areas between 1968 and 1989. The results indicate that precipitation is significantly correlated (p < 0.01) with the catch per unit effort on a monthly scale with a lag of approximately 1 calendar year but the inclusion of the data in a transfer function model does not improve considerably the forecasting power of a simpler autoregressive moving average model of the catch per unit effort. On an annual scale, the catch per unit effort for white shrimp depends significantly [r² = 0.36, p (corrected for autocorrelation)  0.01] on the precipitation that fell the previous December, whereas the residuals of this regression are significantly associated with variations of mean sea level between January and March (the upwelling season in the Panama Bight) of the current year at Buenaventura (r² = 0.61, p (corrected for autocorrelation)  0.01). The inclusion of these two variables in a multiple linear regression model accounted for a substantial proportion of the total annual variance of the mean CPUE (r² = 0.54), suggesting that freshwater contributions (lower salinities) and offshore transport during the main settlement period of postlarvae in the estuaries play a significant role in determining the strength of the cohorts recruited in the fishing areas. The industrial fishing yield decreased sharply after the 1982–1983 El Niño event. However, a high percentage of this change can be explained not by invoking El Niño effects but by a decreasing tendency of precipitation and offshore advection of early life stages between December and March, which took place on a multi-annual scale since the mid 1980s