Abstract

Chilean jack mackerel (Trachurus murphyi) is a highly migratory pelagic species that inhabits the Southern Pacific Ocean, constituting the most important fishery for Chile. This species exhibits an onshore migration during the summer related to coastal food availability, and an offshore migration towards reproductive oceanic areas (beyond Chilean EEZ) in early spring. During the spawning peaks (November) of 1998, 1999, 2000 and 2001, jack mackerel eggs were collected from four systematic surveys using 8-10 fishing vessels, deployed in the spawning area (76-92 W) off central Chile. Spatial distribution of eggs was modeled by geostatistical techniques. Environmental information including SST, wind, sea level anomalies and chlorophyll-a, as well as SST gradients, turbulence and currents were calculated. Exploratory results suggest a higher egg density related to warmer waters (16-19 C), moderate winds (4-8 m s-1) and low currents (< 15 cm s-1) as well as SST gradients (< 0.3 C 10 km-1). Statistical analysis developed with the purpose of providing evidence of habitat-species association, reveal a significant relationship (p<0.05) between egg density and both SST and wind magnitude. The spatial coupling between eggs and environmental data was accomplished by using the spatial Empirical Orthogonal Functions method (EOF), showing that high amplitudes of the first mode were spatially coherent with high density of eggs, warm waters and low magnitudes of wind, suggesting a bio-physical coupling among these variables in the jack mackerel spawning area