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vol.30 número1  suppl.SympOptimal Environmental Window and Positive Effects of `El Niño' Events on Recruitment and Sustainability of Common Hake (Merluccius gayi gayi) off Central ChileEl Niño 1982-1983 and 1997-1998: Effects on Peruvian Jack Mackerel and Peruvian Chub Mackerel índice de autoresíndice de materiabúsqueda de artículos
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Investigaciones marinas

versión On-line ISSN 0717-7178

Investig. mar. v.30 n.1 supl.Symp Valparaíso ago. 2002 

Is the jack mackerel population affected
by ENSO's variability?

Luis A. Cubillos, Dagoberto F. Arcos

Instituto de Investigación Pesquera, Casilla 350,
Talcahuano, Chile, E-mail:,

Jack mackerel, Trachurus symmetricus, supports one of the most important Trachurus fisheries in the world. This species has a wide distribution in the south Pacific Ocean, which extends north-south along the coast of Peru and Chile and east-west from Chile to the New Zealand coast. There are two discrete stocks of jack mackerel in the Humbold Current System (HCS), one of them located off Peruvian waters and the other along the Chilean coast, including the oceanic fraction distributed beyond the 200 nautical mile exclusive economic zone. According to fishery and biological data, the Chilean jack mackerel population is organized in: a) an oceanic reproductive habitat off central Chile, with a main spawning centre from 30° to 40°S and to the 100°W meridion; b) a coastal feeding habitat of adults in the central-southern area off Chile (34°S-41°S), where adults are recruited and then migrate generally westward for spawning in Spring; and c) a nursery habitat north of 30°S in warmer waters.

Fluctuations in recruitment of Chilean jack mackerel in relation to El Niño-Southern Oscillation variability during the spawning or pre-recruitment period is analyzed. The hypothesis that recruitment is affected by environmental conditions occurring in the spawning area during October-December or during the pre-recruitment period, which extends one year before recruitment, is considered. Time series of recruitment, biomass, sea surface temperature (SST) and wind are used to explore relationships. We also used SST from the IRI web site ( covering the period 1982-1999. These data were used to analyze the influence of the 16°C isotherm in the spawning habitat of jack mackerel. The 16°C isotherm can be considered to mark the boundary of egg and larval distribution during October-December.

A significant relationship was found between recruitment at age 2 and environmental conditions during the spawning peak (October-December). However, SST in the spawning area during October-December was not related to SST variability in the Equatorial Pacific. On the contrary, the SST in the nursery habitat was directly related to the El Niño-Southern Oscillation variability. Furthermore, the nursery habitat was swept away during strong and moderate El Niño events, changing the spatial pattern of the population.

Overall, it is concluded that recruitment fluctuations in the Chilean jack mackerel population are strongly affected by two current systems: the intensity and location of the West Wind Drive current system during the spawning period, and El Niño-Southern Oscillation variability during the pre-recruitment period in the nursery habitat. In this context, a degree of non-linearity could be determined depending on the influence of each system.

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