Abstract

Coastal upwelling areas along eastern boundary currents have been recognized for having high planktonic production. In the Humboldt Current System off South America, little is known about the reproductive strategies of mesopelagic fishes and their utilization of highly productive coastal upwelling areas for spawning and early development. In the present study, we first document the spawning and nursery area of the highly abundant mesopelagic fish Maurolicus parvipinnis in the coastal upwelling zone off Talcahuano, central Chile. Second, we propose a mechanism by which ontogenetic and diel changes in vertical distribution of the early life history stages and the utilization of the local hydrodynamics facilitates the development of the larvae of this species over the shelf and nearby slope in a highly productive environment. Our results show that M. parvipinnis spawn during early spring at mid-depth in zones of intense upwelling. Larvae hatch mostly in the spawning area located on the southern edge of the slope, and are then advected northwards along the slope or over the shelf where high larval food concentrations occur. Over the shelf, larger larvae tend to vertically migrate, spending part of the night hours in the shallower layer where the water temperature is higher, and where food is most abundant. During the day, they remain at depth where offshore transport may be decreased. Those larvae that are not retained over the shelf are advected offshore, probably in the surface Ekman layer or in association with cold filaments that usually develop off the central zone along the shelf off Talcahuano. Although information on the spawning strategy of other Maurolicus species worldwide is sparse, there are some similarities in relation to the subsurface spawning, the larval presence in nearshore waters, and the early spring spawning season in association with periods of increased food availability. The spawning strategy described herein, therefore, may be a more common feature than previously believed for Maurolicus species, especially along coastal upwelling areas in eastern boundary currents.