Abstract

The population structure of fishery resources and the impact of environmental factors over its productivity are important processes to be considered in fisheries management. Environmental factors could determine both, the success of larval drift as the population spatial structure and its changes of biomass. In this paper we show the environmental effect over distribution, abundance and spatial structure of nylon shrimp population (Heterocarpus reedi) off central Chile (25°-37°S) from trawling surveys carried out between 1996 and 2011. Environmental variables considered where sea surface concentration of chlorophyll-a and dissolved organic matter. Results show a geographical separation in population around 32°S. Shrimp density is higher in the southern zone, where concentration of chlorophyll-a and dissolved organic matter are high due to presence of river tributaries and coastal upwelling zones. In this area, the bulk of the adult population is concentrated, which could act as "source" population and thereby its influence on larval drift could explain both, the preponderance of juveniles in the northern area as the smallest size of its population (“pseudo-sink” population). In the southern area, a process of spatial and bathymetric expansion had driven the increase in population size over time, where the colonization and individual somatic growth had been the main mechanisms. We found that periods of good environmental conditions explain high densities of shrimp with a delay of two years, which might be related mainly with larval survival and enhanced recruitment and somatic growth. The aim of this study was to understand the spatial-temporal variability of the nylon shrimp density in the study area