Influence of estuarine and continental shelf water advection on the coastal movements of apron ray Discopyge tschudii in the Southwestern Atlantic

Abstract

Evaluated was the seasonal and inter-annual association between habitat variables and distribution pattern of the apron ray (Discopyge tschudii) and its relationship, with the main force on the environmental condition to understand the influence of estuarine and continental shelf processes in the coastal fishes of the Southwestern Atlantic Coastal System (34°–41°S). Two winter and five spring research surveys in the SACS were analyzed and the Perry and Smith methodology applied to determine the seasonal association of depth, temperature and salinity and the abundance of apron ray. The season with the highest inter-annual spatial distribution variation was related to the main external force on environmental conditions (e.g. wind, atmospheric temperature, and Río de la Plata discharge and shelf water intrusion). Apron ray showed persistent habitat selection, with the water temperature (<16°C) and salinity (higher than 31.8) being environmental factors most influencing its spatial distribution. In the spring, the apron ray spatial distribution showed higher inter-annual variation than in winter. The persistence of the spring habitat selection of D. tschudii suggests that its onshore-offshore as well as north-south movements are influenced by water mass movements forced by a combination of local conditions (wind) and regional-scale weather patterns (e.g. strength of the Malvinas Current). This study provides evidence on the importance of considering environmental conditions on the spatial distribution of apron ray and improves the knowledge on interactions between estuarine and shelf water dynamics as determinants of the spatial distribution of a coastal fish species in the Southwest Atlantic Coastal System.