Seawater temperature, -chlorophyll and zooplankton samples support a new paradigm: Coastal waters off northern Patagonia play a major role as spawning and nursery areas for early life-cycle planktonic stages of the Argentine squid Illex argentinus.

AUGUSTO CÉSAR CRESPI ABRIL; PEDRO JOSÉ BARÓN; ENRIQUE MARIO MORSAN

Pucón

Congreso; 5th international zooplankton production symposium. Population connections, community dynamics, and climate variability.; 2011

Illex argentinus sustained the world’s largest cephalopod fisheries during the last decade. Based on the spatial distribution of mature individuals and paralarvae on the confluence of Brazil-Malvinas currents and the mid/outer shelf off northern Patagonia, researchers have interpreted that major spawning stocks having distinct life-cycle chronologies segregate during discrete time periods in specific areas of the mid/outer shelf and shelf break off Argentina to Southern Brazil, and that either: 1) neutrally-buoyant egg-masses drift to the confluence of Brazil-Malvinas currents (B/M-C) where hatching might take place, or 2) mature females migrate long distances to the B/M-C to spawn. However, alternative life-cycle hypothesis involving the use of coastal areas as spawning and nursery grounds have not been explored. In this study we evaluate the suitability of different areas of the species’ range of distribution for early life-cycle development by spatially modeling a combined function of the monthly probability of: 1) embryonic survival, based on experimental data and SST remote sensed information (NOAA-AVHRR), and 2) paralarvae survival, based on primary productivity availability estimates (-chlorophyll concentration, SeaWiFS). Also, we sampled coastal waters off northern Patagonia searching for paralarvae of I. argentinus. Our model shows that coastal areas may play a major role as spawning and nursery grounds of the species that has been neglected previously. Also, we confirmed our predictions by reporting the finding of paralarvae of I. argentinus in zooplankton tows conducted coastal waters off Patagonia and of juveniles (25-39 mm ML) found stranded on the coast at 42.8ºS.