Estimation of embryonic survival rate of an ommasterphid squid from satellite sea surface temperature (NOAA-AVHRR): aplication to Illex argentinus in San Matías Gulf (Patagonia, Argentina)

CRESPI ABRIL, AUGUSTO; WILLIAMS, GABRIELA NOEMÍ; MORSAN, ENRIQUE; GAGLIARDINI, DOMINGO ANTONIO; BARÓN, PEDRO

Puerto Madryn

Workshop; SAC-D/Aquarius Workshop; 2008

CONAE

Illex argentinus is a semelparous and annual species that is characterized by the production of large egg masses that float neutrally in the sea currents. In the San Matias Gulf, this species is fished throughout the year as by-catch in the Argentinean hake (Merluccius hubbsi)bottom trawl fishery and, from1994 to 2005, it was fished by a small fleet of jiggers from June to September; but catches have been widely variable. The oceanographic characteristics of San Matias gulf (41º-42ºS, 63º-65ºW) has been studied from historical data obtained by sporadic oceanographic surveys carried out between the years 1970 and 1990 and by satellite images of low-spatial resolution (NOAA-AVHRR) available since 1985. The analysis of this information allowed to identify some singular oceanographic characteristics as high productivity areas, circulation of the water masses and thermo-haline fronts. The objective of this work is to analyze the temporal and spatial evolution of the embryonic survival rates based on sea surface temperature (SST) estimated from satellite (NOAA-AVHRR) in waters of San Matias Gulf. Each month was characterized by an average image of five years (2000-2005). Over these images a function of embryonic survival rate versus temperature was applied to estimate the areas of highest chances of embryonic development on each month. The results showed that the highest probability of survival (0.7-0.8) was in the in the periods March-April and November-December. In the months January and February, the survival probability decreased because the high sea water temperatures inside the gulf, while in the period between May and October the survival chances declined as a consequence of the lower temperatures of the water. The satellite images are a complementary and useful tool to correlate ecological patterns of species and environmental variables. In this paper, the analysis of the SST images allowed the identification of areas and periods of high embryonic survival rates and these results provided a possible explanation for the spring a summer reproductive peaks observed for I. argentinus in the gulf in previous works.