INIDEP Informe Técnico Nº 54 – 2003

INIDEP Informe Técnico Nº 54 – 2003

Perrotta, R.G., Viñas, M.D., Madirolas, A.O., Reta, R., Akselman, R., Castro Machado, F.J., Garciarena, A.D., Macchi, G.J., Moriondo Danovaro, P., Llanos, V. & Urteaga, J.R. 2003. La caballa (Scomber japonicus) y las condiciones del ambiente en el área “El Rincón” (39º 40′-41º 30′ S) del Mar Argentino. Septiembre, 2000. INIDEP Informe Técnico, 54: 25 p. Ver texto completo

Chub mackerel ( Scomber japonicus ) distribution in “El Rincón” area (39° 40′-41° 30′ S) of the Argentine Sea in relation to environmental conditions. September 2000. Between September 1 st. and 6 th. a research cruise was carried out in the Buenos Aires shelf area of “El Rincón” (39° 40′-41° 30′ S). The total area studied was 2,527.8 nautical mile 2 . Knowledge of the commercial fleet location at the time of the survey allowed to intensify sampling in a “miniarea” of 52,8 nautical mile 2 . The acoustic assessment of chub mackerel biomass was 49,511.9 t, 94% of which corresponded to this last area. Fish samples coming from fishing trawls included only adult individuals of 240-460 mm total length (TL) and ages ranging 2-11 years. The limit age was estimated at 13 years and natural and total mortality rates at 0.23 and 0.54, respectively. Oceanographic conditions were those typical of the winter season, characterized by the vertical homogeneity of the water column in temperature and salinity. The isotherms and isohalines distributed parallel to the 50 m isobath with values progressively decreasing from the coast towards the slope. Salinity values allowed to detect two hydrographic regimes: that of the San Matías Gulf (33.8-34.4) located to the west and covering more than half of the study area and the one of the Shelf Waters (33.5-33.79) occurring towards the East. A positive gradient in chlorophyll a concentration was observed in north-south sense and from the coast towards the shelf break. The highest densities of phytoplankton, with dominance of diatoms, were observed in the southern sector. Low concentrations of Alexandrium tamarense and Prorocentrum minimum , two potentially noxious dinoflagellates, were detected. The highest zooplankton biomass associated to the highest salinity values and salinity gradients, represented mostly by Calanoides cf. carinatus , was also detected in the southern sector. The western sector, influenced by the San Matías Gulf regime and characterized by high densities of both, phytoplankton and zooplankton, may constitute a potentially favourable feeding ground for chub mackerel.