Browsing by Author "Reta, R."
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- ItemLa caballa (Scomber japonicus) y las condiciones del ambiente en el área "El Rincón" (39°40'-41°30' S) del Mar Argentino. Septiembre, 2000(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Perrotta, R.G.; Viñas, M.D.; Madirolas, A.; Reta, R.; Akselman, Rut; Castro Machado, F.; Garciarena, A.D.; Macchi, G.J.; Moriondo Danovaro, P.; Llanos, V.; Urteaga, J.R.Between September 1st and 6th a research cruise was carried out in the Buenos Aires shelf area of "El Rincon" 39°40'-41°30'S, Argentine Sea SW Atlantic. The total area studied was 2,527.8 nautical mile2. Knowledge of the commercial fleet location at the time of the survey allowed to intensify sampling in a 'miniarea' of 52,8 nautical mile2. The acoustic assessment of chub mackerel (Scomber japonicus) 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 Matias 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 N-S 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 Matias Gulf regime and characterized by high densities of both, phytoplankton and zooplankton, may constitute a potentially favourable feeding ground for chub mackerel.
- ItemLas condiciones oceanográficas en el área marplatense (37° 00' S-38° 24' S) y su relación con la distribución de la caballa (Scomber japonicus). Octubre-noviembre de 1999(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2009) Reta, R.; Perrotta, R.G.; Garciarena, A.D.Results obtained during a research cruise carried out along the coastal area of Mar del Plata (Buenos Aires, Argentina) in November 1999 are presented. The objective of the research cruise was to estimate chub mackerel (Scomber japonicus) abundance with acoustic methods and establish its relation to the hydrographic conditions. The information gathered was complemented with data of catches obtained by a commercial vessel that operated simultaneously in the study area. Environmental data from other research cruises and satellite information were also taken into account to obtain contemporary sea surface temperature and wind speed and direction data. The main species of catches of the research cruise and commercial vessel were horse mackerel (Trachurus lathami) and anchovy (Engraulis anchoita). No chub mackerel was detected during the acoustic assessment; however, the species was caught by the commercial vessel in the southern part of the study area and near the thermohaline front. Chub mackerel yields were very low if compared to those regularly recorded in the area and time the purse-seine fleet operates and that are typical of an advanced fishing season (January). The advection of estuarine waters from the de la Plata river, conditioned by the winds field, generated the displacement of low salinity waters over the coastal area that surpassed the regular southern limits. The positive anomalies of sea surface temperature in the region, that reached values close to 3 °C, could have caused the partial exclusion of chub mackerel in the coastal region of Mar del Plata.
- ItemEl ecosistema de la plataforma patagónica austral durante el verano, marzo-abril 2000. Estimación de la biomasa fitoplanctónica a partir de la distribución de clorofila a(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2010) Reta, R.The distribution of chlorophyll-a concentration in the austral Patagonian (SW Atlantic Ocean) shelf between 47º S-54º S with in situ data collected in March-April 2000 is analyzed. Data derived from Niskin samples and continuous in situ fluorometry. Two areas with high chlorophyll values (~- 1.6 mg m-3) on the central shelf corresponding to the area between isolines 100-150 m depth and near the coastal region off Bahía Grande south of the Santa Cruz river (Argentina) were identified. Minimum values (~, 0.5 mg m-3) were found in the coastal zone close to the 50 m isobath and to the southern region of the Patagonian shelf. Fluorescence: chlorophyll-a concentration ratios were more variable at sea surface than at different depths of the water column. The possible causes for the vertical distribution of chlorophyll-a are analyzed.