Browsing by Author "Akselman, Rut"
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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.
- ItemDistribución del plancton a mesoescala en un área de reproducción de la anchoíta en la plataforma bonaerense(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) Akselman, Rut; Carreto, J.I.; Ramirez, F.C.In order to determine the distribution patterns of phytoplanktonic and zooplanktonic species that constitute the main food of the argentine anchovy (Engraulis anchoita), a study was made within a coastal spawning area on meso-scaled space (approximately 7 miles between stations). It was observed the predominacne of the copepod Oithona helgolandica and copepodites stages of other small-sized species, thus inferring the preponderance of nauplii stages which constitute the main food of early anchovy larvae. A high spatial heterogeneity was found in the distrtibution of both phytoplanktonic and zooplanktonic communities. Phytoplankton showed a patchiness distribution both in horizontal and vertical directions. Diatoms, dinoflagellates and coccolithophoirids showed their own distribution patterns with biomass nuclei centered at different stations. The spatial distribution of the components within each taxonomic group seems to be of the contagious-type distribution. The positive correlation (r= 0,64*) as observed between immature stages of copepods and coccolithophorids seems to indicate a trophic direction of these consumers, which is also supported by the finding of coccolithophorids in copepods pellets. The phytoplankton crop as measured by population census and chlorophyll a concentrations (0,0-0,91 mg/m3) indicates an area of a low productive capacity.
- ItemPresencia de veneno paralizante de moluscos en higado de caballa de la región costera bonaerense(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 1993) Carreto, J.I.; Akselman, Rut; Cucchi Colleoni, A.D.; Carignan, M.O.; Pájaro, M.During november 1992 an intense bloom of the toxic dinoflagellate Alexandrium tamarense accurred in coastal waters from Mar del Plata, Argentina. Toxicity testing of Mytilus edulis populations of the region revealed high levels of paralytic shellfish poison. In order to study the possible PSP accumulation in mackerel (Scomber japonicus), mouse bioassay (AOAC) was performed in livers from individuals captured during December 1992. Liver extracts were lethal to mice; the sumptoms observed were typical of those caused by paralytic shellfish toxins. Although PSPS concentration is below the established limit for human consumption, it suggests that mackerel can accumulate PSP toxins from its food. On the basis of stomach content analysis of sampled mackerel and the related literature, the occurrence of possible toxins vector organisms is discussed.
- ItemSuplemento a "Los dinoflagelados del Atlántico Sudoccidental"(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1984) Balech, E.; Akselman, Rut; Negri, R.M.The present work is a supplement of the monography "The dinoflagellates of the Southwestern Atlantic" by E. Balech (in press). Eightenn species belonging to the genera Ceratium, Dinophysis, Diplopelta, Gonyaulax, Heterochisma. Oblea, Oxyphysis, and Protoperidinium are discussed on accurt of their presence, up to the present unknown in the area. Comments on their geographical distributions, ecological requirements and morphological details are included in the work.