Browsing by Author "Ramirez, F.C."

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    Distribución 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.
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    Variaciones de la abundancia numérica y biomasa del zooplancton de red en el Golfo San Jorge (año 1985)
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1987) Pérez Seijas, G.M.; Ramirez, F.C.; Viñas, M.D.
    A study was made on numercial and biomass variations of the zooplankton of the San Jorge Gulf (Argentina), based on samples from five cruises performed during 1985. The sampling was included within a proagramme for the biology and fishery evaluation of the shrimp Pleoticus muelleri. San Jorge, a large gulf of the northern patagonian shelf, comprises major fishery activities. Some fish species of economical importance depend on copepods for their feeding, like anchovy (Engraulis anchoita) or partially on middle-size plankters, like mackerel (Scomber japonicus). As a way for determining the trophic disponibility at the gulf, a study was made in order to express the numerical abundance of copepods, euphausiids and amphipods and other items of lesser importance, as well as their total biomass.
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    Zooplankton biomass in the reproductive area of the southern blue whiting (Micromesistius australis).
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 1999) Sabatini, M.; Álvarez Colombo, Gustavo; Ramirez, F.C.
    Total and size-fractioned zooplankton biomass (larger and smaller than 5 mm) were analyzed over two cruises conducted in the late austral winter (September 1994 and 1995) in the area surrounding Malvinas Islands at the time that massive spawning of southern blue whiting was expected to take place. Biomass was rather uniformly distributed in the area and dominated by the fraction larger than 5 mm in which euphausiids and secondarily chaetognaths were dominating in terms of both weight and number. The smaller fraction was mostly made up of copepods. From the high occurrence of euphausiids and seasonal abundance of the several species of copepods normally present within the area it was hypothesised that the feeding requirements of juvenile and adult blue whiting as well as those of larvae and postlarvae may be met during the winter spawning season. The data were also examined in conjunction with the general pattern of zooplankton biomass occurring in autumn and spring in the Southern Patagonian shelf.