Browsing Revista de Investigación y Desarrollo Pesquero 2008 Nro 19 by Title
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- ItemEl ecosistema de la plataforma patagónica austral, marzo-abril 2000. Composición, abundancia y distribución del zooplancton.(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2008) Sabatini, M.The abundance, distribution and structure of the zooplankton community in southern Patagonia (SW Atlantic Ocean) were studied during late summer (March-April 2000) from samples obtained with Nackthai (390 ~km) and Multinet (150 ~km) samplers. Total concentrations of zooplankton biomass, integrated in the water column, ranged between 1.0 and 14.5 g m-2 (dry weight) and reached the highest values in the mid and outer shelf off Bahía Grande (Santa Cruz Prov., Argentina) (51~'S). The < 5 mm size fraction, composed mainly of copepods represented, on average, 45% of the total; amphipods and euphausiids accounted for 20% and 31%, respectively. Amphipods were, almost exclusively, Themisto gaudichaudii and euphausiids most abundant species Euphausia lucens and Thysanoessa gregaria. Drepanopus forcipatus, Calanus australis and Oithona spp. constituted the dominant copepods with high abundance of the first in the whole area that represented, on average, 85% of the total mesozooplankton. The maximum abundances of Drepanopus forcipatus, recorded in outer waters of Bahía Grande, showed a noticeable decrease towards the inner area and to the north of the bay. C. australis and Oithona spp. concentrations, although much lower, distributed more homogeneously within the whole study area. The distribution of the different populations in the water column varied according to the species: D. forcipatus and Oithona spp. concentrated mainly in the upper layers down to ca. 50 m; C. australis was found between that depth and near the bottom. Copepods populations were dominated by late copepodids.
- ItemEsquema biogeográfico del Mar Argentino(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2008) Balech, E.; Ehrlich, M.D.The fauna of the Argentine (SW Atlantic Ocean) shelf allows to distinguish two biogeographic provinces: the Argentine and the Magellanic that are part of the Subtropical and Subantarctic Regions. The former extends from 30° S-32° S to 41° S-44° S and from the coast to the 82-95 m isobath, between 35° S-39° S, to 70 m depth in the north Patagonia. The latter extends from the Valdés Peninsula to the southern extreme and from 43° S northward, east area of the Argentine Province. The different physiographic characteristics allow to distinguish movable sandy bottoms in the Argentine Province and in the Magellanic gravel bottoms where large algae grow. The climatic differences explain the prevalence of northern winds in the first, where warm and temperate-cold coastal waters alternate and western strong winds in the second with net predominance of subantarctic waters from the Malvinas Current. The factors mentioned explain the differences in the faunal composition of both Provinces; the Argentina is characterized by a marked heterogeneity of its components and the Magellanic by its homogeneity and own taxa. The detailed analysis of the faunal composition of both Provinces performed using benthonic organisms (echinoderms, crustaceans and molluscs) and nektonic (fishes) resulted in subdivisions that correspond to the Uruguayan District, down to 38° S-39° S and the Rionegrin, south of said latitude in the Argentine Province and the Chubutian and Southpatagonic, north and south of 47° S in the Magellanic. The hydrographic regime allowed to establish the Santacrucean and Fuegian Subdistricts within the Southpatagonic District, which supports the warm drift theory in the Uruguayan and Rionegrin Districts of the Argentine Province and in the Chubutian of the Magellanic. The feature that characterizes the Southpatagonic District is the absence of a warm water tongue.
- ItemEstudio preliminar sobre la estructura de edades y el crecimiento de la pescadilla de red (Cynoscion guatucupa, Pisces, Sciaenidae) en el área sur de la provincia de Buenos Aires(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2008) Ruarte, C.O.; Sáez, M.B.Otoliths reading of specimens derived from research cruises carried out in the south of the Province of Buenos Aires (39°S-41°S), Argentine Sea, in 1998 and 1999 allowed to determine stripped weakfish (Cynoscion guatucupa, Pisces, Sciaenidae) age and growth.
- ItemModificación del análisis de cohortes de Pope para extender su aplicación a un rango más amplio de valores de mortalidad natural y mortalidad por pesca(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2008) Hernández, D.R.; Perrotta, R.G.Pope's Cohorts Analysis was modified to extend its application to a wider range of natural mortality, M and fishing mortality, F rate values. The modified method maintains the simplicity of the one established by Pope and does not require to resolve any non lineal equation in each cohort reconstruction process. The relative errors obtained when estimating the number of individuals per age (maximum and mean in absolute value) showed acceptable levels within the five domains (M and F pairs of values) analyzed in this work. The new method can be adapted to a particular situation (M and F values range) simply solving an optimization problem (minimization of the maximum relative error absolute value) easily achieved using a calculation sheet or considering the approximation corresponding to any of the domains herein analyzed.