Revista de Investigación y Desarrollo Pesquero 1986 Nro 5

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    Algunas características del florecimiento del fitoplancton en el frente del Río de la Plata. I. Los sistemas nutritivos
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) Negri, Rubén M.; Carreto, J.I.; Benavides, Hugo R.
    During the spring (H-04/82: october 11-27, 1982) carried out by the Fishery Research Vessel "Dr.E.Holmberg", the distribution of temperature, salinity, nutrients concentration and photosynthetic pigments were studied at the "Rio de la Plata" maritime front. The presence of Sub-Tropical coastal waters in only station did not allow its characterization. Low Chlorophyll a concentration were noted, in association with scarce concentrations of nutrients and high Margalef index values.
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    Evaluación de la biomasa de adultos desovantes, distribución vertical y variación cuantitativa de la intensidad de los desoves de la anchoíta (Engraulis anchoita) durante la primavera de 1982
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) de Ciechomski, J.D.; Sánchez, R.P.; Lasta, C.A.
    Ichthyoplankton was sampled in 9 exploratory cruises in the sea off Buenos Aires province (Argentina), Uruguay and Brazil, during the spawning peak of the anchovy in spring-early summer and mid-autumn. The most abundant speices in the ichthyoplankton was Engraulis anchoita, representing 88. of the eggs and 76. of the larvae collected in all the cruises. These percentages vary boath regionally and seasonally; as regards eggs, the lowest percentage (10% ) was found in January. The distribution of anchovy eggs and larvae, covered almost entirely the surveyed area, with the exception of hte region influenced by the River Plate estuary. Minimum salinity tolerance for the species eggs was 23.5o/oo. The eastern limit of the distribution of anchovy eggs, extends in spring-early summer to the 200 m isobath in the northern part of the study area, whereas in the south rarely extends beyond the 50 m isobath. Anchovy larvae showed a wider distribution, penetrating in November and December in the brackish waters of the Samborombón bay, extending over more off-shore waters in January. As the spawning season progressed a southwards movement of intensive reproduction nuclei was observed. The average daily egg production during spring-early summer was estimated at 260 anchovy eggs/m2/day; in autumn, a ten-fold reduction of this production was observed. On the basis of the seasonal egg production for spring-early summer, calculated at 3.5238 E15 eggs and the larvae census carried out in mid-January a 98.2% mortality during the imbryonic and larval stages of the anchovy could be assumed. The spawning biomass of the anchovy during this period was calculated at 2,514,970 t. Preliminary results on the vertical distribution of anchovy eggs and larvae show that their distribution is generally restricted to the upper 50 m water layer, with higher concentrations at 10 to 25 m depths.
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    Estudio comparativo de caracteres merísticos y morfométricos de la anchoíta (Engraulis anchoita)
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) Ratti, M.M.
    The argentine anchovy (E.anchoita) shows a distributional area between 35° and 47°30' on the continental shelf off Argentina. This paper deals with some meristic and morphometric characters in order to test their power in separating different stocks. Those largely scattered distributions of morphologic features, which had been already pointed out other authors, make difficult to separate different stocks of this species on this basis.
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    Estudio sobre el crecimiento en peso y factor de condición en larvas de anchoíta, Engraulis anchoita Hubbs & Marini. Variaciones regionales, estacionales y anuales
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) de Ciechomski, J.D.; Sánchez, R.P.; Alespeiti, Gabriel; Regidor, H.
    The equation log W=a+bL (where W=dry weight in ug, and L=total length in mm)was used to describe the growth in weight of larval anchovy collected in two areas of the Argentine sea, sampled in different months and several years. Regression lines were compared by covariance analysis applied to two size groups, namely larvae less and over 10 mm total length, as an evident break in the slopes indicated the existence of a chenge of rythm in the trajectory of larval growth in length. Significant differences between the slopes of the growth lines were observed within the smaller size group. No regional or yearly differences could be established fo larvae larger than 10 mm.
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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.