Browsing by Author "Sánchez, R.P."
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- ItemConsideraciones sobre el crecimiento de la caballa (Scomber japonicus marplatensis) durante su primer año de vida(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1982) Sánchez, R.P.Through the analysis of the morphological changes ocurring in the process of growth, it was possible to identify three stages (primary juvenile: 25-75 mm; secondary juvenile: 76-160 mm; and juvenile preadult: 161-250 mm) during the first year of the species life. Regression equations for the different relations studied: body weight/body lenght, body surface/body lenght, body surface/body weight, and metabolic rate/body lenght, have been calculated for each stage. The variation of the number of gill rakers, mean distance between adjacent rakers and mean values of gill rakers lenght in reference to body growth was studied, and the relation between filtering area and body length was established.
- ItemEstimación de la biomasa de adultos desovantes de la anchoíta (Engraulis anchoita) en el área costera bonaerense durante la primavera de 1981 y análisis comparativo de los recuentos de ictioplancton con redes de diferentes mallas(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1984) Sánchez, R.P.; de Ciechomski, J.D.A bongo sampler fifted with nets of two different mesh sizes, 330 and 505 u. was used to collected 137 ichthyoplankton samples in the coastal areas off Buenos Aires Province in October, 1981. The efficiency of the two meshes for catching anchovy eggs and larvae and total ichthyoplankton was examined. The statistical analysis of the samples shows that there are no significant differences between the numbers of anchovy and total eggs collected by the different meshes. As regards anchovy and total larvae the finer mesh showed as significantly higher catching efficiency. The results of this partial estimate do not suggest that a major revision of the total assessment of the complete stock is necessary.
- ItemEstudio 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.
- ItemEstudios sobre las variaciones espacio-temporales en los patrones de distribución de embriones y larvas de la anchoíta (Engraulis anchoita), en relación con la estimación de su intensidad reproductiva(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) Sánchez, R.P.Ichthyoplankton samples were collected during an exploratory cruise carried out by the RV Dr.Holmberg during the spring spawning peak of 1981 in the sea-shelf off Buenos Aires province (Argentina). The cruise was designed to carry out population studies in a restricted area of intense reproduction activity, in order to gather information on the time-space patterns of distribution of the eggs and larvae of the species.
- ItemEstudios sobre reproducción y fecundidad de la polaca (Micromesistius australis Norma 1937) en el Mar Argentino(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) Sánchez, R.P.; de Ciechomski, J.D.; Acha, E. MarceloAn analysis is presented of reproduction aspects of Argentine Sea blue whiting. The species spawns in the study area mostly during August and September, although some spawners have been detected even in November. Total length at 50-per-cent maturity was 35,4 cm for the males and 38.0 for the females. Significant differences between the length of maturity for individuals of the continental shelf compared to those of the slope, have been obtained. The southern blue whiting is a discontinuous spawner, showing one annual reproduction peak. Fecundity was investigated on the basis of samples collected in 1978 by the RV "Walther Herwig" and "Shinkai Maru". A significant positive correlation was also observed at relating oocyte dry weight and gonad factor, whereas no correlation wasobserved between oocyte dry weight and condition factor, and age of the female.
- ItemEvaluación 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.
- ItemIchthyoplankton composition, distribution and abundance on the southern patagonian shelf and adjacent waters.(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 1999) Ehrlich, M.D.; Sánchez, R.P.; de Ciechomski, J.D.; Machinandiarena, L.; Pájaro, M.This paper reviews the information on pelagic and demersal fish eggs and larvae, describing the distribution and seasonality of different species and their arrangement in icthyoplankton assemblages in the Southern patagonian waters. It also reports on 11 surveys conducted by INIDEP during 1992-1995. A total of 488 ichthyoplankton samples were analyzed. Fish eggs have been recognized in 47. of all ichthyoplankton samples. They belong to three species: Coelorhynchus fasciatus, Macrourus whitsoni and Micromesistius australis. Fish larvae of 23 species and 17 families have been identified in 96. of all samples analyzed. Spawning of most species begins in autumn, and progresses through winter, when the southern blue whiting and grenadier fish contribute to more than half of all eggs present in our samples. Nototheniid and myctophiid larvae were caught during all year long. Four larval groups were detected using cluster analysis: the first group, formed exclusively by nototheniids, which occupied a vast area on the continental shelf between 100 and 200 m depth, the second formed by Agonopsis chiloensis, Eleginops maclovinus, Macruronus magellanicus and Sprattus fuegensis in coastal waters, the third formed by myctophiids, Gymnoscopelus spp. and Micromesistius australis, inhabit the outer continental shelf and slope, and the fourth included Protomyctophum spp., Krefftichthys anderssoni and Bathylagus antarcticus, species typically found in Subantarctic waters of the Malvinas Current. Comparing the distribution of eggs and larvae of blue whiting from collections obtained during the 70's and 80's, with those of recent surveys, it is evident, that a significant contraction of the spawning grounds of the species has take place, particularly to the west of the archipelago.
- ItemLarval and juvenile growth of two Patagonian small pelagic fishes: Engraulis anchoita and Sprattus fuegensis(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2010) Brown, D.R.; Sánchez, R.P.Patagonian anchovy (Engraulis anchoita) and sprat (Sprattus fuegensis) constitute the two most important pelagic resources of the Argentine Patagonian shelf (SW Atlantic). Age and growth parameters of larvae and juveniles of both species were determined analyzing otoliths daily increments. A total of 404 anchovies (4.1-33 mm SL) and 157 sprats (5-41 mm SL) were analyzed. The Laird-Gompertz growth model was fitted to the length-at-age data of anchovies: L(t) = 4.2 exp (2.28 (1-(-0.034 t))). The parameters of the model were: L: 41.06 mm; the inflection point: 15.11 mm and 27 days; and the maximum growth rate: 0.51 mm day-1. The length-at-age data of sprat larvae and juveniles were represented in two linear models: L(t) = 0.32 t + 7.6; and L(t) = 0.22 t + 6.6. Slopes represented mean growth rates, 0.32 and 0.22 mm day-1 for larvae and juveniles, respectively. Variations in length-at-age between years were determined through the analysis of individual growth trajectories. Variations were found in sprats, not in anchovies.