2007 - INIDEP Informe Técnico Nro 62-67

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Browsing 2007 - INIDEP Informe Técnico Nro 62-67 by Author "Perrotta, Ricardo G."

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    Estimación de un índice de abundancia anual estandarizado para pescadilla de red (Cynoscion guatucupa), mediante la aplicación de un modelo lineal general; período 1992-2003
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Ruarte, Claudio; Perrotta, Ricardo G.
    The stripped weakfish (Cynoscion guatucupa) has a wide latitudinal distribution (22° S-43° S) and it is object of fishery in Brazil, Uruguay and Argentina (SW Atlantic). In this last country, it is mainly captured in the coastal region of Buenos Aires Province by means of a fleet, which has between 20 m and 30 m length. In Argentina, the average landings in the last 5 years were 9,900 t. It is the second commercial species among the coastal groups. There are two main fishery areas of this species: the Argentinean-Uruguayan Common Fishing Zone (AUCFZ) and the El Rincón area, in the South of bonaerense littoral. Due to the importance of this species, it is necessary to define an index of annual abundance to allow a suitable diagnosis of the fishery condition. The General Linear Model is a suitable model to calculate this index. The factors used in this work were: year, trimester, 4 length categories and 5 sub areas. All of them were significant and reflect spatial-temporal changes in the abundance of this species. The model explained 34% of the total variability in the AUCFZ and 46% in the El Rincón. In general, the trends of catch per unit effort (CPUE) were similar and increasing in both areas, registering a greater increase in the internal areas. On the other hand, the fleet displacements between the areas and the reduction of the total fishery area caused a rise in the annual CPUE and a fall of the captures. These captures were dominated by adults but with an important presence of juveniles in the coastal zone off Mar del Plata city.
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    Muestreo de desembarque de caballa (Scomber japonicus) en el puerto de Mar del Plata (38° S) y determinación de niveles de captura en el área El Rincón; período 1989-2003
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Perrotta, Ricardo G.; Garciarena, A. David; Hernández, Daniel R.
    Chub mackerel caught by the commercial fleet in El Rincón (39°-41° 30’ S) and Mar del Plata (38° S) areas was analyzed. In 2001 and 2002 samples from El Rincón were obtained from landings or collected by scientific observers on board the commercial ships. Samples from Mar del Plata were acquired during the 2001-2002 and 2002-2003 fishing seasons, on board two vessels of the small purse-seine fleet. Landings were mostly adults and only a small fraction of juveniles was observed (< 5%). Length growth parameters from El Rincón samples were estimated, and length-weight and length-age relationships were fitted by Least Squares. The results were as follows: L(mm) = 538.4; k (years-1) = 0.122; t0 (years) = -4.92; Pt = 4*10-7 * Lt 3.536. Natural mortality was estimated at 0.30 and age limit at 10 years. The standardized catch per unit effort (CPUE) annual mean (kg h-1) for the 1990-2002 period was calculated by means of a General Linear Model which justified 41% of total variance. The most significant variables resulted to be the seasonal pattern of exploitation of the resource (month), and its pronounced concentration in the exploitation area (fishing position). Values of the standardized CPUE annual mean fluctuated with trends that were similar to those registered between 1993 and 2002. Due to fluctuations in the Chub mackerel abundance and the possible negative effect caused by the activity of large ships in El Rincón, a maximum annual catch of 13,000 t for 2003 is suggested for this area as a precautionary measure.