2011 - INIDEP Informe Técnico Nro 79-83

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    Parámetros biológicos relevantes para las pesquerías de anchoíta argentina (Engraulis anchoita). Estimaciones resultantes de reunir datos de campañas de investigación (1993 a 2008) y de muestras de capturas comerciales (1986 a 2009)
    (INIDEP, 2011) Hansen, J.E.
    The aim of this paper was to accurately estimate population parameters of northern (“bonaerensis”, latitude < 41° S) and southern (“patagonic”, latitude 41° S) Argentine anchovy stocks and to describe some aspects of their behaviour. The research surveys allowed to obtain data on length, total weight, sex, maturity and age of 27,853 specimens of the northern and 12,787 of the southern stocks. Besides, 20,717 age determinations stemmed from commercial landing samplings of the northern stock were established. Sex proportion in the northern population was 0.50 : 0.50; the southern showed a slight predominance of males (0.52 : 0.48). Data derived from cruises and commercial landings showed statistical differences in the growth ratio of the northern stock where mean size at ages 0-2 proved to be slightly higher in landings; the opposite was observed about ages 5-6. On the other hand, research data showed similarity in mean size at age of both stocks, used to fit a unique von Bertalanffy growth function (L = 194.62; K = 0.456; t0 = -0.86). In the October surveys on the northern anchovy stock higher mean weight at size and age than in December cruises on the southern stock were observed, which resulted in significant differences between both length (mm)-weight (g) relations described, respectively, by equations W = 1.867 * 10-6 * L3.254 and W = 1,467 * 10-6 * L3,290; likewise, a higher asymptotic weight was calculated for specimens of the first group (53.36 g vs 47.47 g). Estimates of natural instantaneous mortality rates, carried out using different methods available in the literature, allow to suggest values M = 1.01 for the northern and M = 0.98 for the southern populations. A marked discrepancy between both stocks was observed in their capacity to reach sexual maturity, the northern group being precocious (L50% = 98,0 mm; t50% = 0,58 years vs 119,2 mm and 1,14 years). The size of specimens in the shoals of both populations, mainly in the southern, was homogeneous whether at day or night time. The preferential spawning period, that ranged 4-10 pm, was common to both stocks; nevertheless, females with hydrated oocytes were more frequent in the samples taken from the northen population, which indicates shorter periods between batch spawning.
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    Distribución y abundancia de huevos y larvas de langostino patagónico (Pleoticus muelleri) (Penaeoidea, Solenoceridae) en las temporadas estivales de 2008 y 2009
    (Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero INIDEP, 2011) Moriondo Danovaro, P.
    The study on distribution and abundance of eggs and early planktonic stages of red shrimp, Pleoticus muelleri (Bate, 1888), contributes to a better knowledge of the species dynamics. Results from processing and analyzing 72 plankton samples collected with Bongo net during two research cruises on board of FV “Arbumasa XVIII” and RV “Capitán Oca Balda”, carried out in the Patagonian littoral in March 2008 and January 2009, are presented. In both cruises, eggs and larval stages were found all over the study area. The highest punctual densities of eggs were recorded in the area known as “La Pared” (46° 45’ S-65° 55’ W and 46° 50’ S-65° 55’ W). Eggs indicate the presence of shrimp reproductive concentrations which, while migrating eastwards towards waters of national jurisdiction, generate production scenarios characterized by high rates of catch per unit of effort and better commercial sizes. In the 2009 cruise, high densities of shrimp eggs were also found near Rawson area.
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    Estimación de un índice de abundancia anual de gatuzo (Mustelus schmitti) a partir de datos de la flota comercial argentina. Período 1992-2008
    (INIDEP, 2011) Pérez, M.; Massa, A.M.; Cordo, H.D.
    Patagonian smoothhound (Mustelus schmitti) is one of the predominant cartilaginous fishes of the Argentine Sea (SW Atlantic Ocean). It is caught, mainly, in the coastal multispecific fishery with nearly other 30 bony and cartilaginous species. The group is known as ‘variado costero’. In this work the smoothhound abundance indices (CPUE) and standardized efforts for the 1992-2008 period in the area between 34~’S-42~’S were estimated. The General Lineal Model (GLM) and data derived from the argentine commercial fleet were used. Other aspects that could affect estimates and trends of the annual indices were also analyzed. Mean CPUE values estimated with the GLM, considered as annual standardized abundance indices, show an increasing trend as of 2000; the highest relative levels correspond to the last three years of the study period
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    Análisis de las capturas de atunes realizadas por dos buques pesqueros de Mar del Plata, Argentina, entre enero y abril de 2010
    (INIDEP, 2011) Garciarena, A. David
    Data obtained by observers on board of two fishing vessels during six trips carried out between January-April 2010 to catch tuna were analyzed. Thirty-four fishing days were completed and of the 59 trawls performed 37 turned out positive (with tuna catches). The fishing gear consisted of a purse seine net. Exploitation took place within the Argentine-Uruguayan Common Fishing Zone, between 36° S-39° S. The main landings occurred in March and consisted of slender tuna, Allothunnus fallai (57%), followed by albacore, Thunnus alalunga (28.5%), in January and bonito, Sarda sarda (14%), in April. Sea surface temperature ranged 16 °C-19 °C. A total of 25 length frequency samples allowed to measure individuals of the species above mentioned and those of skipjack tuna (Katsuwonus pelamis). During fishing operations the death of some magellanic penguins (Spheniscus magellanicus) and soft-plumaged petrels (Pterodroma mollis) as well as catch of anchovy (Engraulis anchoita) were registered
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    Distribución de desovantes y estimación de variables reproductivas del efectivo norteño de merluza (Merluccius hubbsi) (35º'S-41º'S) durante mayo de 2009
    (INIDEP, 2011) Rodrigues, K.A.; Macchi, Gustavo J.
    Spawning and reproductive variables of the northern hake stock were analyzed using macroscopic and histologic gonad information derived from samples collected in May 2009. The study includes estimates of batch fecundity, spawning frequency, oocyte dry weight and size at first maturity. During May 2009 the reproductive activity of the northern hake stock took place mainly near the 50 m isobath, north of 37° S. Spawning occurred within a temperature range of 9 °C-15 °C that coincided with a bottom thermal front. Size at first maturity, much lower than that reported at the beginning of the 1980s, showed differences between males (27.16 cm TL) and females (32.84 cm TL). The reproductive frequency was estimated at one spawning every 13 days and mean batch fecundity (764,545 oocytes) resulted higher than in April 2003. Likewise, oocyte dry weight exceeded that of April 2003, which might be associated to the size composition of each reproductive group