2006 - INIDEP Informe Técnico Nro 57-61

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    Estructura y abundancia del stock reproductor del abadejo (Genypterus blacodes) del Mar Argentino en el período 1995-2000
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2006) Cordo, H.D.
    The structure and abundance of Ling spawning stock were analized from basic biological and oceanographic data recorded during research surveys carried out by INIDEP between 1995 and 2000, to assess the juveniles fraction of common hake stock (January) and of Argentine patagonian squid (February). Jointly both surveys covered the main spawning area of Ling between 44º S and 48º S and approximately between the mouth of San Jorge Gulf (60º W) and 200 m isobath (65º 30’ W) during the summer season (mid-December to mid-March). Size structures and maturity stages confirmed the presence of a spawning unit in the area covered by the surveys. This enabled the estimate of an annual index of Ling spawning stock abundance. Abundance shows a decreasing trend since 1995, even when it seems to stop during 2000. Nevertheless, abundance estimates during 2000 represent 58% of the corresponding figure for 1995. This represents a significant decrease in the reproductive stock over a relatively short period of time. A possible solution to put an end to the decreasing trend would be to establish a fishing ban area, complementary to that created to protect hake juveniles, extended only during Ling reproductive season, namely every year between December 15 and March 15.
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    Desove en cautiverio y calidad de los huevos y larvas del besugo, Pagrus pagrus (L.)
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2006) Aristizábal, Eddie O.
    Spontaneous spawning of red porgy was achieved in captivity by using photoperiod and temperature control systems along the year. During a four-month reproduction period females released in average about 0.2 times their own body weight in oocytes with an energy content of 5.71 J mg-1 wet weight. A total of 28.8 x 106 eggs and approximately 200 g of viable eggs (wet weight) per female kg were obtained. The eggs and larvae quality in terms of hatching and larval survival rates experienced a significant variation during the spawning season ranging between 0%-92% and 0.3%-33.2% respectively. Comments in reference to the probable causes of these variations and the need of carrying on with this line of research are presented.
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    Distribución y estructura de tallas de la palometa (parona signata, carangidae) y el pampanito (stromateus brasiliensis, stromateidae) en relación con las condiciones oceanográficas en la Zona Común de Pesca (34° s-38° s) y estimación de la longitud de primera madurez sexual. Julio de 2001
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2006) Perrotta, Ricardo G.; Guerrero, Raúl A.; Carozza, Claudia R.; Quiroga, Pedro; Macchi, Gustavo J.
    Samples were obtained using bottom trawl nets during a coastal research cruise carried out on board of the RFV “Dr. E. L. Holmberg” between 3rd. and 16th. July 2001. The spatial distribution of surface and bottom temperature and salinity fields was analyzed at the oceanographic stations sampled in each trawl position. The analysis allowed to characterize the oceanographic conditions of the area during the sampling period and to compare them to the historic seasonal mean. 669 leatherjack specimens of 9-55 cm total length (TL) caught at depths ranging 5-29 m and 1,372 butterfish individuals of 6-40 cm total length (TL) caught at depths ranging 4-29 m were sampled. Length at first sexual maturity for both sexes was also estimated. Results were: leatherjack: L50 (cm) = 30.06 and butterfish: L50 (cm) = 23.12. It is worth mentioning that the presence of adult leatherjack near Mar del Plata (Buenos Aires prov., Argentina) suggests that the resource may become one of the target species for the coastal fleet.
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    Nematodes parásitos como indicadores biológicos de Macruronus magellanicus
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2006) Incorvaia, I.S.; Hernández, Daniel R.
    A wide distributional range species can constitute many populations or fishing stocks which can be whole or partly overlapped within their distribution area, reason why they must be clearly identified. Therefore, proper identification of stocks is necessary for fisheries management, as this is the unit to which the fishing effort should be applied. The parasitological method is one of the systems currently used to determine stock. Nematodes parasites of Macruronus magellanicus (longtail hake) collected during surveys enmarked between 45º S-55º S in the Southwest Atlantic were studied. Nematodes that could be used as biological indicators were selected. Mean abundance values of L3 Anisakis simplex and Hysterothylacium aduncum were estimated. Three different areas of abundance were recognized: coastal with high abundance, intermediate with mixed values and continental slope with low abundance.
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    Fecundidad parcial y frecuencia reproductiva del efectivo patagónico de merluza (Merluccius hubbsi)
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2006) Pájaro, Marcelo; Macchi, Gustavo J.; Ehrlich, Martín D.
    Batch fecundity and spawning frequency of Argentine hake inhabiting Patagonian waters south of 41° S were estimated using monthly samples collected during the December 2000-March 2001 reproductive season and at the end of the March 2002 spawning period. Batch fecundity was fitted to a power function of total length and a linear function of ovary-free female weight with values ranging between 100,000 (32 cm total length) and 2,300,000 (87 cm total length) hydrated oocytes. Batch and relative fecundity showed variations during the spawning season with a marked decrease towards the end of the reproductive period (March). The spawning frequency, which ranged between 0.10 and 0.15, was estimated from the proportion of females with day-1 postovulatory follicles and was higher during the spawning peak (January-February). At these frequencies, a female hake would spawn, on average, 14 times between December and March. Both, batch fecundity and spawning frequency showed higher variability within the same reproductive season than between years