Browsing by Author "Cassia, M.C."

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    Evaluación de polaca (Micromesistius australis) en el Atlántico Sudoccidental. Período 1987-2001
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Wöhler, O.C.; Hansen, J.E.; Cassia, M.C.; Cordo, H.D.
    Period 1987-2001. A diagnosis of the current state of Southern blue whiting (Micromesistius australis) stock in the Southwest Atlantic was carried out on the basis of catches corresponding to the period 1987-2001 as reported by the Argentine fleet and also by vessels operating around Malvinas Islands. Abundance and current fishing mortality rates were estimated, and the biomass evolution in the long term resulting from some possible exploitation strategies based on different management strategies were projected. A sequential population analysis calibrated under a conceptual adjustable framework with five independent abundance indices was carried out. The effects on the biomass estimates were analysed by adopting different selection patterns and calibration indices as well as taking into account the under-declaration and discard of catches. Results indicated that the declining trend of Southern Blue Whiting observed in previous studies has continued, but it has been less marked than in preceding years. Total biomass estimates at the beginning of 2001 ranged between 566 and 622 thousand tonnes, whether the under-reporting or discards of catches by the Argentine fleet were taken into account or not. Accordingly, the spawning biomass at the onset of spawning ranged between 403 and 442 thousand tonnes. These values would correspond to 27-29% of the virgin biomass. Current fishing mortality was estimated as 0.27, corresponding to a relatively high exploitation rate (0.56). Projections aimed at four possible management objectives showed that biologically acceptable catches would range 22-84 thousand tonnes in 2002. Catches in the Southwest Atlantic should not exceed 50 thousand tonnes during 2002 in order to stop the declining trend of Southern blue whiting biomass.
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    Observaciones sobre embriones de larvas y juveniles de la pescadilla (Cynoscion striatus)
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1982) de Ciechomski, J.D.; Cassia, M.C.
    Observations on the embrionic and larval development of Cynoscion striatus are presented. The description are made on the basis of material obtained by artificial fertilization. Eggs are pelagic, spherical, 700-840µ in diameter and with single oil globule of 210µ-240µ. The yolk is homogeneous and the chorion has smooth surface. The embryonic development is short and at temperatures of 19°-20°C hatching takes place, 34-36 hours after the fertilization. The larvae at hatching are small, about 2 mm in length and not advanced in their development. The mouth is not functional and the anus is not open. The oil globule is situated in the posterior part of the yolk sac; the position of the anus is close to the posterior end of the yolk sac and the digestice tract forms a straight angle with the anus. The dody and the oil globule are pigmented. The juveniles have a rather deep form of the head and of the body and have their charasteristic pigmentation pattern. The preoperculum is provided with strong spines which disappear entirely in larger specimens.
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    Reproducción y fecundidad del surel (Trachurus picturatus australis)
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1980) Cassia, M.C.; de Ciechomski, J.D.
    Studies on the sexual maturation on the jack mackerel in the area close to Mar del Plata were carried out throughout the whole year, 56 almost ripe females between 160 and 210 mm in total length and between 38 and 78 g is weight were taken into consideration for fecundity determinations. The most important results obtained during these studies are the following: The gonad index was rather high and reached the value of 11.5. The reproduction season is a rather one and the spawning occurs mainly in December and January. It is assumed that a female of this species spawns once over a reproduction season, but shedding numerous batches of eggs in short intervals. The lowest value found for the fecundity was 15.825 ovocites and the highest one was 82.892. It is started that there exist great differences in the fecundity between the females within the same size and weight groups.