Martín Varisco

Reproductive biology of the spider crab Leucippa pentagona (Decapoda: Epialtidae), in Bustamante Bay, Argentina

Sizes at maturity, breeding period, and fecundity of the spider crab Leucippa pentagona in Bustamante Bay, Argentina (45.11oS, 66.56oW) were analyzed. Specimens were collected monthly between May 2006 and February 2008. The size at morphometric maturity was determined based on relative changes in cheliped length for males and abdomen width for females. The presence of spermatophores in the male deferent ducts and of eggs in the female abdomens were the criteria used to determine physiological maturity. The temporal variation of the proportion of ovigerous females was analyzed. Oocyte sizes in ovigerous females were measured to evaluate the occurrence of multiple spawnings. In males, the sizes at morphometric and physiological maturity were 28.05 and 16.7 mm carapace length (CL), respectively. In females, the size at morphological maturity was 18.5 mm CL, whereas size at physiological maturity was 18.25 CL. Ovigerous females were found between June and February in both years. Ovigerous females were found to have oocytes with advanced vitellogenesis. Fecundity was similar in both years and varied between 645 and 7114 eggs. The extended breeding period and the presence of vitellogenic oocytes in ovigerous females suggest the occurrence of two or more spawnings per reproductive season. Finally, the distribution range of this species in the Atlantic Ocean was extended from 43.3° to 45.11°S.

Bycatch of the squat lobster Munida gregaria in bottom trawl fisheries in San Jorge Gulf, Argentina

Varias especies de langostillas son reconocidas como recursos pesqueros potenciales en todo el mundo. La langostilla Munida gregaria es un componente importante de las capturas incidentales en las pesquerias de arrastre en la Patagonia Argentina. Se evaluo la frecuencia de ocurrencia (FO), abundancia relativa (AR) y destino de las capturas incidentales de M. gregaria en: a) la flota congeladora tangonera (63579 lances), b) la flota fresquera de altura (5608) y c) la flota costera (584). Las mayores FO y AR fueron registradas en la flota costera. Sin embargo, dada la magnitud de la flota congeladora tangonera, el esfuerzo de pesca sugiere que las mayores capturas incidentales en terminos de biomasa son producidas por esta flota. Se observo un incremento significativo en FO y AR en los lances de la flota congeladora tangonera en los ultimos anos, siendo este mas marcado en aguas nacionales y provinciales de la provincia de Santa Cruz. La FO y AR de la especie en los lances de la flota fresquera de altura fueron bajas durante todo el periodo analizado. Los resultados confirman que la langostilla es una especie muy abundante y un recurso desaprovechado hasta el presente, y que puede representar una alternativa para la flota costera en el Golfo San Jorge.

La alimentación de Munida gregaria (Fabricius, 1793) (Crustacea: Anomura: Galatheidae) en fondos de pesca del Golfo San Jorge, Argentina

The area encompassing San Jorge gulf and surroundings is one of the most important fishing grounds in Argentina. Heavy fishing pressure affects the dynamics ...

Composición química proximal y perfil de ácidos grasos del mejillón Mytilus edulis provenientes de cultivos y bancos naturales en el Golfo San Jorge, Argentina

espanolSe analizo el contenido de carne, la composicion quimica proximal y el perfil de acidos grasos de la carne de mejillones recolectados en bancos naturales infralitorales y en cultivos localizados en el Golfo San Jorge, Argentina. Se comparo el contenido de humedad, cenizas, lipidos, proteinas y glucidos. El perfil de acidos grasos se determino por cromatografia gaseosa y fue empleado para calcular el indice aterogenico (IA) y el indice trombotico (IT). Los mejillones del banco natural tienen un menor contenido relativo de carne que los ejemplares de cultivo. Se obtuvieron diferencias significativas en la composicion quimica proximal de los mejillones. La carne de mejillon presento un alto contenido de humedad, siendo esta mayor en mejillones de bancos. Las proteinas son el componente bioquimico con mayor porcentaje, seguido por los hidratos de carbono y en menor cantidad por los lipidos. Independientemente del origen de los animales, la carne de mejillon se caracterizo por una mayor cantidad de acidos grasos polinsaturados que acidos grasos monoinsaturados y saturados. El IA en mejillones de banco fue levemente menor que en los ejemplares de cultivo, mientras que el IT fue el mismo en ambos casos. Las diferencias observadas en la composicion quimica proximal de los mejillones de cultivos y bancos naturales se deberian al habitat que ocupan, el cual determina diferencias en la calidad y cantidad de alimentos y diferencias en la energia destinada a mantenimiento. EnglishIn the present study we compared meat yield, proximate chemical composition and fatty acid profile of the blue mussel Mytilus edulis from rocky shores and long line cultures in San Jorge Gulf, Argentina. Moisture, ash, lipids, proteins and carbohydrates were quantified. The fatty acid profile was analyzed by gas chromatography. Mussels from rocky shores had lower meat yield than cultured mussels. The proximate chemical composition was different between the mussels of the two environments. Mussel meat was characterized by high moisture content, with higher moisture in mussels from rocky shores. Proteins were the main biochemical component, followed by carbohydrates and lipids. Regardless of the origin of the mussels, meat mussel was characterized by higher content of polyunsaturated fatty acids than that of monounsaturated and saturated fatty acids. Atherogenic index was lower in cultured mussels, while thrombogenic index was similar in both groups of mussels. Differences in proximate chemical composition between mussels from rocky shores and cultures are related to the habitat in which they grow, which determines differences in the amount and quality of food and in maintenance costs.

Feeding strategy of early juvenile stages of the southern king crab Lithodes santolla in the San Jorge Gulf, Argentina

Resumen.- Se analizo el contenido estomacal de 313 ejemplares juveniles de centolla de ambos sexos con longitudes de caparazon (CL) entre 8,40 y 49,04 mm, estudiandose la influencia del sexo, talla, estado de muda y estacion del ano. Los animales fueron capturados mediante buceo en muestreos estacionales en el infralitoral rocoso del area central del Golfo San Jorge. Se determino la frecuencia de ocurrencia (FO) y abundancia relativa (AR) de las presas halladas, estado de replecion y peso del contenido estomacal. Se registro un 14,4% de animales con el estomago vacio, un 55,1% con replecion menor del 50% y un 30,5% mayor al 50%. Los juveniles no se alimentan antes de mudar, durante la muda ni en postmuda reciente. Se identificaron 27 grupos de presas diferentes, incluidas varias especies de algas, protistas e invertebrados. Las mayores FO fueron registradas en algas coralinaceas (45,1%), ofiuroideos (34,8%), equinoideos (25,1%), isopodos (21,7%), moluscos bivalvos (19,5%), poliquetos (16,9%) y briozoos (15%). En terminos de AR, los principales componentes de la dieta fueron ofiuroideos, isopodos y coralinaceas. La composicion de la dieta es diferente en animales menores de 15 mm CL de aquellos mayores a esa talla, debido a la mayor abundancia de isopodos y briozoos en este intervalo. La gran diversidad de presas registradas indica que los juveniles son esencialmente depredadores macrofagos y omnivoros, que aprovechan los complejos habitats infralitorales rocosos y biogenicos del area estudiada para su alimentacion y refugio durante los primeros anos de vida. Palabras clave: Dieta, depredacion, Lithodes santolla, juveniles, aguas costeras, omnivoria

Growth and maturity of the spider crab Halicarcinus planatus (Brachyura: Hymenosomatidae) females in the southwestern Atlantic Ocean. Can these parameters be influenced by the population sex ratio?

ABSTRACT The Halicarcinus planatus populations of the southwestern Atlantic Ocean show a highly variable sex ratio and a large size overlapping between females in the last immature instar (ADO) and mature (MAT) females. We hypothesized that these facts are related and that female impregnation has a central role in this relation. Non-impregnated ADO females delay maturity and would continue to grow, leading to size overlapping. This scenario is most probable in populations with a scarcity of males and could affect the growth, maturity and population structure. The sex ratio and female size distribution of several populations of the southwestern Atlantic Ocean were analysed. Growth and maturity were studied in two populations with different sex ratios (Camarones, a population with males, and Rada Tilly, a population where no males were found). Size overlapping was not related to the population sex ratio. Size overlapping was due to a variable moult increment and, to a lesser extent, to delayed maturity. Females mated before terminal moult in both populations. However, in Camarones, physiological maturity was not related to impregnation, while in Rada Tilly, vitellogenic oocytes were observed only in impregnated females. Also, differences in the number of spermatophores in female spermathecae were related to the sex ratio. Our results showed that the morphological maturity pattern of females was not influenced by the population sex ratio. However, physiological maturity was related to female impregnation and sex ratio. Also, the variation in the number of spermatophores suggests differences in the mating system related to the sex ratio.