Abstract: Genypterus brasiliensis, a demersal fish of large size (1.3 m of total length), occurs in the southwest Atlantic (23 to 38oS) and well appreciated due to the quality of its flesh. It was analyzed through longline and trawl fisheries, and the average length and weight of 724 specimens were significantly different between them, with the biggest and heaviest specimens caught by the former. The weight-length relationships were significantly different based upon sex: females Wt=4x10-7Lt3.3799; r2=0.97; n=262; p<0.001, and males: Wt=4x10-7Lt3.3886; r2=0.95; n=190; p<0.001. Using the otoliths readings for 153 specimens (APE of 2% and CV of 4.2%), the growth parameters estimates reveal statistical differences between sexes (p=0.05; r2=0.889). The fisheries were composed of individuals aged 1 to 13 (females) and 1 to 14 years old (males), with ring formation in late spring. The back calculated parameters (VBGF) were: Loo=1,452.38 mm, K=0.0996, t0=-0.2757 yr-1 (females) and Loo=983.07 mm, K=0.155, t0=-0.236 yr-1 (males), and longevity as 29.8 and 19.1 years old, respectively. The low biological production allied to the slow growth and a late complete maturation and its endemism, allow classify G. brasiliensis as a vulnerable resource, jeopardizing a sustainable fishery. Until reliable quantitative biological data are available, precautionary management must be considered.

In this paper, an ageing degree characterization of 12Cr1MoV steel using two method of magnetic Barkhausen noise is developed. A study of the microstructural evolution during ageing at operated conditions (15MPa, 550ºC) from 100000 h up to 150000 h was carried out using optic and scanning electron microscopy techniques. In the first method the experiments reveal a decreasing of root mean square of voltage with the ageing time, which is attributed to the decreasing of domain walls number per area units with the grain size increasing. In the second method the spheroidization level/average size of carbides was analyzed too with the total second peak height, determining a decreasing due to the change of the shape, size and acicularity of carbides phase.

En este trabajo se caracteriza el grado de envejecimiento del acero 12Cr1MoV con el ruido magnético de Barkhausen por dos métodos. Para ello se realiza un estudio de la evolución microestructural en condiciones de operación (15MPa, 550ºC) desde 100000 h a 150000 h, utilizando técnicas de microscopía óptica y electrónica de barrido. En el primer método los experimentos revelan una disminución de la raíz cuadrada media del voltaje con el tiempo de explotación, lo cual se atribuye a la disminución del número de paredes de dominio por unidad de área con el aumento del tamaño de grano. En el segundo método se evalúa el nivel de esferoidización y el tamaño medio de los carburos a partir de la altura total del segundo pico de la envolvente de la señal Barkhausen, mostrando una disminución debido a un cambio en la forma acicular y en el tamaño medio de los carburos.

As raias de água doce ou potamotrigonídeos estão restritas às drenagens dos rios Neotropicais. Estas raias tem se adaptado bem aos ambientes de água doce e o número de espécies descritas aumenta gradualmente conforme as pesquisas na área se intensificam. Alguns dos primeiros estudos sobre a sistemática e a historia natural deste grupo foram realizados nas décadas de 1960 e 1970 na região Sul de América do Sul. Porém, há poucos dados publicados sobre potamotrigonídeos em águas uruguaias desde então (com exceção de registros de pescadores esportivos publicados em jornais locais, e espécimes depositados em coleções uruguaias). O presente estudo, portanto, tem como objetivo registrar a ocorrência de duas espécies de potamotrigonídeos no Uruguai capturados por pescadores esportivos assim como realizar uma compilação de ocorrências anteriores presentes na literatura. Como muitos outros elasmobrânquios, estas espécies possuem um papel importante nos ecossistemas dos rios uruguaios, embora não completamente compreendido.

Freshwater stingrays, or potamotrygonids, are restricted to Neotropical river drainages. These elasmobranchs are well adapted to freshwater environments and the number of described species gradually increases as further research is carried out. Some of the first studies on their systematics and natural history were carried out in the 1960s and 1970s in southern South America. However, there is no new published data on potamotrygonids from Uruguayan waters since then (except for local journal reports from sportive fishermen and specimens deposited in Uruguayan collections). The present study aims to record the recent occurrence of two species of potamotrygonids caught by sport fishermen, with comments on other published historical records for the same area. As many other elasmobranchs, these species have an important, but not always well understood, role in the Uruguayan rivers ecosystems.

The Plata pompano, Trachinotus marginatus (Cuvier, 1832), is an endemic carangid of the Southwestern Atlantic Ocean, occurring from Rio de Janeiro to Uruguay. This study describes the reproductive period, spawning type, the size at first gonadal maturation and the length-weight relationship of individuals sampled from landings of the artisanal and commercial fishing fleets in Rio Grande that operate along the coast of Rio Grande do Sul state, southern Brazil (~ 32ºS) to the Uruguayan border (~ 34ºS). Monthly collections from September 2008 through January 2010 yielded 274 individuals ranging from 142 to 444 mm in total length (TL). The gonadal development stages were defined according to the histological examination of the ovaries and the testes. The relationship between TL (mm) and total weight TW (g) was statistically different between males (TW = 0.000463*TL2.7655) and females (TW = 0.000361*TL2.8131), showing negative allometric growth for both sexes. The sizes at first maturity were 187.2 mm and 254.9 mm for females and males, respectively. The presence of two modal groups of oocyte diameters suggested that total spawning occurred. The interpretation of the monthly variations of the condition factor and gonadosomatic index, which are associated with higher frequencies of the more advanced stages of gonadal development, identified the spring and summer months as the reproductive period, with a peak in the reproductive activity during November and January. These results suggested that the species has an opportunistic reproductive strategy.

A garoupa-verdadeira, Mycteroperca marginata, é uma espécie de importância comercial que atualmente é considerada como ameaçada mundialmente e sobre-explotada no Brasil. Embora sua biologia reprodutiva tenha sido estudada em outras regiões, nenhuma informação está disponível sobre populações que habitam o extremo sul da sua distribuição na costa brasileira. O presente trabalho investiga a estrutura de idade, crescimento e reprodução de indivíduos que habitam dois molhes de pedra, com cerca de 4,5 km de extensão cada, localizados na desembocadura da laguna dos Patos no município de Rio Grande, no Atlântico Sudoeste. Foram analisados 130 indivíduos obtidos entre fevereiro de 2007 e maio de 2009, com comprimento total entre 260 e 800 mm. O coeficiente de crescimento no presente estudo (K: 0,069) foi inferior aos valores reportados para oMediterrâneo (0,087) e sudeste da África (0,09). Essa diferença pode estar relacionada a temperaturas médias maiores nessas regiões comparadas ao presente local de estudo ou devido a menor qualidade de habitat em termo de abrigos para os indivíduos de garoupa-verdadeira estabelecerem seus territórios. Análises microscópicas dos ovários dos indivíduos durante esses três anos de amostragens revelaram somente a ocorrência de indivíduos imaturos e fêmeas em repouso. A ausência de indivíduos ovados ou em pós-desova, associada com baixos valores do IGS (<0,2), ao longo de todos os meses de coleta, indica que a garoupa-verdadeira não utiliza esse substrato rochoso construído pelo homem como um local de desova. A estimativa de um L50 de 451,3 mm indica que a maioria dos indivíduos capturados nessa região é imatura. Pressão de pesca sobre indivíduos imaturos, associada com a sua lenta taxa de crescimento e complexo modo reprodutivo, ameaça a sustentabilidade da atual pesca da garoupa-verdadeira na área de estudo.

The dusky grouper, Mycteroperca marginata, is an important commercial marine fish that is currently considered an endangered species worldwide and listed as overexploited in Brazil. Although its reproductive biology has been studied elsewhere, no information is available for populations in its southernmost distribution limit on the Brazilian coast. The present work investigates age structure, growth and reproduction of individuals inhabiting a pair of rocky jetties, about 4.5 km long each, located in the mouth of Patos Lagoon in the municipality of Rio Grande, in the southwestern Atlantic Ocean. A total of 130 individuals obtained between February 2007 and May 2009 were analyzed, with total length ranging from 260 to 800 mm. The growth coefficient found in the present study (K: 0.069) was lower than values reported for dusky grouper populations from the Mediterranean Sea (0.087) and southeast Africa (0.09). This difference could be related to higher average water temperatures in these regions compared to the current study site or due to poorer habitat quality in terms of the shelters available for dusky grouper individuals to establish their territories. Microscopic ovarian analyses of individuals during three years of sampling revealed only the occurrence of immature and resting females. The absence of ripe or post-spawning individuals, associated with low GSI values (<0.2) over the studied months, indicates that the dusky grouper did not use this man-made rocky substrate as a spawning site. The current L50 estimate of 451.3 mm indicates that most individuals captured in this area are immature. Such fishing pressure on immature specimens, associated with its slow growth rates and complex reproductive characteristics, threatens sustainability of the current dusky grouper fishery at the study site.

Um total de 4824 Mustelus schmitti foi amostrado. As fêmeas apresentaram comprimento total de 25-93 cm na primavera e 28-90 cm no verão enquanto os machos apresentaram 34-82 e de 28-77 cm, respectivamente. A composição de comprimentos da população mostrou diferenças significativas entre primavera e verão sendo as fêmeas maiores do que os machos. A distribuição de comprimento total não variou significativamente entre cruzeiros. A densidade variou significativamente entre cruzeiros nos machos sendo que a variação não foi expressiva nas fêmeas. No cruzeiro da primavera, ambos os sexos ocorreram em profundidades menores do que 50 m, as fêmeas ocorrendo em toda a área de estudo, as adultas somente acima da latitude 35°30'S. Os machos adultos foram observados em toda a área sendo que os imaturos somente em dois arrastos na Bahia de Samborombón. O cruzeiro de verão mostrou uma distribuição descontínua da espécie ao longo da área de estudo, resultando na segregação espacial em dois grupos, com predominância de fêmeas imaturas em ambos.

A total number of 4824 Mustelus schmitti was sampled. Females ranged from 25 to 93 cm in spring and from 28 to 90 cm in summer. Males ranged from 34 to 82 and from 28 to 77 cm, respectively. Length composition of the population showed significant differences between spring and summer being females larger than males. Total length distribution did not show significant differences between cruises. Males density varied significantly between cruises while for the females no significant variation was observed. In the spring cruise, both sexes occurred at depths lower than 50 m. Females occurred in the whole area with adult occurrence only above 35°30'S. Mature males occurred throughout the area, immature males occurring in two trawls in Samborombón Bay. The summer cruise showed a discontinuous distribution of the species along the study area resulting in spatial segregation in two groups with immature females predominating in both of them.