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SUMMARY: Specimens of Rioraja agassizi were collected at Guarujá pier, São Paulo State, Brazil, from March 2005 to March 2006. A total of 275 males were captured. Based on the analysis of the clasper length, gonad weight, clasper gland length, alar thorns and lobule diameter, the size-at-maturity was estimated to be 32 cm. There were 1049 females in the record. Size-at-maturity was calculated in 40 cm. Sexual resting females were observed. Gonadosomatic and hepatosomatic indexes varied significantly in both sexes throughout the year. However, ovulation, egg-laying and presence of sperm in the seminal vesicle were observed all year round. For this reason, an annual cycle with at least one peak in the sexual activity is proposed for this species. De acuerdo con el análisis de la longitud del clasper y de la glándula del clasper, el peso de las gónadas, el diámetro de los lóbu-los y el número de espinas alares, el tamaño de primera madurez sexual fue estimado en 32 cm. Se capturó un número de 1049 hembras. El tamaño de primera madurez sexual fue calculado en 40 cm. Se observó reposo sexual en hembras de esta especie. Los índices gonadosomáticos y hepatosomáticos variaron significativamente en ambos sexos a lo largo del año. Sin embargo, la ovulación y la deposición de cápsulas ovígeras sucedieron continuamente durante todo el año, así como la presencia de esperma en la vesícula seminal en ejemplares adultos. Por este motivo, se propone para esta especie, un ciclo reproductivo anual, con por lo menos un pico en la actividad sexual. KeywordsPalabras clave: clasper, elasmobranquios, glándula nidamentária, deposición de cápsulas ovígeras, gónadas. and hatch. Oviparity in skates is single (external) (Musick and Ellis, 2005) and all Rajids have the same general reproductive cycle, in which egg capsules are deposited in pairs with intervals of 0-5 days between successive depositions (Holden et al., 1971). In the wild, there is a peak in egg laying during the summer and spawning occurs throughout the entire year (Clark, 1922).The Rio skate Rioraja agassizi Whitley, 1939 (Rajidae: Arhynchobatidae) is endemic to the southwestern Atlantic coast of South America (Compagno, 2005) and occurs from coastal waters to depths of up to 130 m (Figueiredo, 1977). Females deposit egg capsules with mean dimensions of 47x31 mm (Oddone et al., 2006). Apart from the description of the egg capsule, the reproductive biology of R. agassizi-i.e. its sexual development, size-at-maturity and cycle-is unknown.The assessment of chondrichthyan populations requires a quantitative approach to the study of reproductive biology, size-at-maturity being a key parameter to be estimated (Walker, 2005). In addition, over the past thirty years, catches of rajids have increased in the western Atlantic, mainly as a bycatch of target fisheries, but sustainable catch rates are completely unknown (Frisk et al., 2002). Thus, knowledge of the reproductive parameters, in particularly size-at-maturity, is especially important for making decisions on stock management. I...

The marine catfish Genidens barbus was once one of the most important estuarine fishery resources in the Patos Lagoon (southern Brazil), which had the largest population known for the species. However, clear signs of overfishing have been observed since the 1980s. Growth parameters for this population were estimated by combining length frequency data for juveniles and selected published data on annuli reading from adult otoliths. This methodology yielded a more realistic set of parameters using both the specialized and generalized von Bertalanffy growth model. The species growth can be described as:The growth performance index u¢ was estimated as 2.78 for the special (classical) model. Stock rebuilding is expected to be slow, as the species is slow-growing, has a low natural mortality rate, and mouthbreeds a small amount of large eggs. ResumoO bagre marinho Genidens barbus foi um dos recursos pesqueiros mais importantes no estua´rio da Lagoa dos Patos (RS, Brasil), sendo esta a maior populac¸a˜o conhecida da espe´cie. A partir dos anos oitenta, no entanto, comec¸ou a mostrar claros sinais de sobrexplorac¸a˜o. Os paraˆmetros de crescimento desta populac¸a˜o foram calculados utilizando dados de frequ¨eˆncia de comprimento dos juvenis e leitura de ane´is de crescimento em oto´litos dos adultos. A metodologia utilizada para determinar os paraˆmetros de crescimento neste trabalho mostrou resultados mais realistas que os previamente calculados, tanto quanto utilizados o modelo especial quanto o generalizado de von Bertalanffy. O crescimento desta espe´cie pode ser descrito por L t ¼ 118.6[1 ) e )0.043(t+1.505) ] ou L t ¼ 104.6[1 ) e )0.137D(t+4.013) ] 1/D com um fator de superfı´cie D ¼ 0.542. O paraˆmetro u¢ foi calculado em 2.78 para o modelo especial (cla´ssico). Presume-se que a recuperac¸a˜o deste estoque pesqueiro seja demorada ja´que a espe´cie apresenta crescimento lento, mortalidade natural baixa e tem baixa fecundidade.

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The anadromous catfish, Genidens barbus, is a commercial and vulnerable species from South America. The aims of the present study were to assess whether the nursery areas can be discriminated by using microchemical signatures of lapillus otoliths, to assess the accuracy of classifying fish in relation to natal nursery area and to discuss the possibility of existence of homing behaviour. Thus, the otolith-core chemical signatures (barium (Ba):calcium (Ca), lithium (Li):Ca, magnesium (Mg):Ca, manganese (Mn):Ca, strontium (Sr):Ca, and zinc (Zn):Ca ratios) of adult fish were compared among different estuaries (De La Plata River in Argentina, and Patos Lagoon, Paranaguá Bay and Guanabara Bay in Brazil). PERMANOVA analysis showed significant differences in the multi-element signatures of the otolith core among sampling sites for all cohorts (2002, 2003, 2006 and 2007), indicating that the technique has considerable potential for use in future assessments of population connectivity and nursery areas of G. barbus. Via quadratic discriminant function analysis, fish were classified to natal nursery areas with 80–100% cross-validation classification accuracies. These results suggested that a high level of spatial segregation exists in adult catfish life and homing behaviour could not be ruled out on the basis of our data.

The purpose of this paper is to assess the use of multi-elemental otolith fingerprints as a tool to delimit catfish Genidens barbus fish stocks in four estuaries from the southwestern Atlantic Ocean. Barium:Calcium (Ca), Magnesium:Ca, Manganese:Ca, Sodium:Ca and Strontium:Ca ratios in the otolith edge were determined by LA-ICPMS. PERMANOVA analysis reveal significant differences in the multi-element signatures among estuaries (p=0.0001-0.002). Reclassification rates of quadratic discriminant analysis are high, averaging 89.9 % (78-100%). The new data presented here show that the otolith chemistry is a potential tool for stock identification, and indicates the presence of at least four stocks which should probably be handled independently.

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Life-history characteristics such as growth, mortality, and size at sexual maturity of the seahorse Hippocampus reidi were investigated in situ in north-eastern Brazil from August 2006 to July 2007. The von Bertalanffy growth constant K was estimated at 1.195 year−1 and L∞ was set as 20 cm according to Taylor's relationship, using a Lmax of 19 cm. The smallest male with a brood pouch and the smallest male with a fully mature pouch measured 9 and 9.5 cm (height), respectively, while the smallest mature female measured 8.8 cm. Appropriate reproductive individuals were recorded throughout the study, with peaks from May to November. The size of first effective reproduction (carrying embryos) was 12.4 cm for males, a value higher than previously reported. Estimated instantaneous rate of natural mortality ranged from 1.43 to 1.58 year−1. The estimated life span for the species was 30 months.