Size and sex composition of two species of the genus Atlantoraja (Elasmobranchii, Rajidae) caught by the bottom trawl fisheries operating on the Uruguayan continental shelf (southwestern Atlantic Ocean)

In this work we analyzed the spatial and seasonal variation of length distribution, sexual proportion and mature dominance for Atlantoraja cyclophora and A. castelnaui, at the Uruguayan continental shelf. There were significant differences in total length (TL) composition between sexes, being females bigger than males for both species. Atlantoraja cyclophora showed a relatively uniform length distribution between inner and outer shelf. There were no major variations in the sex compositions and in the mature dominance between seasons, suggesting no temporal variation. Atlantoraja castelnaui showed a significant variation in its spatial and seasonal distribution. Individuals were smaller in inner shelf, pointing out the existence of juvenile zone in areas up to 50 m depth. A tendency to capture smaller individuals towards the end of the year was observed. In all seasons over 50% of females were caught below the estimated size at maturity, suggesting that this species is highly susceptible to exploitation.Neste trabalho foi analisada a variação espacial e temporal da distribuição de comprimento, proporções sexuais e dominância de maduros para Atlantoraja cyclophora e A. castelanui, na plataforma continental uruguaia. Houve diferenças significativas na distribução do comprimento total (TL) entre os sexos, sendo as fêmeas maiores que os machos para ambas espécies. Atlantoraja cyclophora mostrou uma distribuição relativamente uniforme de comprimento entre a prataforma interna e externa. Não houviram grandes variações nas composições do sexo e na dominância de maduros entre as estações do ano, sugerindo que não ha variação temporal. Atlantoraja castelnaui mostrou uma variação significativa na sua distribuição espacial e sazonal. Os indivíduos foram menores na plataforma interna, apontando para a existência de uma zona de juvenis em áreas de até 50 m de profundidade. A tendência para a captura de indivíduos menores no final do ano foi observada. Em todas as estações do ano mais de 50% das fêmeas foram capturadas em um comprimento menor ao tamanho estimado de maturidade observado na literatura, sugerindo que esta espécie é altamente suscetível à explotação

Tracing the occurrence of the Critically Endangered smalltooth sawfish Pristis pectinata at its southernmost distribution in the Southwest Atlantic Ocean

Sawfishes are the most globally threatened group of sharks, rays, and chimaeras. One of the 5 sawfish species is the Critically Endangered smalltooth sawfish Pristis pectinata. Although it is currently found in only a small portion of its historical range, this species was once distributed along tropical and subtropical coasts on both sides of the Atlantic Ocean. Its historical distribution included the Southwest Atlantic in Brazil and Argentina, with its presence in Uruguay assumed from its occurrence in neighboring countries. However, occurrence records in this region have only been compiled for Brazil. The aim of this study was to characterize the occurrence of P. pectinata in the Argentinean-Uruguayan Common Fishing Zone (AUCFZ). Quantitative sampling data revealed no sawfish specimens during 150 bottom trawl cruises and 8490 hauls (1905 in winter; 1647 in fall; 3141 in spring; 1797 in summer months) in the AUCFZ between 1981 and 2015. Nevertheless, qualitative data based on interviews (N = 275; researchers, fishing companies, fishermen, and recreational anglers) supports the occasional presence of sawfish in the AUCFZ. Five new oral reports were obtained and, although these records lack reference material, they have an associated capture year: 2 records from the 1950s, 1 record from the 1990s, and 2 records from the 2010s. Two of these records are the first for Uruguay and were reported by experienced fishermen. We conclude that the species was always a vagrant to the region, and suggest that the view of P. pectinata as extirpated from Uruguay and northern Argentina should be revisited.Fil: Cuevas, Juan Martín. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados; Argentina. Wildlife Conservation Society; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: García, Mirta Graciela. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Hozbor, Natalia. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Faria, Vicente V.. Universidade Federal Do Ceara; BrasilFil: Paesch, Laura. Dirección Nacional de Recursos Acuáticos; Urugua

Change in size-at-maturity of the yellownose skate Dipturus chilensis (Guichenot, 1848) (Elasmobranchii: Rajidae) in the SW Atlantic

A total of 3518 specimens (1607 males, 1911 females) of Dipturus chilensis were sampled. Males ranged from 44.0 to 99.0 cm and females from 45.0 to 110.0 cm. Total length composition of the grouped catches differed significantly among sexes, with females being larger than males. The sex ratio favored the females. The total length at which 50% of the specimens were retained by the gear was 69.0 cm for the males and 73.0 cm for the females. A sub-sample of 124 specimens (48 males, 76 females) was analyzed for reproductive assessment. For the males, size at 50% maturity was estimated at 78.5 cm, while for the females this parameter was estimated at 81.4 cm. Preliminary observations on the description of the egg capsules are also provided

Representatividad de la composición de tallas del gatuzo Mustelus schmitti (Chondrichthyes, Triakidae) capturado por la flota artesanal y de arrastre comercial en la costa atlántica uruguaya: Representativeness of the size composition of the narrownose smooth-hound shark Mustelus schmitti (Chondrichthyes, Triakidae) caught by the artisanal and commercial trawl fleet on the Uruguayan Atlantic coast

The determination of the optimal sample size is important to obtain an adequate estimation of the size frequency distribution, as well as consistent estimators of the population parameters corresponding to the size composition, such as the mean value. In this work, the optimal sample size was determined to obtain a consistent estimate of the mean and a representative length frequencies distribution for Mustelus schmitti caught by artisanal and industrial fisheries off the Uruguayan coast. With representative samples, the mean estimators, its confidence interval, and the median with the 25 and 75% quartiles could be used to analyze temporal trends related to changes in the size structure

Size at maturity and egg capsules of the softnose skates Bathyraja brachyurops (Fowler,1910) and Bathyraja macloviana (Norman,1937) (Elasmobranchii:Rajidae) in the SW Atlantic (37º 00' - 39º 30' S)

The softnose skates Bathyraja brachyurops and Bathyraja macloviana represent an important portion of the skate catches of the Uruguay an traw lingfleet in the south western Atlantic. From March to October 2004, specimens of these species were collected at 75-200m depth range in the area situated between latitudes 37 00¢–39 30¢S. For B.brachyurops, total leng that which 50% of the specimens were retained by the gear was 68.0cm for both sexes; TL50 was estimated at 65.4cm for males and 67.0cm for females. For B.macloviana, total length at which 50% of the specimens were retained was 56.0 – 57.0cm for both sexes; TL50 was estimated at 53.5cm for males and 52.0cm for females. Egg capsule length varied from 79–91mm in B.brachyurops and 69–75.5m min B. macloviana.In both species, capsules displayed striated surfaces and similar gross morphology, although egg capsules of B.macloviana had more robust anterior horns and a smaller size than those of B.brachyurops. Egg capsules of the latteral so exhibited microscopical prickles. Capsule edges were laterally keeled with a groove along the keel,and a straight and transverse velum was present in the egg capsules of both species

Size Structure, Abundance and Preliminary Information on the Reproductive Parameters of the Shortspine Spurdog (Squalus mitsukurii) in the Argentinean-Uruguayan Common Fishing Zone from the mid–1990s

A total of 1 893 males and 1 124 females of Squalus mitsukurii were collected from latitudes 34º 30' S and 37º 00' S, in the south-western Atlantic Ocean, during early autumn, late autumn and spring 1995, early autumn 1996 and early autumn 1998. Length-frequency distributions signifi cantly varied between sexes for all seasons (P<0.05). Mature males predominated in all seasons throughout the analyzed area, according to their presence in the catches. In all periods sampled, immature females predominated except for late autumn 1995 where mature females were dominant. Signifi cant differences in density among seasons were recorded for immature and mature females and mature males (P<0.05). Density of immature females and mature males were signifi cantly different (P<0.05) for late autumn 1995 and early autumn 1996. Size-at-maturity was 43.1 cm and 55.9 cm total length for males (n = 1 181) and females (n = 862) receptively. The percentage of pregnant females ranged from 21.4% in spring 1995 to 49.8% in late autumn 1995. Ovarian fecundity varied significantly between early autumn 1995 and late autumn 1995 from 1–15 and uterine fecundity from 1–10, respectively. Embryo total length varied from 0.5–22.0 cm, attaining the highest values in autumn months. Size-at-birth was estimated to be 22–24 cm total length