Distribution, abundance and morphometry of Atlantoraja cyclophora (Regan, 1903) (Elasmobranchii: Rajidae) in southern Brazil, Southwestern Atlantic

Abstract

A total of 459 individuals of Atlantoraja cyclophora were captured along the Rio Grande do Sul coast between latitudes 30°40'S and 34°30'S. Two surveys were performed, in the winter 2001 and in the summer/autumn 2002, using bottom-trawl between the depths of 100 and 600 m. This species occurred between 100 and 300 m deep, without significant differences in the frequency of occurrence and abundance (CPUE; kg/hour) between latitudes, depth and seasons. The sex ratio was not significantly different from 1:1 in all depths. In the study area, temperature ranged between 10.0 °C and 17.6 °C and salinity between 35.2 e 36.0 ppm. There was no correlation between CPUE and depth, temperature and salinity. Mean total length of females (53.2 cm) was significantly larger than males (50.9 cm). No differences were detected in mean total length between seasons, but mean total length was significantly larger in depths of 100 m and 200 m. The distribution of the frequencies of total length was asymmetric, indicating rareness or lack of juveniles in the samples.Foram capturados 459 exemplares de Atlantoraja cyclophora na costa do Rio Grande do Sul entre as latitudes 30°40'S e 34°30'S, em dois cruzeiros realizados respectivamente no inverno de 2001 e no verão/outono de 2002, com rede de arrasto de fundo, operada entre 100 e 600 m de profundidade. A espécie ocorreu nas profundidades de 100 a 300 m, não havendo diferenças significativas na freqüência de ocorrência nem na abundância (CPUE; kg/hora) entre latitudes, estratos de profundidade em ambas estações do ano. A proporção sexual não foi significativamente diferente de 1:1 em todas as profundidades. Na área estudada a temperatura variou entre 10,0 °C e 17,6 °C e a salinidade entre 35,2 e 36,0 ppm. Não houve correlação entre CPUE e profundidade, temperatura e salinidade. O comprimento total médio das fêmeas (53,2 cm) foi significantemente maior que o dos machos (50,9 cm). Não houve diferença no comprimento total médio entre estações do ano, mas sim entre profundidades, sendo significantemente maiores nos estratos de 100 a 200 m. As distribuições de freqüências de comprimento total foram assimétricas, indicando ausência ou escassez de indivíduos juvenis.

The feeding habits of the eyespot skate Atlantoraja cyclophora (Elasmobranchii: Rajiformes) in southeastern Brazil

“…Females also reached larger size than males, as observed in other studies with A. cyclophora (ODDONE & VOOREN 2004, ODDONE et al 2008. Skates were more abundant in the summer (Jan-Feb-Mar 06 and Jan-Feb-Mar 07).…”

“…Skates were more abundant in the summer (Jan-Feb-Mar 06 and Jan-Feb-Mar 07). Summer is the season of greatest upwelling of the South Atlantic Central Water (SACW), which generates the oceanographic conditions favored by this species (ODDONE & VOOREN 2004).…”

“…The species is found from 30 to 300 m depth (mainly below 50 m) (GOMES et al 2010), generally in cold waters of the continental shelf and upper continental slope, and does not seem to have a preference for any peculiar granulometry of the sediment. Normally, females of A. cyclophora are heavier and wider than males (ODDONE & VOOREN 2004). The species is caught as bycatch in coastal demersal fisheries, and has suffered growing fishing pressure.…”

Sexual dimorphism in sister species of Leucoraja skate and its relationship to reproductive strategy and life history

“…Others, however, are not well understood and their utility, if any at all, is not obvious. For example, sexually dimorphic pectoral fins have been cited in Neoraja stehmanni , Raja straeleni , and Raja miraletus (Ebert et al ) as well as Atlantoraja cyclophora (Oddone and Vooren ). In all instances, males took on a “bell‐shaped” body form at maturity (Ebert et al ).…”

Reproductive biology of Psammobatis rutrum (Chondrichthyes: Arhynchobatidae) in south Brazil, south‐west Atlantic

“…Differences between sexes for the L T ‐ W D relationship may reflect a sexual dimorphism, clearly visible in the form of the disc, with males having a bell‐shaped body. Sexual dimorphism in W D may occur in species with sexual differences in length‐width relationships (Ebert et al, ) and has been observed in other rajoids (Oddone & Vooren, ; Orlov & Cotton, ). Such dimorphism may be related to the onset of maturity, since it becomes evident in developing and adult individuals (Martinez et al, ).…”