Size composition, monthly condition factor and morphometrics for fishery-dependent samples of Rioraja agassizi (Chondrichthyes: Rajidae), off Santos, Southeast Brazil

Abstract

Specimens of Rioraja agassizi were collected monthly off Santos, Southeast Brazil, between latitudes 23°37'S and 27°40'S, from March, 2005 to March, 2006. A total number of 278 males and 1023 females were captured. Observed depth range was 10-120 m, being the species absent above 120 m. Sex ratio significantly favored females. The entire length range of R. agassizi was observed. Females ranged in length from 16.0 to 59.4 cm and males from 13.0 to 47.2 cm. Mean female length was significantly higher than that of males. For grouped length distributions, asymmetry patterns were observed in both sexes. Length-width functions were sexually dimorphic. Males with lengths < 24.5 cm were relatively wider than females. Length-total weight curves were significantly different than length-gutted weight ones, in both sexes. Females were heavier than males for a given TL class. The angular coefficient b was significantly <3 (negative allometry) in the males, and also for the females with exception of spring when b was >3 (positive allometry). The monthly variation of the condition factor showed significant differences in both sexes.Espécimes de Rioraja agassizi foram mensalmente coletados em águas ao largo de Santos, sudeste do Brasil entre as latitudes 23°37'S e 27°40'S, desde março de 2005 até março de 2006. Um total de 278 machos e 1023 fêmeas foi capturado. A amplitude de profundidade de ocorrência foi 10-120 m, estando a espécie ausente em profundidades >120 m. A razão sexual favoreceu as fêmeas. A amplitude completa de comprimentos de R. agassizi esteve representada e oscilou nas fêmeas entre 16.0-59.4 cm comprimento e nos machos entre 13.0-47.2 cm. O tamanho médio das fêmeas foi significativamente maior do que dos machos. A distribuição de freqüência de comprimentos por amostras agrupadas foi assimétrica em ambos os sexos. As curvas da relação comprimento-largura foram sexualmente dimórficas. As fêmeas foram mais largas que os machos em todas as classes de comprimento maiores do que 25 cm. As curvas comprimento-peso total foram significativamente diferentes das curvas comprimento-peso eviscerado em ambos os sexos. As fêmeas foram mais pesadas do que os machos para uma determinada classe de comprimento. O coeficiente angular b foi <3 nos machos (alometría negativa) e nas fêmeas, mas com exceção da primavera, onde a alometría foi positiva (b>3). O fator de condição variou significativamente ao longo do ano em ambos os sexos.

Length-weight Relationships, Condition and Population Structure of the Genus Atlantoraja (Elasmobranchii, Rajidae, Arhynchobatinae) in Southeastern Brazilian Waters, SW Atlantic Ocean

“…Therefore, it can be assumed that males and females share the same area throughout the year and total segregation between sexes does not occur. This has been previously documented for A. castelnaui and R. agassizi (Ponz Louro, MS 1995;Oddone et al, 2007) in this area and for A. cyclophora (Oddone, MS 2003;Oddone and Vooren, 2004) and A. platana (Marçal, MS 2003) in Southern Brazilian waters.…”

“…al., 2007) and the length-weight and length-width curves (Braccini and Chiaramonte, 2002;Mabragaña et al, 2002;Oddone and Vooren, 2004;Oddone et al, 2007). A growth pattern in which males have a wider disc width than females in the first life stages, and in later stages females become wider, was also observed for R. agassizi and for samples of A. cyclophora from Southern Brazil (Oddone, MS 2003;Oddone and Vooren, 2004;Oddone et al, 2007).…”

“…In most rajids, sexual dimorphism is commonly reflected in the mean size (Jardas, 1973;Nottage and Perkins, 1983;Oddone and Vooren, 2004;Oddone et. al., 2007) and the length-weight and length-width curves (Braccini and Chiaramonte, 2002;Mabragaña et al, 2002;Oddone and Vooren, 2004;Oddone et al, 2007).…”

“…Braccini and Chiaramonte (2002) recorded isometric growth for males and positive allometry in females of Psammobatis extenta. In R. agassizi, growth was allometric, with b <3 for both sexes (Oddone et al, 2007). The study of fish condition assumes that heavier fish of a given length are in better state, and this has been used by fish culturists as indicators of the general 'well-being or fitness' of the population under consideration (Jones et al, 1999).…”

Reproductive biology of the skates Sympterygia acuta Garman, 1877 and S. bonapartii Müller & Henle, 1841 (Chondrichthyes: Rajoidei) in south Brazil

“…However, in adolescents and mature individuals just the opposite was observed. Such morphometrics differences throughout the ontogeny were also recorded in Atlantoraja cyclophora and Rioraja agassizi (Muller & Henle, 1841) in southern Brazil (Oddone & Vooren, 2004;Oddone et al, 2007b). On the other hand, the growth pattern in S. bonapartii demonstrated that, in this species, females had larger DW than males for any TL considered.…”