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)

Abstract

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. R E S U M ONeste 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.

Reproductive cycles of the southern banded guitarfish Zapteryx xyster and the Velez ray Raja velezi caught as bycatch in a bottom-trawl fishery

“…Moreover, egg-bearing females and neonates were observed year-round. These findings are in agreement with similar observations in several other species of the family Rajidae: Amblyraja radiata (Donovan 1808) in the Gulf of Maine (Sulikowski et al 2005), Atlantoraja cyclophora (Regan 1903) in Uruguay and Brazil (Oddone & Vooren 2005, Oddone & Velasco 2006, Orlando et al 2011, Bathyraja albomaculata (Norman 1937) in southwestern Atlantic (Henderson et al 2005, Ruocco et al 2006, Leucoraja erinacea (Mitchill 1825) in Delaware Bay (Fitz & Daiber 1963), Malacoraja senta (Garman 1885) in the Gulf of Maine (Sulikowski et al 2007b), Beringraja binoculata (Girard 1855) in Gulf of Alaska (Ebert et al 2008), Raja clavata Linnaeus 1758 in the Black Sea (Saglam & Ak 2012), Beringraja rhina (Jordan & Gilbert 1880) in Gulf of Alaska (Ebert et al 2008), and Raja texana Chandler 1921 in the Gulf of Mexico (Williams et al 2011). On the other hand, some skates, such as Rioraja agassizii (Müller & Henle 1841) in Brazil, have conspicuous reproductive peaks (Oddone et al 2007, Oddone & Capapé 2011.…”

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

“…Sexual dimorphism in these relationships has been described for S. bonapartii (Mabragaña et al, 2002) and for other SW Atlantic rajoids (Mabragaña & Cousseau, 2004;Oddone & Vooren, 2004;Oddone & Amorim, 2007;Orlando et al, 2011).…”

“…Characteristics related to reproduction such as the maturity size may change in oviparous skates that are affected by fishing (Ebert et al, 2008;Paesch & Oddone, 2008;Orlando et al, 2011). As it is the case of Sympterygia spp., it is essential to have current data on reproduction.…”

Reproductive biology of the Brazilian guitarfish, Pseudobatos horkelii (Müller & Henle, 1841) from southeastern Brazil, western South Atlantic

“…() observed a slightly smaller size in southern Brazil (129 cm for males, 135 cm for females). Differences in length among the geographic distribution were observed in other species such as P. percellens in southeastern Brazil (Rocha & Gadig, ) and Colombia (Grijalba‐Bendeck, Acero, & Gonzalez, ); and for the skate Atlantoraja castelnaui in southeastern Brazil (Oddone & Amorim, ) and Uruguay (Orlando, Pereyra, Paesch, & Norbis, ). Such differences may occur due to methodological variations, such as gear selectivity.…”