Reproductive biology of Zearaja chilensis (Chondrichthyes: Rajidae) in the south‐east Pacific Ocean

Abstract

Between 2000 and 2002, three artisanal landing sites were sampled in southern Chile, with data on population structure and reproductive development collected from 5477 yellownose skates Zearaja chilensis. Total length (L(T) ) ranged from 33 to 158 cm for females and 34 to 155 cm for males. No sexual dimorphism was evident in disc size (length or width) or in L(T)-mass relationships. The smallest mature female was 95 cm L(T) and the size at which 50% were mature (L(T50) ) was 109 cm. Males matured between 80 and 90 cm L(T) with a L(T50) of 88 cm. Although the largest Z. chilensis captured by the artisanal fishery was 155 cm L(T) , 89% of landings comprised relatively small, immature fish. This situation may compromise the stock integrity if intrinsic vulnerability and probable long-life span of Z. chilensis are considered. Consequences for the survival of the species and possible signs of a fishery collapse must be reviewed by management authorities by consideration of both artisanal and industrial landings in Chile.

Skate-ing on thin ice: molecular ecology of longnose skates in the Southeast Pacific Ocean

“…Estalles et al, 2011;Kyne & Sympfendorfer, 2007;Lamilla et al, 2009. Last & Gledhill, 2007;Menni & Lucifora, 2007;Kyne & Simpfendorfer, 2010;Lamilla et al, 2010;Vargas-Caro, 2010;Mabragaña et al, 2011b;Perier et al, 2011;Queirolo et al, 2011;Arkhipkin et al, 2012;Bustamante et al, 2012;Concha et al, 2012;Deli Antoni et al, 2012;Lamilla et al, 2012a, b;Naylor et al, 2012;Bovcon et al, 2013;Lamilla et al, 2013;Bustamante et al, 2014a, b;Espindola et al, 2014Sáez et al, 2014;Vargas-Caro et al, 2016a. Menni et al, 2010;Naylor et al, 2012.…”

“…Other large skate species, such as Bathyraja griseocauda (Arkhipkin et al, 2008), D. batis (Du Buit, 1972), D. innominatus (Francis et al, 2001), Raja binoculata and R. rhina (McFarlane & King, 2006) also live to over 20 years of age. The concern is that larger species that have slow growth rates and are long lived are particularly vulnerable to population collapse, as has been suggested for Z. chilensis (Agnew et al, 2000;Bustamante et al, 2012). …”

“…The minimum and maximum sizes reported for Z. chilensis are 156 mm and 1580 mm LT respectively, with females growing to a larger sizes than males (Norman, 1937;Bahamonde, 1953;De Buen, 1959;Leible, 1987;Leible et al, 1990;García de la Rosa, 1998;Cousseau et al, , 2007Gomes & Picado, 2001;Cedrola et al, 2005;Licandeo et al, 2006;Paesch & Oddone, 2008;Estalles et al, 2011;Lamilla et al, 2012a, b;Bustamante et al, 2012). In comparison, D. trachyderma reaches 2540 mm LT for females and 2320 mm LT for males (Leible & Stehmann, 1987;Cousseau et al, , 2007Gomes & Picado, 2001;Cedrola et al, 2005;Lamilla et al, 2012a, b).…”

“…For Z. chilensis the ovaries initiate development of vitellogenic oocytes, indicative of maturity, when females reach 940 -1039 mm LT, whereas males mature at 760 -900 mm LT Oddone et al, 2005;Licandeo et al, 2006;Paesch & Oddone, 2008;Colonello, 2009;Quiroz et al, 2009;Bustamante et al, 2012;Colonello & Cortes, 2014;Wehitt et al, 2015). For D.…”

“…For example, no additional information (molecular or morphological) has been produced to appraise the genus re-assignment of Last & Gledhill (2007). Recent changes in the taxonomic status of longnose skates has resulted in confusion that is of considerable importance in the context of South American fisheries management, where two sympatric and morphologically similar species, originally in the genus Dipturus, are now in separate genera, Dipturus and Zearaja, (Menni & López, 1984;Agnew et al, 2000;Bustamante et al, 2012).…”