Reproduction and population aspects of the yellownose skate,Dipturus chilensis(Pisces, Elasmobranchii: Rajidae), from southern Chile

Abstract

Summary The total length (TL) at sexual maturity by sex, fecundity characteristics, and some population aspects (size structures and sexual proportions) are presented for the yellownose skate, Dipturus chilensis, in the eastern South Pacific Ocean. Samples were taken between January 2003 and August 2004 from three zones (principal fishing grounds for the species) in Chile’s southern channels (41°30′S–55°10′S). TL at which 50% of the individuals reach maturity was significantly different by sex, with females estimated to mature at 103.9 cm and males at 89.7 cm. The average estimated fecundity was 23.4 (SD 6.4) ova per female. We report on the relationships of clasper lengths and oviducal gland widths with TL and the stages of maturity. Length compositions were statistically different by sex in the same zone (P < 0.05) and between zones for combined sexes (P < 0.05). The proportion of females increased when these reached the TL at which 50% attained maturity, becoming highly available to the fishing gear, possibly in relation to the reproductive strategy. Finally, the results yielded valuable knowledge about population responses to exploitation through fishing.

Reproductive biology of the cockfish, Callorhinchus callorynchus (Chondrichthyes: Callorhinchidae), in coastal waters of the northern Argentinean Sea

“…The total number of ovarian follicles was dependent on female body size in C. callorynchus, as was observed in other holocephalans (Barnett et al, 2009;Nibam, 2011;Bell, 2012) and oviparous elasmobranchs (Ebert, 2005;Quiroz et al, 2009;Perier et al, 2011;Scenna, Díaz de Astarloa, 2014), which suggest that reproductive potential increases with size. However, it is important to consider that the method of simply enumerating mature follicles to estimate fecundity, under the assumption that all oocytes will be ovulated and become viable egg cases, may be inadequate for oviparous species that reproduce continuously, as enlarged follicles are always present and ovulation may occur at any time (Barnett et al, 2009;Bell, 2012).…”

REPRODUCTIVE BIOLOGY OF THE VENEZUELA ROUND STINGRAY Urotrygon venezuelae SCHULTZ FROM THE COLOMBIAN CARIBBEAN

“…Size at sexual maturity in U. venezuelae was lower in females than in males, backing the hypothesis proposed by Braccini & Chiaramonte (2002) for some small sized skates of the family Rajidae, where females reach size of sexual maturity before males, Psammobatis extenta and U. venezuelae are good examples of this. In large size species, such as Dipturus chilensis sexual maturity size is lower in males than females (Quiroz et al 2009). …”

“…Other authors have attempted to relate fecundity with length (Villavicencio-Garayzar 1995, Fahy et al 2007, Quiroz et al 2009), but they have not kept in mind other factors that could be more important for fecundity, such as cloaca diameter, liver weight and even weight. Mejía-Falla et al (2012) reported a linear relationship between DW and fecundity as was described by Hleap et al (2009), nevertheless relationship between breeding size and maternal morphometric must be consider in further studies.…”

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

“…Zearaja chilensis appears to be relatively common at depths of between 14 -100 m depth (Menni & López, 1984;Leible et al, 1990;García de la Rosa, 1998;Concha et al, 2012), is abundant between 150 to 350 m (Menni & Gosztonyi, 1977;Menni & López, 1984;Leible, 1987;Leible et al, 1990;Licandeo et al, 2006;Quiroz et al, 2009;Arkhipkin et al, 2012), but can be found at depths of up to 450 m (Ojeda, 1983;Menni & López, 1984;García de la Rosa, 1998). In contrast, D. trachyderma appears less abundant in shallow waters (a single specimen reported from 20 -22 m in the Beagle Channel (Lloris & Rucabado, 1991), and catches reported from 87 -97 m in San Jorge Gulf (Cedrola et al, 2005), seems most common at 180 m -350 m (Krefft & Stehmann, 1975;Menni & Gosztonyi, 1977;Bizikov et al, 2004;Lamilla et al, 2010;Menni et al, 2010;Arkhipkin et al, 2012), but there are records from 400 -500 m (Leible & Stehmann, 1987;Gomes & Picado, 2001).…”

“…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.…”