Exploring nursery sites for oviparous chondrichthyans in the Southwest Atlantic (36°S–41°S)

ABSTRACT

The aim of this paper was to explore egg-laying areas of oviparous chondrichthyans occurring in the northern part of the Southwest Atlantic Ocean (36°S–41°S) at between 50 and 200 metres depth and the Mar del Plata Canyon (from 200 to 3447 m). A total of 515 capsules were collected corresponding to 10 species. Four species accounted for 87.6% of the total catch: Psammobatis normani, Bathyraja macloviana, Amblyraja doellojuradoi and Bathyraja brachyurops. The remaining corresponded to Schroederichthys bivius, Psammobatis rudis, Zearaja chilensis, Bathyraja albomaculata, Psammobatis lentiginosa and Bathyraja sp. Most hauls were monospecific and relatively few hauls contained four or five species (southern part of the area, in sites located at 75 and 94–105 m depth). No egg capsules were recorded between 1712 m and 3447 m. Highest densities (>3000 capsules/km²) were mainly found between 39°46.2′ and 40°29.9′S from 85 to 105 m and they were also recorded near the Mar del Plata Canyon at 37°59.7′S and at 852 m. The highest value recorded was 12,326 capsules/km² (located at 40°18.9′S and 85.4 m). The highest densities for each of the most abundant species are discussed. The finding of high densities of egg cases near the Argentine shelf-break front indicates that many skate species use this area as a nursery site. The egg-laying areas explored here are the first reported sites of this kind in the Southwest Atlantic Ocean. Recognizing and protecting egg-laying habitats may be important steps to a long-term conservation of oviparous chondrichthyan populations.

RESPONSIBLE EDITOR:

• Keiichi Sato

KEYWORDS:

• Argentine shelf-break front
• egg cases
• nursery sites
• oviparous chondrichthyans
• Southwest Atlantic

Acknowledgements

We thank the crew of the research vessel Puerto Deseado (CONICET) for the assistance in the collection of samples. We also thank Dr Claudia Bremec, Dr Laura Schejter and Richard Gavilan for providing samples from commercial vessels. We appreciate the collaboration of Matías Delpiani, Daniel Bruno and Nicolás Lajud (Universidad Nacional de Mar del Plata) in the collection of samples from research vessels. Finally, we thank Dr Franz Uiblein and two anonymous reviewers, whose suggestions greatly improved this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was partly supported by funding from Consejo Nacional de Investigaciones Científicas y Técnicas, PIP CONICET 11220130100339, Agencia Nacional de Promoción Científica, PICT-2014-0665, Fondo iBOL Argentina and Universidad Nacional de Mar del Plata (EXA669/14) (Argentina).