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/km 2 ) were mainly found between 39°4 6.2 ′ 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/km 2 (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 shelfbreak 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.

Trophic ecology of young‐of‐the‐year elasmobranchs in a critical habitat within the Río de la Plata outer estuarine waters

“…Recently, Vazquez et al . () have shown that high densities of egg cases from at least four skate species occur within the Argentine shelf‐break front, which coincide with chondrichthyans diversity hotspots in the region (Lucifora et al . ).…”

Egg cases of the graytail skateBathyraja griseocaudaand the cuphead skateBathyraja scaphiopsfrom the south‐west Atlantic Ocean

“…Recently, nursery sites of elasmobranch fishes in the SWA, including Bathyraja spp. have been recorded in the northern part of the ACS and near Mar del Plata Canyon (Vazquez et al, ). Neither egg cases nor egg‐bearing females of B. griseocauda and B. scaphiops , however, have been observed thus far (Mabragaña et al, ; Scenna, ).…”

“…This reproductive mode is characterized by the production of fertilized eggs that are encapsulated in a structurally complex protein capsule produced by the mother and deposited onto the seafloor (Hamlett et al, ). Egg case morphology is species‐specific (Ishiyama, ; Ebert & Davis, ; Oddone & Vooren, ; Mabragaña et al, ; Concha et al, ), which has made egg cases a useful tool not only for species identification, but also for understanding reproductive biology and phylogenetic relationships (Ishiyama, ; Jañez & Sueiro, ; Luer et al, ; Hoff, ; Ishihara et al, ; Fischer et al, ; Mabragaña et al, ; Vazquez et al, ).…”

“…, which has made egg cases a useful tool not only for species identification, but also for understanding reproductive biology and phylogenetic relationships (Ishiyama, 1958;Jañez & Sueiro, 2007;Luer et al, 2007;Hoff, 2010;Ishihara et al, 2012;Fischer et al, 2014;Mabragaña et al, 2015;Vazquez et al, 2016).…”

Comparative embryonic development patterns in three deep-water skates from the southwest Atlantic

“…First studies focused on marine life inhabiting the depths of the Argentine sea began only a few years ago, with 4 cruises sampling up to 3500 m depth (Flores et al, 2019;Penchaszadeh et al, 2019). During these expeditions egg case nursery sites were identified for several oviparous chondrichthyans, including those of genera Bathyraja and Amblyraja (Vazquez et al, 2016).…”