Use of a nursery area by cownose rays (Rhinopteridae) in southeastern Brazil

Abstract

Using non-lethal methods for data collection of individuals and participatory monitoring by fishermen, we provide the first empirical evidence of the use of a nursery area by neonate and young-of-the-year cownose rays Rhinoptera bonasus and R. brasiliensis in southeastern Brazil. Two methods were used to collect data: (1) information provided by fishermen (reports, pictures, and videos) and (2) field sampling by researchers. A total of 746 cownose rays were captured; 113 have been identified as R. bonasus, 15 as R. brasiliensis, and 618 were reported by fishermen and could not be identified to the species. Records of newborns were made only in late spring and summer in 2015, 2016, and 2017, which suggests an annual reproductive cycle, with birth in late spring, extending to summer. A repeated use of this area by R. bonasus suggests that it is potentially important to the reproduction of this species. However, R. brasiliensis requires more studies. Small increases in mortality, resulting from increased fishing or other anthropogenic stressors, can have a disproportionately large effect on population viability. Thus, management of areas used during critical stages of the life cycle of rays is crucial to their conservation.

Resource partitioning between two young‐of‐year cownose rays Rhinoptera bonasus and R. brasiliensis within a communal nursery inferred by trophic biomarkers

“…Despite this, R. brasiliensis did not show an essential FA deficiency in liver and muscle tissue as previously reported for young placental sharks at birth ( i.e ., DHA and ARA < 6%; Belicka et al, ; Wai et al, ). Considering that liver tissue was principally analysed for YOY < 50 cm W D R. brasiliensis (< 4 months old, Fisher et al, ; Rangel et al, ) and it has a relatively fast turnover rate (Figure ; c . 3 weeks; Beckmann et al, ), differences in liver FA profiles between the two species suggest access to different resources, most likely during the prenatal phase ( i.e ., variable maternal resources; Figure ).…”

“…data) of R. bonasus and R. brasiliensis were collected in Bertioga, south‐eastern Brazil (23° 49′ 35.02” S, 46° 5′ 41.69” W) between March 2016 and February 2017. The region functions as a nursery area for the two cownose ray species (Rangel et al, ), according to the criteria proposed by Heupel et al (). All specimens were sampled following incidental capture by fishermen using beach seine nets targeting snook Centropomus spp.…”

“…All specimens were sampled following incidental capture by fishermen using beach seine nets targeting snook Centropomus spp. (Rangel et al, ). Sampling was limited to these opportunistic fisheries captures as R. bonasus and R. brasiliensis are classified as Near Threatened and Endangered in the IUCN Red List assessment, respectively (Barker, ; Vooren & Lamónaca, ), while R. brasiliensis is categorised as Critically Endangered in the Brazilian national assessment (ICMBio, ).…”

“…In rays, the formation of heterospecific groups has been observed, for example, in sub‐adult stingrays Pastinachus sephen (Forsskål ) and Himantura uarnak (Gmelin ) (Semeniuk & Dill, ) and juvenile cownose rays Rhinoptera bonasus (Mitchill ) and Rhinoptera brasiliensis (Müller, ) (Figure ; Rangel et al, , ). Co‐occurrence has been hypothesised as a strategy adopted to increase survival, by reducing predation pressure per individual and increased foraging success to meet energetic requirements (Semeniuk & Dill, ).…”

Lipí­dios e isótopos estáveis como indicadores de investimento materno e estratégias nutricionais neonatais em raias viví­paras histotróficas

“…O termo útero-lactação foi introduzido para referir-se as similaridades estruturais da lactação em mamíferos (Hamlett et al, 1996), presumindo que a produção de histotrofo rico em lipídios tenha evoluído em resposta às pressões seletivas que favoreceram o aumento do investimento parental em sua prole (Oftedal, 2002). fêmeas apresentam ciclos anuais contínuos e são mais suscetíveis à pressão da pesca durante a residência nos berçários, que são geralmente em áreas estuarinas ou costeiras (Omori e Fisher, 2017;Rangel et al, 2018). Estudos sobre a migração de R. bonasus no hemisfério norte, revelam que as fêmeas migraram no início do outono da Baía de Chesapeake (área de berçário e reprodução) para o sul da Flórida (área de alimentação), diferentes dos machos, que migraram para o norte e para o sul da Nova Inglaterra, EUA (Omori e Fisher, 2017).…”