Skates and rays (Batoidea) play a significant ecological role, contributing to ecosystem services through bioturbation and acting as vital intermediate components of the trophic chain in various aquatic environments. Despite their wide global distribution and ecological importance, batoids receive less attention than their shark relatives, resulting in substantial knowledge gaps that might impede a comprehensive understanding of their conservation status. This review addresses critical aspects of their capture, handling, tagging, and release to provide readers with crucial information needed to perform research on batoids. Protocols for analgesia, anaesthesia, and euthanasia are also discussed, taking into account the ethical and logistical considerations necessary for research involving this group of species. This information can give researchers and ethics committees the knowledge to conduct and approve studies involving batoids, thereby promoting more effective and ethical research practices.

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements.

In order to elucidate the main aspects related to dolphinfish reproduction around Saint Peter and Saint Paul Archipelago, 862 individuals caught in that area by commercial handline fishing were examined between 2007 and 2011. From those specimens, it was possible to assess the sex in 782 specimens (271 males and 511 females) and the levels of gonadal maturation in 536 of them (175 males and 361 females). The fork length (FL) of the examined specimens varied between 27 and 150 cm. Sex ratio found was 1.0 male: 1.9 females, but the difference was not statistically significant in April (χ2=0.08), August (χ2=0.82) and October (χ2=3.63). However, by size interval, sex ratio was 1.0 male: 1.0 female for FL between 120 and 130 cm. The gonadal index showed the highest values in February for males and in April for females. Most spawning-capable specimens were found in February (males 36.4%) and in May (females 42.2%). The length of size-at-50%-maturity (L50) was estimated at 70.66 cm FL for males and 68.60 cm FL for females. The results suggest that the period of highest reproductive activity occurs between April and June.

From October 2005 to March 2010, a total of 480 pelagic stingray, Pteroplatytrygon violacea, specimens, 188 females and 292 males (0.64 female : 1 male), were taken in the equatorial and south-western Atlantic by the commercial tuna longline fishery and their reproductive biology was studied. Disc widths (DW) ranged from 28.0 to 66.0 cm for females and from 34.0 to 59.6 cm for males. Size at first sexual maturity was estimated at ~48.0 cm DW (first pregnant female) for females and ~41.0 cm DW for males. Ovarian fecundity, considering only follicles larger than 0.5 cm in diameter, ranged from 1 to 17 follicles per female, while the uterine fecundity of embryos in pregnant females in Stages 2 and 3 ranged from 1 to 5 embryos per female. The sex ratio between the embryos was almost equal (1.08 female : 1 male) and the size at birth was 19.0 cm DW.

The wahoo, Acanthocybium solandri, a cosmopolitan species distributed in tropical and subtropical waters of the Atlantic Ocean, is often caught by commercial fishing vessels in the vicinity of the Saint Peter and Saint Paul Archipelago (SPSPA) (Brazil). The aim of the present study was to investigate the reproductive biology of wahoo caught around the SPSPA, between July 1998 and June 2006. During this period, a total of 1,500 specimens were measured and 1,162 were sexed (610 males and 552 females), among which 774 had their gonads collected and fixed in a 10% formaldehyde solution. Fork length of the sampled specimens ranged from 63 cm to 197 cm. The results suggest that the peak of reproductive activity in the area occurs in April-May. Size at first maturity was estimated at 110 cm FL for females and 102 cm FL for males. The estimated batch fecundity was equal to 1,317.235 oocytes, ranging from 287,040 to 2,494.512. Spawning seems to be multiple and protracted throughout several months between February and September, with a clear seasonal reproduction cycle.

The oogenesis is a key stage in the reproductive development of an organism, which can be best understood from histological analysis of ovaries in different maturity stages. In order to provide information on the reproductive biology of the black triggerfish, M. niger, in particular on its oogenesis process, this study aimed at identifying and characterizing the oocyte development stages and its organization within the different stages of ovarian maturation based on specimens from São Pedro e São Paulo Archipelago. In this present report, a number of 294 ovaries were histologically analyzed. It was verified that they are composed of ovigerous lamellae containing oocytes at different development stages. Five different stages of oogenesis were identified: young cells, with an average size of 12.9 ìm; previtellogenic oocytes (perinucleolar), with an average size of 53.5 ìm; cortical-alveoli oocytes with an average size of 83.1 ìm; vitellogenic oocytes, with an average size of 160.4 ìm and mature oocytes, with an average size of 289.8 ìm. In addition to the germ cells, some somatic structures were also identified, such as: ovarian wall, follicular cells and blood vessels. Based on the type and number of oocytes observed, four stages of ovarian maturation were identified: early maturation, represented by only 2.2% of the sample; middle maturation, represented by 9.9%; mature, represented by 44.2% and resting, represented by 43.9%. The identification of five oocyte development stages in the ovarians from M. niger, suggested that the specie follows a pattern similar to that described for other marine fish.

SUMMARY The pelagic stingray, Pteroplatytrygon violacea, is the only member of the Dasyatidae family with an entirely pelagic behavior. In the present work a total of 367 specimens, 137 females (37.3%) and 230 males (62.7%), were examined, with a view to study their reproductive biology. The specimens were collected between October 2005 and January 2008, by observers onboard of Brazilian commercial longliners. The disc width (DW) ranged from 28.0 to 63.2 cm for females and from 34.0 to 59.6 for males. Females were classified as immature (n= 30; 22.4%); maturing (n= 41; 30.6%); pre-ovulatory (n= 25; 18.7%); pregnant in early gestation (n= 14; 10.4%); pregnant in mid gestation (n= 8; 6.0%); pregnant full term (n= 2; 1.5%); postpartum (n= 4; 3.0%); and resting (n= 10; 7.5%). For the 24 (17.9%) pregnant females the DW ranged between 46.0 and 60.8 cm. The monthly distribution of the reproductive stages does not indicate any clear seasonality for the reproductive cycle of the species. Ovarian vitellogenesis seems to happen simultaneously with gestation, indicating that females are ready to ovulate close after parturition. Size at first sexual maturity was estimated at around 45 cm DW for females, and at or below 34 cm for males, since all sampled specimens were equal or larger than this size and were all already mature.