Rocas Atoll is an important reproductive area for two shark species.

For the Atlantic Nurse Shark, historical scientific surveys were conducted in this area in 1998 (April) and 1999 (May, August, and November; Castro & Rosa 2005). During May 1999, mature males and females exhibited behaviours related to mating activity, such as patrolling by males, ‘pre-copulatory’ behaviour, male and female parallel swimming or lying parallel on the substrate, and copulation (Castro & Rosa 2005). Males were less frequent in August when many females appeared to be gravid and aggregating. The number of males increased in November, but fewer mature individuals were found. A similar situation was observed in April 1998 (Castro & Rosa 2005). One neonate (~30 cm TL) was observed in August 1999, and five empty egg cases were brought ashore by the tides (Castro & Rosa 2005).

In 2018, Underwater Visual Census (UVC) surveys to photo-identify this species were conducted across the inner part of the atoll: 22 UVCs in April/May, 39 in August/September, and 50 in October/November (Bettcher et al. 2023). Most (92%) of the UVCs were conducted at low tide. Aggregations of ~10–20 pregnant females were generally observed during high tide at the shallowest bank (Zulu Bank), which is dry during low tide. Across the expeditions, 444 individual sightings were recorded (including repeat sightings), with 47.3% females, 5.2% males, and 47.5% unsexed individuals (Bettcher et al. 2023). The total length (TL) was estimated using laser photogrammetry. Males measured 130–310 cm TL in August (n = 9) and 100–250 cm TL in November (n = 8), with mature males (>210 cm TL) observed in both months (n = 3 each). Pregnant females with distended abdomens were observed in August (n = 28, including four measuring 220–320 cm TL) and November (n = 2; 220–250 cm TL; Bettcher 2019). Of the 30 presumably pregnant females observed, 25 were recorded at Zulu Bank, which is flooded only during high tide. During three sampling events at Zulu Bank in August, 49 sharks were observed, though only 25 had visibly distended abdomens. Some females did not show a clear distended abdomen, while others swam away before closer observation was possible. Pregnant females enter the inner atoll as the tide rises and leave as it recedes (V Bettcher Brito pers. obs. 2018–2022). Pregnant females enter the inner part of the atoll and go to this area when the tide is rising and leave when the tide recedes (V Bettcher Brito pers. obs. 2018–2022).

Scientific surveys focused on habitat sampling were also undertaken in October 2020 and August 2022 in this area. In August 2022, ~25 Atlantic Nurse Sharks, visually estimated to measure (>200 cm TL, were sighted from the boat at the shallow bank where pregnant females were previously recorded. Of those, seven were observed underwater, with five showing distended abdomens. This confirms the regular use of the area by pregnant Atlantic Nurse Sharks. In September 2022, two egg cases were also opportunistically found on the beach on the same day (V Bettcher Brito unpubl. data 2020–2022). Although extensive movements of adult Atlantic Nurse Sharks have been recorded along continental coasts (541 km ([Kohler et al. 1998] and 335 km [Pratt et al. 2018]), Rocas Atoll is surrounded by deep water (up to 4,000 m), which is likely to serve as a barrier to movement. Neonates and young-of-the-year (YOY) individuals likely remain within the atoll and use smaller caves and burrows to hide in the inner part of the atoll under the reef or at the outer reef.

For Lemon Sharks, historical data collected between 1999–2003 indicate that this species uses this area regularly and predictably for reproductive purposes. Across nine sampling trips, a total of 347 juvenile Lemon Sharks were captured, including recaptures (n = 157 tagged individuals) (Freitas et al. 2006). Lemon Sharks were caught at a variety of sites within this area, including in pools (16%) and the central lagoon (6%), but predominantly in the Baía da Lama (78%). Lemon Sharks measuring <70 cm TL were most abundant (34%), followed by individuals measuring 70–80 cm TL (18%) and 80–90 cm TL (16%). Lemon Sharks with completely or partially open umbilical scars were captured during the four sampling trips in March and one in May 2003 (the other months sampled were August, September, October, and November) (Freitas et al. 2006).

Two field trips to Rocas Atoll were also conducted in 2015. One survey lasted 23 days in austral summer (January/February), and the second lasted 22 days in winter (June/July; Corrêa et al. 2023). Data were obtained using a visual census from a natural elevated point on Farol Island. A total of 2,306 sightings of individuals (including possible resights over days) were recorded in 2015, with 1,168 during the summer (240 visual counts), of which 880 were neonates, and 1,138 during the winter (37 visual counts), all ranging from 65–150 cm TL. Neonates were defined as smaller than 65 cm TL. The mean abundance of Lemon Sharks within the bay (~1 km²) in summer was 29.20 (± 5.04) per day, ranging from 12–35 animals. Neonate and juvenile Lemon Sharks enter and leave the bay following flood and ebb currents, respectively. Neonate Lemon Sharks were only observed in summer, in aggregations of 10–30 individuals, but YOY are with the juveniles observed in winter (Corrêa et al. 2023). Additionally, in 2018, 2020, and 2022, during scientific surveys focusing on other species, aggregations of ~20 neonates/YOY Lemon Sharks based on the size ranging from 60–80 cm TL were observed mainly at Baía da Lama within the area (V Bettcher Brito pers. obs. 2018–2022).

In addition, adults with mating scars/injuries and neonates (60–80 cm TL) are regularly and predictably observed, mainly during summer months (V Bettcher Brito pers. obs. 2018–2022). The size-at-birth of this species is 60–65 cm TL (Ebert et al. 2021). Individuals display restricted but repeated movements between small tide pools on reef flats at low tide and a small, shallow (50 cm) tidal creek nearby at high tide within this area (Wetherbee et al. 2007). Records of adult Lemon Sharks with mating scars, aggregations, and mating attempts in 2021–2023 are also available on social media.