Milman Island is an important reproductive area for one shark and one ray species.

Between 2019–2021, three research expeditions were conducted around Milman Island to monitor sea turtles, during which opportunistic observations of Blacktip Reef Sharks were obtained (Freeman & Wright 2021; A Freeman unpubl. data 2025). Body sizes of animals were visually estimated (Freeman & Wright 2021). Over four weeks in January–February 2020, nine aggregations of between 5–10 neonate and young-of-the-year (YOY) Blacktip Reef Sharks with an estimated size of 50 cm total length (TL) were observed in very shallow water (0.5 m) adjacent to a sandy beach (Freeman & Wright 2021). Published size-at-birth for the species in the region ranges between 51─54 cm TL (Chin et al. 2013), indicating that these were neonates or YOY. In northern Australia, Blacktip Reef Sharks give birth from December to March (Chin et al. 2013). Aggregations of neonates/YOY (estimated size 50 cm TL) were also recorded in February 2021, ranging from 6–7 individuals, while similar sized individuals were also recorded in February 2019. However, in 2019 only solitary individuals were sighted (A Freeman unpubl. data 2025). During all turtle monitoring field trips in 2019–2021 during January and February, adult and juvenile Blacktip Reef Sharks were also regularly observed in the area (A Freeman unpubl. data 2025).

Between 2015–2023, four turtle monitoring field trips were conducted on the island, during which opportunistic observations of Giant Guitarfish were obtained. In 2019, standardised surveys specific for Giant Guitarfish (n = 22) were carried out along a 450 m beach transect for 10-min at the water’s edge. Individuals were counted during the day and night, with a maximum of two transects surveyed per day (Freeman 2019). Size data were obtained by comparing a subset of individuals (n = 15) against a submerged builder’s tape laid on the benthos, while prior to 2019, sizes were visually estimated (Freeman 2019). Between 2015–2023, an estimated 487 neonate and YOY Giant Guitarfish were observed, though this estimate may include duplicate counts across some transects (Freeman 2019; A Freeman unpubl. data 2025). Measured individuals ranged between 35─45 cm TL (Freeman 2019). Size-at-birth for the species ranges between 38─40 cm TL (Last et al. 2016), and nearly all the animals recorded were within this size range, indicating they were neonates or YOY. The number of individuals counted per transect ranged between 1–61 with the highest estimates coinciding with the highest tides when the lagoon was 1.5─3.0 m deep (Freeman 2019). In 2019, the average number of animals counted when tide height was less than 2 m was 7.6 individuals, while higher than 2 m, the mean number of rays was 28 individuals (Freeman 2019). Giant Guitarfish occurred in extremely shallow water, sometimes as little as 0.1 m deep at high tide, occasionally exposing their dorsal fins, and exhibited behaviours ranging from burying in the sand to moving parallel to the shoreline. The shoreline margin may provide a critical resting area and a refuge from predators. Several predators are present in the wider area, including small to medium-sized Estuarine Crocodiles Crocodylus porosus, which have occasionally been sighted in the lagoon, as well as Whitetip Reef Sharks Triaenodon obesus and Blacktip Reef Sharks (A Freeman unpubl. data 2025).