Sunshine Coast Rivers is an important reproductive area for one shark species.

Bull Shark neonates, young-of-the-year (YOY), juveniles, and pregnant females are regularly observed in this area (BJ Holmes & JA Gustafson unpubl. data 2025). A short pilot study captured and tagged six Bull Sharks in this area (three YOY, one juvenile, two adults) in 2018–2020. A passive acoustic tracking study then captured Bull Sharks mainly on baited drumlines in the Noosa River, Maroochy River, Mooloolah River, and Pumicestone Passage between September–May in 2023–2025. Additional adults and sub-adults were captured and tagged in coastal waters of this area. Their total length (TL) was measured, life stage assessed, and tagged internally. Age classes were defined as neonate (open umbilical scar; 50–81 cm TL), YOY (closed umbilical scar; 82–99 cm TL), juvenile (100–200 cm TL; non-calcified claspers in males), and adult (>200 cm TL; calcified claspers in males). A growth rate of 30 cm per year was used to identify potential changes in age classes over time of tagged sharks. Their movements were monitored on 295 receivers (27 in rivers, 268 coastal). Bull Shark movements in this area are wholly confined to a single river system for the first 5–6 years of their lives, highlighting that neonate, YOY, and juveniles can be considered when assessing the area’s importance for the early life stages of the species (Werry et al. 2011; BJ Holmes & JA Gustafson unpubl. data 2025).

In the Noosa River, four YOY and 23 juveniles were captured and tagged seasonally between October–March in 2023–2025 (BJ Holmes & JA Gustafson unpubl. data 2025). All individuals <150 cm TL were only detected in the Noosa River and not in adjacent coastal waters, with detections throughout the year. These YOY and small juveniles were detected up to 20 km upstream, where the last receiver was located, although recreational fishers regularly report catches up to 40 km upstream (JA Gustafson pers. obs. 2025). Six of the small juveniles that were between 130–150 cm TL at the time of tagging have since displayed movements out of the river and into coastal waters of this area (BJ Holmes & JA Gustafson unpubl. data 2025). Most of the large juveniles were captured and detected in the inter-lake region between Lake Cooroibah and Cootharaba. This makes the Noosa River unique compared to the other rivers along the Sunshine Coast. Additionally, commercial fishers operate in the Noosa River and regularly catch Bull Sharks, including neonates and pregnant individuals (JA Gustafson pers. obs. 2025).

In the Maroochy River, three YOY were tagged in May 2018, and they were detected for two years until the receivers were removed in April 2020. They were first detected outside the river in coastal waters in April 2022, when they were ~5 years old. Since receivers were placed again in the river in June 2023, these individuals have been occasionally recorded at the river mouth and estuary of the Maroochy River and also in the Noosa River, Mooloolah River, Pumicestone Passage, and Moreton Bay, highlighting the connectivity within this area. Two of these sharks, both females, were detected in the upper river six years after tagging, during the known pupping season in November–February. This may indicate that they have reached maturity and returned to the river to pup. In 2023–2025, six neonates, 13 YOY, and 11 juveniles were captured and tagged. These have only been detected in the Maroochy River so far, up to 20 km upstream from the river mouth where the last receivers are located (BJ Holmes & JA Gustafson unpubl. data 2025). Reports from recreational fishers indicate that Bull Sharks are captured up to 40 km upstream in this river (JA Gustafson pers. obs. 2025). Additionally, commercial fishers operate in the Maroochy River and regularly catch Bull Sharks, including neonates and pregnant individuals (JA Gustafson pers. obs. 2025).

In Pumicestone Passage, two neonates, five YOY, and 19 juveniles were tagged in 2023–2025. Most of these individuals have only been detected in Pumicestone Passage so far. Detections reached up to 20 km from the passage mouth, and recreational fishers report catches up to 30 km upstream (JA Gustafson pers. obs. 2025). The three largest juveniles tagged (150–167 cm TL) have also been detected in local coastal waters, demonstrating the move away from the river systems at this life stage (BJ Holmes & JA Gustafson unpubl. data 2025).

Only one juvenile was tagged in the Mooloolah River, but receivers in this river also detected Bull Sharks during their staging phase when they start to use coastal marine waters and move between rivers. The coastal waters that link the river systems are important for the juveniles starting to leave rivers but not being fully marine. Bull Sharks in this area appear to acclimate to the novel marine environment before recruiting fully into adult populations. A total of 17 tracked sharks periodically moved in and out of both their home rivers, and neighbouring river mouths, slowly expanding their home range while still seeking the additional shelter that each river mouth provides. This staged movement occurs for up to five times a year, before returning for a similar amount of time, and increasing their time spent outside the home river, venturing up to 445 km away before exiting the rivers completely. This integrated estuarine and coastal habitat use appears to be essential for an additional two to three years, after ~5 years spent in the rivers as neonate, YOY, and small juveniles, before they fully mature and undertake larger migratory movements along the Australian east coast. These larger movements have ranged between 1,600–2,550 km up to Cape York (BJ Holmes & JA Gustafson unpubl. data 2025).