Wheeler Reef is an important area for undefined aggregations of one shark species.

Passive acoustic telemetry data show that Grey Reef Sharks regularly aggregate in this area (Espinoza et al. 2015; M Espinoza unpubl. data 2025). A total of 40 Grey Reef Sharks (20 females, 20 males) were tagged with internal acoustic transmitters in the broader region around Wheeler (n = 7), Lodestone (n = 13), Helix (n = 10), Glow (n = 5), and other reefs (n = 5) between January 2012 and August 2013 (Espinoza et al. 2015). Their size ranged from 52–142 cm fork length (FL), and included 10 immature and 10 mature males, and six immature and 14 mature females. Of these, five females and two males were detected on the receivers in this area, with records between April 2013 to April 2014. Aggregations were defined as three or more tagged individuals detected at a receiver within five minutes. Aggregations in consecutive 5-minute bins were grouped into an event, and its duration was calculated.

There were ~240,000 detections recorded at this reef, but three receivers had few detections (0.8, 1.4, and 9.3%, respectively) and recorded only sporadic aggregations. These were excluded and the remaining two receiver locations were used to define the boundary of the area. There were 6,732 five-minute bins with aggregations recorded within the area, grouped into 4,543 aggregation events that lasted between 0.2–159 min (mean = 5.6 min). Aggregations comprised 3–6 individuals (mean = 3.2 individuals) or 43–86% of the seven tagged Grey Reef Sharks that were detected in this area. There was a seasonal signal, with more aggregations, aggregations persisting longer, and more individuals in aggregations during May–August. This was partly driven by mature females being detected less frequently during October–February, potentially related to mating and parturition outside the receiver array. Aggregations were recorded on 342 of 359 monitoring days (95%). Combined, the data show that specific locations in the northwest of this small reef (i.e., this area) regularly host aggregations of Grey Reef Sharks that last up to ~2.5 h. Only three of 11 reefs with receivers in this study off Townsville had significant aggregations of Grey Reef Sharks. Additionally, only 14 of 40 Grey Reef Sharks tagged in this group of reefs were detected at reefs other than their home reef, generally only spending a few hours to days before returning to their home reef. At Wheeler Reef specifically, no individual was detected at other reefs. This highlights their high residency and site fidelity, and the individual importance of Wheeler Reef (Espinoza et al. 2015; M Espinoza unpubl. data 2025). More information is required to understand the nature and function of these aggregations.