Drivers of bull shark (Carcharhinus leucas) occurrence in nearshore waters: Insights from the Queensland Shark Control Program, Australia

Shark bites are widely reported and geographically dispersed, and reported incidence in Australia has increased in recent decades. Bull sharks, which are cosmopolitan across subtropical and tropical regions, are among the most common species involved in these interactions. Identifying the environmental and temporal correlates of nearshore bull shark capture may inform ecological understanding and support risk communication strategies for shark management agencies. As such, long-term datasets from shark control programs can help characterise the conditions associated with nearshore visitation of bull sharks through analysis of capture rates. Here, we examined the influences of these variables by modelling a 27-year (1996–2022) fisheries-independent dataset obtained from the Queensland Shark Control Program (QSCP) using generalised additive mixed models. Our models retained SST, rainfall, swell height, oceanic currents, and season as covariates associated with variation in nearshore bull shark catch per unit effort (CPUE). However, the relative influences of these factors varied with the gear and the shark’s size class. Here, large sharks (≥ 2.2 m total length) showed regionally distinct CPUE-environment relationships across zones. In tropical north Queensland, catches were positively associated with SST, peaking near 27 °C. In the southern sub-tropics, large shark CPUE was positively associated with warmer waters and higher rainfall. Seasonally, large sharks were most frequently caught during summer and autumn months across all regions. These findings suggest that measurable environmental conditions are associated with variation in nearshore capture rates, which may support broad, region-specific risk communication and bycatch-reduction discussions.