Each winter, over 100,000 giant Australian cuttlefish (Ascarosepion apama) aggregate along an 8 Km stretch of shallow reef in the upper Spencer Gulf, South Australia to mate and lay their eggs. This dense aggregation is ecologically unique and, as of 2023, National Heritage Listed. However, the aggregating population of cuttlefish is also subject to extreme fluctuations, falling to just 13,000 individuals in 2013 and increasing to over 247,000 in 2020. The factors influencing these fluxes are broadly unknown. Environmental data has been continuously collected in the Spencer Gulf region for decades, thus we used a modelling approach to investigate potential drivers of change in giant cuttlefish aggregation numbers. We aimed to suggest potential contributors to population decline and growth, as well as explore whether future population changes can be forecasted using the routinely collected environmental data. Particularly, we identified the idiosyncrasies and interconnectedness between environmental drivers and food availability for cuttlefish during their peak body growth phase from juvenile to adult. This work has implications for the management of tourism at the aggregation site, as well as for recreational and commercial fishing, and for the ongoing industrial development of the Spencer Gulf region.