Whoʼs the biggest fish in the pond? The story of bull sharks (Carcharhinus leucas) in an Australian golf course lake, with deliberations on this speciesʼ longevity in low salinity habitats

Abstract

This article addresses the history of a resident population of bull sharks (Carcharhinus leucas) in an isolated stagnant body of water in subtropical Australia. From 1996 to 2013, six bull sharks were landlocked in a golf course lake near Brisbane. The adjacent Logan and Albert rivers trapped sharks due to major floodings. When floodwaters receded, these sharks remained in the lake, which is normally isolated from the riverʼs main channel. While this event was extensively reported in the media and recieved much public attention, it has not been investigated in depth, yet it provides an opportunity for insights into the tolerance of bull sharks to low salinity habitats and euryhalinity in this species. Currently, information on the extent of the bull sharkʼs capability to endure low salinity conditions and its longevity in these environments is scarce. The case reported here provides information on the occurrence of bull sharks for 17 years, which represents the longest uninterrupted duration in a low salinity environment that ever has been recorded in this species. Bull sharks arrived first in the lake as juveniles but through time, they have reached maturity. This occurrence presents not just another ordinary bull shark record from a low salinity environment but instead a record of physiological and scientific importance. Therefore, details of the residency of C. leucas in an Australian golf course lake are reported here.