Environmental spawning cues of the temperate freshwater Murray Cod (Maccullochella peelii) in a changing climate

Spawning patterns in fish that use temperature as a spawning cue are responding to long-term changes in the climate. The threatened Murray Cod, Maccullochella peelii (Mitchell), is an important apex species in inland south-eastern Australia. Information from 1461 spawnings collected from hatcheries over 40 years was combined with environmental, meteorological, and astronomical data to (1) identify factors affecting spawning and (2) detect changes in spawning associated with climate change. The spawning season extended over four months, from late-August at low latitudes to mid-January at high latitudes, but locally lasted 1-2 months. Spawning events were preceded by an increase in temperature in the days leading up to spawning, whereas a decline in temperature inhibited spawning. In the Murray-Darling River basin, the spawning season of Murray Cod began earlier and shortened in duration inversely with the mean spring temperature anomaly. Spawning is predicted to occur up to 4 weeks earlier by 2090 in response to future temperature projections in the Murray-Darling River basin. Since climate change is affecting aquatic environments globally, findings from this study have implications to the long-term management of temperate freshwater species that are the subject of regulations aimed to protect fish during the spawning season.