Small changes in water temperature during the early life history of fishes can affect their growth, recruitment, abundance and distribution. However, there is little information available about the influence of temperature on functional traits of freshwater fish larvae or how these vary across spatial gradients.
The aim of this study was to examine temperature-specific growth, survival and development of Murray cod (Maccullochella peelii) larvae from four regions across the Murray-Darling Basin (Northern, Macquarie, Lachlan and Southern). Larvae from each of these regions were reared from 0-28 days post hatch (dph), at five temperatures ranging from 14 to 30°C. Total length was measured and development stage observed at fixed intervals and survival was recorded daily.
Larvae from the Lachlan region experienced significantly higher mortality at temperatures of 26°C and above, compared to larvae from all other regions. Significant regional differences in somatic growth were observed among larvae at different ages and temperatures (P<0.05), however these were not consistent until 24 dph at 26°C. A decline in growth among larvae from all regions at temperatures of 26°C and above indicates that predicted temperatures increases associated with climate change above this threshold will negatively impact larval growth and recruitment success.
These results support hypotheses suggesting that populations of widely distributed freshwater fish species have unique adaptations to local environmental conditions. Conservation and population recovery strategies for native fish may need to be modified to consider regional differences among populations and their unique responses to anthropogenic pressures such as river regulation.