Growth and temperature relationships for juvenile fish species in seagrass beds: implications of climate change

The effect of water temperature on growth responses of three common seagrass fish species that co-occur as juveniles in the estuaries in Sydney (34 degrees S) but have differing latitudinal ranges was measured: Pelates sexlineatus (subtropical to warm temperate: 27-35 degrees S), Centropogon australis (primarily subtropical to warm temperate: 24-37 degrees S) and Acanthaluteres spilomelanurus (warm to cool temperate: below 32 degrees S). Replicate individuals of each species were acclimated over a 7day period in one of three temperature treatments (control: 22 degrees C, low: 18 degrees C and high: 26 degrees C) and their somatic growth was assessed within treatments over 10days. Growth of all three species was affected by water temperature, with the highest growth of both northern species (P. sexlineatus and C. australis) at 22 and 26 degrees C, whereas growth of the southern ranging species (A. spilomelanurus) was reduced at temperatures higher than 18 degrees C, suggesting that predicted increase in estuarine water temperatures through climate change may change relative performance of seagrass fish assemblages.