A major expense in the operation of bivalve nurseries is the culture of high-quality live microalgae feeds, with efforts to develop effective alternative feeds having limited success. Juvenile bivalves are known to be able to absorb dissolved nutrients but this ability has received minimal attention as a route for supplementary feeding. This experimental study assessed the capacity of juvenile green-lipped mussels (Perna canaliculus ) to uptake and assimilate dissolved glucose and sucrose as a supplement to cultured microalgae. Growth and survival of the mussels was measured over three weeks. All concentrations of glucose and sucrose improved the performance of spat compared to the controls without sugar, the best performance came from a concentration of 1 mg ml-1 of dissolved glucose which enhanced daily spat growth 2.7 times that of the control diet.
Survival was high (i.e., > 95 %) among all treatments except for the highest experimental concentrations of glucose and sucrose, where a concentrations above 1 mg ml-1 resulted in mean mortalities of between 16 and 24 %. Mussel spat supplemented with dissolved sugars accumulated greater lipid and carbohydrate content per mg g -1 of ash-free dry weight compared to those in the control treatment, indicating they were in greater nutritional condition. This demonstration that dissolved glucose and sucrose can be readily utilised by Greenshell™ mussel spat at concentrations as low as 10 mg ml-1 opens up the possibility for delivering other soluble nutrients to cultured juvenile molluscs. Dissolved nutrients have the potential to improve the performance of spat in nursery systems while simultaneously reducing the reliance of cultured microalgae as a sole feed input.