Investigating Dissolved Glucose as an Alternative Nutrient Source for Bivalve Larvae

The production of live microalgae represents a major cost in the operation of bivalve hatcheries, as it is the primary food used for larval rearing. This study investigated whether dissolved glucose could reduce the reliance on live microalgae as a sole feed input without negatively affecting bivalve larval performance during the rearing of Greenshell™ mussels (Perna canaliculus). Larvae from a single spawning cohort were raised to Day 10 post-fertilisation and then split into two feeding treatments: (1) control, fed only live microalgae in a continuous flow-through system and (2) glucose treatment, fed live microalgae in a continuous flow-through system, which was interrupted for 2 h, daily during which 10 μg mL^-1 of glucose dissolved in seawater, with a 20 min tank flush before and after exposure. The larvae were raised to settlement, during which time growth, microalgae consumption, losses of larvae at screening, settlement success and stable isotope composition (δ ¹³C and δ ¹⁵N) were assessed. Under these experimental conditions, substituting microalgae with glucose for 2 h daily did not alter the performance or isotopic composition of the larvae despite substituting an estimated 8.3% of live feed. This result provides a foundation to further test and refine the delivery of soluble nutrients, like glucose, as a means to reduce operational costs in bivalve hatcheries.