The microbial community of a maritime scallop hatchery and the impact of selected bacteria on larval health.

Control of disease is just as critical to the success of a shellfish hatchery as it is to the successful operation of a poultry or cattle farm. Bacteria have been suspected as the causative agent of sudden high mortalities among hatchery scallop larvae. However, very little specific information about the microbial load in shellfish hatcheries has been reported.

In the current study, the microbial load of the water in a sea scallop (Placopecten magellanicus) hatchery was monitored during larval development. The microbes present in water samples were cultured and enumerated on Marine 2216 agar and Vibrioaceae selective agar. To obtain a profile of the microbial community capable of growing under hatchery conditions, representative colonies were isolated from agar plates and the biochemical profile of each isolate determined. The microbial populations associated with the broodstock before and after depuration were also surveyed and included in the study.

Six to 8-day-old larvae were challenged with representative isolates of all characterized bacteria. After 4 days incubation with the bacteria, the health of the larvae was measured by comparing the size, swimming pattern and feeding behaviour of the exposed larvae with similar larvae that had not been exposed to the bacteria. From this assessment, bacteria were identified as neutral, potential pathogens or possible probionts.

(Institute for Marine Biosciences, National Research Council, Halifax, Nova Scotia, Canada B3H 3Z1)