Bivalve aquaculture production is more dependent on high quality microalgae than any other aquaculture sector. Because bivalves filter-feed almost exclusively on microalgae, the quantity and quality of available microalgae is critical at every life stage, and especially every stage of hatchery production: Broodstock, larvae, hatchery set, remote set, and nursery. Bivalve hatcheries today employ a combination of algae naturally found in local waters with algae produced in their own facilities to meet this demand.
The microalgae bottleneck
One of the greatest bottlenecks in bivalve production is an inadequate supply of quality microalgae when it is needed most. Algae production can be compromised by weather and season (where natural sunlight is used), equipment failures, or human error, and it must be timed to match the demands of the hatchery. Short day lengths, low light levels and suboptimal temperatures dramatically reduce winter algae production. To overcome this shortage, hatcheries culture algae, usually indoors, and production of microalgae is responsible for a major fraction of the infrastructure, labor, and other operating costs of a bivalve hatchery.
Algal culture requires specialized equipment and skilled labor, which entail costs with no return during the seasons when algae are not needed. Any shortfall in algae production can result in reduction or even failure of bivalve production.
Even when conditions for algae production are good, hatchery cultures can experience unexplained crashes or contamination by unwanted algae or zooplankton, limiting the availability of nutritionally critical microalgal species. Algae that is produced but cannot be used (because timing of production was misjudged, or an anticipated hatch was not successful) is an often overlooked, although significant, contributor to the total cost of algae production. An additional concern is that algae from both local waters and hatchery cultures can be sources of shellfish pathogens.
As an option commercially-available microalgae concentrates provide an economical supplement or replacement for ambient phytoplankton or hatchery-cultured microalgae.
Microalgae Concentrates
Refrigerated or frozen algae concentrates or “pastes” have been in commercial production for more than 15 years. These products, which are most often viscous liquids, have proven to be effective feeds for all life stages of bivalves. The concentrated microalgae are suspended in media that preserve cellular integrity and nutritional value, although the cells are usually non-viable. Non-viable concentrates have the advantage that they pose no risk of introducing exotic algal strains to a locality. Concentrates produced at inland facilities free of pathogen vectors greatly reduce the danger of introducing diseases along with the feed.
- See more at: http://hatcheryinternational.com/husbandry/the-case-for-concentrates/#sthash.EUYv5woc.dpuf
By Eric Henry, Research Scientist, and Tim Reed, Founder and President, Reed Mariculture, Inc., USA (www.reed-mariculture.com)