Increase in larval shellfish survival and expansion of shellfish seed availability through novel feed sources

View the project report

Commodities

• Animals: shellfish

Practices

• Animal Production: aquaculture

The ability to grow large quantities of microalgae is a factor limiting seed output in shellfish hatcheries. Shellfish larvae, and subsequent post-metamorphosis seed requires greater and greater amounts of cultured microalgae as they grow, prior to feeding on naturally growing microalgae once they reach a minimum of 1mm shell height. This can start at 25,000 cells per day per animal immediately after fertilization to well over 1 million cells per day by the time they are ready to eat on algae provided by the natural environment. This drastic increase in algae needs over a period of less than 30 days puts a strain on the hatchery’s ability to feed all of the animals at once, and is the primary limiting factor of hatcheries seed production as the algal needs reach a peak in the spring. Growing microalgae heterotrophically allows for over 100 times greater biomass produced per unit volume as opposed to typical photoautotrophic culture methods. Growing greater biomass of microalgae per unit volume will allow for greater quantities of larvae to be grown, and will also allow for shellfish to be grown to a larger size prior to being shipped to growers. This would also allow for greater efficiency and lower cost per unit to produce shellfish seed, which would allow for lower prices for farmers to purchase shellfish seed.

This project seeks to grow two different species of dinoflagellate microalgae through heterotrophic methods, and feed the microalgae to larval and post-set shellfish to investigate clearance rates and subsequent survival. The two species to be cultures are Crypthecodinium cohnii and Tetraselmis suecica, and the larvae and post-set shellfish to be fed the cultures will be eastern oysters (Crassostrea virginica) and bay scallops (Argopecten irradians).

Obj 1. Culture Crypthecodinium cohnii and Tetraselmis suecica in flasks and carboys.

-Initial cultures in 125 ml continuously shaken flasks in the dark.          
-Scaled up to 250 ml and 1 L flasks prior to inoculation into 4 L carboys.

Obj 2. Evaluate shellfish larvae clearance rates of the species of interest.

-Feed day 6 larvae of each shellfish species at 25,000 cells/ml of each microalgae species in additional to control feeding regimen of 25,000 cells/ml of Tisochrysis lutea or Tetraselmis suecica.

Obj 3. Evaluate shellfish post-set clearance rates of the species of interest.

-Feed post-set shellfish of each species at 100,000 cells/ml of each microalgae species in additional to control feeding regimen of 100,000 cells/ml of Tisochrysis lutea or Tetraselmis suecica.