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

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.