Tasks Accomplished: 5) Produce Shellfish Seed
Seed shellfish for the project were produced in the Martha's Vineyard Shellfish Group's Solar-assisted Hatchery.
5) Produce Shellfish Seed --
1999--With matching funds of $5,255 from the Massachusetts Department of Food and Agriculture, over 1.6 million (2 mm and over) oyster seed were produced at the Martha’s Vineyard Shellfish Group’s solar-assisted shellfish hatchery. Stock cultures of phytoplankton were grown to volumes sufficient to feed broodstock, larvae and juvenile oysters. On 12. February 1999, 26 broodstock oysters, some selected for their resistance to SSO disease, were put into ripening systems to condition them for spawning. During the seven week conditioning process, the oysters were slowly raised to 20C, held at that temperature for five weeks, and fed cultured phytoplankton.
On 2. April, the oysters were spawned, and 40 million embryos were introduced into four 400 liter larval culture tanks. Over the course of the next three weeks, oyster larvae were cultured in 5 micron bag filtered seawater heated to about 24C. The larvae were fed cultured phytoplankton daily, and every other day the tanks were drained, cleaned, and refilled with filtered seawater. Following a draindown, the larvae were sieved, counted, culled and resuspended in clean seawater in the tanks. At the end of their swimming larval cycle, over 6.8 million eyed larvae were transferred to downweller sieves with crushed oyster and eggshell cultch provided as setting surfaces for the metamorphosing larvae.
Set juveniles were held for several weeks in closed, heated seawater systems before being moved to slow flows of bag filtered ambient seawater. Shortly thereafter, an increase in mortalities, apparently due to biofouling, was observed. Despite these mortalities, more than enough seed oysters were available for the project. As ambient seawater temperatures rose in May, the oyster seed was moved to upweller silos in the MVSG shellfish nursery on Chappaquiddick.
2000-- Single oyster seed was also produced for the project in 2000. Using the same methods employed in 1999, 28 broodstock oysters were conditioned for spawning over an eight week period culminating in a successful spawning on 23. May of over 54 million eggs. Following a 3 week larval culture period, the swimming larvae metamorphosed into spat which cemented themselves to crushed poultry shell provided on downweller sieves in heated, closed systems of recirculating seawater enriched with cultured phytoplankton food. The effort resulted in the production of over one million (2mm and larger) single oyster seed.