Spawning Shellfish: Broodstock & Conditioning

An adult clam and oyster.

Broodstock clams being cleaned before going into the conditioning tank.

A well conditioned clam gonad.

A group of broodstock oysters.

Have you ever wondered how a hatchery produces millions of shellfish? Shellfish reproduce through spawning. Spawning is the release of male and female gametes into the water column for fertilization to take place. In order to spawn shellfish in a hatchery setting, you need shellfish! 

The term broodstock refers to a group of mature individuals that are used in aquaculture for breeding purposes. These shellfish are usually selected based off of certain qualities such as known gender, fast growth, size, disease resistant, color morphs, and general health. Once selected, the broodstock’s shells are thoroughly scrubbed and rinsed to remove any fouling, organisms, or sediment before bringing them inside the hatchery. The broodstock are often split into several different groups to spawn over a period of time

Four conditioning tanks and a look at our algae SEACAP bag system.

Prior to spawning, the broodstock go through a conditioning period. Conditioning is the process of inducing the gonad, or the reproductive gland containing gametes, to mature and prepare the shellfish to spawn. During this period, they are placed into special conditioning tanks. These tanks are equipped with a heater/chiller to regulate the temperature. To acclimate the broodstock, the temperature is gradually increased over time to reflect warmer spring water temperatures. This temperature is then held for several weeks while the gonad develops. Throughout this process, the shellfish are fed a diet of nutrient rich cultured microalgae. The broodstock are held in these conditioning tanks for 4-8 weeks. The tanks are cleaned every other day leading up to the day of the spawning event. 

Currently, we have both clams and oysters conditioning in our hatchery! Follow us here, and on our social media, to learn more each week and to stay up to date with what’s going on in our hatchery!