Shaking oyster bags is an important part of oyster farming. Oyster farmers shake bags for several reasons:
To Increase Water Flow
Oysters are filter feeders – they feed by filtering water through their gills and ingesting plankton and other nutrients. Shaking the bags increases water flow through the oyster bags. This brings fresh seawater containing plankton and nutrients to the oysters so they can continue to feed and grow.
Oysters that don’t get enough water flow can suffocate or starve. Shaking the bags prevents stagnant pockets of water inside the bags and ensures each oyster gets plenty of fresh flowing seawater.
To Strengthen the Oyster Shells
Oysters have fragile shells when they are young. As the oyster grows, the shells harden and become stronger. Shaking exercises the oyster adductor muscle that opens and closes the shell. This muscle activity strengthens the growing shells.
Strong shells protect the oyster meat inside. Weak, brittle shells are prone to damage from predators like crabs and oyster drills. Shaking bags develops hardy oysters with sturdy shells that can withstand harvesting, shipping, and shucking.
To Prevent Clumping
Oysters are social creatures and tend to attach to each other forming clumps if left undisturbed. Shaking the bags breaks up any clumps and prevents the oysters from cementing together.
Clumped oysters can suffocate each other by blocking water flow. Shaking ensures each oyster has space and access to fresh flowing seawater.
To Clean the Shells
Shaking dislodges dirt, debris, and biofouling that collects on the oyster shells. This keeps their shells clean for optimal growth. The abrasion from other shells rubbing together scours away accumulations.
Clean shells allow better water flow, gas exchange, and feeding. Oysters with crusted or fouled shells may have trouble opening and closing properly.
To Distribute Space Evenly
As oysters grow, the ones in the middle of a clump tend to get crowded while excess space remains around the outside. Shaking redistributes them evenly throughout the bag.
Even spacing ensures all the oysters have enough room to open their shells fully for feeding and optimal growth. No oyster is trapped in the middle getting stunted.
To Monitor Size
Shaking allows the oyster farmer to inspect samples of the growing oysters. Size and growth rates can be checked to determine if the oysters are thriving.
If growth seems slow, steps can be taken such as moving the bags to an area with more plankton. Regular shaking and monitoring ensures optimal growth.
To Condition the Meat
The adductor muscle that opens and closes the shell is the oyster meat people eat. Shaking exercises and tones this muscle. The result is firmer, more robust oyster meat.
Conditioned meat has a longer shelf life and better texture when shucked. Shaking produces premium grade oysters with quality meat.
To Prevent Pests
Shaking removes mud worms, parasites, oyster drills, and other pests that may be present. It disturbs their habitat and dislodges them from the shells.
Pests can damage or weaken the oysters. Shaking discourages infestations and keeps the oysters healthy.
When and How Often to Shake Bags
Oyster farmers shake the bags frequently in the first 6 months while shells are fragile and clumping is common. Vigorous shaking 2-3 times per week is typical during this rapid growth phase.
After 6 months, when shells harden, shaking frequency can reduce to 1-2 times per week. Gentler shaking is sufficient to provide water flow, prevent clumping, and monitor growth.
The table below summarizes a typical shaking schedule:
| Oyster Age | Shaking Frequency | Shaking Intensity |
|---|---|---|
| 0-6 months | 2-3 times per week | Vigorous |
| 6-12 months | 1-2 times per week | Moderate |
| 12+ months | 1 time per week | Gentle |
Additional shaking may be warranted during spawning season or in response to water conditions and growth rates.
Shaking Methods
Several methods exist for shaking oyster bags:
Manual Shaking
Farm workers manually pick up each bag and shake it vigorously. This is labor intensive but allows thorough inspection of each bag.
Mechanical Tumblers
Bags are loaded into large mechanized tumblers that rotate and agitate them. This automates the shaking process but doesn’t provide the same visibility.
Boat Wake
No active shaking required. Bags are arranged so boat wake provides enough motion to prevent clumping and fouling.
Longline Rocking
Bags hung from longlines are rocked by waves and tidal currents. Eliminates labor but provides less control over frequency and intensity.
Conclusion
Shaking oyster bags is a vital practice in oyster aquaculture. It provides water flow, exercise, cleaning, pest control and conditioning that results in robust oysters with premium meat quality. Understanding the reasons for shaking oyster bags helps farmers optimize results.