Phase Two - Red Rock Crab Predator Management

Summary:
Intertidal shellfish culture is under intense predation from the Red Rock Crab at some sites in B.C. This project involved the installation of four styles of subsurface barriers to test the success of the system in getting crabs to exit a barrier that lead away from the seeded shellfish farm area into deeper habitat. The treated area was contained within a trench boundary, and an adjacent non-treated area was used as a control in the trials. In the trials, both the treated area and the control area had 300 oysters laid out in a similar method.

The main objective of the study was to determine if the Crab Trench Trap was effective in reducing the crab predation. We had expected that several crabs could remain in the trench system and either leave, succumb to high temperature, or be preyed upon by birds. Now we are certain that the crabs did exit through the trench system, it promises to be a non-lethal approach to predator management.

The study as conducted did provide strong support for the objectives of the research.

• Documented a high degree of crab predation on intertidal oyster culture.
• The trenches have minimal siltation over the winter storms.
• The larger trenches reduce predation on intertidal shellfish.
• This results in increased production and reduced seed costs.
• This allows a larger portion of the tenure useable for grow out.
• This results in increased production per area.
• This improves the market value of the land for the farmer.

Project Lead: Below Sea Level Oyster Co.

Total Project Cost: $18,400
           
DFO-AIMAP Contribution: $10,000

Other Financial Support:

• Recipient: Below Sea Level Oyster Co.
• Dr. Chris Pierce & Ms. Kerry Marcus

For more information please contact the regional officer.

Pacific Region: Sean.Irvine@dfo-mpo.gc.ca