Clams

The offshore clam fishery on Canada's East coast started with a test fishery on the Scotian Shelf in 1986. Since that time the fishery has expanded to Grand Bank, and developed into an industry that employs approximately 450 people with annual sales exceeding $50M.

figure 1 - Landings and export values for the Arctic Surfclam fishery
Landings and export values for the Arctic Surfclam fishery

The fishery uses large freezer-processors (Figure 2), to harvest the surfclams, most of which are exported.

figure 2 - The Ocean Concord, one of the vesssels fishing for Arctic Surfclams
The Ocean Concord, one of the vesssels fishing for Arctic Surfclams

The clams have a purple color on the outer section of the foot, siphon and mantle, which turns red when blanched, similar to lobster and shrimp. The red and white coloration made it attractive to the sushi and sushimi market, where it commands a high price.

figure 3 - Package of processed blanched surfclams.  The main product is the foot portion, and blanching produces the red coloration, similar to lobster or shrimp
Package of processed blanched surfclams. The main product is the foot portion, and blanching produces the red coloration, similar to lobster or shrimp

Japan was the initial market, as it is similar in appearance to a local species, the Japanese hen clam, but the market has expanded to China and southeast Asia. Currently Japan and Hong Kong are the largest consumers.

figure 4 - Destination countries percentage exports by weight for Arctic surfclams for 2010
Destination countries percentage exports by weight for Arctic surfclams for 2010

As the fishery has progressed it has started looking at other large clam species, especially Ocean Quahogs (Arctica islandica), Greenland Smoothcockles (Serripes groenlandicus) and Northern Propellerclams (Cyrtodaria siliqua) (Figure 5)

figure 5 - Large clam species of commercial interest in the Maritimes Region.  There is a currently a commercial fishery for the Arctic Surfclam (Mactromeris polynyma) and a licence for Ocean Quahogs (Arctica islandica).  The Greenland Smoothcockles (Serripes groenlandicus) and Northern Propellerclams (Cyrtodaria siliqua) are currently caught as a by-catch in the Arctic Surfclam fishery
Large clam species of commercial interest in the Maritimes Region. There is a currently a commercial fishery for the Arctic Surfclam (Mactromeris polynyma) and a licence for Ocean Quahogs (Arctica islandica). The Greenland Smoothcockles (Serripes groenlandicus) and Northern Propellerclams (Cyrtodaria siliqua) are currently caught as a by-catch in the Arctic Surfclam fishery

Although some of the species involved in the fishery such as Ocean Quahogs, are well studied, others, such as the Artic Surfclam, Greenland Smoothcockle and Northern Propellerclam, are not, and very little is known about their life history. Growth rates for these species on the Scotian Shelf are currently being studied. The longest lived of these species is the Ocean Quahog. The oldest quahog aged to date from Sable Bank was 210 years old, and there has been one aged from Iceland at 405+ years. This has large implications for management of a fishery, as it means that productivity will be low and the allowable catch will be a very small percentage of the biomass. Although faster growing than Ocean Quahogs, most of the clam species of commercial interest , including the Arctic Surfclam, have relatively long life spans. This influences management methods and types of scientific studies being done to provide advice on these species. Low harvest rates and long life spans mean that there will be little detectable change in biomass, due to fishery or natural processes, on time scales of a few years to a decade or more.

The offshore clam fishery is one of few fisheries where surveys and associated research have taken place at the start of the fishery. This means that data from the unfished populations is available for comparison as the fishery develops. This should help ensure the development of a sustainable and stable fishery.

The results from the Sable and Banquereau surveys illustrate the distribution of different large bivalve species on the eastern Scotian Shelf (Figure 6).

figure 6 - Catch of major bivalve species caught during the Sable Bank (2003) and Banquereau (2004) offshore clam surveys
Catch of major bivalve species caught during the Sable Bank (2003) and Banquereau (2004) offshore clam surveys

For more information, click the posters below.

figure 7 - A poster detailing information on clam ageing
A poster detailing information on clam ageing
figure 8 - A poster detailing information on the Arctic Surfclam fishery
A poster detailing information on the Arctic Surfclam fishery