Shellfish Enhancement

cockleweb

Razor Clams, Littleneck Clams, Cockles (pictured above) and Purple-Hinged Rock Scallops

Shellfish have been a major component of Alaskan’s subsistence, recreational and commercial fisheries. In recent years populations have dramatically decreased to where the fisheries are closed and opportunity lost.  Some of the most common causes cited are decadal shifts in oceanographic conditions, increased predation, over harvest and habitat degradation.   APSH has led several shellfish enhancement projects based on the out-planting of juveniles. Shellfish enhancement is a tool used to repopulate areas that have suitable habitat for shellfish but for some reason do not have viable populations. Some of the prospective causes are predation and highly variable recruitment due to temperature changes and limited contributing populations. Shellfish are stocked on beaches, with predator control netting and allowed to grow to harvestable size. Many of the shellfish are left unharvested to serve as a spawning sanctuary. Littleneck clams were enhanced near the villages of Tatitlek, Chenega Bay, Eyak and Valdez in the Prince William Sound and Port Graham and Nanwalek in lower Cook Inlet.
Many of the hard shell clam populations such as cockles, littleneck clams and butter clams are at historically low levels throughout south central Alaska. The cause of the decline in these populations is unknown but it’s likely a combination of factors such as predation, over harvest, environmental changes and irregular recruitment. The Chugach Regional Resources Commission, operator of APSH, has made investigating clam restoration a priority to help maintain healthy food options for residents in coastal communities. CRRC has been developing clam restoration techniques focused on creating shellfish sanctuaries. Areas are selected near villages where clams once existed. The beach area sampled applying a Habitat Suitability Index to insure that the area can support clam populations. Adults are collected and aggregated in an area where they are protected by netting or rocks. These adults are sampled to determine if and when they become reproductive. The same beach areas seeded with clams produced at APSH. The juvenile clams are monitored to determine their growth and mortality. Tracking the complete lifecycle of the clams will help determine the potential for bottleneck populations recovery.

 

Seeding littleneck clams at Powder Island near Seldovia

         
 

Seward High School students assisting in beach surveys

       
     

Juvenile butter clam after a year of growth near Port Graham

           

Daisy, David, J. Hetrick, K. Brooks, and J. Agosti. 1998. Clam Restoration Project, Exxon Valdez Oil Spill Restoration Project Annual Report (Restoration Project 98131), Chugach Regional Resources Commission, Anchorage, Alaska