Shellfish
This indicator describes opening and closure status and trends in commercial shellfish areas in Puget Sound, and trends in direct-harvest closures in Georgia Basin. The indicator also describes the implications of shellfish area closures for the economy, human health and community traditions throughout the Puget Sound Georgia Basin.

Why is this happening?

Shellfish need clean water to thrive and for humans to safely eat them. The pathogens and bacteria that can make shellfish eaters sick make their way to the marine waters along four main pathways:

• Direct discharge into marine waters from such sources sewage outfalls, boaters, and marine mammals;
  
• Polluted drainages (ranging in size from bulkhead storm drains to rivers) that carry wastes from the shoreline and land situated upland from the water;
  
• Subsurface (directly under the ground) flows from shoreline on-site sewage systems; and
  
• Polluted surface runoff from parking lots, lawns, pastures and other developed areas that contain chemicals, oils, pathogens and other contaminants.
  

Reported Causes of Shellfish Closures in the Georgia Basin in 2004

Natural:

• Wildlife, seals and hinterland drainage

Human-caused (Anthropogenic):

• Marine vessels/marinas vessels – discharges, marinas, wharves, ferries, float homes, float camps, boat anchorage, cruise ships, grey water waste
  
• Sewage discharges – septic seepage, sewage outfall, sewage treatment plants, raw discharge, sewage, straight pipe, sewage lagoons, server overflow
  
• Runoff – upland runoff, urban runoff, urban drainage, agricultural runoff, sheep, livestock, rural runoff
  
• Multiple sources – combination of any of the above as well as non point source pollution, unknown sources and combination sources
  

Shellfish Closures by Probable Cause, Georgia Basin, 2004
Cause	Hectares
Natural	339.85 (0.5%)
Marine Vessels	2078.03 (2.9%)
Sewage Discharge	2564.80 (3.6%)
Runoff	16,375.05 (22.9%)
Multiple Sources	50,142.62 (70.1%)
Total	71,500.36

Source: Environment Canada Shellfish Closures

Key Sources of Pollution

Urbanization and Polluted Runoff

The greater the degree of urbanization, the greater the threat to shellfish growing areas.³ Urbanization is defined as the transformation of natural landscapes, such as wetlands and forests, to built environments. These built environments contain large swaths of impervious surfaces such as concrete, asphalt, roofs and other materials that quickly carry pollutants to the inland waters of the Puget Sound Georgia Basin. In Puget Sound, the eastern shoreline stretching from Everett to Tacoma is so developed that it prohibits commercial shellfish harvesting in the adjacent tidelands.

Sewage and Septic System Discharges

Sewage from malfunctioning sewage treatment plants, weaknesses in aging sewage collection systems, and failure of home on-site septic systems release fecal coliform (waste) and other dangerous bacteria and pathogens into shellfish growing waters. In the U.S., there are automatic closure zones (zones of safety) around Sewage Treatment Plant outfalls, Combined Sewer Overflows in a few places, and other occasional problems with the systems. However, because most shellfish growing areas are located in rural areas, the biggest threat is from failing septic systems and animal farms.

Marinas and Boaters

Some boaters do not discharge their waste into pump-out stations, but rather discharge human waste directly into marine waters. In addition, if marinas do not have adequate pump-out facilities or have structural weaknesses in their operations, additional raw sewage may be discharged. The Puget Sound has an estimated 279,000 boats for recreational use.⁴ Untreated discharge from one weekend boater is equivalent to discharging treated sewage into the water from a city of 10,000 people.⁵

Farm and Domestic Animals

Animal waste from farms enters shellfish growing areas from runoff and the problem can be exacerbated with large animal feeding operations. When farm animals enter streams, or manure washes off pastures, or manure lagoons are improperly managed, raw feces enter shellfish growing areas during rain events. Our pets are no less a problem. EPA estimates that for watersheds of up to twenty-square miles draining to small coastal bays, two to three days of droppings from a population of about 100 dogs would contribute enough bacteria and nutrients to temporarily close a bay to swimming and shellfishing.⁶

Naturally Occurring Events

In addition to human-influenced factors, shellfish beds can close due to biotoxins including paralytic shellfish poisoning (PSP) and domoic acid, which are produced by certain phytoplankton, and from naturally occurring bacteria such as Vibrio parahaemoliticus. Although originally a coastal phenomenon, domoic acid, which produces amnesic shellfish poisoning (ASP), caused the closure of several areas in Puget Sound this year.

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