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Due to deteriorating environmental conditions in the Pacific Ocean and coastal estuaries, shellfish hatcheries in the Pacific Northwest are unable to produce adequate oyster seed for farmers. The problem is further evidenced and compounded by the fact that there has been virtually no natural (wild) oysterseed set in Willapa Bay for four years. Willapa Bay relies heavily on wild set oyster seed and, as the largest producer of oysters on the West Coast (more than 50%), the West Coast oyster industry is facing imminent collapse.
Bivalve mollusk culture is the most important marine aquaculture activity on the Pacific Coast of the United States. As of 2005, the annual commercial production of oysters, clams, geoduck and mussels on the West Coast had a farm-gate value of $111 million (Pacific Coast Shellfish Growers Association and Western Regional Aquaculture Center). Out of this total, oyster production made up 76% of all shellfish produced, with a farm-gate value of $85 million. West Coast farms employ approximately 3,000 employees, and including related service sectors and suppliers, the total economic contribution of shellfish aquaculture on the West Coast is estimated to be approximately $278 million annually.
Environmental conditions in the Pacific Ocean off the Oregon and Washington coasts and adjacent estuaries such as Puget Sound, Willapa Bay, and Netarts Bay have severely impacted hatchery production of seed oysters upon which both large and small farms depend. Simultaneously, wild sets of oyster seed that make up the back-bone of the oyster industry in Willapa Bay, the single largest oyster producing region on the West Coast, have been virtually non-existent for the past four years. These conditions have led to dire economic consequences for two of the four hatchery operators that produce oyster seed for farmers, including the largest producer of oyster larvae on the West Coast that accounts for approximately 75% of all larvae utilized by farmers. Without emergency action, these hatcheries and the shellfish farmers that depend on them may be forced to close or markedly curtail their businesses in the next few months. Aside from the loss of shellfish for human consumption, jobs will continue to be lost and the economic impact to coastal communities will be significant. Furthermore, significantly reduced populations of bivalves, a critical keystone species in the marine ecosystem, is bound to have significant environmental consequences. The reduction in water filtering performed by these shellfish will impact water quality, and diminished shellfish assemblages will reduce forage and refuge opportunities these three dimensional structures normally provide for a host of marine flora and fauna.
Shellfish hatcheries have historically used coarsely filtered but otherwise untreated seawater for larval culture with few problems, and larval shellfish have thrived in water in the Pacific Ocean and coastal estuaries. Upwelling of deep, cold, nutrient-rich water from the continental shelf off the coast of Oregon and Washington is typical during summer months in this region and drives high primary productivity. Since 2003, however, increased areas and intensities of deep acidic, hypoxic water have been reported off the Oregon and Washington coasts, which have contributed to the formation of persistent dead zones. These events have produced fundamental changes in the character of our coastal bays, which contribute to high larval mortality throughout the entire year.
For the past four years, ocean conditions in the Pacific Ocean have caused massive oyster seed mortalities in two of our largest shellfish hatcheries, and for the past four years, there has been virtually no natural set of oyster seed in the largest oyster producing region on the West Coast – Willapa Bay, and very little set in Hood Canal, another major growing area in Washington. Based on the past four years, and assuming nothing is done to intercede, the total contribution of shellfish aquaculture to the economy is projected to be reduced by at least 30 percent in the year ahead – approximately $83 million - with even steeper declines in the years ahead as broodstock populations in the wild become more depleted.
A team made up of oyster growers, hatchery personnel, scientists, and USDA and NOAA staff have banded together to forge solutions to these problems, with a goal of implementing various short-term as well as long-term solutions in hopes to prevent the collapse of this economically and environmentally valuable industry. One of the identified priorities was to accelerate studies to establish on-site, real-time sensitive and specific assays for pathogenic vibrio bacteria, particularly V. tubishii, that will enable hatchery operators to take immediate action with known management methods to prevent infections.
V. tubiashii and other pathogenic vibrios were recognized in the 1960’s as a significant shellfish pathogens but commercial production is still plagued by the often rapid onset of vibriosis and high mortality rates. Low-level chronic exposure to the pathogen is even more insidious, causing developmental deformities and slow growth that waste culture resources and eventually kill larvae and juvenile product. Intensive work by our team demonstrated that the secreted toxin (a metalloprotease released by the bacteria) is a highly efficient killer of shellfish seed.
Once the presence of pathogenic vibrios can be confirmed in hatchery water, incoming seawater, larvae or juvenile shellfish, actions can be taken to manage and reduce the impact of the disease. While additional refinement of water treatment methods will undoubtedly contribute to an overall solution, hatchery management experience and detailed research to date shows that the impact of marine hatchery vibriosis can be prevented in many cases and greatly reduced in nearly all cases if early detection is possible. This reduction has proven effective in commercial hatcheries by applying known effective management and sanitation methods and providing the knowledge for hatchery managers to be able to make production decisions based on the known risk of exposure to vibriosis. Thus, the primary impediment today for marine hatcheries to make such management decisions is the lack of an on-site, real-time sensitive diagnostic method for the early detection of vibriosis. Diagnosis can be made with laboratory support, but involves a time lag of two to four days. The development of a specific antibody-based method usable in hatcheries, for the detection of Vibrio tubiashii and its primary known toxigenic factors, would markedly advance the productivity and efficiency of marine hatcheries. Previous work by the Häse lab has shown that the extracellular metalloprotease secreted by V. tubiashii is highly toxic to Pacific oyster larvae. The development of a fieldable, rapid, reliable, sensitive and cost-effective early detection method for the pathogen and its key secreted toxic protein would have an enormous impact on the effective management of water quality in shellfish hatcheries and can be expected to ultimately help this entire industry to survive this challenge.