After their “discovery” by R. H. Espy and Isaac Clark,
oysters became big business on Washington State’s Willapa Bay in the 1800s.
(1,2) Vast quantities of the mollusks were shipped to California in the decades after the
Gold Rush. Naturally this overharvesting depleted the native oyster population, which led to the introduction of non-native oysters such as the
Eastern Oyster (Crassostrea virginica) and later the Pacific or Miyagi Oyster (Crassostrea gigas) from Japan.
Unfortunately during the transplantation of the Eastern oysters, an invasive species of cord grass (aka Spartina) was introduced to the Bay. At first it went almost unnoticed, but over the decades the grass continued to spread across the intertidal mudflats. In 1991 Spartina covered about 2,500 acres, but by 2002 it had spread to 15,000 acres, or about one-third of the Bay’s tidal area..(3)
As Spartina began to choke out the open tide flats, it started to wreak havoc on the Bay’s $30 million dollar oyster industry, and also had a negative impact on native shore birds and salmon. Efforts to eradicate the grass began in the 1990s, at first concentrating on mechanical methods such as mowing and pulling the grass to avoid polluting the bay with chemicals. Due to their dense roots, these mechanical methods were ineffective, so more aggressive chemical means were required.
Happily, these efforts appear to be successful and Spartina has been almost completely eradicated from the bay. Unlike some invasive species whose seeds can be viable for decades, Spartina’s seeds have a life span of only one year, so the goal of eradication is possible. “To contrast eradication with control… Once eradication is accomplished, treatments can stop; with control, treatments must continue year after year into the future without end.”.(4)
- Chief Nahcati’s role in the discovery of oysters: http://sydneyofoysterville.com/tag/nahcati/
- Univ of WA info on Willapa Bay’s oysters:
http://depts.washington.edu/jlrlab/historical.php
- Spartina growth: http://www.ecy.wa.gov/programs/sea/coast/plants/spartina.html
- Spartina Survey Report 2011: http://www.onrc.washington.edu/MarinePrograms/SpartinaSurvey2011.pdf