Sea Grant: Pacific Oysters "may be in the early stages of a full-fledged, non-native species invasion."

Non-native Pacific oyster

from Drakes Bay Oyster Company

They grow bigger, faster.



Sea Grant writes in a July 2, 2013 article that the Pacific oyster "may be in the early stages of a full-fledged, non-native species invasion." The article goes on to note:

The traits that make it so suited to culture could also make it a formidable invader..."Our worry is that native oyster restoration efforts may backfire and we will end up creating habitat for the invasive oyster,” said Danielle Zacherl, a professor at Cal State Fullerton, who has been documenting the Pacific oyster’s spread in San Diego and Orange counties and is involved in native oyster bed restoration in Southern California.

Native Olympia oyster (left)

vs. Invasive Pacific Oyster (right)

 

Drakes Bay Oyster Company has claimed that the waters of Drakes Estero are "too cold" for the non-native invasive Pacific oysters it cultivates to spawn in. However, this is strongly countered by the introduced population of Pacific oysters in Willapa Bay, a similar estuary, almost 600 miles to the north on the coast of Washington state which experienced a commercially sized "set" last year and appears poised for another this year.

Nature finds a way
While in recent years the Pacific oyster had no natural sets of commercial size in Willapa Bay, perhaps due to ocean acidification, perhaps due to various chemical treatments of "aquaculture pests" by the shellfish industry (e.g., native Ghost shrimp, a primary food source for the Green sturgeon, an ESA Species of Concern), last year saw a "set" in commercial numbers. This summer, gonads have developed in the Pacific oysters. With the continued warm weather an environment suitable for spawning and another natural set in commercial quantities is most likely in the making.

Drakes Estero National Seashore

Schooner Bay and Drakes Bay Oyster Company

Drakes Estero is similar to Willapa Bay and in some ways more conducive to Pacific oysters. For example, with only a small stream draining into Schooner Bay, it takes up to 20 days to flush this shallow finger in Drakes Estero. The very same finger where Drakes Bay Oyster Company's facilities are located. Similar to portions of Willapa Bay which take weeks to flush (click here for an interactive map representing flush rates for Willapa Bay), Schooner Bay's resident time of up to 20 days for waters allows it to have higher temperatures than the main body of the Estero. The other "fingers" of the Estero are similar. Global climate change will only add to the probability of a habitat conducive to this invasive species of oyster displacing any native populations.

As noted in the Sea Grant article:

“The stars have aligned for it [the Pacific oyster] now, and we don’t know why, but it’s worth tracking because of its ability to massively modify habitats,”

Unless the non-native and invasive Pacific oyster in California is contained it will find itself in the same situation as Willapa Bay to the north - another ecosystem transformed by the shellfish industry at the expense of native species.