Willapa Bay: Critical Habitat for Green Sturgeon, a
A study by Kim Patten with Washington State University has shown strong support for the use of the longline ("off bottom") method to grow oysters in beds which have burrowing shrimp in Willapa Bay. Willapa Bay was listed in 2009 as critical habitat for the endangered southern distinct population (SDP) of the Green Sturgeon, once far more abundant. Unlike salmon who pass through this important estuary on their way to the open ocean, the Green Sturgeon relies "...heavily on estuarine habitats over their lifespans." (from 2009 listing) Included is reliance on burrowing shrimp as a food source.
2009 Habitat Listing Challenged by Pacific Legal Foundation
Earlier this year the Pacific Legal Foundation (PLF) asked the Supreme Court to review whether regulators had the discretion to determine whether to not exclude areas from being considered critical habitat. The court ruled those decisions are not subject to judicial review. It is unlikely the Supreme Court will consider Mr. Damien's case during the Long Conference, scheduled for September 26. (see here for PLF's response brief)
Not to Exclude is still discretionary.
While not involved in the lawsuit, in comments to NMFS on the then proposed 2009 decision, shellfish growers in Willapa Bay did ask for shellfish beds to be excluded from being considered critical habitat during the comment period. In response to that request, the National Marine Fisheries Services responded:
"Telemetry data show that tagged green sturgeon disperse widely throughout these estuaries, most likely for foraging. In addition, anecdotal accounts have noted observations of sturgeon in intertidal aquaculture beds in the past, likely when populations of sturgeon were more abundant in these estuaries."
Can oyster growers, an endangered specie, and that specie's food source co-exist?
According to Mr. Patten's recently published study, yes. His study finds an abundance of "foraging pits" in areas using longlines to grow oysters with burrowing shrimp >10/square meter. In fact, it was only in areas with no shellfish activity the forage pits were in greater density. Further, in a study published in 2007, it noted that "... these large predators [Green Sturgeon] may have performed an important top down control function on shrimp populations in the past when they were more abundant."
Bad conclusion to a good study - there is not a "surplus of foraging habitat". There are lower numbers of Green Sturgeon. It's why they're endangered.
As highlighted in the comments quoted above, sturgeon used to be more abundant. So much so one of the studies believes Green Sturgeon may have both played an important role in controlling shrimp populations and, contrary to Mr. Patten's observations, included shellfish beds in their foraging (something which would seem to support the grower's statement that shellfish beds improve the habitat). One of the stressors which reduced their population has been the past use of the pesticide Carbaryl by shellfish growers. Loss of spawning habitat and over-fishing no doubt also played roles as well. But the important point is the population of Green Sturgeon is not what is was. That is why there appears to be a "surplus of foraging habitat" and, more importantly, why they are considered endangered.