The USDA just released a census of Aquaculture in the US.  As far as I can see, the data has some serious limitations--and it is not the fault of the USDA.  It was a voluntary survey and the results show that the majority of farms didn't return the surveys.  Here are a couple of highlights:

1) Alabama: USDA says there are 3 mollusk farms in Alabama.  Bill Walton of Auburn University count 22 farms.  I can list off 19 farms.  In other words, ~15% of the active farms Alabama are included.  

2) Maryland: USDA has 30 mollusk farms.  Matt Parker of Maryland Sea Grant counts over 100 leaseholders in Maryland. Roughly 30% of farms included.  In addition, there is one mystery farm in Maryland that sold over 23 million shellfish--more than the entire state reported in the previous year. 

3) Maine:   USDA has 42 mollusk farms. Maine Aquaculture Association counts over 190 farms. 22% of farms included.  

This by no means scientific, but my sample of three shows huge variations from reality (insert joke about Washington reality here).  

Although funny, it does matter.  Government support on issues like better crop insurance and disaster relief, support for research programs on better seed, policies on fair use of public waterways, and Jones Act exemptions all often hinge on the value of the industry.  If the government is significantly under counting the shellfish industry it really matter.  

Next time you get that survey?  Probably worth filling out.