The shrimp fishery has been reclassified from a Category III to a Category II fishery under the Marine Mammal Protection Act. That means all shrimp vessels must have an authorization certificate onboard.
More info is here, and the certificate can be downloaded and printed from two different links on this page.
http://sero.nmfs.noaa.gov/pr/mm/mmap.htm
Commercial shrimpers with valid permits are automatically registered for the program, but will need to carry the certificate with them while at-sea.