Expansion of federal waters red tide closure for a public health emergency : environmental assessment Emergency action to close waters to the harvest of gastropods due to paralytic shellfish poisoning (PSP) environmental assessment (RIN 0648-BD84)

"This action will prohibit the harvest and possession of gastropods from the areas referred to as the Temporary PSP Closed Areas, which are currently closed to the harvest of bivalves but not gastropods. Gastropods include carnivorous snails and whelks that feed on bivalves. The bivalves, if contaminated with the toxin that causes PSP, transfer the toxins on to the whelk when ingested. While there are not a lot of data available on how susceptible gastropods are to PSP, the little data that are available indicate that gastropods typically have higher levels of PSP and retain it longer than bivalves taken from the same waters. Gastropods feed on bivalve molluscs and may accumulate and retain much higher levels of toxicity. In 2006, a year following the initial closure for the harvest of bivalves, whelk and moon snails were found to contain toxins in excess of the guidance level; however, gastropods were not included in the initial closure because there was no commercial harvest at that time"--Cover letter.