How often are NH waters closed due to Red Tide?
NH shellfish waters are closed for harvesting when the PSP toxin levels in blue mussels reach 80 micrograms of poison per 100 grams of mussel tissue. However, PSP toxin levels can change very rapidly over the course of just a few days. Therefore, waters may be closed for lower amounts of toxin, especially when NH stations are showing rising levels of toxin, and nearby stations in southern Maine or northern Massachusetts are showing levels higher than the 80 microgram limit. High levels of toxin and resultant closures to shellfishing have occurred with greater frequency in recent years. After a period of generally low toxicity and few closures from 1994 through 2003, high toxin levels have been observed each year at Star Island since 2004, with the highest toxin levels recorded during the historic red tide closures in the summer of 2005. Offshore closures have typically begun in May and have remained in place until mid-to-late summer. High toxin levels have also been more frequent in ne
