Traditionally, bivalve shellfish aren't harvested in months that don't have an R in them on the west coast, because of the potential for Red Tide poisoning. That would be May, June, July and August. There is a ryhme, that I can't remember right now, that reminds people of this. The red is caused by a blum of Diatomacious(sp?) algea which excrete a neuro-toxin when touched. Most shellfish can deal with the toxin but most fish, birds, and all mammals are suceptable if taken internally in varying amounts. The shellfish quickly become poisonous themselves.

Tight lines,
Wade