Entire bio sector has been getting hammered lately, it's not just AMRN - see http://data.cnbc.com/quotes/XBI/tab/2 for last 5 days, compare to NASDAQ biotech index too (XBI). Only one of my bios (have 5) have been up in the last week, POZN, on no news/low volume - likely just HFT's pushing it up to short it again - happens almost once a month with that stock.