As was reported, about 30 thousand tonnes of herring died in Kolgrafafjord in December 2012 and specialists from the Marine Research Institute repeatedly visited the site this past December and January. On February 1 a second mass death was observed in Kolgrafjord. A group of specialists from the Marine Research Institute returned to Kolgrafafjord on Monday, February 4 aiming to study the environmental conditions, to estimate the amount of dead herring and the size of the area affected. The study was conducted onboard the boat Bolli SH. The study included oceanographic conditions (temperature, salinity, oxygen) and inspection of the bottom by underwater camera. In addition, the beaches were closely inspected and the amount of dead herring on the shore was estimated. The preliminary analysis is completed.