What is as clear as the pristine seas north of Norway, Sweden, Iceland, Finland, Denmark (including Greenland), Russia, the United States, Canada is that fish will only travel where they can find enough food. That's why many marine scientists are trying to better understand current and future primary productivity there. "We are talking about some of the most productive ecosystems found in the waters adjacent to the Arctic Ocean," said Paul Wassmann, an Arctic biologist at the University of Tromso. These waters are brimming with Greenland halibut, cod, capelin, Kamchatka king crab, along which those higher up in the food web--whales, seals and other marine mammals. He cautioned, however, that it is "an open question" how shifts in primary productivity in various locations will translate into fish stocks.