In this April 2011 photo released by the U.S. Geological Survey, Alaska Fish and Game researchers return to a base camp for a study examining the preferred diet of invasive northern pike in Alexander Creek in the Susitna Basin of south-central Alaska. A federal and state study says northern pike that gobble up salmon fingerlings in Alaska streams can thrive long after that valuable species has been decimated. The study concludes that nonnative pike prefer juvenile salmon but will turn to other native fish when salmon are less abundant. (AP Photo/U.S. Geological Survey, Adam Sepulveda)
