D. Albrey Arrington of the University of Alabama in Tuscaloosa and his colleagues have done plenty of fishing, mostly in rivers and marshes. They've caught bass in North America, eels in Africa, and piranhas in the neotropics. In all, they've landed nearly 38,000 specimens–representing 254 species–and meticulously tallied how many had empty stomachs.
Their data, reported in the August Ecology, show that many fish eat all the time, while some others spend the majority of their days running on empty.
Though just 16 percent of the total catch had empty stomachs, the chance of finding such fish tended to correlate with species. Members of some species always bore evidence of