A fishing-boat dock at Grimsby, U.K., at the turn of the 20th century. Over the last century or so, trawlers have gotten more powerful engines, fish-detecting radar, lighter nets, and vast onboard freezers. What the fleets might really need, though, is a time machine.After all, bottom-fishing fleets in United Kingdom waters today have to work 17 times harder to catch the same amount of fish as their sail-powered Victorian counterparts did, according to a new study.To address innovations have made fishing more efficient over the years, the study authors devised a new measure: units of "fishing power."After analyzing historic...