During 2002–2004 a voluntary, profit sharing harvesters’ co-operative was allowed to operate in the Chignik Salmon fishery in Alaska. Regulators split the fishery’s total allowable catch between the co-op and independent harvesters. Our economic model predicts that the co-op would centrally coordinate its members’ activities, resulting in more efficient effort deployment than in the independent fleet. Empirical analysis of relevant data supports these predictions. We find that, in contrast to the independent fleet, the co-op concentrated effort among its most efficient members, fished closer to port, spread harvesting over a longer time span, and shared information on stock locations.