A Test of Swarm Intelligence with Great Uncertainty: Can Anglers Estimate the Size of a Harvestable Fish Stock in a Fishery They Manage as a Community?

Swarm intelligence is generally the realisation that group living can facilitate solving cognitive problems that go beyond the capacity of single individuals. In German freshwater fishing clubs, the “swarm” of anglers organized in a club are not only users of local fisheries, but also the collective managers using tools such as size-limits or stocking of fish. To manage fisheries information about the state of fish stocks is needed. In the absence of scientific stock assessments, one means by which an angler community can approximate the status of a fishery is by asking each member of a club for his or her estimate of fish stock size and average the result. In theory, this average estimate should closely match reality within bounds of uncertainty. We tested this prediction by first assessing the size of northern pike (Esox lucius) in 18 stillwaters managed angling clubs. We then surveyed a random sample of anglers. In addition we conducted workshops with club heads. Workshop participants very closely estimated the true stock size, while results for anglers were mixed. Swarm intelligence may therefore be a suitable method to “assess” fish stocks in the absence of scientific data, but results shall be interpreted with caution.