ANGLERS are legendary for telling tall tales about the size of their catches. But these small lies, along with the temptation to cheat a bit by keeping small fish they ought to throw back, can send struggling fisheries into total collapse.
The problem is that the fewer fish there are, the more anglers tend to lie about numbers and break the rules, according to a Canadian fisheries biologist who has measured these all too human failings. That not only prevents managers from identifying any decline in stocks, it also accelerates the fishes鈥� demise.
Biologists often estimate fish populations by counting the catches in anglers鈥� creels. They also ask the anglers how many fish that are too small to legally keep they catch and then release. But Michael Sullivan at the Alberta Fish and Wildlife Service in Edmonton decided to check the reliability of these accounts by commissioning a squad of volunteers to fish for the highly prized walleye in 22 lakes in Alberta throughout the fishing season. The volunteers recorded every walleye they caught and noted its length. This told Sullivan the true ratio of the numbers of fish above and below the legal size threshold in each lake.
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When he compared this with the ratio reported by anglers, he found that the anglers claimed to have caught and released about 2.2 times as many fish as the true ratio predicted. They exaggerated even more if surveyed later in the season by phone or mail, probably because people tend to selectively remember good times. But crucially, the anglers overstated their catch most in lakes where the catch rate was lowest 鈥� threefold if surveyed on the spot, and more than tenfold if asked later 鈥� probably to avoid the embarrassment of appearing inept. 鈥淥utdoorsmen don鈥檛 like to be seen as incompetent,鈥� says Sullivan.
That means that anglers say they have made big catches even when actual catches tail off sharply, potentially masking any decline of fish populations and leaving managers in the dark about overfishing, Sullivan reports in a forthcoming issue of the North American Journal of Fisheries Management.
What鈥檚 worse, Sullivan also found that anglers are much more likely to keep undersized walleyes when fishing is poor, instead of throwing them back (see Graph). He estimates that in the most depleted lakes, anglers illegally keep half or more of the undersized fish they catch, easily enough to override efforts to preserve the population. In other words, the minimum-size limits designed to protect fish stocks are least effective just when they need them most.
Similar forces might well be acting on commercial fisheries worldwide, says Daniel Pauly, a fisheries biologist at the University of British Columbia in Vancouver. Commercial fishers also have an incentive to bend the rules when fishing is poor, since that鈥檚 when they need the income most desperately. And that extra level of cheating could be the final straw for fisheries on the brink.