“Naive” Fish Are Easy Targets

Big fish that have grown up in marine reserves don't know enough to avoid divers with spear guns waiting outside the borders. An Australian research team working in the Philippines has found that there is an unexpected windfall awaiting divers who obey the rules and respect reserve boundaries - just wait outside them for big, innocent fish wandering out of the reserve.

"Educated fish normally turn tail and flee when a diver armed with a speargun approaches within firing range of them," says researcher Fraser Januchowski- Hartley. "But in our studies of marine reserves in the Philippines, Vanuatu and Papua New Guinea, where spearfishing remains a major way of harvesting table fish, we discovered that reserve-reared fish were much less wary and allowed people to get much closer. The fish are literally more catchable."

Studying fish movement across the boundaries of marine reserves, the team used underwater markers and measuring tapes to measure a large fish's 'flight initiation distance, and how close a diver can approach one before it decides to flee. Marine-protected fishes' typically scurried off when a diver got within 15 feet of them. But those living in fished areas were typically much warier and took flight at distances from 18 to 21 feet away. They also established that the "naivete radius," where fish spill out of the marine reserves, extended for at least 500 feet from the boundary.

The findings may help fishers become more supportive of marine reserves, says team co-leader Nick Graham. "In these parts of the oceans, spearfishing is still very much about survival and putting food on the table, so it's important that local fishers feel they're deriving some benefit from having a local area that is closed to fishing, or they may not respect it."