Using local knowledge to make a global impact
Every night, local fishers paddle their tiny outrigger boats over the Danajon Bank, a rare double barrier reef system in the central Philippines. With only the glow of a lantern to illuminate their way, they slip into the black water in search of seahorses and other small fishes. If they’re lucky, a night’s work will yield a single seahorse among their catch, which they will sell to traders.
It wasn’t always this way.
“The older guys told me that in the 1970s they would catch a hundred seahorses in a night, sometimes more. It seemed like an unbelievable number,” says Kerrie O’Donnell, a PhD student with Project Seahorse, of her interviews with longtime lantern fishers.
As part of her research, O’Donnell interviewed the fishers about the species and volume of seahorses they caught in the 1970s and 80s. Using their recollections and extrapolating from existing data, she recreated a history of seahorse fishing on Danajon Bank. She wanted to understand how these populations changed between the 1970s and 1996, when Project Seahorse first began tracking seahorses there.
"Memory is a fragile thing,
so we needed to adjust for bias.”
“To truly understand the situation right now, to understand the threats to seahorses and to identify solutions, we need to know what was happening ten, twenty, thirty years ago,” she says. “In many areas of the world, we don’t have baseline data for seahorses or most other fisheries, so it’s difficult to know how much fish populations have declined in recent decades.”
In order to reconstruct these historical fisheries, O’Donnell needed to account for the vagaries of memory. ‘Wishful thinking’ and other factors can influence how fishers remember their catches in the distant past. Using existing interviews, logbooks, catch rates from 1997 and later, she developed a novel methodology that allowed her to adjust the older historical data for accuracy.
Today, small-scale fishers in the Philippines and other developing countries contribute to the global wild seahorse trade, which totals over 25 million animals per year. The seahorses they catch and sell — for about $0.40 each — end up on display in aquariums, as dried specimens in traditional Chinese medicine, and as curio souvenirs for tourists around the world.
“By comparing Project Seahorse data from the past fifteen years with the information we gleaned from the fishers about the more distant past,” says O’Donnell, “we can better gauge the current rate of population decline and adapt our conservation work accordingly. Of course, memory is a fragile thing, so we needed to adjust for bias.”
A lack of historical data hinders conservation efforts for many threatened marine species around the world. O’Donnell’s new methodology will help conservationists to retrieve this vital information from the past accurately and effectively.
- O'Donnell, KP, Pajaro MG, Vincent ACJ. “How does the accuracy of fisher knowledge affect seahorse conservation status?” Animal Conservation 13(6): 526-523.
- O'Donnell, KP, Pajaro MG, Vincent ACJ. “Improving conservation and fishery assessments with local knowledge: future directions” Animal Conservation 13 (6): 539-540.