- A new study investigated how the memories of about 400 fishers from traditional communities in Brazil can serve as sources of data on historic fishing effort and catch size.
- It measured the reliability of this “harvest recall data” by comparing it to other data collected by standard scientific methods.
- The researchers found that when considered as a whole, the fishers’ memories agreed with standard data collection methods about 95% of the time, which suggests that this recall method can be an effective fisheries management tool.
When Leandro Castello graduated with his degree in oceanography in 1998, he didn’t immediately get a job related to the ocean. Instead, he found himself in the Middle Solimões region of the Amazon, studying fisheries for arapaima (Arapaima gigas), freshwater behemoths that come the surface to breathe air. These fisheries had been banned in many places due to overfishing.
“I met incredibly knowledgeable fishermen,” Castello, now a fish conservation biologist at Virginia Polytechnic Institute and State University in the U.S., told Mongabay. “We tested the idea of whether this fisherman could count the numbers of fish, just like people do with whales in the ocean, and whether those counts of those fish could be used to foster management.”
Castello said these counts were “incredibly accurate” and “200 times cheaper and faster” than assessing local fish stocks using an equivalent scientific method. In 2004, Brazil’s environmental protection agency, IBAMA, even issued a regulation that gave fishers special authorization to harvest arapaima if they presented their count data, and several NGOs and government organizations also began promoting and implementing these methods, Castello said. Currently, more than 400 fishing communities in Amazonas harvest arapaima based on fishers’ counts, which allows fishers to sustainably manage these fisheries, he said.
“That experience taught me there’s a lot [one can do with] local knowledge,” Castello said.
About 20 years later, Castello began another research project focused on local knowledge, this time investigating how scientists can translate Brazilian fishers’ memories of past catches into “harvest recall data” that can be used to manage fish stocks in places with little to no fisheries data. Many other studies have also explored how fishers’ memories can serve as data sources, including a previous one by Castello that focused on small-scale fisheries in the Congo Basin. This new study, recently published in Frontiers in Ecology and the Environment, went a step further, seeking to measure the reliability of this data by comparing it to data collected by standard scientific methods. This study is one of the most comprehensive efforts to study the reliability of harvest recall data, using a large sample of fishers and many different fisheries.
Castello and his colleagues identified 24 artisanal and industrial fisheries along Brazil’s coast for which researchers or government agencies had collected data on fish catches and fishing effort. Then, to test whether fishers’ memories could also be a useful data source, they interviewed about 400 individuals involved in these fisheries, most of whom were recognized as Caiçaras, traditional inhabitants of southern and southeastern Brazil.
The research team produced a questionnaire asking about the type of fishing the fishers did, the gear they used, the species they targeted, and how old they were when they conducted their fishing activities. It then asked for specific information about “typical harvests,” “good harvests,” and “poor harvests,” including how many kilograms they caught on each trip and how much time they spent fishing. The researchers requested these estimates for the first few years they fished as well as the last few years.
The research team found that fishers’ memories were particularly accurate when they were recalling extreme events, such as an unusually productive or poor fishing season. However, factors like elapsed time and the interviewees’ age made some memories less accurate. Overall, though, the researchers found that, collectively, the fishers’ memories agreed with the other data about 95% of the time.
“Some people will remember [harvests] to be greater than they actually were, and others will remember things being lower than their original catch,” study co-author Priscila Lopes, an associate professor at the Federal University of Rio Grande do Norte in Brazil, who studies the social aspects of small-scale fisheries, told Mongabay. “But the average is consistent. So on average, people’s memory is really reliable.”
Both Castello and Lopes say the recall methods described in their study can be particularly useful in countries like Brazil, where fisheries data is scarce, or when it’s financially impossible to gather the data needed to implement sophisticated fisheries management schemes governed by Western science.
“Quick interviews with fishermen can produce historical fish catch data at a tiny fraction of the cost of conventional (scientific) data,” Castello said in an email. Besides providing information about catch data, he said, fishers’ memories can be used to assess historic trends, such as declines in catches, increases in catches, and periods of stability. These results can then be used to make critical management decisions, he added.
William Cheung, a professor and director of the Institute for the Oceans and Fisheries at the University of British Columbia, Canada, who was not involved in this research, praised the new study for the “robustness” of its analysis. This makes the study stand apart from others that have also looked at the usefulness of fishers’ memories for data collection, he said.
“I think part of the reason why they found this high reliability [in fisheries’ memories] relates to the detailed design of their methods, and how they tried to develop common questions that could also help people to recall information more accurately,” Cheung told Mongabay. “This [high accuracy] is one thing that I find really promising and something that stands out to me.”
Castello said he and his colleagues have had trouble in the past engaging with government officials about implementing these harvest recall methods in fisheries management. But now, he said, he’s hopeful the tide is turning. This month, he and his colleagues will present their findings at a public event run by ICMBio, the Brazilian environment ministry’s administrative arm, and also discuss the implementation of their methods in smaller groups.
Castello said it’s his “dream” for local knowledge to be used to manage traditional fisheries, not only in Brazil, but in other parts of the world too.
“We have millions of fishers that have been living in these places, fishing for a long time,” Castello said, “and they have all these memories that we could easily and quickly gather to produce data. It is not perfect, but according to the best scientific estimate, it’s 95% accurate and reliable. Is it going to promote management that is as good as management that has been done in North America or Europe? No, definitely not. But it’s much better than the status quo of almost no management, no data, no information, no action.”
Banner image: A fisher casts a net in Laguna, Brazil. Image by Fabio G. Daura-Jorge via Flickr (CC BY-SA 2.0).
Elizabeth Claire Alberts is a senior staff writer for Mongabay’s Ocean Desk. Follow her on Mastodon, @ECAlberts@journa.host, Blue Sky, @elizabethalberts.bsky.social, and Twitter @ECAlberts.
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Citations:
Castello, L., Martins, E., Sorice, M., Smith, E., Almeida, M., Bastos, G., … Lopes, P. (2024). Local knowledge reconstructs historical resource use. Frontiers in Ecology and the Environment. doi:10.1002/fee.2726
Castello, L., Carvalho, F., Ateba, N. O., Busanga, A. K., Ickowitz, A., & Frimpong, E. (2023). An approach to assess data-less small-scale fisheries: Examples from Congo rivers. Reviews in Fish Biology and Fisheries, 33(3), 593-610. doi:10.1007/s11160-023-09770-x