Dr. Castello’s talk focussed on the impacts of deforestation, hydrology and overfishing on Amazon fisheries and how involving the local fishermen and using their knowledge can make these fisheries more sustainable. During the wet season, the Amazon River floods the surrounding forest and the fish migrate into these flooded forests where food is abundant. However, due to deforestation, these forests disappear, bringing with them the fish and the catch of the local fishermen decreases with decreasing forest cover. For hydrology, drought during the dry season also affects the local fisheries. If drought is severe, lakes and rivers shrink in size forcing all the fish into a smaller body of water where water quality tends to be mediocre and where bigger fish have an easier time catching smaller fish. Some fish will even just leave the fishing lakes and go back to the main channel of the Amazon. Finally, overfishing has also taken its toll on the local fisheries and Dr. Castello took the arapaima fisheries as an example. Arapaima are air-breathing fish that can reach more than 7 ft. in length. Local fishermen traditionally fished them with harpoons but gill nets slowly replaced these, making it easier to capture more of them at once. Fisheries on the Amazon are also spread out, hard to monitor and there are very few resources allocated to enforce fishing regulations.

It was interesting to know how one community of fishermen worked to make their arapaima fishery more sustainable. Dr. Castello and an NGO worked with the community as a link between them and the government to establish new management regulations. The fishermen were responsible for the data collection and counted the juvenile and adult arapaima in 15 closed lakes. Their counts, which took about 20 minutes each and a few men, turned out to be as accurate as standardized mark-recapture studies which took two weeks to do. Thanks to their knowledge of the arapaima, the fishermen were able to tell the age of the fish as it surfaces to breathe, thing that scientists that have never lived in the Amazon cannot do.  Since they did the data collection themselves, the fishermen realized the severity of overfishing and went on to implant their own management policies. From 1996, they went from 2500 arapaima in their lakes to over 23 000 in 2006 and their catch and income increased. Other communities hearing about their success adopted similar strategies with varying levels of success.

In terms of methods, Dr. Castello spoke a little about mark-recapture studies which are also used in ornithology, often to estimate survival rate of birds after migration. While I will not be doing an actual mark-recapture study, I will be banding birds during my master’s to see if returning adult birds change their song from one year to the next, following a similar idea.

Overall, Dr. Castello answered every question clearly and in sufficient detail. As an additional question, I would have liked to know if there is any other community-based management going on for different species of fish in the Amazon.