As a fish guy I may be biased, but let me start off by saying Leandro Castello’s colloquium presentation about fish conservation in the Amazon was one of the best I’ve seen in my many years at UNBC, and it’s unfortunate more people weren’t able to attend it. Leandro gave a good overview of the three main threats to fish populations in the Amazon including deforestation, hydrological alteration (dams), and overfishing (particularly of the arapaima). These threats lead to less fish, which leads to less harvest by people living in the Amazon who heavily rely on fish as a source of food and economic income. One of the first things Leandro talked about that was new and interesting to me, was that the heavy rain and flooding the Amazon receives is beneficial for many fish species as it allows them to travel to floodplain habitats that have lots of vegetation and nutrients. These fish can migrate back into the main channel as the water level subsides. This was interesting to me as the flooding that happens around here tends to displace fish and they are often unable to successfully return to the main channel.
Leandro made it clear how important these flooded areas are for the health of fish populations, and throughout his presentation talked about how the threats of deforestation and hydrological alteration impact these important areas. Deforestation alters the hydrology of the watershed and reduces the floodplain vegetation that many fish rely on. Hydrological alteration, specifically dams, not only block movements of fish, but also change the hydrology in the watershed by reducing the amount of water in the system so that fish are not able to move to these important floodplain areas. The idea of fish habitat alteration caused by dams is relevant to my own project, as it ultimately came about due to a dam on the Nechako River altering critical habitat for Nechako white sturgeon.
Leandro spent most of his presentation talking about the third threat to fish conservation, overfishing. He focused on the beastly arapaima which has been overfished for years and mis-managed because of dispersed fisheries, under-developed agencies, and an open access regime. Leandro said the government can’t be depended on with this issue, and therefore a study was conducted that involved the actual fishermen as researchers. The study showed that observational counts by fishermen were more cost-effective than mark-recapture, but were just as accurate. This showed observational counts were an effective population monitoring tool and could easily be performed by fishermen themselves. Leandro said that by involving fishermen themselves to do counts, they are more likely to restrict harvest.
Leandro answered question very well, including one I asked him regarding the impact of deforestation and dams on arapaima specifically. If I were to ask him another question, I would have asked about the impact of hydrological alterations by dams on the spawning success of different species. Leandro gave a fantastic presentation and I encourage anyone who missed it to view it online!