As noted in prior posts, deforestation happens for a variety of reasons: greed, creating farmland or pasture, and global warming. Much of the debate about deforestation notes the loss of habitat for terrestial species, and the decrease in an important carbon sink. However, researchers have identified a new adverse impact, less food for fish which leaves [no pun] them undersized and underfed.
Researchers have found that the amount of food available to young fish affects their size and the number that eventually reach adulthood. Although plankton raised on algal carbon is more nutritious, organic carbon from trees (think leaf litter) that washed into streams and lakes is a very important food source for freshwater fish. More dissolved forest matter means more bacteria, which means more zooplankton, which means larger, fatter fish (to complete the food chain).
The research was carried out around Daisy Lake, Canada, which is part of the boreal ecosystem. Researchers found that where there was the more forest cover, there were fatter fish.
This is not mere abstract science. Freshwater fishes make up 6+% of the world's annual animal protein supplies for humans, and the major and often only protein for low income individuals in Bangladesh, Indonesia, and the Philippines.
Although the researchers focused their study on boreal regions, they believe the results are applicable globally.
The study can be found at: http://www.nature.com/ncomms/2014/140611/ncomms5077/full/ncomms5077.html.