Deforestation starves fish

A press release from the University of Cambridge: Research shows forest debris that drains into lakes is an important contributor to freshwater food chains – bolstering fish diets to the extent that increased forest cover causes fish to get ‘fat’ and sparse forest leaves smaller, underfed fish. Debris from forests that washes into freshwater lakes supplements the diets of microscopic zooplankton and the fish that feed off them – creating larger and stronger fish, new research shows.

The researchers warn that, as forests are eroded through human activities such as logging, the impacts will be felt in aquatic as well as terrestrial food chains. In fact, the study was conducted at a Canadian lake chosen because it had suffered ecological disaster during the mid-20th century: acid rain as a result of the local nickel smelting industry.

Despite moves to reduce environmental impact, many areas of vegetation surrounding the lake are still in recovery. This enabled scientists to study Yellow Perch fish from different parts of a lake that has varying degrees of surrounding forest coverage.

Carbon from forest debris has a different elemental mass than carbon produced by algae in the aquatic food chain. By analysing the young Perch that had been born that year, scientists were able to determine that at least 34% of the fish biomass comes from vegetation, increasing to 66% in areas surrounded by rich forest. Essentially, the more forest around the edge of the lake, the fatter the fish in that part of the lake were.

Scientists say that the young fish in lake areas with scant forest cover were much smaller, and consequently much less likely to survive and breed. “We found fish that had almost 70% of their biomass made from carbon that came from trees and leaves instead of aquatic food chain sources,” said Dr Andrew Tanentzap from Cambridge’s Department of Plant Sciences, and lead author of the new study, published today in the journal Nature Communications....

US Fish and Wildlife image of yellow perch