Dam removal allows greater access to spawning grounds

A study of spawning Atlantic salmon by the International Association for Great Lakes Research shows that removal of a dam allowed for greater access to suitable spawning grounds.

The study tracked removal of the Willsboro Dam in New York state’s Boquet River as part of the landlocked Atlantic salmon restoration program in Lake Champlain.

Researchers noted that habitat degradation is among the greatest threats to freshwater biodiversity, particularly for migratory species using different habitats throughout their life cycle. Dams and weirs often impede upstream migration, which can decrease access to traditional spawning and rearing habitat and lead to severe population declines.

Lake Champlain once had a thriving landlocked Atlantic salmon population which supported commercial fisheries in the U.S. and Canada, which disappeared in the 1800s.

A stocking program was initiated in Lake Champlain and its tributaries in 1962, but a self-sustaining population has yet to be established, in part, researchers said, because dams obstruct most rivers in the Lake Champlain basin.

Researchers conducted spawning habitat surveys downstream of the dam site in 2014, 2016 and 2017, and in historical spawning grounds upstream in 2016 and 2017. Their goal was to determine whether removal of the dam increased access to higher quality spawning habitat.

Researchers concluded that overall removal of the Willsboro Dam had a positive impact toward re-establishing a naturally reproducing Atlantic salmon population in Lake Champlain. By translocating salmon upstream, they showed that salmon were able to rind spawning habitat within suitable range or the species. Further monitoring is needed to confirm whether fish passage has improved since dam removal, but researchers said their data suggests that improvements in spawning habitat below a former dam site can occur within a few years.

The International Association for Great Lakes Research published its findings online with Elsevier, a global information analytics business who aim is to help institutions and professional advance science for the benefit of humanity.