The finding is proof major changes to such ecosystems can be reversed over time, said a Canadian study by the Bedford Institute of Oceanography in Dartmouth, Nova Scotia, published Wednesday in the scientific journal Nature.
The study authors say it's encouraging news for other cod populations further north on Canada's East Coast that have yet to recover, Canadian Broadcasting News reported Wednesday.
The waters east of Nova Scotia, once teeming with millions of cod, have been dominated by much smaller, plankton-eating fish such as herring for more than a decade, despite a cod fishing moratorium since 1993.
That had led to fears of an irreversible change in the ecosystem.
The overpopulated plankton-eaters finally began running out of food, and their population started to decline steadily in the early 2000, putting the ecosystem into a "recovering" state around 2005, the study said.
At that point cod populations began to increase and have approached the levels of the early 1990s, the study authors said.