The quiet return of the river otters

For the first time in four decades, river otters have been recorded along every major tributary of the Calder basin.

Volunteers counted otter tracks on 212 of the 230 survey sites this winter, up from just 9 sites in 1986.

Cleaner water, more fish

Biologists credit the recovery to a ban on organochlorine pesticides and to decades of patient wetland restoration.

"The otters came back because the fish came back," said hydrologist Arun Mehta, who has studied the basin since 1994.

The next survey will focus on whether young otters are dispersing into the smaller upland streams.