Cobbossee clean-up, fish rally to return April 17 Share GARDINER — After one year off because of the virus, Upstream is again sponsoring the Cobbossee Earth Day Waterside Clean-Up and Rally for Fishes. Upstream will gather on the new and wider Bridge Street bridge from 10 a.m. to noon Saturday, April 17, and will send out small teams to special zones on Cobbossee Stream and several spots on lower Pleasant Pond. Gov. Janet Mills and others have been invited to join in as Maine begins to reawaken from a long winter. Everyone will be outside, socially distanced and masked up as they work with others to pick up trash.