The Mystic Environmental Art and Film Festival will be held next weekend at the Hyatt Place hotel on Riverside Avenue behind City Hall. An opening reception is scheduled for Friday from 6 to 9 p.m. Three short films will be shown, and the top 20 entries in an art competition will be announced. The art will be on display all weekend. On Saturday, the documentary “The Mystic Herring Run: The Return of 2012 and Beyond” will be shown at 7 p.m. The Mystic River Watershed Association estimates the river’s herring run numbered 200,000 last year. Admission to the festival is free, but reservations are required for the Saturday showing. Contact www.mysticriver.org .