The first full day of a strike by 31,000 Stop & Shop workers has wreaked havoc on the supermarket chain, leading to closures, delays, and empty stores.

At least three of the chain’s Connecticut supermarkets—in Danbury, New Haven, and Trumbull—never opened April 12. Others opened under shortened schedules, offering only dry goods because their delis, seafood counters, and floral shops were closed. Pharmacies and banks located within the Stop & Shop stores were open for regular hours.

“The majority of our stores are open today from 8 a.m.-8 p.m. and we have contingency plans in place to minimize disruption,” said...