The number of sales in Manhattan fell and inventory increased in the first quarter, according to several market reports released by brokerages. According to a report prepared by real estate appraisal firm Miller Samuel for Prudential Douglas Elliman, sales fell by 34 percent compared to last year’s first quarter, down to 2,282 apartments from 3,474. Brown Harris Stevens and Halstead reported a 1 percent drop in sales, while Corcoran also reported a slight fall. “We’re starting to see a hesitancy in the marketplace,” said Diane Ramirez, the president of Halstead. “What I look at very carefully is the signed contracts, the deals that are coming to us right now. I’m starting to see a slowdown.” Miller Samuel reported that 6,194 apartments were on the market, compared to 5,923 last year.