In April, for the fourth month in a row, revenues for the Peconic Bay Region Community Preservation Fund were down from last year. Thus far in 2019, $23.94 million has been collected, over 24 percent less than in 2018, Assemblyman Fred W. Thiele Jr. announced on Tuesday. The preservation fund, which provides money for land preservation and water quality improvement, receives the proceeds of a 2-percent real estate transfer tax. The money goes to the five East End towns: East Hampton, Southampton, Shelter Island, Southold, and Riverhead.The real estate market here has been experiencing its biggest slowdown since the 2008 financial crisis, according to a quarterly report by the Douglas Elliman agency. C.P.F. revenues declined by 29 percent in the first quarter of 2019. On the bright side, the $7.4 million collected in April was the highest of the year, compared to $5.47 million in January, $6.51 million in February, and $4.56 million in March.“April marked a return to revenues more in line with the last few years,” said Mr. Thiele in a statement. Southampton, which posted the largest decline in C.P.F. revenue in the first quarter, raised just over $12 million in April, compared to more than $17 million in 2018, a decrease of more than 31 percent. In East Hampton, April revenue was down by a little over 13 percent; it had been down by 14 percent in the first quarter. Riverhead, which had been the only town in which the tax revenue increased this year, did not continue that trend last month. Its C.P.F. income fell by more than 25 percent over April 2018. Shelter Island’s were down nearly 7 percent, and Southold’s by almost 19 percent.