Astoria Financial Corp. of Lake Success said Wednesday that first-quarter earnings fell by 39 percent from a year earlier, when net income was buoyed by a big income tax reduction.

Also Wednesday, five-branch Gold Coast Bank, of Islandia, said its first-quarter net income rose 81 percent from a year earlier to $257,000, or nine cents a share.

Astoria, the parent of 87-branch Astoria Bank, said it earned $19.3 million or 17 cents a share in the three months ended March 31. The quarter a year earlier included an $11.5 million New York State income tax reduction.

Total assets fell from the previous quarter by less than 1 percent to $15.5 billion as the loan portfolio shrank.

Astoria said net interest income, the difference between the revenue generated from a bank's assets and the expenses associated with liabilities, fell by 2.6 percent from a year earlier to $85.7 million.

Net interest margin, a measure of the difference between the interest a bank earns on its assets such as loans and the interest it pays out to depositors, was 2.34 percent for the first quarter, compared to 2.30 percent for the previous quarter and 2.36 percent for the 2014 first quarter.

Monte N. Redman, president and chief executive, said in a statement, "In a period where interest rates are under pressure and many of our competitors are experiencing shrinking margins, we are encouraged by the fact that our net interest margin expanded."

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Noninterest income was $12.9 million, down 5.8 percent from a year earlier.

At Gold Coast, total assets on March 31 were $344 million, up 6.2 percent from the previous quarter and up 36 percent from a year earlier. Net interest income was $2.3 million in the quarter, up 22 percent from a year earlier.

Gold Coast Bank said last week that it planned to open a sixth branch, in Southampton.