The company is set to raise membership fees in June

ISSAQUAH, Wash. — Costco Wholesale Corp. reported net income of $515 million in its second quarter, a decline of 5.7% from the same period a year earlier. For the year’s first half, the wholesale club operator’s net income rose modestly to $1.06 billion from $1.03 billion last year, Costco said on Thursday.

Second quarter net sales rose 6% to $29.1 billion from $27.5 billion last year, the company said. Net sales for the first half increased 4% to $56.6 billion. The company said earnings in the 12 weeks to February 12 were affected by higher gas prices and investments on digital efforts and price cuts. Gasoline accounted for around 10% of company sales.

Sales rose 3% in stores open at least a year, while store visits rose 2% in the second quarter. The average amount spent increased 1%. Costco said traffic took a slight hit after the company began to offer fewer coupons, opting instead lower prices on more products.

Costco also announced that, effective June 1, the price of entry into its U.S. and Canada stores will be $60 for individual and business cardholders, an increase of $5. Executive members will see their fees go up by $10, to $120. Costco last raised its membership fee in 2011. The changes will impact 35 million members, roughly half of whom belong to its executive program. Costco makes most of its money from membership fees.

Membership fees rose 5.5% to $636 million in the second quarter.

Costco operates 728 warehouses, including 508 in the United States and Puerto Rico, 94 in Canada, 37 in Mexico, 28 in the United Kingdom, 25 in Japan, 13 in South Korea, 13 in Taiwan, eight in Australia and two in Spain. Costco also operates e-commerce websites in the U.S., Canada, the United Kingdom, Mexico, South Korea and Taiwan.