LOS ANGELES -- Arden Group, parent company of Gelson's and Mayfair Markets here, reported decreased sales and earnings for the third quarter ended Oct. 1. Arden's third quarter marks the first period that includes supermarket sales only. Year-ago results reflect two discontinued operations: Arden sold GPS Pool Supply last May and Telautograph Corp. in September 1993. Net income fell 69.4% to $1.3 million for the 13-week quarter and 48.6% to $3.5 million for the 39 weeks. Earnings for the year-ago periods include $2.8 million from GPS for the quarter and $3.9 million for the year to date. Sales fell 3.3% to $59.7 million for the quarter and rose 0.3% for the year to date. Same-store sales for the 12 supermarkets increased 3.8% for the quarter and 3.7% for the 39 weeks.