Abu Dhabi’s benchmark index has fallen the most in almost five months as Emirates Telecommunications Corp. declined amid concern its smaller rival is increasing market share and European stocks retreated. Etisalat had dropped to the lowest level in almost two months. Abu Dhabi’s ADX General Index fell by 1.3percent, the most since March 2, to 2,638.52 at 1:09 p.m. in the emirate. The measure has dropped 2.4 percent this month. The Bloomberg GCC 200 Index, which tracks the biggest 200 companies in the Persian Gulf region, declined 0.4 percent. Since July 18, when Etisalat said that their second quarter profits have declined by 15 percent, their shares have tumbled by almost 7 percent. The United Arab Emirates’ second phone company, Emirates Integrated Telecommunications Co., or Du, is unchanged for the period as the debt crises in Europe and the U.S. dragged U.A.E. shares down