Mosquitoes will generally only lay their eggs in still, stagnant water.  If the mosquitoes happen to lay eggs in your pond and the mosquito larvae hatch, the fish in your pond will consider them a treat and will pick them off the water’s surface with great enthusiasm.  Your skimmer will sweep up whatever the fish miss.  In fact, a pond full of hungry fish makes a great defense against the West Nile Virus problems in your neighborhood!