The Nevada Department of Wildlife is pumping about $1 million a year into the battle to block the spread of the quagga mussel in Nevada’s lakes and rivers. The mussel, native to the Dnieper River in the Ukraine, has become so pervasive in Lake Mead that, according to Wildlife’s Patrick Cates, the state had to shut down the fishery there. The thumbnail-sized mussel causes major damage to pumps, intakes and other structures, reduces water quality in general and can deplete oxygen in the water. Cates said there are a number of aquatic invasive species the department is worried about, but …