Two mussel researchers independently determined that the mussels found in Lake Mead on January 6 were not zebra mussels but quagga mussels. Quagga mussels are in the same genus as zebra mussels (FAQ) and actually can out-compete them. In eastern Lake Erie, they have nearly eliminated zebra mussels. They also live in deeper water than zebra mussels and can attach to other substrates such as sand and pebbles. They have been found thriving in the cold waters of Lake Michigan in waters as deep as 300 feet. Link.

If you are wondering about the name quagga, the quagga mussel is named after a less striped relative of the zebra known as the quagga which went extinct in the 1800s.