Smallmouth bass spawn in spring, May to early June, when water temperatures reach 60 to 70 degrees. The male builds the nest. The male fans a circular depression in gravel or sand with his fins. The nest is 14 to 30 inches in diameter and usually in three or four feet of water, although it may be more than 20 feet deep in clear water, as in Lake Erie. Smallmouths in lakes often move into tributary streams to spawn. Several females spawn on the same nest, adding 2,000 to 7,000 eggs per pound of body weight. Because the females spawn at different times, the eggs the male is guarding do not all hatch at the same time. Depending on water temperature, the eggs hatch in two to nine days. The young fish are ready to leave the nest five or six days after that. In rivers and streams, flow and temperature can affect the survival of young smallmouth bass. High flows can sweep eggs and fry downriver, where they may perish. Conversely, moderate flows may lead to high fry survival. These early season events frequently lead to low or high densities of adult smallmouth bass. Young smallmouths eat tiny crustaceans. Then they graduate to insect larvae, crayfish and fish. Smallmouths may reach 20 inches or more in length. The Pennsylvania smallmouth angling record is over seven pounds.