Boshers dam vertical slot fishway, James River, Virginia, U.S.A., opened in 1999 and restored connectivity to 543.3 km of spawning habitat for anadromous fish. The fishway also allowed local movement of resident species. Video observation from 2001-2005 was used to evaluate environmental predictors of American shad (Alosa sapidissima) and sea lamprey (Petromyzon marinus) passage. The ecological effects of restoring connectivity to upstream habitat for gizzard shad (Dorosoma cepedianum) and blue catfish (Ictalurus furcatus) are also discussed. Regression analysis determined that the best predictor of increased daytime American shad passage is higher water temperatures and discharge and for increased daytime sea lamprey passage, a higher water temperature and increasing water temperature trend. Day length, and indirectly, barometric pressure also played a role in passage. Sea lamprey and American shad peak passage rates were dissimilar when comparing preferred water temperature ranges. Sea lamprey peaked (5.30/hr) at 16-17.99°C, while American shad peaked (1.05/hr) at 20-21.99°C. The diel pattern of passage for American shad indicated a strong diurnal tendency. All passage occurred during daytime hours, peaking from 1100 to 1900 hours. Diel patterns of sea lamprey indicated a strong nocturnal tendency (66% of passage occurring at night), with peak passage between 0300 and 0700 hours. More complete nightly passage data and passage data from periods when the water is too turbid for video observation would improve the accuracy of determining environmental predictors of passage.