First-year growth patterns of seven fish species were determined with weekly or monthly samples taken from water intake screens of a power plant located along Navigation Pool 9 of the Mississippi River (River Mile 679). Mean total lengths of mooneye (Hiodon terqisus), gizzard shad (Dorosoma cepedianum), freshwater drum (Aplodinotus qrunniens), and white bass (Morone chrysops) were at least 110 mm by winter (November through March), but mean lengths of black crappie (Pomoxis nigromaculatus), channel catfish (Ictalurus punctatus), and flathead catfish (Pylodictis olivaris) were 67 to 74 mm by winter. Mean total lengths at capture of all species except channel catfish increased significantly with time (P< 0.05) until September or October, after which lengths did not change. Mean lengths of channel catfish increased significantly through winter until February. Mean lengths of flathead catfish and white bass did not increase after water temperatures in fall dropped below 18 °C, and mean lengths of gizzard shad, black crappie, and freshwater drum did not increase after water temperatures dropped to 9–11 °C. Water temperature when mooneye and channel catfish ceased growing was not determined. Earlier hatching fish species were longer by winter than later hatching species.