Abstract: Fish are cultured in one or more flumelike watercourses or "raceways" bounded by raceway-defining means. The water flow rate is such that the fish swim substantially continuously to maintain position. The fish are configured too closely to assert territorial rights, as they do when held at lower concentration. Water enters via a well enclosure at the upstream end, as by airlift upwelling; flows through the watercourse, sweeping waste materials along; and departs via a weir-like enclosure at the downstream end, where dissolved or undissolved waste is removed. Water is preferably supplied from and returned to a surrounding natural or man-made body of water, which also preferably floats the physical raceway means, facilitating water depth adjustment. Distribution of fish to adjacent raceways without any netting or handling conducive to injury is accomplished via airlift means. Fish so cultured remain healthy and grow rapidly and uniformly.