A scalable fish rearing raceway system is provided, incorporating a fish containment structure having two semi-circular end sections, and two or more parallel fish raceways, surrounding a central zone for housing water treatment systems and a secondary fish crop. Heavy particulates are eliminated from the main fish rearing channels by use of conical areas located at either end of the parallel elongated raceways. Continuous removal of dead or dying fish from the raceway is accomplished by means of a floating mortality catcher consisting of a screened ramp at the surface of the cones which continuously collect moribund and dead fish. Grading bars separate and move fish underwater to an adjacent raceway through a common fish transfer channel. This larger scalable fish production system substantially reduces the direct labor and capital costs associated with the production of fish as compared with conventional circular fish rearing tanks.