Effects of Baffles on Raceway Cleaning, Fin Erosion, In‐Hatchery Survival, and Postrelease Angler Catch of Catchable‐Sized Hatchery Rainbow Trout

Abstract

Hatchery fish exposed to exercise training often exhibit physiological and behavioral benefits compared with unexercised fish, but results from previous studies have been equivocal and have rarely examined postrelease performance of stocked fish. We evaluated various in-hatchery and postrelease consequences of rearing catchable-sized (~254-mm) Rainbow Trout Oncorhynchus mykiss in a raceway installed with baffles, the intent being to self-clean the raceway and exercise fish. Installing baffles increased water velocities experienced by fish, with some velocities exceeding 0.26 m/s (1.0 body length per second). In contrast, the maximum velocity experienced by fish in the control raceway was 0.07 m/s (0.27 body lengths per second). Prior to stocking, fin erosion (as measured by relative dorsal and pectoral fin lengths) did not differ between the baffled and unbaffled raceways, but surprisingly, survival was reduced for baffled fish. Catch by anglers and mean time to capture did not differ between raceways but did differ by water type (i.e., lentic, lotic, and community pond waters). While the augmented velocities along the bottom of the baffled raceway assisted with clearing some fish waste, they were not entirely effective and raceways still required some sweeping. Taken collectively, our results suggest that installing baffles in production-scale raceways rearing catchable-sized Rainbow Trout is not advantageous.