Effects of Suspended Wood Fiber on Brown and Rainbow Trout Eggs and Alevins

Abstract

Brown and rainbow trout (Salmo trutta and S. gairdneri) eggs were held in continuous-flow suspensions of 0-, 60-, 125-, and 250-ppm conifer groundwood fiber 6 to 8 days before hatching. Resulting alevins were held in the same fiber concentrations until swimup (14 to 16 days), then removed and maintained in clean water for up to 91 days. Suspended fiber had no effect upon egg survival, respiration rate of embryos, or growth rates of alevins and juveniles from eggs incubated in fiber but hatched and grown in clean water. When alevins were held in wood-fiber suspensions, survival was reduced from 98 to 100 per cent in controls to 0 to 72 per cent in 250-ppm fiber; respiration rate from 336.6 mm3/g per hour in controls to 146.3 in 125-ppm fiber; breathing rate from 1.39 to 1.92 respiratory movements per second in controls to 0.52 to 0.97 in 250-ppm fiber; heart rate from 1.50 to 1.60 beats per second in controls to 0.67 to 1.33 in 250-ppm fiber; and instantaneous growth rate (g) from .0213 to .0345 in controls to .0061 to .0062 in 250-ppm fiber. Growth rate of rainbow trout juveniles in clean water after exposure to fiber during the alevin stage was significantly reduced only in the 250-ppm-fiber group. Concurrent tests indicated that observed effects were due to the fiber and not to residues of a mercuric slimicide added to the fiber at the paper mill.