Effect of Low Salinity on Yolk Sac Absorption and Alevin Wet Weight of Rainbow Trout Larvae (Oncorhynchus mykiss)

Abstract

Growth, yolk sac absorption, and maximum wet weight of alevin rainbow trout (Oncorhynchus mykiss) stocked in fresh water (0 salinity), water with 4‰ salinity, or water with 8‰ salinity were determined. Larvae were sampled on the 329th degree-day when 50% of the eggs hatched, and on degree-days 361, 396, 432, 467, 496, 528, 557, and 584. Sampled larvae were anesthetized in benzocaine solution (20 mg/l) and preserved in 10% formaldehyde. At hatching, mean length was 14.25±0.63 mm and total wet weight was 58.16±9.98 mg. Larvae reached the swim-up stage at 96.94±8.71 mg on the 28th day in fresh water, at 120.29±9.26 mg on 19th day in 4‰ salinity, and at 102.80±5.88 mg on 22nd day in 8‰ salinity. The total length and dry weight of the larvae at the swim-up stage differed significantly among treatments (p<0.001). There was a significant relationship between larvae dry weight and degree-day. The best growth, yolk sac consumption, and alevin wet weight were obtained in 4‰ salinity.