Eisler, R. 1957a. Some effects of visible light on hatching, mortality and early growth of salmonids. Thesis, University of Washington, Seattle, Washington. 68pp.

Region: PNW Species: Juvenile chinook salmon

Study Objective: Determine the effects of light on chinook eggs and embryo and fingerling growth.

Study Methods: Eggs: Two lots of chinook and one lot of silver salmon eggs were exposed to varying to varying intensities of a fluorescent light source characterized by a wave-length rage of 3350-6000 Angstrom unites (excludes infa-red, and ultra-violet radiation), with a mean at approximately 5800 Angstrom unites (yellow portion of light wave spectrum). Each sub-lot of eggs was continuously exposed to one light intensity commending a24 hours after fertilization and terminating when the yolk-sac was absorbed. The experimental light intensities ranged from .02 to 157 foot-c. Fingerlings: Four groups of chinook salmon fingerlings were fed a uniform diet while continuously subjected to a light intensity of .02, 88, 116 and 157 ft-c, respectively.

Results: Eggs: Visible light acts as a lethal agent upon both chinook and silver salmon eggs and larvae. High intensities of the light source killed 100% of the eggs before hatching with lower light intensities killing proportionally few eggs and larvae. Dark-reared groups (.02 ft-c) had the highest (760-91%) survival of all groups. Visible light was found to significantly decrease the time (by 2-3 days) necessary for hatching. Fingerlings: The light-reared fingerlings gained on average of 57% more in weight, and 41% more in length, than the dark-reared group. No difference was found between light-reared groups. No significant change in the weight-length relationship between groups was observed.