|Document Type:||Journal Article|
|Title:||Tattoo marking of fingerling salmonids with fluorescent pigments|
|Author:||Richard N. Duncan, Ivan J. Donaldson|
|Journal:||Journal of the Fisheries Research Board of Canada|
Tattooing is a useful method for marking fish because a number of different marks may be made by combinations of color, number, and location. Non-fluorescent pigment tattoos have been retained up to 5 months. Although 5 months is sufficient for many experiments, a longer–lasting pigment would extend the usefulness of the method.
Fluorescent pigments for tattoo–marking of fingerling salmonids were first used in studies of fish mortality in turbines at Shasta Dam. These pigments were first considered by the U.S. Bureau of Commercial Fisheries because of the need for more marks consisting of single tattoos in a standard location on the fish. Marks that require multiple tattoos and multiple locations are more time–consuming and susceptible to error. Because fluorescent and nonfluorescent pigments of the same color can be readily differentiated under ultraviolet (UV) light, the number of usable pigments could be doubled by using both types of pigments.
Since 1963, over 100,000 coho salmon (Oncorhynchus kisutch), chinook salmon (O. tshawytscha), and rainbow trout (Salmo gairdneri) have been tattooed with fluorescent pigments by the Bureau for studies on mortality of fingerlings in turbines of hydroelectric dams on the Columbia and Snake Rivers. The fluorescent pigments have proved to be reliable, easily recognized marks. These studies, each lasting only a few days, gave no opportunity for determining long–term retention of the tattoos. Therefore, two groups of coho fingerlings were marked with fluorescent–pigment tattoos and held in hatchery ponds to determine the effective life of the marks. Because growth during these tests was small (about 45 mm), the effect of growth on mark visibility was not tested. This note presents the data on long–term retention of tattoo marks.