Evaluation of Techniques for Fixing, Preserving, and Measuring Salmon Eggs

Abstract

In a comparison of Stockard's solution with 5% buffered formalin for the preservation of coho (Oncorhynchus kisutch) and chum salmon (O. keta) eggs, formalin caused a lesser alteration in weight regardless of whether the eggs were preserved before or after waterhardening or fertilization. Coho and chum salmon eggs responded similarly to the various treatments. Time before preservation (3, 7, and 24 h) and fertilization had little effect on the final size of eggs. Waterhardening, in which the egg was placed in standing water, caused a 23% increase in fresh egg weight. Preservation in Stockard's solution, especially after waterhardening, increased egg weight by 48% and was least consistent in its effect. By contrast, 5% buffered formalin added to fresh eggs caused no significant alteration in weight, even after 5 mo of preservation. The latter was therefore the most suitable technique of preserving egg size. The use of egg weight as a measure of egg size was more accurate and consistent than linear measures of diameter. Finally, some empirical relationships for correcting published data on preserved egg weight are presented.