Fixation Shrinkage of Herring Larvae: Effects of Salinity, Formalin Concentration, and Other Factors

Abstract

The most important factors affecting the degree of larval shrinkage of Pacific herring (C. h. pallasi) larvae during fixation are the salinity and formalin concentrations and initial larval size. In low formalin concentrations (2-5% formalin) shrinkage increased from < 2% shrinkage at low salinities to .apprx. 10% shrinkage in seawater formalin. In high formalin concentrations (20-30% formalin) shrinkage was fairly uniform, ranging from .apprx. 3% shrinkage in low salinities to .apprx. 5% in seawater. Shrinkage in fixatives stored at 0, 5, 10, 20 and 30.degree. C was slightly higher (1-2%) at the higher temperatures. Buffering agents and starvation had no effect on shrinkage. Small, young larvae shrank relatively more than larger older larvae.