Shrinkage of Inland Silverside Larvae Preserved in Ethanol and Formalin

Length measurements of preserved larval fish are necessary in many types of larval fish surveys. If the fixative causes significant shrinkage, then the preserved lengths cannot be used to indicate accurate live lengths. The objective of this study was to determine how preservation in two different concentrations of formalin and ethanol affects the total length of larval inland silversides Menidia beryllina. Larvae were measured (nearest 0.1 mm) and individually fixed in one of four fixative treatments (80% ethanol, 100% ethanol, 5% buffered formalin, and 10% buffered formalin). Fish were remeasured (nearest 0.1 mm) at 15 min; 4 h; and 1, 7, 14, and 21 d after preservation. Most shrinkage occurred within the first day after preservation in all four fixatives. Initial length was positively correlated with absolute shrinkage, but percent shrinkage was not affected by initial length. We found no difference in percent shrinkage between the 80% and 100% ethanol concentrations. The 10% buffered formalin caused more percent shrinkage than 5% buffered formalin. Furthermore, ethanol (80% and 100% combined) caused greater percent shrinkage than either 5% or 10% buffered formalin.