Shrinkage of Gobiocypris rarus, Procypris rabaudi, and Sinilabeo rendahli preserved in formalin

Length measurements of preserved fishes are necessary in many types of fish surveys because logistics often do not allow for fish measurement immediately after catch. If the fixative causes significant shrinkage, then the preserved lengths cannot be directly used to indicate accurate live lengths. The objective of this study was to determine how preservation in formalin affects standard length of Gobiocypris rarus larvae (24‐day‐old and newly hatched), larval Procypris rabaudi (4‐day‐old), and larval Sinilabeo rendahli (12‐day‐old). Fishes were measured (to nearest 0.01 mm) and individually fixed in the appropriate formalin solution (2.5% or 5.0% formalin), then re‐measured at 0.5, 1, 3, 7, 14, 30, 45 and 75 days after preservation to follow the time course of shrinkage. Most of the shrinkage occurred within the first half day after preservation. The 5.0% formalin caused a higher relative shrinkage rate than did the 2.5% solution; however, the difference was not statistically significant. In G. rarus, initial shrinkage of newly hatched larvae was higher than that of 24‐day‐old larvae.