Delta Smelt Formalin Fixation and Preservation Effects on Fish Weight and Length

Natural history museum specimen are invaluable for a variety of conservation and ecological applications. Fishes are commonly preserved in formalin; however, formalin preservation is associated with reduced fish length and increased weight, but the magnitude and timing of these changes may vary among species. Unaccounted for preservation-driven shifts in fish length and weight may have drastic effects on any conservation or ecological conclusions drawn from specimen preserved for various durations as well as when compared to fresh, unpreserved specimen. The ​purpose of this study was to ​test whether formalin fixation and preservation affects endangered Delta Smelt, Hypomesus transpacificus, lengths and weights with implications for the use of data collected on preserved and fresh specimen. Fresh Delta Smelt were lengthed and weighted, then fixed and preserved in 10% buffered formalin​. Repeated measures of specimen length and weight were recorded weekly for 4 weeks, fortnightly from preservation week 4 through preservation week 24, and then approximately annually through 6 total years of preservation.