The Influence of Preservation on Fish Morphology in Museum Collections

Museum collections allow us to look at specimens from a vast timeframe and immense scale. However, preservation can affect a specimens’ morphology. The objectives of this study were to determine whether the morphology of two centrarchids changed proportionally during preservation and how long it takes for their morphologies to stabilize. During a six-week period, bluegill (Lepomis macrochirus) and green sunfish (Lepomis cyanellus) were preserved in a 10% formalin solution. The fish were then transferred to 70% ethyl alcohol for 46-weeks. Fish were photographed using a Sony DSC W350 14MP camera with Zeiss MacroZoom lens at 0, 3, 6, 12, 24, 39, and 52 weeks of preservation. Standard lengths and maximum depths were measured from the photographs using Sigma Scan Pro. These measurements were then used to generate aspect ratios (standard length/maximum depth) for each fish. Additionally, the photographs were digitized using 10 landmarks in tpsDig ver. 2.11 and a relative warp analysis in tpsRelW ver. 1.45 was performed. During fixation, fish morphology changed proportionally with the depth of the fish decreases over time and stabilizing after 52 weeks. We showed that fish did shrink with preservation, but did so proportionally, allowing fresh fish morphometric comparisons with preserved specimens.