How Preservation Techniques Effect Fin Ray Stiffness in Yellow Perch

Fish use their fins for propulsion and maneuvering in a three dimensional environment. In addition, many fishes use their fins for more specialized behavior like crawling or holding onto the substrate. The bony, segmented fin rays (lepidotrichia) support and control the relative shape and position of the fins, and are therefore critically important for fin function overall. The yellow perch, Perca flavescens, is a species that uses its fins for a variety of behaviors. Specifically, the pelvic fins can be used to interact with the bottom as well as for maneuvering in the open water. Our main question is, what is the relationship between fin function and fin stiffness? It is not always possible to get fresh specimens, therefore we are also interested in how preservation techniques, (freezing and preserving with formalin), affects fin stiffness. We performed three point bending tests using an Instron model 5942 testing apparatus to compare stiffness in a sample of fin rays from all soft fins (pelvic, pectoral, soft dorsal, anal and caudal) of the yellow perch. For fresh and frozen specimens, we found that the pelvic rays were significantly stiffer than the other fins and the pectoral fins the least stiff. We also found no significant difference between fresh and frozen specimens. We predict that the fixed fin rays from the preservation in formalin and storage in 95% ethanol will be stiffer than the fin rays of fish preserved by freezing. However, we also predict that the relative stiffness results will follow the same trends as we found in fresh and frozen fin rays. If there is no significant difference in stiffness due to preservation techniques, this would allow us to test the stiffness of the fin rays of museum specimens and explore more extreme functional adaptations of fins in a more diverse sample of fishes