Polarization in Marine Fish: A Different Kind of Camouflage

Light properties are utilized by for communication and concealment. Most studies of crypsis have focused on light properties that humans can see (brightness and color), however many fish are sensitive to polarized light. Polarization light fields depend on scattering events from sunlight or moonlight, and fields vary between environments (open-ocean versus seagrass). Our work focuses on the polaro-crypsis strategies (polarization camouflage) of fish from two different habitats (seagrass and open-ocean). Real-time laboratory videopolarimeter measures of lookdowns (Selene vomer – opean-ocean) and pinfish (Lagodon rhomboids – seagrass), were used to calculate the fishes’ Meuller matrices (mathematical descriptor of polarization reflections). Lookdown measurements corresponded to the optimal Mueller matrices for polarization crypsis in this environment. Pinfish polarization contrast was found to be sub-optimal in open-ocean environments, suggesting lookdown polaro-crypsis may be a specialized adaptation to a polarized open-ocean environment. Greater understanding of habitat variables for fish communication, predator avoidance and prey detection is important for further conservation of species diversity. In this case, polarization cues are affected by habitat structures and water turbidity. Pollution and human induced habitat alterations could potentially disrupt polarized cues for predator-prey interactions, con-specific communication and navigation.