Meeting Abstract
Creole wrasse and Bar jack are evolutionarily distinct, yet they have converged to school together in a particular pelagic environment above coral shelves in the Caribbean. In this environment, each fish uses a different reflection method to match the water column color with high fidelity. The creole wrasse has a blue coloration that matches the blue color of the water column where they forage above the coral. This species has a high polarization reflection that may aid the creole wrasse with camouflage from the polarization sensing copepods they hunt. The bar jack has broadband silvery skin that reflects the color of the water column. It can also be found in and among sea grass where the color of the water column is much greener. Bar jack have a high degree of depolarization and their polarization reflection is more complicated. We use a custom-built high definition color polarization camera with vertically stacked color photodetectors that has been engineered to be diver operated under water. We use a modified the computer vision tool, perspective from n points (PnP), to fit a virtual 3D model to the 2D image. Using this 3D model, we model the polarization reflections in virtual space and compare with the measured animal. We find that the creole wrasse performs similar to the bar jack in weber contrast with few exceptions but performs much better in the polarization channel. There are distinct differences in body positioning patterns between the two fish.
