FISH MUCUS: IN SITU MEASUREMENTS OF POLYMER DRAG REDUCTION
The external layer of mucus on fish was investigated as a drag reducing polymer. Comparing velocity profiles for water flow over rainbow trout (Salmo gairdneri) and wax models of trout with and without hydrodynamically smooth surfaces revealed that the integumental mucous secretion can significantly reduce the rate of momentum transfer through the boundary layer. The difference in momentum transfer is expressed as a reduction in friction drag and discussed in view of the overall drag experienced by fish.