A Bio-Inspired Oscillating Underwater Fin for Generating Water Movement that Saves Plankton and Fish Larvae

Abstract

The global human population is growing and so is the demand for food. At the same time, climate change and the loss of biodiversity is an increasing problem. The company BlueLinked is developing a saltwater fish farm on land, efficiently breeding both new wild fish and fish for consumption with the motto “one fish on your plate and one fish in the sea”. In big specially designed tanks, a tiny natural sea is mimicked. Here, small fish larvae are raised. To make the conditions as natural as possible, live algae and small food organisms are kept in the same tank. Everything is completely in balance. With this, the fish larvae are surrounded by their diet and the right size of food is available at all times. It is important that the water in the tank remains well mixed. A normal flow pump is not suitable for this, because it causes a lot of turbulence. The fish larvae and other small organisms are very vulnerable and will not survive this wild water. This project investigated how a water flow can be created that leaves the fragile organisms in the water intact. This is done inspired by nature. As a result of millions of years of evolution, only the best functioning mechanisms in nature have been preserved. The tail fin of a whale is such a highly developed product of natural selection. Whales can swim very smoothly and efficiently through the water thanks to their tail fin. Its shape and flexibility ensure that the drag and pressure of the water are used in advantage for the movement through the water, using minimal energy. Prototypes have been made based on three different shapes of tail fins, which can be attached to a special device that moves vertically up and down above the breeding tank. The experiments conclude that the underwater fin based on the gray whale’s tail fin can is the most efficient in creating a proper flow. This oscillating fin is now used to create with minimal electricity needs a calm propulsive current in the breeding tanks at BlueLinked, in which all tiny organisms can survive. Inspired by nature and realised by science, the problem has been solved and a contribution is made to sustainable fish farming.