Building a swim tunnel facility to test the impact of sound on the migratory decisions of fishes
Many people are surprised to learn that all fishes can hear, which means athat their behaviour can be affected by sound. SATURN researchers at the University of Leiden have been testing the impact of ambient noise on the movement decisions of a variety of species. To do so, we’ve designed a novel experimental swim tunnel facility that will test the impact of exposure to underwater sounds on fishes, called the MIGRADROME. The Migradrome consists of a 5 meter long tilted flume swim tunnel, nested within a larger tank measuring 7 meters. On either side, pairs of in-water speakers ensonify the swimway in five locations. Acoustically disconnected pumps can vary the flow, while the tilt can provide a gradient of flow from upstream to downstream.
Over the next year, we’ll be conducting small-scale explorative studies with migratory sticklebacks (Gasterosteus aculeatus) and ide (Leuciscus idus), which will represent different hearing ranges, as well as two larger model species of conservation concern, the sturgeon (Acipenser sturio/ruthenus) and the eel (Aquila aquila). Fish will be able to choose between fast and slow currents and decide to swim upstream or downstream. Both currents are fully and independently under control, and can be manipulated independently for fixed exposure periods, with acoustic conditions that are typical for aquatic habitats or that reflect anthropogenic activities. We will be testing the basic impact of sound conditions on migratory decisions, but we can also compare and weigh fish decisions in different physical (flow speed, temperature, light) and chemical conditions (presence of food or predator extracts, aversive chemicals), to various levels of sound. Underlying physiological changes in fish will also be assessed by measuring, for example, the rate at which the gill openings beat, or their consumption of oxygen via micro-crystal sensors.
Fish are able to sense pressure and particle motion, which we will control within the cylindrical swim tunnels using the speakers, and partners at TNO have modelled sound pressure and particle motion conditions for various tank sizes, using varied tank wall materials and thicknesses, for fine-tuning exposure conditions. The Migradrome will be ready for pilot testing with sticklebacks this year (2022), and the prototype design and technology will be publicly available for replication and application in laboratories across Europe.