Creating fish-friendly environments
Fish such as salmon are inextricably drawn back to the place of their birth so that they too can procreate and continue the cycle. Some fish follow specific migration routes, and those that inhabit rivers and estuaries impacted by dams and power plants are at risk. Research aimed at protecting these fish is being conducted at the University of Southampton, led by Dr Paul Kemp, from the university's International Centre for Ecohydraulics Research (ICER). This European science centre is fast making a name for itself around the world as it helps engineers develop hydropower to understand fish behaviour and come up with innovative ways to keep them away from turbines and intake systems.
Dr Kemp is focusing his efforts on investigating behavioural attraction and repulsion along with other aspects of fish behaviour, including distribution and routes of migration. Some fish, such as salmon and trout, will alter their behaviour according to specific hydrodynamic cues, such as acceleration of flow. This can reduce the number of fish that may go down a dangerous abstraction point, for example into a turbine or other water supply off-take, but is negative in the case of safe fish passes that also tend to have accelerating flows.
Developing fish-friendly constructions is not a new occurrence, as Dr Kemp explains. 'Fish ladders are not new technology. There are records in 13th century England of a need to provide a space within weirs to allow salmon to reach upstream spawning grounds, which had to be wide enough to allow a well-fed pig to stand sideways without touching the sides,' says Dr Kemp. 'It's thought this "King's Gap" dates back to the days of Richard the Lionheart, but we need to be more sophisticated now to protect species from harm. What we really want to do is to tap into aspects of fish behaviour to manipulate their distribution and movement to increase the probability of deterring them from hazardous areas, such as turbine and water supply intakes, while diverting or attracting them to other preferred routes, fish passes for example,' Dr Kemp adds.
Historically, work in this area has focused on salmon; recently, however, it has broadened to include several species of fish that could be threatened by engineering work to modify rivers and control the flows of water. Research is currently under way around the world, including at China's Yangtze River, and the mighty Amazon in South America. The scientists at Southampton use the flumes at the university's science park to examine fish behaviour in response to hydrodynamics encountered at dams.
Another major area of Dr Kemp's research concerns eels, whose population has dropped by 90 per cent over the past 2 decades. The adults, which leave freshwater rivers to swim thousands of miles to the Sargasso Sea in the middle of the North Atlantic Ocean to spawn and die, are replaced by their tiny young, known as elvers, which make the arduous trip back to populate European rivers. Due to the collapse in eel stocks, this species is now protected by EU legislation and the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
However, both adult eels and elvers are still at risk of being sucked into water-cooling systems at power stations or being chopped up by hydropower turbines. Much work remains to be done in protecting the eels; researchers at Southampton are investigating whether changing the lighting or acoustics near inlet pipes could encourage the fish to keep away.
Dr Kemp adds: 'Eels are slightly different and less sensitive to hydrodynamic cues than some other species of fish, and alternative approaches are needed for them. We are looking at the combined effects of different types of cues — hydrodynamics, acoustics and lights, for example, to increase the probability of inducing a desired response.'