Blue LED light
New trials to measure the effects that optimised, low-energy lighting units may have on the post-hatch fry of two species of cleaner fish are currently underway in Britain. Although both projects are currently on a small scale and are still at an early stage, their long-term results could have an impact on commercial aquaculture.
The LED systems used in the trials are part of the AquaRay range made by Tropical Marine Centre (TMC), better known in aquaculture circles as “TMC Commercial” for their recirculation filtration systems, widely used by hatcheries around the world.
Based in the English county of Hertfordshire, the company has traditionally focused on providing lighting systems for home and public aquaria use, where requirements are defined by aesthetic and welfare considerations, rather than in terms of productivity in a commercial sense. However, over the course of the last seven years, TMC has been increasingly interested in the biological impact that lighting can have.
As Gyles Westcott from TMC’s AquaRay lighting division reflects: “There is an increasing amount of scientific literature which proposes specific photic conditions as biological drivers in the early-stage culture of certain species, and within this lies the broad acceptance that blue light plays a particularly critical role.”
“The shorter wavelength of light from this part of the spectrum means that it is available to marine organisms for longer, which has profound implications for organisms that have evolved in these aquatic zones.”
“At the obvious end, visual acuity in the blue range will have been optimised in evolutionary terms as a physical advantage, directly affecting overt behaviour such as feeding success, sexual behaviour and survival from predation.”
“Less obviously, but now more widely accepted, is the role that light plays in regulating more subtle metabolic processes, for example in the stimulus of non-optical photoreceptors, and their role in regulating key metabolic processes. A good example of this is the way in which L/D cycles have been shown to regulate melatonin production in salmon. Again, these photic responses are regulated most efficiently by light in the blue range of the colour spectrum.”
“All of these factors have the potential to deliver dramatic improvements in yield and product quality. This applies especially during the initial production phases (hatching and larval rearing), when resource can be applied more directly and outcomes more directly assessed.”
“Further refinement of this package means that we can now combine different products from our commercial lighting range into a single, integrated and fully-controllable system which delivers a specific spectral profile, optimised to match the photic requirements of the culture species. One of products in this range is the patented ‘Nature Perfect’ platform which delivers the blue peak typically seen as an integral part of the underwater environment, while still providing an overlay of visible white light.”
Added advantages are that the system is scalable and can be installed quickly and easily – units are typically deployed in banks of either 4 x 28 watt or 8 x 14 watt units, with full photoperiod control including sunrise and sunset phases
This increasingly compelling body of evidence – combined with the technological advances made by companies such as TMC – has helped persuade two aquaculture projects to trial the “Nature Perfect” platform. The first of these involves lumpsucker/lumpfish, which are being cultured for their potential use as cleaner fish in Scotland’s Atlantic salmon industry. Taking place in Devon, in Southwest England, the trial involves the deployment of one of the company’s 28 watt LED units over each of the 12 post-hatch fry tanks.
After three weeks the results have been promising, although, as Gyles admits, the trial is still in its infancy. “We’ve had very encouraging behavioural results so far,” he reflects, “and we’re confident that closer analysis will reveal effects at the biological level, allowing us to optimise our system further.”
The second trial also involves cleaner fish, although this time ballan wrasse on the west coast of Scotland. Again, initial results have been encouraging.
However, neither of these trials is concerned with the potential effects of optimised light on incubation and pre-hatch larval development.
“Many farmed species are affected by poor hatch rates and high incidences of deformity,” Gyles points out. “Of course, there is a complex mix of environmental drivers at play here, but light is an important one. A relatively small effect at this point of production could bring significant commercial benefits, and we are keen to engage with the industry and related researchers to explore this further.”
Underlining all of this, he adds, is the energy-efficiency of LED technology. “LED has proven itself as a technology and is an important platform in the drive to reduce energy costs and carbon emissions. This has important implications for operating costs, as well as environmental credibility, especially in an industry under scrutiny over its environmental impact – taken together, the benefits on offer make LED technology a potential game-changer for the aquaculture industry.”
— Rob Fletcher