The installation of double streetlights along the walkways between sea cages to improve employee safety had an unforeseen effect, marking the beginnings of light management in the aquaculture industry.
Lighting along the walkways of the fish farm resulted in large, well-formed salmon that did not reach sexual maturity. Student Kenneth Brandal was intrigued by the accidental discovery and wrote a semester paper on the topic at Akvaforsk – The Institute of Aquaculture Research.
Mr Brandal was later offered the position of operations manager at the Beitveit aquaculture facilities. His first project was to install 150 W sodium bulbs in all the sea cages at the facility, which led to nearly immediate results. Today Mr Brandal is the head of Region West at Marine Harvest Norway.
“Although the lights are very expensive, the results are fabulous,” says Mr Brandal to News from the AQUACULTURE programme no. 2/2007 (recently issued).
The story behind the use of light management in the aquaculture industry is an example of a cohesive approach to a set of complex problems. In this case, the aquaculture industry collaborated with the supplier industry and various research groups over a number of years, studying the effect of light on fish biology, development and welfare, while at the same time further developing methods and technology.
1. Diodes and spectrums
Underwater lights with a daylight spectrum are commonly used today. These types of lights distribute light well and have a good effect on shoaling, growth and controlling sexual maturation, but they are energy intensive. The aquaculture lighting manufacturer Idema Aqua is currently developing new light systems with lower energy consumption.
In cooperation with the Institute of Marine Research, the company is testing a new type of diode bulb, with promising results. The bulbs are costly, but their life span is 30 times longer than that of traditional metal halide lamps, with half the energy consumption.
There is still a need for greater knowledge about the use of underwater lights of different colours. “There is considerable confusion surrounding the placement of lights and the use of various coloured lights to obtain optimal biological effects”, explains Morten Malm at Idema Aqua.
Intravision Group has successfully tested the use of narrow bandwidth light on salmon and turbot. The company is currently carrying out experiments on cod and has received grants from both the Research Council of Norway and the EU.
Among other research activities the company is testing several alternative light technologies and has developed underwater light systems in which all light is within the most biologically interesting spectrum. “We believe it is possible to prevent sexual maturation in cod while using half the energy consumed by metal halide lamps,” says Per-Åge Lyså at Intervision Group.
2. Twenty years of light management
Sævereid Fiskeanlegg was the first company to install lights in sea cages to control smoltification in salmon.
In the 1980s researchers investigated whether smoltification could be induced regardless of the season, thus enabling continual production and greatly improving the exploitation of facilities for both fingerlings and food fish.
Researchers at the Institute of Marine Research and the University of Bergen came up with the idea of controlling smoltification by changing the light rhythm in the tanks. This led to Nordic test production at the Sævereid Fiskeanlegg facility, with support from the Nordic Fund for Technology and Industrial Development. On 5 June 1987 the light in the sea cages was adjusted to simulate the light of 1 February, after which it was gradually increased day and night to simulate the light of spring.
The result was top-quality smolt that reached a weight of 2.5 kg after one and a half years in the sea.
3. Controlling growth and welfare
According to Geir Lasse Taranger at the Institute of Marine Research, light affects the life and development of fish, and the proper use of light systems in aquaculture may improve fish welfare, delay sexual maturation, facilitate rapid growth and increase survival rates.
“However, the amount and quality of the light are decisive,” he emphasises.
In salmon farming lights are used in sea cages in the winter to extend and shift the growth period. Lights are also used to delay sexual maturation.
Mr Taranger points out that recent experiments have shown that light is actually of greater significance than feed composition for the age of onset of sexual maturation in cod. Early maturation leads to serious losses and welfare problems in cod farming.
While considerable experience with and insight into the use of light management has been gained in aquaculture, there are still many areas in which researchers lack sufficient knowledge.
“The biological clock of fish is set according to the light, but the mechanisms behind this are not yet fully understood,” says Mr Taranger.
Like human beings, fish release melatonin when it is dark outside, and it has been proven that using light at night can limit the level of melantonin in the blood. Mr Taranger is currently studying how light of various wavelengths affects fish’s production of melatonin.
“The aim is to discover the relationship between the type of light and the release of melatonin and how this influences sexual maturation and growth over time,” he explains.