Effect of LED lighting on juvenile Atlantic salmon prior to sea transfer

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Cristina Tanase, Innovation Program Manager, Philips Lighting Aquaculture aquaculture@philips.com

The parr–smolt transformation of salmonids is a series of changes at behavioral, morphological, and physiological level that prepare them for sea water migration. This transformation is size dependent and in natural environment occurs in spring, mediated through both photoperiod and temperature triggers (Ref 1). It is recognized that photoperiod is the dominant environmental cue (Ref 2). Specific photoperiod regimes can advance the timing of the changes that occur during smoltification such that today farming of Atlantic salmon is season-independent of smolt production and sea water transfer and shortening the production cycle (Ref 3). Yet, light impact on juvenile Salmon does not limit to only smoltification. Research studies show the influence of light on growth and development of juvenile salmon in fresh water. Exposed to specific photoperiod regimes juvenile salmon shows different swimming behavior (Ref 4), growth dependency on changes in day length (Ref 5), increased stress level (Ref 6). The development and sea water adaptation are stimulated by several hormones such as growth hormones, cortisol and thyroid hormones and increasing tolerance to salinity (Ref 7).

However to date, lighting strategies in the salmon industry are far from being optimized in order to improve smoltification, growth and post-transfer development. Although there are many signs that lighting can further support these factors, both fundamental research and the translation to commercial scale are often lacking. Philips supports both the fundamental research as well as bringing this knowledge applicable to farming practices.

Developing new lighting strategies became available in the last years by the use of LED lighting solutions during juvenile fresh water stage of salmon. Innovative lighting strategies beneficial for salmon farming are tested and implemented at commercial scales. The LED lighting used is specifically designed for this purpose: optimizing the intensity and exposure time, the light distribution throughout the tank. In order to reduce stress and improve light accommodation, dimming of light is implemented in the solution (Fig. 1). This article presents the results of a commercial trial conducted by Marine Harvest and Philips at the site of Kvingo. The trial has been designed and organized by Marine Harvest Norway with the newly designed LED lighting system from Philips. The trial has been conducted in 16 m diameter covered tanks according to local operations at Kvingo. The trial started in November 2012 with 2 tanks accommodated with LED lighting and 2 tanks accommodated with metal halide as control group. The fish in all tanks has been exposed to photoperiod of day/night and continuous lighting regime in order to prepare and induce smoltification. In the Philips group the light was increased to 100% and decreased to 0% slowly during the day/night lighting regime. Each tank had at the start of the trial roughly 300 000 fish at approximately 50 g. During the trial fish was fed using standard commercial diet and the weight of the fish was measured every two to four weeks in batches of 100 fish (regularly) and 200 fish (during vaccination). The fish were acclimated to normal sea water and transferred to sea cages in May 2013 for observations on survival and growth during the summer and autumn under natural thermal and photoperiod conditions. The result of the trial has been evaluated based on measurements of the fish weight, monitoring of the feeding and mortalities.

The salmon development expressed in weight and SGR have been compared over the trial period. Evaluation has been done based on data collected along the trial, e.g. feed, fish weight, temperature and smoltification observation. The analysis of the data showed that at sea release the Philips groups had a significantly higher mean weigh with 18 %, compared to the metal halide group (Fig. 2), while the growth rate was higher with 42 %. The smolt was transferred to sea cages according to production schedule. As a consequence of this, some of the fish was mixed between the metal halide and LED test groups when put into the sea cages. According to measurements at 30 days after sea transfer, the mortality was significantly higher in the metal halide cages with 2.7 % compared to 0.1 % in the Philips cages (Fig. 3). The mortality was mainly due to incomplete smoltification in the metal halide cages. The results after 60 days showed the same differences. The advantages of improved growth and decreased mortality after sea transfer show significant decrease of production costs, while enhancing fish welfare by using Philips LED lighting solution. Improving lighting regimes for the benefit of Salmon farming has been reinforced by extended research programs at the University of Stirling and the University of Bergen in close collaboration with Philips in order to investigate and understand the importance and impact of type of light on juvenile and on-growing salmon. This article shows how fundamental research can be translated into tangible solutions to be applied by farmers and bridging the gap of research and the farming operations. The lighting system is now being used commercially. According to technical coordinator at Sjøtroll Havbruk AS, Svein Nøttveit “the lights have high intensity which is important to secure good smoltification in large tanks. The slow ramp up and dim down is very positive for not stressing the fish”. New developments show that with this success also new research can be funded to fuel a next wave of innovative solutions. The final goal is to create a healthy and sustainable ecosystem of knowledge institutes, suppliers and farmers for the benefit of society such as lowering the environmental footprint of the industry, improve fish welfare and production practices, and become more efficient and cost effective.

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