WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 25 Advantages of LED Lighting Systems in Larval Fish Culture Juliette Delabbio Fish need light to survive and grow; it is one of the essential inputs to life. In aquaculture there are natural and artificial sources of light. Regardless of source, environmental lighting in an aquaculture facility drives key biological processes that influence performance and ultimately affect production and profitability. Incandescent and fluorescent lighting are traditional artificial sources for environmental lighting, but LED lighting now offers another option for hatchery managers. Applications of LED lighting in aquaculture facilities have only recently become economically feasible, with the cost of lamps offset by accrued energy savings. More importantly, traditional light sources, such as incandescent or fluorescent lamps, do not provide the opportunity to change light spectrum and intensity and do not provide optimum lighting conditions for larval culture. Newly-developed LED lighting systems provide flexible adjustment of light intensity, photoperiod and spectrum in a single light source, thus serving as a powerful tool to influence growth and survival in larval fish culture. The Significance of Environmental Light to Larval Production Light intensity, spectrum and photoperiod have a significant effect on fish at all life stages (Boeuf and Le Bail 1999, Ruchin 2004, Han et al. 2005, Marchesan et al. 2005). The larval stage of any fish species is exceptionally sensitive to environmental conditions and newly hatched animals are particularly fragile. Light receptivity in larval fish changes during development and this affects feeding behavior, feed intake and survival (Fig. 1). The effects of light on marine fish larvae have been studied in the laboratory (Barahona-Fernendes 1979, Puvanendran and Brown 1998, Downing and Litvak 1999a and b, Trippel and Neil 2002, Migaud et al. 2008, Yoon et al 2010, Vollset et al. 2011) and the field (Blaxter 1966, 1968, Suthers and Sudby 1996, Gibson et al. 1998). In total, this research indicates that environmental lighting is an important and complex parameter with broad effects on growth and survival of marine fish larvae. The Effect of Light Intensity on Marine Fish Larvae Performance The larvae of many marine fish species are born predators, suggesting that the intensity of light in the rearing environment can significantly affect survival and growth. Marine fish larvae rely on visual photoreception to establish the location of prey and poor lighting can cause abnormal eye development, resulting in decreased visual acuity (Rahmann et al. 1979, Zeutsius and Rahmann 1984). Therefore, most fish larvae need a minimal threshold of light intensity to survive, which has evolved in relationship to the ability to localize, catch and ingest prey in its natural habitat. Larval-rearing environments in hatcheries usually use artificial lighting conditions that are quite dissimilar to the larvae’s natural environment. Teleost larvae need a minimum light intensity of 0.1 lux to locate prey properly (Blaxter 1986). This is a very general statement; later research has indicated that, under aquaculture conditions, finding the correct environmental lighting for marine fish larvae is a complex issue with several complementary factors to consider. A Complex Issue: Environmental Lighting Requirements Differ with Species Peña et al. (2004) studied the effect of environmental lighting on the first feeding stage of spotted sand bass Paralabrax maculatofasciatus. With a fluorescent lighting source, prey capture increased with light intensity. Light intensities of 0, 100, 400 and 700 lux were measured at the air-water interface and capture success was assessed by prey content in individual digestive tracts. Bass larvae were more successful at capturing prey at 400 and 700 lux than at 0 and 100 lux. Because there was no statistical difference in prey capture between 400 and 700 lux, it was postulated that there may be threshold levels of light intensity to activate feeding behavior but, once those thresholds are reached, increases in light levels do not increase feeding activity until an upper threshold negative response occurs. This research clearly showed that lighting in a specific intensity range was a factor in first-feeding activity. Inasmuch as high larval mortality is a common occurrence in aquaculture, there is a need to establish threshold light levels for larval stages of different commercially produced fish species. Compared to conventional lighting sources, LED lights can smoothly reduce intensity from 100 to 0 percent without affecting spectral output. In the laboratory, an increase in light intensity coincided with greater success rates of prey capture by haddock larvae (Downing and Litvak 1999a). Atlantic cod Gadus morhua larvae held at high light intensity (680 lux) had lower feeding intensity than larvae held at low light intensity (8.5 lux) (Puvanedran and Brown 1998). (CONTINUED ON PAGE 26) FIGURE 1. Research on the effects of ONCE LED lighting on growth performance of red drum larvae is currently underway at the University of Texas Marine Science Institute. Photo by Cypress Hansen.
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