Since the cultivation of aquatic organisms has become popular for being an economically and ecologically sustainable activity, various studies have been carried out on the control of physical-chemical parameters and their interaction with the productive efficiency of the organisms cultivated. This leads us to the review of research on the influence of lighting on fish production, whether positive or negative, of lighting on the different stages of the life cycle of some aquatic species, mainly commercial for consumption and for ornamental purposes.

It is from these studies that we know that the photoperiod and even the intensity of light can condition feed intake, the use of energy and even the social behavior of farmed fish. The lighting on fish production influences the growth and survival of the farmed species.

Of course, it has been found that the photoperiod is of great importance with respect to the production and release of reproductive hormones, i.e. it directly influences the reproduction of fish.

Effect of lighting on different life stages of cultured fishes

Different lighting programs which shows the influence of lighting on fish production are explain.

• Schemes of 16 hours of light and 8 hours of darkness have shown a positive effect on the growth and reproduction of fry of some fish species such as cod (Gadus morhua), trout (Oncorhynchus mykiss), sea bream (Sparus aurata) and red snapper (Pagrus major). Species in which feed consumption and feeding efficiency are higher under this photoperiod, because they are more active and have a better visibility of their feed.
• The influence of lighting on fish production, and specifically prolonged light patterns, is not always a formula that leads to successful reproduction of our fish. Some aquatic species prefer short light periods such as turbot (Scophthalmus maximus) crops managed under 12:12 and 08:16 light-dark patterns, which have higher feed conversion efficiency and thus higher growth.
• In the case of catfish (Clarias gariepinus), a constant presence of light in early stages of development generates distress, which causes a delay in growth, increased aggressiveness that can even lead to the presence of cannibalism, directly influencing the survival of the fry. In this same species maintained under extended light schemes, high levels of lactate and cortisol have been reported due to constant activity and increased aggressiveness. A prolonged period of darkness in catfish generates a dark coloration of the dermis, which increases its price in the market.

Photoperiod in aquaculture reproduction

The management of the photoperiod in an aquaculture production is useful to increase the reproductive efficiency of our reproducers by improving the synchronization of their sexual maturity and inducing spawning. The positive effect of the influence of lighting on fish production is achieved by exposing the pineal gland and the hypothalamus to variations in light to produce gonadotropin-releasing hormone, estradiol, progesterone and testosterone, which together will regulate gonadal development in the fish.

Long periods of light do not have a good result in the reproduction of some species, such is the case of Atlantic cod (Gadus morhua) in which such exposure to light causes a delay in spawning, lower fecundity and a smaller diameter in their eggs.

In contrast, natural light or 16:08 light-dark photoperiods positively influence the gonadal development of perch (Perca fluviatilis), reporting high levels of testosterone and estradiol when exposed to this type of pattern. These same light periods generate higher sperm production in males and higher egg production in female perch.

One of the most studied species in the reproductive aspect has been the Nile tilapia (Oreochromis niloticus) which in long day photoperiods (18:06 and 14:10) its maturation has been much earlier, increasing its fecundity, raising its egg production and the production of estradiol, testosterone and gonadotropin releasing hormone.

The increase of its reproductive efficiency under these light schemes is thanks to the action of melatonin. It works as a neurotransmitter released in the brain by the action of light variation signals and which sends orders to the pituitary gland and hypothalamus for the release of reproductive hormones.

In contrast, the reproductive activity of O. niloticus decreases in short day periods (06:18 and 06:06). When we expose this species to continuous light schemes, i.e. zero hours of darkness, we find that it presents a low gonadal development and an increase in its growth due to a higher food consumption and the diversion of the energy needed for gonadal development towards the growth of muscle mass and energy reserves.

The influence of lighting on fish production can also affect the social behavior of aquatic species, such as the neotropical cichlid (Cichlasoma dimerus) which, when exposed to long periods of light, show an aggressive behavior compared to short periods of light; this aggression is related to competition for territory and reproduction. The decrease of aggressive behavior in short light periods is related to the low levels of the GnRH3 hormone, in charge of stimulating aggression in fish during the reproductive period.