Introductory Chapter: Importance of Plant and Invertebrates in Aquaculture Introductory Chapter: Importance of Plant and Invertebrates in Aquaculture

Aquaculture is an economic activity that presents a rhythm of global production with a sustained growth of 10–11% per year during the last years, with expectations of equating production by extractive fishing in 2025 [1]. It currently contributes about 50% of the world fish supply, and is considered to be one of the main economic activities of this century. In 2010, world aquaculture production was around 59.9 million tons; where freshwater fish dominated production (56.4%), followed by the cultivation of invertebrates such as mollusks (23.6%) and crustaceans (9.6%) [2].


Introduction
Aquaculture is an economic activity that presents a rhythm of global production with a sustained growth of 10-11% per year during the last years, with expectations of equating production by extractive fishing in 2025 [1]. It currently contributes about 50% of the world fish supply, and is considered to be one of the main economic activities of this century. In 2010, world aquaculture production was around 59.9 million tons; where freshwater fish dominated production (56.4%), followed by the cultivation of invertebrates such as mollusks (23.6%) and crustaceans (9.6%) [2].
It is an activity that encompasses very varied practices, and a wide range of species, systems and production techniques. Aquaculture can be defined as the production of aquatic organisms with techniques aimed at making their performance more efficient. It is worth mentioning that more than half of the total amount of food of aquatic origin consumed today by the world population, as well as products destined for non-food uses, comes from aquaculture farms where fish, crustaceans, micro algae, mollusks and other invertebrates are raised [1,4,5]. Particularly, invertebrates make up 95% of the animals that inhabit our planet. Due to its great biodiversity, it has not been possible to study in its entirety. There are species of mollusks, crustaceans and echinoderms that are consumed by man and therefore are the object of artisanal or massive fishing, which can lead to problems of population reductions, local extinctions or loss of genetic diversity [3], thus Aquaculture is a good alternative to solve this problem.

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The capture and cultivation of aquatic organisms in paddy fields has a long history and tradition, especially in Asia, where the availability of rice and fish has been linked to prosperity and food security. Rice-based ecosystems provide habitats for a wide variety of aquatic organisms used extensively by the local population. They also allow the improvement and breeding of aquatic organisms. A wide variety of aquatic species such as carp, tilapia, catfish and breams are being raised in the rice fields. Prices and market preferences can provide decisive opportunities for farmers to further diversify the use of species, especially eels, loaches and various crustaceans, to sell and market higher value biological products [7]. The problems associated with the breeding of aquatic organisms in paddies do not differ from those related to the development of aquaculture in general. These include the availability and access to seeds, feed and capital, as well as natural risks related to water control, diseases and predation [8].
Molluscs are currently the group of cultivable marine organisms that offers better prospects in terms of production and economic profitability, their production costs are not high and are a valuable source of food. To perform its cultivation requires detailed knowledge of the basic biology of the species, supply sources of seed, growth parameters and mortality in culture, and the effect of environmental conditions as well as their spatial and temporal variability. The cultivation of bivalve mollusks represents an economically viable alternative due to the possibility of large-scale operation, in addition, this activity can be environmentally sustainable by helping to reduce fishing effort in coastal areas [6].
The constant increase in world population necessarily implies a challenge in terms of food production in large volumes and with high nutritional quality. To achieve the economically profitable production of healthy animals with a limited environmental impact, it is necessary to improve growth rates and feeding and reproduction efficiency, decreasing the losses caused by diseases, by improving the immune response, diagnostic techniques and prophylactic measures [6,9]. In an intensive aquatic production system, control of the disease plays a key role, where an intimate relationship between the host and bacteria is present [10,11]. There is currently a widespread concern that antibacterial agents in aquaculture will lead to the emergence of antibiotics resistant bacteria [12]. Probiotics and the use of homeopathy, which act mainly on the innate response of cultured organisms, constitute a viable, promising and economic strategy to make aquaculture process more sustainable, since it reduces the indiscriminate use of antibiotics and chemotherapeutic product.
In case of treatment with probiotic, it has been carried out successfully in mollusks [13], fish [14,15] and crustacean species [11,16,17]. Wherein the probiotics used in aquaculture studies include Gram-positive and Gram-negative bacteria, bacteriophages, yeasts and unicellular algae [18], and the beneficial effects include growth and feeding efficiencies in culture systems [19].
Homeopathy in the aquaculture of freshwater and marine species is a potential alternative for the world aquaculture industry, because their medicines are free of relevant adverse reactions and do not bio-accumulate toxic substances in the harvested product. The studies realized, although scarce, suggest that homeopathy can be applied with prophylactic and therapeutic criteria. Among its mechanisms of probable action stands out the stimulation of the innate and acquired immune system, and consequently the increase in the resistance of the treated organism, against the pathogens that normally proliferate proportionally to the level of intensification of the culture. Higher survival, growth and reduction of stress levels have been reported, as well as notable changes in other parameters observed, such as less inclusion of lipids in the liver, greater hypertrophy of the muscle fiber, production of mucin-producing cells that are related to the inhibition to the entrance of parasites, and changes in blood parameters. These are indicators of improvement in health and nutrition of the organism cultivated, and if all this can be achieved by applying "ultra-diluted" doses, production costs are reduced and harmful effects are mitigated to the environment making aquaculture homeopathy an eco-sustainable alternative [20].