An ecosystem is the complete set of living and nonliving components within a region of interest. The term aquatic refers to water, so an aquatic ecosystem refers to living and nonliving parts of a waterbody and the interactions that take place among them. Aquatic ecosystems include oceans, lakes, rivers, streams, estuaries, and wetlands. Within these aquatic ecosystems are living things that depend on the water for survival, such as fish, plants, and microorganisms. These ecosystems are very fragile and can be easily disturbed by pollution. Aqua farming may take place in the ocean or on land, and can be used to grow marine or freshwater species. The environmental impact of farmed seafood is to a great extent determined by the farming method used

Aquaculture is the fastest growing animal food producing sector. With growing demand for aquatic products (fish and shrimp) comes increasing concern about the reliable supply of raw materials needed to support this growth. Aqua feeds traditionally depend on fishmeal as a protein source, but the trend in recent years has moved towards replacing fish meal with less expensive sources of protein of plant origin. As a result of this trend, aquaculture feeds have a higher risk of contamination by one or more types of mycotoxins. Aqua feeds contaminated by mycotoxins occur particularly in countries with humid tropical climates owing to many factors, among which are climatic conditions conducive to mold growth and inappropriate methods of feed processing and storage. However, increasing trade globalization and the incorporation of imported raw materials in aqua feeds expose feed manufacturers and their clients to the risk of combinations of mycotoxins either from multiple mycotoxins in the same raw material or from different mycotoxins in different ingredients in the same formulation. In addition, rising feedstuff prices have led feed manufacturers to look for more economical raw materials to avoid increasing feed prices. The use of more affordable raw materials of lower quality, such as DDGS, might increase the risk of mycotoxin contamination in feeds.

The ultimate objective of an aquaculture feed manufacturer and aquaculture food supplier is to ensure that the feed or food produced is both safe and wholesome. Reported food safety risks, which may be associated with the use of commercial animal feeds, including compound aquaculture feeds, usually result from the possible presence of unwanted contaminants, either within the feed ingredients used or from the external contamination of the finished feed on prolonged storage. The major animal feed contaminants that have been reported to date have included Salmonellae, mycotoxins, veterinary drug residues, persistent organic pollutants, agricultural and other chemicals (solvent residues, melamine), heavy metals (mercury, lead, cadmium) and excess mineral salts (hexavalent chromium, arsenic, selenium, fluorine), and transmissible spongiform encephalopathies. Apart from the direct negative effect of these possible contaminants on the health of the cultured target species, there is a risk that the feed contaminants may be passed along the food chain, via contaminated aquaculture produce, to consumers. In recent years, public concern regarding food safety has increased as a consequence of the increasing prevalence of antibiotic residues, persistent organic pollutants, and chemicals in farmed seafood.

Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hypothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure; membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.

Hydroponics means growing plants in water without soil. The discovery that plants can grow without soil was made long ago by several civilizations that lived in the desert. Growing crops in a desert area is difficult because the soil is poor and there is little water. People living in the deserts had to find ways to grow crops with very little water.  It seems strange that growing crops in water is the best way to use the least amount of water. In fact, plants grown using hydroponics use less water to grow than plants grown in the soil. Most of the water that is given to plants grown in soil goes through the soil and never reaches the plants. When plants are grown in water, almost all of the water goes to the plants. Scientists all over the world continue to use genetics and hydroponics to help farmers produce food crops that will feed the world’s population in the years ahead. Hydroponics will find use in medicine because many plants are responsible for producing medicines we currently use. Pharmaceutical scientists have found that they can make many of these drug producing plants release drugs through their roots. It is far easier and less expensive for companies to remove chemicals from water than it is to remove the same chemicals from soil. Pharmaceutical or drug companies will continue to work on finding ways of producing plants that can release drugs through their roots and into the water they are growing in.  Drugs produced by hydroponics will cost less money to produce and less money to the consume.

The main cause of the decrease fish production is the occurrence of diseases caused by different pathogens. The need for enhanced disease resistance, feed efficiency, and growth performance of cultured organisms is substantial for various sectors of this industry. It is preferable that, in the case of commercial aquaculture, the costs production to be reduced. Because the cost of antibiotics used for prevention and treatment of disease, and hormones used for growth performance is high, and from the desire to search for new options, several studies have been carried out to test new compounds, from which the aquaculture industry has developed the concept of functional additives”. This category includes also phytobiotics. Thus, it was proved that their use in fish diet led to improvement of the innate immune system for infection with various bacteria (Aeromonas hydrophila in particular) in different species of fish. In conclusion are needed further studies to find out the effective use of various phytobiotics with special reference to the timing, dosage, and method of administration.

Since communication between individuals of a species of fish by chemical agents (pheromones) was first demonstrated in 1932, such a process has been suggested in many aspects of fish behaviour and development. Scientists  observed on such mechanisms in shoaling behaviour and beneficial conditioning of water, homing of migratory fish, communication of alarm, ‘crowding factor’ (which adversely affects growth, survival and fecundity in dense population), pair formation and spawning, and a range of other social interactions to know about fish communication. Some of the chemicals involved have been isolated and identified, but most are indicated by behavioural observations. Pheromones are of great significance in fish behaviour and ecology, and are likely to be an important factor in culture operations. For "communication" to occur between individuals, an intentional signal must be generated by one or more individuals and received and interpreted by one or more recipients. Among the many ways of communicating in aquatic environments, sound is perhaps the most effective, especially over long distances. Sounds produced by fishes for communication are generally associated with either reproduction or stressful situations.

Aquaculture is normally included basically in the Fishery Sector Development Policy, document. It is also mentioned in other strategic policy documents; those for Industry and Environment are the two major policy documents concerned. In the absence of specific policy, aquaculture development is mainly based on development plans elaborated by the authorities in charge for the administering the sector but without formal approval. Participatory mechanisms concerned with the definition of policy mostly comprise unofficial consultations, with three exceptions. The first is in Spain where a formal Consultative Committee on Fisheries and Aquaculture has been established in Cataluña which includes representatives from the aquaculture sector. The second exception is Greece, where there is an Agricultural Policy Council (APC) operating within the Ministry of Agriculture; this is a consultative body within which representatives from the Ministry itself, scientific organisations, producers, and universities participate. The third exception is France, where there are "inter-professional committees.

Fish diseases affect the survival and growth rates of fìsh under culture. Given that drug treatments are expensive, fìsh diseases invariably lead to lower harvest and higher cost. Fish farmers often suffer hefty economic losses due to fìsh diseases. To alleviate such losses, it is crucial to take precautions to prevent fìsh diseases and reduce pathogen levels in water bodies. It is also important to prevent water quality from deteriorating and to strengthen the natural resistance of the fìsh stock. Regular monitoring of fìsh health is an effective way to identify disease uses and appropriate treatments. One major cause of serious fìsh kill is overlooking the contagiousness of fìsh diseases and thus delaying treatment. As such, adequate care and treatment should be given to infected fish promptly.

The difference between maximum metabolic rate and standard metabolic rate is referred to as aerobic scope, and because it constrains performance it is suggested to constitute a key limiting process prescribing how fish may cope with or adapt to climate warming. Owing to climate change, water temperatures have increased in marine and freshwater habitats around the world. Current projections predict a mean rise in temperature of 2–4°C globally by the end of this century, although locally the increase can be higher. For aquatic ectotherms, this may pose challenges of sufficient oxygen uptake to sustain their metabolic demand. The high thermal conductivity of water makes it challenging for aquatic ectotherms to maintain an internal temperature that differs from the surrounding water.

The growth in aquaculture has led to an increase in the use of feeds applied to water for improved production. The wastes that result from the use of aquaculture feeds are very much harmful for aquaculture. The management of aquaculture wastes has become a topic of intense regulatory scrutiny, as the Environmental Protection agency develops new waste management regulations for the entire industry.

Aquatic animal species are in constant interaction with potential pathogens that can strongly impair growth performance and result in significant economic losses for livestock production. Biosecurity encompasses all measures designed to prevent diseases from occurring and from spreading by isolating, as much as possible, animal farm populations from external contamination. Recurring or prolonged contact with external environments (water, sediment, wildlife) favours the development of new diseases. For this reason, non-recirculated aquaculture systems are more difficult to isolate than closed water circuits. Major Biosecurity goals are:

â–  Animal management—obtaining healthy stocks and optimizing their health and immunity through good husbandry

â–  Pathogen management—preventing, reducing or eliminating pathogens

â–  people management—educating and managing staff and visitors.The ease with which a specific pathogen can enter a facility, spread from one system to another, and cause disease depends on the species, immune status, condition, life stage, and strain susceptibility of the cultured fish;

â–  Major environmental factors such as water quality, water chemistry, and husbandry practices;

â–  characteristics of the pathogen, such as biology and life cycle, potential reservoirs, survival on inanimate objects, options for legal treatment, regulatory status (exotic vs. endemic disease, report ability, and federal, state and local laws); and Workers’ understanding of biosecurity principles and compliance with biosecurity protocols.

Selective breeding has a very high potential for improving the genetic makeup of fish in aquaculture production. It just takes a few generations to accomplish major improvements in economically important traits. Selective breeding is the process where the genetic variation present in desirable traits within a population is used to improve production quality, efficiency and sustainability. A good example of the possible benefits of selective breeding is the selection for growth in fish. The genetic improvements that have been obtained for growth in aquaculture species are in general three to five times higher per generation than what is found for terrestrial livestock species in general. The benefits of the breeding scheme come through the additional and cumulative improvement of genetics of the offspring that enter the production system.