The current methods of the acquirement of fish and shellfish is primarily deep sea trawling.The current problems with conventional fishing methods are:
•Specific species of fish and shellfish can only be caught at certain times of the year making them expensive.Also they can only live in certain habitats and oceans.
•Quotas can affect their availability and as well as the fact that the oceans have been divided up between nations making the catching of fish in outer territories politically risky.
•Fishing boats use large amounts of energy usually in the form of fossil fuels and furthermore trawlers tend to use small nets that catch smaller fish thus leading to unsustainable over fishing
•Catching and transporting fish to landlocked areas is energy intensive and requires too much human labour.Even if the catching of fish could be automated it would still be inefficient and time consuming as well as waste of energy in transportaiton.
•Conditions such as pH, temperature and nutrient levels can vary over long periods of time and is unpredictable.
•Pollution of the oceans has led to the bio accumulation of pollutants such as mercury,radioactive materials that can build up in the fat of fish especially oily fish and thus bio accumulate in the human body
•Climate change is affecting the growth of certain species of fish and pushing them out of their native area making them invasive species that effect ecosystems.Also ocean acidification is destroying plankton and algae the main food source of fish.Since plankton are at the bottom of the food chain this can have disastrous effects on the populations of predators.Furthermore shellfish cannot form strong enough shells and so die off.
•This and ocean warming and acidification are also killing off coral reefs and the species that depend on them. Also coral that is remaining is being harvested usually illegally thus affecting them negatively.

Conventional methods of fishing are simply unsustainable due to corruption, sloppiness and climate change. Solutions to this are recirculating aquaculture systems as well fish farming:

•Recirculating aquaculture systems can rear any types of species of fish and shellfish any time of the year.This includes native and non-native species ranging from those for human consumption,tropical fish for pets and even those for pedicures such as Garra rufa fish for use in salons as well as at home.Both freshwater and seawater fish and shellfish can be reared alongside tropical fish.Due to controlled conditions such as temperature, food supply and lack of predators in RAS systems fish and shellfish can grow much faster and bigger.
•Fish, caviar and shellfish can be produced cheaply and abundantly regardless of quotas and political issues regarding divisions of the oceans.
•Recirculating aquaculture systems uses less energy than trawlers in their operation and can be powered by geothermal heat or solar heaters as well as renewable energy from the grid. Furthermore fish are reared in enclosed areas and can be used to alleviate dwindling stocks in two ways: firstly simply using them allows stocks in the sea to recover.Endangered species can be reared solely for conservation efforts to rapidly increase their numbers and then released back into the wild when their population is increased.Aquaponic systems can be introduced that produce two crops as the plant crop can grow from manure produced by fish and this can reduced the need for filters cutting energy usage.It also negates the need to automate the trawling process.
•Fish can be reared in controlled environments with regards to aquaculture systems preventing their exposure to pollutants and even pathogens
•These aquaculture systems can allow for fish and shellfish to be reared in landlocked areas such as villages, cities and even deserts cutting down on energy costs in transportation and allowing these areas easier access to a wider variety of fish and shellfish in their diet.Recirculating aquaculture systems are fully automated and come in a range of sizes with small systems placed in kitchens or spare rooms of homes or in basements of vertical farms.
•Conditions such temperature, pH, salinity and nutrient levels are controlled and monitored 24/7.Alterations can be made to suit the needs of a specific species as well as for use in scientific studies.Fish can be checked for diseases at the start to ensure stocks reared this way are free from disease forever.
•This system can rear fish in controlled environments preventing them from having to retreat to colder or warmer oceans.Native species affected by invasive species led to new areas due to warming oceans can reared in these systems and then returned to their native habitat once invasive species have been removed or move away.Shellfish can thrive in controlled conditions and returned to the wild once pH conditions become more favourable.To deal with ocean acidification terrestrial based carbon sequestration can be employed alongside extracting carbonic acid from the oceans in desalination processes which in turn can be sequestered.Also plankton species could genetically engineered to tolerate lower pH.Also GM salmon which are triggered to grow faster and bigger can be reared in these systems thus preventing them from affecting wild stocks.
•Coral can be grown in recirculating aquaculture systems for use in jewellery and conservation efforts.It can be reared by this method permanently or then moved into landlocked ocean parks where it grown over longer periods of time as a temporary home and then returned to the ocean when conditions become more favourable.Another proposal is to genetically alter or breed corals to become more heat and acid resistant.Rare species of shellfish and shell forming fauna can also be reared for the same reasons.