Wild caught vs farmed fish

Wild fish refers to fish that live in their natural environment, without human input, until they are harvested for sale as food.  This is the last remaining example of large-scale harvesting of any creature from the wild as agriculture has successfully turned almost every other food source into one produced by human ingenuity and effort.
 
Global aquaculture produces more than 130 million tons of fish, shellfish, crustaceans and seaweeds every year.  Fish are generally farmed in earth ponds, tanks with powerful filtration systems, or cage placed in lakes or in the ocean.  Farmers breed the fish and rear them to market size in captivity, thus ensuring a constant supply of fish reared according to the required standards and to the optimal size for the market, as the entire process is controlled.
 
Wild fish, on the other hand, feed on the natural foods available to them, and according to their species, this could be algae, plants, crustaceans, molluscs or smaller fish.  Sometimes wild-caught fish have a muddy taste or off-flavour, which is most common in freshwater fish, but also in marine fish from an environment with lots of algae.  Farmed fish can display the same off-flavour, especially when farmed in earth ponds, but, with appropriate systems and management, such off-flavours can be excluded such that these farmed fish are as delicious as their wild caught counterparts.
 
A growing problem facing global food chains is the increasing incidences of plastic and heavy metal bioaccumulation found in wild-caught fish.  Small fish eat algae or crustaceans that have ingested plastics or taken in heavy metals, and these pollutants accumulate each time the small fish, then bigger fish, is eaten by the predator on the next step in the food chain.  Thus, the top predators are especially at risk and wild-caught fish such as tuna, swordfish and marlin are especially at risk of contamination with plastics and mercury, due to their position near the top of the food chain.
 
The converse may be true where farmed fish could have elevated levels of antibiotics or other pesticides used to control pathogens and other infectious agents on the farm.  In reality, this is a problem in some parts of the Far East, but is almost unheard of with fish being produced locally.
 
An additional consideration relates to environmental impact.  Farmed fish generate faeces and other wastes that need to be disposed of in an appropriate and sustainable manner.  In the past this was seen as waste and a problem for which a solution needed to be found, in modern times it is recognised that these wastes are in fact fertilisers which are ideal for growing crops, either extensively via fertigation or intensive as aquaponics.  In effect, the waste has now become an income stream.  A benefit of farming fish is that it reduces the pressure on wild fish stocks, most of which are over harvested and many of which are in a critical state.  Since 2013 most of the fish eaten globally is farmed.
 
The supply of wild-caught fish can be subject to seasonal fluctuations due to the movement patterns of the fish and weather conditions.  Fish sizes also vary depending on what is caught, with a trend towards catching fish that are on average smaller and smaller.  As farmed fish are produced under controlled conditions they can be harvested once they attain the target market size, enabling the farmer to supply highly consistent sizes of fish to the market.  This is especially important when the fish are to be processed for value addition; here size makes a big difference as the proportion of usable meat compared to off-cuts is a function of size per product being produced.
 
Wild fish can have firmer flesh than farmed fish, although this does vary according to species and the infrastructure type in which they are reared.  The market generally prefers flesh that is firm, favouring wild-caught fish.  Again, in value-added products this difference is insignificant.
 
The final consideration relates to the ability of farmers to match market preferences in their fish, e.g. the orange colour of trout.  In nature, trout flesh is a pale pink colour, yet the market prefers a more intense orange colour.  This desirable flesh colour is achieved by including carotenoids in the trout feed for the final month of farming prior to harvest.
 
In previous years, preference was displayed by the markets for wild-caught fish on the assumption that they are better tasting, free of pollutants and more environmentally sustainable.  However, over time the fish farming industry has developed to the point where these factors have often been reversed, and farmed fish is favoured over wild-caught.  The justifications used include availability, environmental appropriateness, convenience and product safety.  As we move away from being hunter-gatherers to being farmers of fish, we can rely on the many benefits farmed fish offer over wild caught fish to grow the industry.
 
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