The negative impacts of aquaculture

Although aquaculture has been projected as a panacea for Third World poverty, its advocates ignore the fact that it spawns a whole host of problems for which there are no solutions.

AQUACULTURE, or production of aquatic organisms in an artificial system has been in practice for over 4,000 years in some Asian countries. In China, fish were reared in ponds as early as 475 B.C. just as modern farm animals are bred for conversion efficiency and rapid growth rate. Fish of various species have, in recent years, also been subjected to such planned breeding. As in the Green Revolution high yield varieties (HYVs) plants, fisheries also have been the object of selective breeding for high-fecundity, large egg size, high hatching percentage, rapid growth, early maturity, high temperature tolerance, disease resistance, etc.

Hybridisation (cross-breeding) between various species and strains have also been done for commercial salmon and trout. Genetically-engineered organisms for human consumption are not too far away in the future, if not already in the market. If we recall the Green Revolution, the creation and use of HYVs plants have created numerous serious problems.

Introduction of exotics

Introduction of species (accidental or deliberate), has high adverse impacts. They may alter or impoverish the existing communities and populations of the receiving ecosystems through inter-breeding, predation and competition for food, space, habitats, etc. Genetic pollution of indigenous stocks is possible. Some countries recognise the danger of genetic pollution and have taken preventive measures. In Norway, the number of salmon escaping from fish farms exceeds the wild population, resulting in wild types diminished due to introgression of domestic stocks, loss of genetic adaptation to local conditions as well as potential susceptibility to diseases. It has prohibited siting of salmon farms within 30km of important salmon runs. Introductions (deliberate or accidental) may result in populations replacing the original communities of the area, thus altering the ecosystem e.g. Penaeus japonicus (shrimps) from Japan but farmed in European lagoons have colonised vast areas of European marine areas.

Marine environment and preservation of the marine biodiversity does not only concern developing countries but more so than ever concerns the industrialised countries which have lost much of theirs.

In a similar way, genetically modified organisms (GMOs) including micro-organisms may do the same. Spectrum of risks posed by GMOs include adverse effects on humans and animals as well as disruption of ecological processes. Currently, there are no effective regulations of control. The releases can be deliberate or unknown (waste products of biotechnological industry laboratories).

Spawning difficulties

Some organisms depend on certain factors to trigger specific biological reactions e.g. spawning.

Penaeid prawns, which form a crop of major economic importance, is an estuary-dependent species which, although breeds at sea, grows and shelters in the mangrove areas during its post-larval and juvenile stage.

After spawning, adult prawns/blue crabs/gray snapper remain on the reef, while the young and post-larval move inshore to mangrove proproots to seek protection and food. Then, they move upstream into low-medium salinity reaches. When mature, they move out from the low-medium salinity zones to the estuary and reefs to spawn.

In the process, they inhabit and utilise more than 10 different types of critical habitats in succession, in addition to daily diurnal migration between numerous habitat types.

Numerous researchers have found high direct correlations between prawn yield (kg/ha) and intertidal wetlands area world-wide. The yield is proportionate to the presence of wetlands area. For example, shrimp production on the west coast of Peninsula Malaysia (where a lot of mangroves still exist) is higher compared to the catch in the east coast where there is not much mangrove.

Many cultured organisms cannot be bred in captivity. Captive spawning is possible with artificial spawning or fertilization, in some cases with hormonal injections, as in the case of sturgeon and salmon. In prawns, the eyes of the females are callously cut to induce spawning.

The culture of many other species is dependent on fries captured in natural waters. Shrimp culture is partly dependent on hatchlings from a brood stock in captivity (one-eyed female prawns), partly on egg-bearing (gravid) females caught at sea which fetch high prices, and partly on larvae and juveniles caught on the coast.


In aquaculture, organisms are immersed in water, hence they are more intensely exposed to the environment as compared to terrestrial animals. Thus, aquatic animals are more sensitive to pollution whether chemical or their own excrement. And as in the Green Revolution, many problems have cropped up with regard to diseases.

Out of greed to make maximum profits, intensive aquaculture utilise a dense stocking rate (overcrowding). Studies have shown that dense stocking rate may induce stress problems and increase susceptibility to diseases. Overcrowding leads to poor water quality due to decreased oxygen level, high accumulated metabolic products and excrement, rapid growth and transmission of noxious parasites, micro-organisms and pathogens.

A University Science Malaysia (USM) scientist said that many fish species in aquaculture such as siakap (giant sea perch), kerapu (grouper), and jenahak (golden striped snapper) are threatened by diseases which can result in high mortality rate. Fish diseases such as epizootic ulcerative syndrome (EUS) and vibriosis with symptoms such as boils on the skin, tail-rot, etc. started spreading in the early 1980s in Indonesia, Malaysia, Thailand, and the Philippines, incurring a great loss to fish farmers.

Water pollution by aquaculture

Aquaculture, technically is a process akin to the fermentation process where it has to be seeded and it also produces an effluent discharge, which must be regarded as a potential pollutant.

The prime factor for aquaculture is control of water quality, especially in high stocking density. Fish excretion is high in ammonia, nitrite and nitrate. Nitrite binds with the haemoglobin of blood in the fish and can be fatal. Moreover, overfeeding must be avoided in order to avoid fouling of the water. To maintain a viable limit of oxygen (6-9 mg/l), energy-consuming mechanical aeration is also sometimes necessary.

Locals deprived

One of the basic tenets of aquaculture is to increase food production. The important question is, for whom? Aquaculture, which has been hailed as THE answer to cheap production food for the millions in the poor Third World countries has instead been utilised to produce luxury delicacies such as fat prawns for the consumption of the already over-fed, affluent and wasteful societies in developed countries such as Japan and US.

It has also brought a huge amount of profits to industrialists and investors who deal with high-technology gadgetry in pellet fishfood and vaccine research and production, ice production, processing, transport, etc.

Meanwhile, the small-time fishermen and fish farmers lose out and the diet of local people gets impoverished. In Malaysia, tiger prawn is sold for about 32 ringgit (US$13) per kg, double the cost of a kg of beef, out of reach for the general local population.

It is ironic then, that most of the world's top suppliers and exporters of shrimps and fish are countries where most of its own people are undernourished: Thailand, Philippines, Indonesia and India.

Volatile prices

What is worrying is that, like any commodity, when the supply exceeds the demand, the price will drop drastically. Already, experts are forecasting that real prices could drop as much as 6-10% annually over the next few years, making shrimp farming not as lucrative as they were, and even resulting in great losses to small fish farmers who could not cope with the low price but high expense aquaculture activities. The biggest losers would be the locals who would have lost in terms of mangrove destruction, river pollution, loss of livelihoods, etc.

Water pollution contaminates prawns/fish

Aquaculture, which uses water from the river, estuary, coastal area, is prone to external pollution and the produce (fish, prawns) can be a health risk if consumed.

A study done by the national university of Malaysia on a tiger prawn project which uses water from the Inanam River estuary in Sabah is a case in point. Light industries (workshops, etc), pig and poultry farms located near the estuary are sources of pollution. The water of the Inanam River and prawn ponds was monitored. Dissolved cobalt and lead were found to be higher than the recommended values of 0.05 mg/l. Suspended solids were found to be higher than the maximum value recommended (40 mg/l) by WHO.

There is concern over the safety/edibility of prawns and fish produced under contaminated environment. Fear of heavy metal bioaccumulation and lead poisoning affecting human health is not an exaggeration.-TWR