Shellfish – a more sustainable option?

In terms of enduring popularity, many species of prawn, shrimp, lobster, crab, scallop, abalone, mussel, and oyster are highly rated. This is particularly apparent in regions of North Asia, where the ability to source exotic seafood is frequently seen as an important status symbol. In the wild, these creatures depend upon a clean environment with plentiful stocks of marine plankton, fish and other organisms. Many of the crustaceans are natural scavengers, living among floating sea grasses, rocky shelves and reefs. They provide an essential service by consuming marine detritus before it spoils and alters water quality. The bivalves, including clams, oysters, scallops, and mussels, obtain most of their nutrients through fluid filtration, leaving them particularly vulnerable to adverse changes in water quality. Many of these creatures are harvested from the wild by commercial and amateur fishers. There is also captive rearing which has been practiced for centuries in many regions of the world.

Prawn farming

Commercial prawn farming attracts levels of controversy similar to that of farmed salmon. While their food conversion efficiency is almost twice that of salmon, they are dependent on the same unsustainable supplies of fish meal and oils.

As an industry, some of the largest commercial prawn farming operations have been established in developing countries with extensive coastal access. In attempts to increase their efficiency and profits, prawn farmers have encroached upon important marine habitats such as the coastal wetland and mangrove forests of tropical Asia. These habitats which are also destroyed by other forms of land reclamation and development are among the most ecologically diverse on the planet. Within Asia alone, several million acres of pond have been developed for the farmed prawn industry. This enables several hundred thousand tons of prawns to be produced each year along with jobs and income for the respective regions.

The impact on coastal environments

From an environmental perspective, these short term economic advantages are often outweighed by their lack of sustainability and negative impact on other natural resources. The damage caused by poorly managed farms is often dramatic. When biological waste and other pollutants get drained from concrete ponds into coastal waterways, they influence water chemistry by increasing salinity and reducing the oxygen carrying capacity. At the same time, untreated prawn effluent encourages disease and bacterial organisms to multiply.

It is however unrealistic to avoid the fact that the prawn industry has enabled some previously isolated regions to develop an infrastructure of housing, roads, hospitals, and schools.

The most practical solution at this point appears to be a combination of industry restructuring and the implementation of tighter controls. From an environmental perspective, an efficient and effectively regulated farming sector is required since the demand for prawns cannot be attained by other sustainable means. Net trawling not only kills several endangered species of fish and turtle, it rakes sediment and can alter the normal growth of natural corals and kelp plantations.

Oyster and mussel farming

For centuries, oysters and mussels have been raised in captivity either as a food source or for the cultured pearl industry. Unlike farmed prawns, they gather their nutrients directly from seawater and have minimal impact on the surrounding environment.

In recent times, some of the food scares associated with edible farmed bivalves have resulted in stricter hygiene regulations and increased monitoring of water conditions.

On a regional basis, the farmed oyster industry has experienced difficult times. This has been attributed to climate change, decreased water purity, and the social and economic factors which influence such labour intensive operations.

The traditional model of building farms along the harbours and tidal rivers of populated areas is rapidly declining. Despite numerous restrictions which have resulted in cleaner waterways with improved safety, there are still too many risks for farms situated near population centres. This has resulted in a gradual shift toward species which can be accommodated in remote cooler regions with less exposure to industrial discharge, sewage, and other forms of pollution. They are reared in seawater enclosures and distributed directly to fresh produce markets and restaurants.

Organic certification and the future of farmed shellfish

Organic standards for farmed shellfish are slowly coming into effect, and there are predictions that bivalves such as oysters and mussels will be highly successful in terms of their sustainability, cost efficiency and popularity with consumers. Organically farmed prawns are currently available in Europe and the United States. There is increased investor interest in prawn farming precipitated by the development of cost effective organic feeds and a water sterilisation system based on ultra violet radiation.

Consumers are increasingly aware of the environmental damage and health risks associated with conventional farming practices. They are looking for healthy shellfish raised in controlled environments, unaltered by chemical toxins, genetic modification, or antibiotics.