1.2 Aquaculture, ranching, enhancement and wild catch fisheries

Aquaculture is not a single standardised practice or a uniform industry, rather it embraces the culture of a wide range of species, in many differing environments, freshwater, brackish and marine, and using a variety of different rearing techniques.

Certain species are reared in natural or man-made ponds, lagoons, parcs and vallis; others are held in tanks or floating cages, while others may be placed on the seashore in bags. In some cases, there is a natural flow through of water but it is also possible to pump or recirculate water through an advanced holding facility. Indeed, in the case of most species there are a number of different rearing options with the choice of system being dictated by management preference, available investment funds and local conditions.

Aquaculture is a diverse and dynamic industry, drawing on knowledge from a series of different scientific and commercial disciplines (e.g. biology, engineering, marketing, finance), and it is constantly evolving and incorporating new methodologies and technologies.

Aquaculture may be simply defined:

However, it is important to develop this definition and there would appear to be two critical factors in defining aquaculture:

i) intervention in the rearing cycle
ii) ownership of the farmed fish or shellfish 

Intervention in the rearing cycle is taken to mean any action that is performed on a particular stock in the course of its life history, which enhances production. This would include all standard husbandry practices e.g. feeding, grading and maintenance of health status. It is important to note that the intervention should result in an enhanced yield from the stock. It is generally recognised that there are two broad forms of aquaculture namely 'intensive' and 'extensive'. These are poorly defined and the distinction is usually made on the basis of the level of intervention - e.g. the stocking densities at which the animals are held, the intensity of the labour inputs to maintain the stocks, the type and complexity of the rearing technology - and, very often, on the level of investment. Based on these criteria, the production of salmon in sea cages or sea bass juveniles in modern hatcheries would be classed as 'intensive' whereas, the rearing of mussels laid on a seabed or the use of natural lagoons to hold shellfish would qualify as 'extensive' culture.

Ownership, the second critical element in the definition of aquaculture, implies that the stock is owned, by a particular individual, company or organisation, through to harvest and the produce is sold (implicitly for financial gain). Wild catch fisheries can be readily distinguished from aquaculture since they involve the exploitation of a common resource by any person or entity. The contrast between aquaculture production and wild catch fisheries is apparent and they can be considered as the two extremes of a gradation.

AQUACULTURE ?¨ Ranching ?¨ Enhancement ?¨ WILD FISHERIES

(Intervention & private ownership) ?¨ (Common public resource)

The situation is less clear when one includes such activities as ranching and enhancement, where aquaculture techniques may be employed as part of the overall process.

Ranching is carried out on many species across the globe but is probably best known in salmon. The ranching process involves the production of large quantities of juveniles (using aquaculture techniques) and their subsequent release into the natural environment where they feed naturally. The juveniles are released at a particular location and return to a fixed point for capture by the group operating the scheme and very often the stocks are specifically tagged so that their origin/ownership is known. Thus, with ranching, while there is intervention for parts of the life history, and it is anticipated that there will be a 'return' to the promoters, much of the growth of the animal takes place naturally in the wild and it is not possible to recapture (harvest) all of the animals stocked into the system.

Enhancement practices are closely related to ranching though they differ in one important aspect. In enhancement programmes, aquaculture techniques are again used to generate large quantities of juveniles that are then released into the wild. However, this activity is primarily conducted in an effort to enlarge the existing natural population and the stocks become part of the common resource available to the public. With this system, it is not envisaged that there will be a direct financial return for those who promote the initiative. Very often, enhancement activities are undertaken by the State or local fisheries groups and are largely funded from common or public resources. Interestingly, it is now more and more common for those undertaking enhancement activities to seek to protect their efforts and investment by placing some control on the exploitation of the stocks.