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Introduction
John S. Lucas
CHAPTER MENU
1.1 What is and What isn't Aquaculture?
Give a person a fish and you feed them for a day;
Teach a person how to fish and you feed them for their life-time;
Teach a person how to grow fish and you feed them and their neighbours for their life-times.
(modified from a Chinese proverb)
Aquaculture continues to develop rapidly, especially through its growth in Asia. World aquaculture production is increasing much more rapidly than animal husbandry and capture fisheries, the other two sources of animal protein for the world's population. There is widespread recognition that seafood production from capture fisheries is at its peak, and that aquaculture will become increasingly important as a source of seafood production, and ultimately the main source. There is widespread public interest in aquaculture. This is the context in which this textbook is written and we trust that it will convey some of the excitement of the rapidly developing discipline of aquaculture.
The term 'seafood'1 is used inclusively in this textbook, i.e., for all animal and plant products from aquatic environments, including freshwater, brackish, and marine and hypersaline environments. The term 'shellfish', according to common usage, is used to describe aquatic invertebrates with a 'shell'. In this way, bivalve and gastropod molluscs, decapod crustaceans and sea urchins are combined, while recognising the extreme diversity of morphology and biology within this grouping. The two groups that overwhelmingly constitute shellfish are the bivalves (oysters, mussels, clams, etc.) and decapod crustaceans (shrimp1, crayfish, crabs, etc.). The other major group of aquatic animals that is cultured is the fishes, also known as finfish. 'Fish farming' is used in the sense of aquaculture of fishes, crustaceans, molluscs, etc., but not plants.
There are many different forms of aquaculture and, at the outset of this book, it is important to establish what aquaculture is, what it isn't and what distinguishes it from capture fisheries.
'The definition of aquaculture is understood to mean the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding and protection from predators. Farming also implies individual or corporate ownership of stock being cultivated.'
For statistical purposes:
- aquatic organisms that are harvested by an individual or corporate body that has owned them throughout their rearing period are classed as aquaculture products.
- aquatic organisms that are exploitable by the public as a common property resource, with or without appropriate licences, are the harvest of fisheries.
According to the FAO definition2, the two essential factors that together distinguish aquaculture from capture fisheries are:
- Intervention to enhance the stock.
- Ownership of the stock.
Thus, a structure to which fish are attracted and caught, e.g., a fish-aggregating device (FAD) floating in the open ocean may be owned, but this does not confer ownership of the stock of attracted fish. Furthermore, the FAD facilitates capture, but does not enhance the fish stock that is being captured. This is capture fisheries production. Hatchery production of juvenile fishes is aquaculture: they are owned by the hatchery and may be sold as fingerling fish. Their ultimate capture, after being released into rivers to which they eventually return to breed is fishing. The released fingerlings enhance the stock, but they become a common property resource. The same applies where hatchery-reared fish fingerlings are sold to fishing clubs and local government bodies to stock lakes and dams to improve recreational fishing.
Hydroponics and aeroponics, the cultivation of terrestrial plants with their roots in dilute nutrient solutions aren't aquaculture. These are alternative methods for growing terrestrial plants.
Activities constituting aquaculture production, according to FAO3 are:
- hatchery rearing of fry, spat, postlarvae, etc.;
- stocking of ponds, cages, tanks, raceways and temporary barrages (e.g., dams) with wild-caught or hatchery-produced juveniles to be reared to market size;
- culture in private tidal ponds (e.g., Indonesian 'tambaks');
- rearing molluscs to market size from hatchery-produced spat, transferred natural spatfall or transferred part-grown animals;
- stocked fish culture in paddy fields;
- harvesting planted or suspended seaweed;
- valliculture (culture in coastal lagoons).
1.2 Origins of Aquaculture and Agriculture
The New Stone Age (Neolithic Age ca. 8,000-4,000 BC) was distinguished by the invention of farming. There were at least seven independent origins of farming during this Age: in China, New Guinea, Mexico, West Africa, the Andes, the Amazon basin and the Middle East (Figure 1.1). Wheat, rice, maize, barley and millet, which are still the major cereal crops, and the major root crops, potatoes and cassava, were all domesticated at various of these geographical locations during this period. Similarly, the husbandry of pigs, cattle, chickens, sheep, goats and horses, which are still major farm animals, was developed during the Neolithic Age. The origins of the plants and live-stock that we farm go back a long way.
Figure 1.1 The court bakery of Ramses III. From the tomb of Ramses III in the Valley of the Kings, twentieth dynasty. (The Oxford Encyclopaedia of Ancient Egypt.)
(Courtesy of Wikimedia Commons).
These changes from hunting-gathering to agriculture and animal husbandry caused profound changes in lifestyle, from a nomadic to a settled existence. They resulted in greatly increased productivity from the land for human consumption and increased human populations per unit land area as a consequence. There were, however, disadvantages. The heavy dependence on a crop could lead to nutritional deficiencies and, if the crop failed, to starvation. Close proximity to other humans, domestic animals and opportunistic vermin led to the transmission of diseases. The hunter-gatherer probably tended to be healthier, wih a more varied diet and less exposure to diseases.
The origin of aquaculture came some thousands of years after the Neolithic Age when culture of common carps (Cyprinus carpio) was developed in China where the carp is a native species (Figure 1.2). There is a long history of aquaculture in China (section 1.6). Common carps may have been farmed as early as 2000-1000 BC.4 The first aquaculture text is attributed to a Chinese politician, Fan Lei, and is dated about 500 BC. Fan Lei attributed the source of his wealth to his fish ponds: so his fish culture was more than a hobby. However, on three continents, Africa, America and Australia, aquaculture was not practised until it was introduced in recent centuries.
Figure 1.2 The common carp (Cyprinus carpio).
Source: Photograph by Piet Spaans. Reproduced under the terms of the Creative Commons Attribution License, CC-BY-SA 4.0.
The late origin of aquaculture compared with agriculture and its failure to develop in some continents is partly because humans are terrestrial inhabitants. We cannot readily appreciate the parameters of aquatic environments. There are some environmental factors that may profoundly affect aquatic organisms, such as:
- the very low content of O2 in water (<1%) compared with air (21%);
- high solubility of CO2 in water;
- pH;
- salinity;
- buffering capacity;
- dissolved nutrients;
- toxic nitrogenous waste molecules;
- turbidity;
- heavy metals and other toxic molecules in solution;
- phyto- and zooplankton concentrations; and
- current velocity.
Many of the diseases that afflict aquatic organisms are quite unfamiliar to us. Furthermore, virtually all the animals used in aquaculture are poikilotherms (their body temperature is variable and strongly influenced by environmental temperature) ('cold blooded'). Their metabolic rates, and all functions depending on metabolic rate, are profoundly influenced by environmental temperature in ways that we do not experience as 'warm-blooded' mammals (Figure 1.3).
Figure 1.3 Metabolic rate over a temperature range in a poikilothem. Metabolic rate will be reflected in the rate of the animals's oxygen consumption. Reproduced with permission...
