Livestock contributes significantly to the life of small farmers, nomads and foresters all over the world and increases their productivity, income, employment and nutrition. This contribution is expected to rise. The world population will rise from its present 4.8–5.4 billion people to at least 10 billion in the next 100 years. The population of Asia can be expected to double over that same period. The demand for food will rise even more as the standard of living also rises. Along with this will be a rise in the need for draught power to produce the increased food required. According to Ramaswami and Narasimhan (1982), 2 billion people in the developing countries depend on draught animal power for farming and rural transportation. Draught power is critically short at the time of crop planting and is insufficient for other purposes throughout the year. Draught power will remain a major source of energy in agriculture into the foreseeable future, and the lack of draught power in some places may be the primary constraint to increasing crop production.

Animal draught power was the first supplement to human energy inputs in agriculture. Mechanized power has been used in agriculture only in the last century or so. In Asia, a greater proportion of farmers depend on animals for draught power than in any other parts of the world. A large proportion of these animals belong to farmers who have limited resources and cultivate small areas of land. In most parts of Asia, animal power is supplied by bullocks, buffalo and camels. Bullocks will continue to be the common source of farm power, mainly because they are adequate and live on waste residues. Elephants are also used in some places.

Production

In Asian countries, there are three main sources of power used in agriculture: human, mechanical and animal. Human beings provide the main source of power in developing countries for hoeing, weeding, rice transplanting, seed broadcasting and harvesting of crops. Mechanical power with its versatility is used for practically all the field operations, and the intensity of usage varies considerably from one developing country to another (Khan 1983). Animal power is generally used for tillage operations, haulage and operation of some water-lifting devices. A draught cow is a multipurpose farm animal, providing power, milk, dung, calves and meat. Normal draught power of various animals is presented in table 1.

Table 1. Normal draught power of various animals

Source: FAO 1966.

To have better draught animal power the following aspects should be considered:

For landless people to repay a loan for purchase of bullocks, feed them, and earn sufficient income to meet everyday costs, they must be able to work their animals for six hours per day.

• Draught animal nutrition. Animal nutrition is a principal factor in increasing the productivity of draught animal power. This is possible only if the necessary feed is available. In some areas, more effort is made to ensure the best use of available resources, such as treating straw with alkali (molasses urea block (MUB)) to improve its nutrient availability. As draught power availability is presently limiting the production of staple crops (there is an estimated 37% deficiency in draught requirements at the time of harvest), a primary objective is to produce draught animals and improve the efficiency of draught power. The opportunity to use improved nutritional technology (e.g., MUB) may assist draught power development through improved animal work capacity and reproduction rates in the female herd as well as better growth of young animals, which will lead to larger body size.

• Breeding and selection. Culling of local unproductive breed bulls and selection of the best local bull is necessary. Draught animals are currently selected according to their conformation, temperament and health; however, farmers often must rely on what is available locally.

Some crossbreds show a significant increase not only in milk and meat producing capability, but also in draught power. In India, Pakistan and Australia there have been tremendous efforts made in cross-breeding buffalo, cattle, horses (to produce mules) and, in some places, camels. This has produced very encouraging results. In many other Asian countries, especially developing countries, this research work for improving draught power as well as milk and meat production is very much needed.

• Equipment. Most farm equipment is old and unproductive. Much of the equipment that is used in conjunction with draught animals (harnesses, cultivation tools and carts) is of traditional type, the design of which has not changed for hundreds of years. In addition, farm implements are often badly designed and achieve low work output.

• Health. The stress of working may upset the balance which often exists between healthy animals and parasites.

Management

The daily feeding of draught animals varies according to work season. Both draught cattle and buffalo are fed in confinement (year-round) through a cut and carry system, with little or no grazing. Rice straw is fed all year long, depending on farmer preference, at either a measured rate of 8 to 10 kg per day or as necessary. Other crop residues such as rice hulls, pulse straw and cane tops are fed when available. In addition to these crop residues, cut or grazed green grass from roadsides and embankments is fed during the rainy season (April into November) at the rate of 5 to 7 kg/day and may be increased during times of heavy work to 10 kg/day.

Draught animal feed is usually supplemented with small amounts of by-product concentrates such as brans, oil cakes, pulses, rice hulls and molasses. The predominant means of feeding concentrates to draught animals is in a liquid form with all of the ingredients mixed together. The types and amounts of ingredients vary according to the daily workload of the animal, the geographical area, farmer preference and capability. Increased amounts of concentrates are fed during the heavy work seasons, and they are reduced during the monsoon season, when the workload is light.

Animal feed ingredients are also chosen by farmers based on availability, price, and their perception and understanding of its feeding value. For example, during the work season from November to June, daily rations may be: 200 g of mustard seed oil cake along with 100 g (dry weight) of boiled rice; 3/4 g of mustard seed oil cake, 100 g boiled rice and 3/4 g of molasses; or 2 kg total of equal parts sesame oil cake, rice polish, wheat bran and boiled rice, along with salt. On actual workdays during this period (163 days), animals are fed an extra 50% of these same rations. If animals are fed any concentrates at all during the non-working season, the rate ranges from 1/4 to 1/2 kg.

Draught Power in Australia

The Australian continent was first colonized by Europeans in 1788. Cattle were introduced with the first ships, but escaped into the surrounding forest. During those days ploughing and other land preparation was done with the heavy bullock plough, and light cultivation either with bullocks or horses. The bullock cart became the standard means of land transport in Australia and remained so until road building and railway construction began and became more widespread following the gold rushes from 1851 onwards.

In Australia other draught animals include the camel and the donkey. Although mules were used, they never became popular in Australia (Auty 1983).

Draught Power in Bangladesh

In Bangladesh livestock play a vital role in the economy, providing both draught power and milk and contributing up to 6.5% of the gross domestic product (GDP) (Khan 1983). Out of the 22 million head of cattle, 90% are used for draught power and transportation. Of this total, 8.2 million are dual purpose, supplying both draught power and dairy products, such as milk and meat (although in minimal amounts) for household consumption and trade. Adding energy value from draught power and dung (fertilizer and fuel), livestock contribute an estimated 11.3% to the GDP.

It has been observed that some cows are used for draught purposes, despite problems with fertility and health complications, which result in lower milk production and fewer calvings per lifetime. While cows are not usually worked during lactation, they contribute significantly to the annual supply of draught power in Bangladesh: 2.14 million (31%) adult female cattle and 60,000 (47%) adult buffalo cows supply animal power (Robertson et al. 1994). When combined with the male workforce, 76% of all adult cattle (11.2 million) and 85 to 90% of all adult buffalo (0.41 million) are used for draught purposes (Khan 1983).

There is no aggregate shortage of draught animals. Rather, the shortfall is based on the quality of draught power available, since malnourished animals are largely unproductive (Orlic and Leng 1992).

There are various breeds of cattle used for draught purposes, including pure deshi cattle and deshi cattle crossed with Sahiwal, Haryana and Red Sindhi cattle and Manipuri, Nili-Ravi and Murrah breeds of buffalo. Deshi bullocks weigh an average of 225 kg, crossbreds are slightly heavier at 275 kg and buffalo weigh an average of 400 kg. Bulls, cows, heifers and bullocks all provide animal power, but bullocks constitute the main workforce.

In Bangladesh, land preparation employs the highest percentage of draught animals. Research workers recommend that land be ploughed six to seven times prior to sowing. However, due to the shortage of draught power, many producers plough only four to five times in preparation for each crop. All ploughs in Bangladesh require two animals. Two bullocks can plough 1 acre in 2.75 (at 6 hours each day) (Orlic and Leng 1992; Robertson et al. 1994).

Draught Power in China

China has a long history of buffalo raising. The animals were used for farming as early as 2,500 years ago. Buffalo have a larger body size than the native cattle. Farmers prefer to use buffalo for farm work because of their great draught power, long working life and docile temperament. One buffalo can provide draught power for the production of 7,500 to 12,500 kg of rice (Yang 1995). Most of them are kept by small-scale farmers for draught purpose. The imported dairy buffalo, Murrah and Nili/Ravi, and crossbreds with these two breeds, are mainly raised on state farms and in research institutes. For centuries, buffalo have been reared mainly for draught purposes. The animals were slaughtered for meat only when they become old or disabled. Milking of buffalo was rare. After generations of selection and breeding, the buffalo have become extremely suitable for working, with deep and strong chests, strong legs, large hoofs and a docile temperament.

In China, buffalo are mainly used for paddy land and for field haulage. They are also employed in raising water, pudding clay for bricks, milling and pressing the juice from sugarcane. The extent of such use is declining due to mechanization. Training of buffalo usually starts at the age of two years. They begin to work a year later. Their working life is longer than that of cattle, usually more than 17 years. It is possible to see buffalo more than 25 years old still working in the fields. They work 90 to 120 days per year in the rice-growing area, with intensive work in the spring and autumn, when they work as long as 7 to 8 hours per day. The working capability varies widely with size, age and sex of the animal. The draught power reaches its maximum between the age of five and 12 years, remains high from 13 to 15 and begins to decline from 16 years. Most of the buffalo bulls are castrated (Yang 1995).

The Shanghai buffalo, one of the largest in China, has an excellent working capability. Working for 8 hours a day, one animal can plough 0.27 to 0.4 hectare of paddy land or 0.4 to 0.53 hectare of non-irrigated land (maximum 0.67 hectare). A load of 800 to 1,000 kg on a wooden-wheeled, bearingless vehicle can be drawn by a buffalo over 24 km within a working day. A buffalo can raise enough water to irrigate 0.73 hectares of paddy land in 4 hours.

In some sugar-producing areas, buffalo are used to draw stone rollers for sugar cane pressing. Six buffalo working in shifts can press 7,500 to 9,000 kg of sugar cane, requiring 15 to 20 minutes for every 1,000 kg.

Draught Power in India

According to Ramaswami and Narasimhan (1982) 70 million bullocks and 8 million buffalo generate about 30,000 million watts of power, assuming the Indian Council of Agricultural Research (ICAR) average of 0.5 hp output per animal. To generate, transmit and distribute this power at the same multitudinous points of application would call for an investment of 3,000,000 million rupees. It has also been estimated that an investment of 30,000 million rupees has gone into the Indian bullock cart system as against 45,000 million rupees in railways.

The Ministry of Shipping and Transport estimated that 11,700 to 15,000 million tonnes of freight in the urban areas is carried by cart each year, as against the railway haulage of 200,000 million tonnes. In the rural areas, where railroad service is not available, animal-drawn vehicles carry approximately 3,000 million tonnes of freight (Gorhe 1983).

Draught Power in Nepal

In Nepal, bullocks and male buffalo are the main source of draught power for tilling the fields. They are also used for carting, crushing sugar cane and oil seeds and for tracting loads. Due to the topographic nature of the country as well as the high cost of fuel, there is little opportunity for farm mechanization. Therefore, the demand for draught animal power in the country is high (Joshi 1983).

In wheat production, the contribution of bullocks in terms of labour days is 42% in ploughing, 3% in transplanting and 55% in threshing. In paddy production, it is 63% in ploughing, 9% in transplanting and 28% in threshing (Joshi 1983; Stem, Joshi and Orlic 1995).

Depending on the task, draught animals are generally worked a consistent number of hours each day and for a predetermined number of consecutive days before being allowed to rest. For instance, a full day of ploughing averages 6 hours for a bullock, and the average workday for a cow ranges from 4 to 5 hours per day. Animals used for ploughing follow a pattern of 6 to 8 consecutive days of work, followed by 2 days of rest. In the case of threshing, cows or lighter-weight animals usually work for 6 to 8 hours each day. The length and pattern of use for threshing and transport varies according to need. A bullock in full-time ploughing (maximum heavy labour) typically works for 163 days per year.

Draught Power in Sri Lanka

The total cattle population in Sri Lanka is estimated at 1.3 million. Various breeds are used as draught animals. Cattle breeds are used for draught purposes such as transport and ploughing of both wet and dry fields, as well as in farm operations. Indigenous animals have been used popularly in road transport for several decades. Crosses of Indian breeds with the indigenous cattle have resulted in larger animals that are used extensively for road transport. Out of a total buffalo population of 562,000, the number available in the work age range of three to 12 years is estimated at 200,000 males and 92,000 females.

Potential Hazards and Their Control

Other articles in this chapter address hazards and preventive actions for the draught animals discussed in this article. General information on animal behaviour and a checklist for livestock rearing safety practices are found in articles on these subjects and in the article “Animal husbandry”. Horses are addressed in the article “Horses and other equines”. Cattle (and by close association, bullocks and buffalo) are addressed in the article “Cattle, sheep and goats”. “Bull raising” also offers pertinent information on potential hazards and their control.

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While the term bull refers to the male of several species of livestock (elephant, water buffalo and cattle) this article will deal specifically with the cattle industry. The National Traumatic Occupational Fatalities (NTOF) surveillance system in the United States, based on death certificates and maintained by the National Institute for Occupational Safety and Health (NIOSH), identified 199 fatalities from 1980 to 1992 associated with the agricultural production industry and inflicted by livestock. Of these, about 46% (92) were directly attributed to beef and dairy bull handling.

Cattle raisers have for centuries used castration of male animals as a means of producing docile males. Castrated males are generally passive, indicating that hormones (largely testosterone) are related to aggressive behaviour. Some cultures place high value on the fighting character of bulls, which is utilized in sports and social events. In this case, certain bloodlines are bred to maintain and enhance these fighting characteristics. In the United States, demand has increased for bulls used in rodeos as these entertainment events have increased in popularity. In Spain, Portugal, parts of France, Mexico and parts of South America, bullfighting has been popular for centuries. (See the article “Bullfighting and rodeos” in the chapter Entertainment and the Arts.)

The cattle industry can be divided into two major categories—dairy and beef—with some dual-purpose breeds. Most commercial beef operations purchase bulls from pure-bred producers, while dairy operations have moved more toward artificial insemination (AI). Thus, the pure-bred producer generally raises the bulls and then sells them when they are of breeding age (2 to 3 years of age). There are three systems of mating currently used in the cattle industry. Pasture mating allows bull to run with the herd and breed cows as they come into oestrus (heat). This can be for the entire year (historically) or for a specific breeding season. If specific breeding seasons are utilized, this necessitates separating the bull from the herd for periods of time. Hand mating keeps the bull isolated from the cows, except when a cow in oestrus is brought to the bull for mating. Generally, only a single mating is allowed, with the cow being removed after service. Finally, AI is the process of using proven sires, through the use of frozen semen, to be bred to many cows by AI technicians or the producer. This has the advantage of not having a bull at the ranch, which is a reduction of risk for the producer. However, there is still potential for human-animal interaction at the point of semen collection.

When a bull is removed from the herd for hand mating or kept isolated from the herd to establish a breeding season, he may become aggressive when he detects a cow in oestrus. Since he cannot respond naturally through mating, this can lead to the “mean bull” complex, which is an example of abnormal behaviour in bulls. Typical antagonistic or combative behaviour of bulls includes pawing the ground and bellowing. Furthermore, disposition often deteriorates with age. Old breeding stock can be cantankerous, deceptive, unpredictable and large enough to be dangerous.

Facilities

To ensure movement of animals through facilities, chutes should be curved so that the end cannot be seen when first entering, and the corral should be designed with a gap to the left or right so that animals do not sense that they are trapped. Putting rubber bumpers on metal items which create a loud noise when they close can help lessen the noise and reduce stress to the animal. Ideally, facilities should maximize the reduction of hazards due to physical contact between the bull and humans through use of barriers, overhead walkways and gates that can be manipulated from outside the enclosure. Animals are less likely to balk in chutes built with solid walls instead of fencing materials, since they would not be distracted by movement outside the chutes. Alleyways and chutes should be large enough so the animals can move through them, but not so wide they can turn around.

Guidelines for Handling

Male animals should be considered potentially dangerous at all times. When bulls are kept for breeding, injuries can be avoided by having adequate bull-confinement and restraint facilities. Extreme caution should be practised when handling male animals. Bulls may not purposefully hurt people, but their size and bulk make them potentially dangerous. All pens, chutes, gates, fences and loading ramps should be strong and work properly. Proper equipment and facilities are necessary to assure safety. Ideally, when working with bulls, having the handler physically separated from contact with the bull (outside the area and protected by chutes, walls, barriers and so on) greatly reduces the risk of injury. When handlers are with the animal, escape passages should be provided to allow handlers to escape from animals in an emergency. Animals should not be prodded when they have no place to go. Handlers should stay clear of animals that are frightened or “spooked” and be extra careful around strange animals. Solid wall chutes, instead of fencing, will lower the number of animals that balk in the chute. Since bulls see colours as different shades of black and white, facilities should be painted all in the same colour. Properly designed treatment stalls and appropriate animal-restraint equipment and facilities can reduce injuries during animal examination, medication, hoof trimming, dehorning and hand mating.

People who work with animals recognize that animals can communicate despite being unable to speak. Handlers should be sensitive to warnings such as raised or pinned ears, raised tail, pawing the ground and bellowing. General information and guidelines for working with bulls are provided in the checklist and article on animal behaviour in this chapter.

Zoonoses

Handlers should also be concerned with zoonotic diseases. A livestock handler can contract zoonotic illnesses by handling an infected animal or animal products (hides), ingesting animal products (milk, undercooked meat) and disposing of infected tissues. Leptospirosis, rabies, brucellosis (undulant fever in humans), salmonellosis and ringworm are especially important. Tuberculosis, anthrax, Q fever and tularaemia are other illness that should be of concern. To reduce exposure to disease, basic hygiene and sanitation practices should be used, which include prompt treatment or proper disposal of infected animals, adequate disposal of infected tissues, proper cleaning of contaminated sites and proper use of personal protective equipment.

The most sanitary method of carcass disposal is burning it at the site of death, to avoid contamination of the surrounding ground. A hole of appropriate size should be dug, flammable materials of sufficient quantity placed inside and the carcass placed on top in order that it can be consumed in its entirety. However, the most common method of carcass disposal is burial. In this procedure, the carcass should be buried at least 4 feet deep and covered with quicklime in soil that is not susceptible to contamination by drainage and away from flowing streams.

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Processes

Institutional animal programmes involve four major processes:

1. receipt, quarantine and separation of animals
2. separation of species or animals for individual projects when necessary
3. housing, care and sanitation
4. storage.

Husbandry tasks include feeding, watering, providing bedding, maintaining sanitation, disposing of waste including carcasses, controlling pests and veterinarian care. Materials handling is significant in most of these tasks, which include moving cages, feed, pharmaceuticals, biologics and other supplies. Handling and manipulating animals is also fundamental to this work. Sanitation involves changing bedding, cleaning and disinfecting, and cage washing is a significant sanitation task.

Institutional animal facilities include cages, hutches, pens or stalls within a room, barn or outdoor habitat. Adequate space, temperature, humidity, food and water, illumination, noise control and ventilation are provided in a modern facility. The facility is designed for the type of animal that is confined. Animals that are typically confined in institutional settings include group-housed rodents (mice, rats, hamsters and guinea pigs), rabbits, cats, dogs, mink, non-human primates (monkeys, baboons and apes), birds (pigeons, quail and chickens) and farm animals (sheep and goats, swine, cattle, horses and ponies).

Hazards and Precautions

Persons involved with the production, care and handling of pet, furbearer and laboratory animals are potentially exposed to a variety of biological, physical and chemical hazards that can be controlled effectively through available risk reduction practices. The biological hazards intrinsic to the various animal species of concern to personnel include: bites and scratches; highly sensitizing allergens in dander, serum, tissues, urine or salivary secretions; and a wide variety of zoonotic agents. Although the biological hazards are more diverse and potentially more devastating in the work environments supporting these types of animals, the physical and chemical hazards generally are more pervasive, as reflected by their contribution to illness and injury in the workplace.

Personnel involved in the care and production of pet, furbearer or laboratory animals should receive appropriate training in handling techniques and behaviour of the animal species in question, because incorrect handling of an intractable animal frequently is a precipitating cause of a bite or scratch. Such injuries can become contaminated with micro-organisms from the animal’s rich oral and skin microflora or the environment, necessitating immediate wound disinfection and prompt and aggressive antimicrobial therapy and tetanus prophylaxis to avert the serious complications of wound infection and disfigurement. Personnel should appreciate that some zoonotic bite infections can produce generalized disease and even death; examples of the former include cat scratch fever, rat bite fever and human orf infection; examples of the latter include rabies, B virus and hantavirus infection.

Due to these extraordinary risks, wire-mesh, bite-proof gloves can be beneficial in some circumstances, and the chemical restraint of animals to facilitate safe handling is sometimes warranted. Personnel also can contract zoonoses through the inhalation of infectious aerosols, contact of the organisms with the skin or mucous membranes, ingestion of infectious materials or transmission by specific fleas, ticks or mites associated with the animals.

All types of zoonotic agents occur within pet, furbearer and laboratory animals, including viruses, bacteria, fungi and internal and external parasites. Some examples of zoonoses include: giardiasis and campylobacterosis from pets; anthrax, tularaemia and ringworm from furbearers; and lymphocytic choriomeningitis, hantavirus and dwarf tapeworm infestation from the laboratory rodent. The distribution of zoonotic agents varies widely according to host animal species, location and isolation from other disease reservoirs, housing and husbandry methods, and history and intensity of veterinary care. For example, some of the commercially produced laboratory animal populations have undergone extensive disease eradication programmes and been maintained subsequently under strict quality control conditions precluding the reintroduction of diseases. However, comparable measures have not been applicable universally in the various settings for pet, furbearer and laboratory animal maintenance and production, enabling the persistence of zoonoses in some circumstances.

Allergic reactions, ranging from ocular and nasal irritation and drainage to asthma or manifesting on the skin as contact urticaria (“hives”), are common in individuals who work with laboratory rodents, rabbits, cats and other animal species. An estimated 10 to 30% of individuals working with these animal species eventually develop allergic reactions, and persons with pre-existing allergic disease from other agents are at higher risk and have an increased incidence of asthma. In rare circumstances, such as a massive exposure to the inciting allergen through an animal bite, susceptible persons can develop anaphylaxis, a potentially life-threatening generalized allergic reaction.

Good personal hygiene practices should be observed by personnel to reduce their likelihood of exposure to zoonoses and allergens during work with animals or animal by-products. These include the use of dedicated work clothing, the availability and use of hand washing and shower facilities and separation of personnel areas from animal housing areas. Work clothing or protective outer garments covering the skin should be worn to prevent exposure to bites, scratches and hazardous microbes and allergens. Personal protective equipment, such as impervious gloves, safety glasses, goggles or other eye protection, and respiratory protection devices (e.g., particle masks, respirators or positive air pressure respirators) appropriate to the potential hazards and the individual’s vulnerability, should be provided and worn to promote safe work conditions. Engineering controls and equipment design also can effectively reduce the exposure of personnel to hazardous allergens and zoonoses through directional air flow and the use of isolation caging systems that partition the workers’ and animals’ environments.

Personnel also encounter significant physical and chemical hazards during animal care. Routine husbandry tasks involve moving or lifting heavy equipment and supplies, and performing repetitive tasks, affording personnel the ubiquitous opportunity to develop cuts and crush injuries, muscular strains and repetitive motion injuries. Work practice redesign, specialized equipment and personnel training in safe work practices can be used to curb these untoward outcomes. Equipment and facility sanitation frequently relies on machinery operating on live steam or extremely hot water, placing personnel at risk of severe thermal injury. The correct design, maintenance and utilization of these devices should be assured to prevent personnel injury and facilitate heat dissipation to provide a comfortable work environment. Personnel who work around large equipment, as well as around rambunctious dog or non-human primate populations, may be exposed to extremely high noise levels, necessitating the use of hearing protection. The various chemicals used for cage and facility sanitation, pest control within the animal facility and external parasite control on animals should be reviewed carefully with personnel to ensure their strict adherence to practices instituted to minimize exposure to these potentially irritating, corrosive or toxic substances.

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Background

Rearing marine organisms for food has been a widespread practice since ancient times. However, large-scale farming of molluscs, crustaceans and bony fishes has rapidly gained momentum since the early 1980s, with 20% of the world’s seafood harvest now farmed; this is projected to increase to 25% by 2000 (Douglas 1995; Crowley 1995). Expansion of world markets contemporaneous with depletion of wild stocks has resulted in very rapid growth of this industry.

Land-based aquaculture takes place in tanks and ponds, while water-based culture systems generally employ screened cages or moored net pens of widely varying designs (Kuo and Beveridge 1990) in salt water (mariculture) or fresh rivers.

Aquaculture is performed as either an extensive or intensive practice. Extensive aquaculture entails some form of environmental enhancement for naturally produced species of fish, shellfish or aquatic plants. An example of such a practice would be laying down oyster shells to be used as attachment substrate for juvenile oysters. Intensive aquaculture incorporates more complex technology and capital investment in the culture of aquatic organisms. A salmon hatchery that uses concrete tanks supplied with water via some delivery system is an example. Intensive aquaculture also requires greater allocation of labour in the operation.

The process of intensive aquaculture includes the acquisition of broodstock adults used for production of gametes, gamete collection and fertilization, incubation of eggs and juvenile rearing; it may include rearing of adults to market size or release of the organism into the environment. Herein lies the difference between farming and enhancement aquaculture. Farming means rearing the organism to market size, generally in an enclosed system. Aquaculture for enhancement requires the release of the organism into the natural environment to be harvested at a later date. The essential role of enhancement is to produce a specific organism as a supplement to natural production, not as a replacement. Aquaculture can also be in the form of mitigation for loss of natural production caused by a natural or human-made event—for example, construction of a salmon hatchery to replace lost natural production caused by the damming of a stream for hydroelectric power production.

Aquaculture can occur in land-based facilities, on-bottom marine and freshwater environments and floating structures. Floating net pens are used for fish farming, and cages suspended from raft or buoy flotation are commonly used for shellfish culture.

Land-based operations require the construction of dams and/or excavation of holes for ponds and raceways for water flushing. Mariculture can involve the construction and maintenance of complex structures in harsh environments. Handling of smolt (for bony fishes) or tiny invertebrates, feed, chemical treatments for water and the animals being raised and wastes have all evolved into highly specialized activities as the industry has developed.

Hazards and Controls

Injuries

Fish farming operations afford many injury risks, combining some of those common to all modern agriculture operations (e.g., entanglement in large machinery, hearing loss from prolonged exposure to loud engines) with some hazards unique to these operations. Slips and falls can have particularly bad outcomes if they occur near raceways or pens, as there are the dual added risks of drowning and biological or chemical contamination from polluted water.

Severe lacerations and even amputations may take place during roe-stripping, fish butchering and mollusc shelling and can be prevented by the use of guards, protective gloves and equipment designed specifically for each task. Lacerations contaminated by fish slime and blood can cause serious local and even systemic infections (“fish poisoning”). Prompt disinfection and debridement is essential for these injuries.

Electrofishing (used to stun fish during survey counts, and increasingly in collection of broodstock at hatcheries) carries a high potential for electrical shock to the operators and bystanders (National Safety Council 1985) and should be done only by trained operators, with personnel trained in cardiopulmonary resuscitation (CPR) on site. Only equipment specifically designed for electrofishing operations in water should be employed and scrupulous attention must be paid to establishing and maintaining good insulation and grounding.

All water poses drowning risks, while cold waters pose the additional hazard of hypothermia. Accidental immersions due to falls overboard must be guarded against, as must potential for ensnarement or entrapment in nets. Approved personal flotation devices should be worn by all workers at all times on or near the water, and some thermal protection should also be worn when working around cold waters (Lincoln and Klatt 1994). Mariculture personnel should be trained in marine survival and rescue techniques, as well as CPR.

Repetitive strain injuries may also occur in butchering and hand-feeding operations and can be largely avoided by attention to ergonomics (via task analysis and equipment modifications as necessary) and frequent task rotations of manual workers. Those workers developing repetitive strain injury symptoms should receive prompt evaluation and treatment and possible reassignment.

Sleep deprivation can be a risk factor for injuries in aquaculture facilities requiring intensive labour over a short duration of time (e.g., egg harvest at salmon hatcheries).

Health hazards

Diving is frequently required in construction and maintenance of fishpens. Predictably, decompression illness (“bends”) has been observed among divers not carefully observing depth/time limits (“dive tables”). There have also been reports of decompression illness occurring in divers observing these limits but making many repetitive short dives; alternative methods (not using divers) should be developed for clearing dead fish from and maintaining pens (Douglas and Milne 1991). When diving is deemed necessary, observing published dive tables, avoiding repetitive dives, always diving with a second diver (“buddy diving”) and rapid evaluation of decompression-like illnesses for possible hyperbaric oxygen therapy should be regular practices.

Severe organophosphate poisoning has occurred in workers incidental to pesticidal treatment of sea lice on salmon (Douglas 1995). Algicides deployed to control blooms may be toxic to workers, and toxic marine and freshwater algae themselves may afford worker hazards (Baxter 1991). Bath treatments for fungal infections in fish may use formaldehyde and other toxic agents (Douglas 1995). Workers must receive adequate instruction and allotment of time for safe handling of all agricultural chemicals and hygienic practices around contaminated waters.

Respiratory illnesses ranging from rhinitis to severe bronchospasm (asthma-like symptoms) have occurred due to sensitization to putative endotoxins of gram-negative bacteria contaminating farmed trout during gutting operations (Sherson, Hansen and Sigsgaard 1989), and respiratory sensitization may occur to antibiotics in medicated fish feeds. Careful attention to personal cleanliness, keeping seafood clean during butchering and handling and respiratory protection will help ensure against these problems. Workers developing sensitivity should avoid subsequent exposures to the implicated antigens. Constant immersion of hands can facilitate dermal sensitization to agricultural chemicals and foreign (fish) proteins. Hygienic practice and use of task-appropriate gloves (such as cuffed, insulated, waterproof neoprene during cold butchering operations) will reduce this risk.

Sunburn and keratotic (chronic) skin injury may result from exposure to sunlight. Wearing hats, adequate clothing and sunscreen should be de rigueur for all outdoor agricultural workers.

Large quantities of stored fish feeds are often raided by or infested with rats and other rodents, posing a risk for leptospirosis (Weil’s disease). Workers handling fish feeds must be vigilant about feed storage and rodent control and protect abraded skin and mucous membranes from contact with potentially contaminated feeds and soiled pond waters. Feeds with known contamination with rat urine should be handled as potentially infectious, and discarded promptly (Ferguson and Path 1993; Benenson 1995; Robertson et al. 1981).

Eczema and dermatitis can easily evolve from inflammation of skin macerated by constant water contact. Also, this inflammation and wet conditions can foster reproduction of human papillaviridae, leading to rapid spread of skin warts (Verruca vulgaris). Prevention is best accomplished by keeping hands as dry as possible and using appropriate gloves. Emollients are of some value in the management of minor skin irritation from water contact, but topical treatment with corticosteroids or antibiotic creams (after evaluation by a physician) may be necessary if initial treatment is unsuccessful.

Environmental Impacts

Demand for fresh water can be extremely high in all of these systems, with estimates centring on 40,000 litres required for each 0.5 kg of bony fish raised to maturity (Crowley 1995). Recirculation with filtration can greatly reduce demand, but requires intensive application of new technologies (e.g., zeolites to attract ammonia).

Fish farm discharges can include as much faecal waste as that from small cities, and regulations are rapidly proliferating for control of these discharges (Crowley 1995).

Consumption of plankton and krill, and side effects of mariculture such as algal blooms, can lead to major disruptions in species balance in the local ecosystems surrounding fish farms.

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