Background

The role of aquaculture in providing food, employment and foreign exchange income – often as a complementary alternative to the outputs from the capture fishery sector or as a supplementary economic activity – is ever increasing.

Currently the fastest growing food production sector in the world, aquaculture production has increased at an average compound rate of 9.2 percent since 1970, compared with only 1.4 percent for capture fisheries and 2.8 percent for terrestrial farmed meat production systems (FAO 2002c). In 2000, the global aquaculture production of foodfish (fish, crustaceans and molluscs) totalled nearly 36 million tonnes, plus another 10 million tonnes of aquatic plants (FAO 2002a). The total annual value of foodfish produced by aquaculture had reached nearly US$ 51 billion by 2000. Most of the global aquaculture output is located in developing countries, significantly in low-income, food-deficit countries (LIFDCs), with China by far the dominant country. In 2000, over 38 million tonnes (including plants) was produced in LIFDCs. Expansion has been rapid; global production of foodfish through aquaculture increased by a factor of 2.5 between 1991 and 2000 (FAO 2002a). Providing aquaculture production remains responsible, it has the potential to supply increasing yields without reducing the production from wild stocks.

Aquaculture can be viewed as a potential means of relieving pressure on fish stocks, as well as a means of filling the increasing supply-demand gap for marine fishes (Williams 1996). With the yields from many capture fisheries now fixed at their maximum, and with the increasing demand for fish and fishery products, expectations for aquaculture to increase its contribution to the world’s production of aquatic food are very high. There is also hope that aquaculture will continue to strengthen its role in contributing to food security and poverty alleviation in many developing countries (FAO 1997b). The Code of Conduct for Responsible Fisheries (CCRF) stresses: “States should consider aquaculture, including culture based fisheries, as a means to promote the diversification of income and diet. In so doing, States should ensure that resources are used responsibly and adverse impacts on the environment and local communities are minimized” (FAO 1995).
The actual effects of aquaculture, including wild seed capture on global capture fisheries in general, has only recently received serious attention (Naylor et al. 2000). The potential impacts of the removal of juveniles from the wild for capture-based aquaculture on stocks (and whether or not production is actually enhanced through this kind of mariculture practice), are rarely considered. A critical problem is whether mariculture practices based on the capture of juveniles from the wild are sustainable, or could be modified to become so (Sadovy and Pet 1998). The focus of research and understanding should be: the biology of the species; the fisheries for the juveniles; and the potential impacts on remaining wild stocks that are or could be caught for grow-out systems (Johannes 1999).
The capture-based aquaculture industry is going through a transitional phase: it is at a critical crossroads between research and development, and both public and private sectors will need to continue to evaluate trends as the sector develops.
The scientific and technical aspects of capture-based aquaculture are firmly established, and they constitute the necessary basis for its economic development. However, after 30 years of research and development (and many millions of US dollars invested) there are still no economically viable mass-scale technologies to reproduce bluefin tuna in captivity, although recent claims from Japan suggest that this is now possible (www.intrafish.com). This time span is similar to that needed to obtain penaeids in Japan, salmon in Norway, and seabream and seabass in the Mediterranean; hatchery technology for these species now exists. With continuing high market demand and prices, it is likely that the sector will succeed in developing economically viable means of sustaining the practice. It is important, as for the other species, to take into account several ecological parameters that are still poorly investigated or unknown, and to invest rationally in experimental and research activities that could improve and achieve a total control of a species life cycle (Doumenge 1999).
Capture-based aquaculture is a worldwide aquaculture practice and has specific and peculiar characteristics for culture, depending on areas and species. An overview (Badalamenti et al. 1998; Ciccotti, Busilacchi and Cataudella 1999; Doumenge 1999; Tucker 1999; Garcia 2000; Nakada 2000; Sadovy 2000; EIFAC/ICES 2001; Tibbetts 2001; Clarke 2002; Hair, Bell and Doherty 2002; Katavic, Vicina and Franicevic 2003a) shows a worldwide distribution of this practice. Some examples of the species/groups harvested as wild juveniles and the various countries/regions where capture-based aquaculture is practized is presented below:
? shrimp (Penaeidae) in South America and South-East Asia;
? milkfish (Chanos chanos) in the Philippines, Sri Lanka, Pacific Islands and Indonesia;
? eels (Anguilla spp.) in Asia, Europe, Australia and North America, mainly in China, Japan, Taiwan Province of China, The Netherlands, Denmark and Italy;
? yellowtails (Seriola spp.), mainly in Japan, Taiwan Province of China, Viet Nam, Hong Kong, Italy, Spain, Australia and New Zealand;
? tunas (Thunnus spp.) in Australia, Japan, Canada, Spain, Mexico, Croatia, Italy, Malta, Morocco and Turkey; and
? groupers (Epinephelus spp.), which is now widespread in Indonesia, Malaysia, Philippines, Taiwan Province of China, Thailand, Hong Kong, People’s Republic of China, and Viet Nam, and in other parts of the tropics, for example in southeastern USA and Caribbean. Grouper culture is also on-going in India, Sri Lanka, Saudi Arabia, Republic of Korea and Australia.
These species are caught and farmed using various techniques and systems, depending on different local cultural, economic and ethnical traditions. The cultural and ethnical heterogeneity, as well as the economic differences, are partly reflected in the organization of the fishing sector. In some areas this is typically artisanal, rather than industrial in nature. The collection methods of grouper “seed” for capture-based aquaculture systems are local and artisanal, e.g. gangos (Philippines) and temarang (Malaysia), offering an important source of employment and income to the poorest segment of the coastal population. Fishing for juvenile reef fish requires an extremely low capital investment (US$ 27 per family in the Philippines) (Johannes 1997). At the other end of the scale, bluefin tuna fisheries in the Mediterranean are wholly industrialized enterprises, which need heavy capital investment: a purse seine boat can cost up to
US$ 500 000, and helicopters are often used to locate shoals.
Most fishing fleets have adapted to technological progress and are using larger, more powerful boats, incorporating sophisticated electronic fish finding equipment, and advanced catching systems. These developments have fundamentally altered the dynamics of the sector, widening the “gap” between artisanal and industrial fisheries.
Capture-based aquaculture could be considered as an unsustainable aquaculture practice, due to the increasing pressure on fish stocks, and one that could cause successive stock depletion; low recruitment; stock collapse; reductions in genetic biodiversity; and subsequent impact on the ecological dynamics and processes in the wider aquatic environment. Capture-based aquaculture could pose a threat, not only to wild stocks, but also to the industry’s own long term potential.
However, Hair, Bell and Doherty (2002), believe that there is a need to highlight the importance and potential of this type of aquaculture. With recent advances in the knowledge of larval biology and aquacultural engineering, there is a tendency to assume that further development of aquaculture will be focused on the mass production of juveniles in hatcheries. While the use of hatchery technology may be the only way to produce sufficient numbers of juveniles for stocking or increasing their supply beyond current levels for many species, much of the world’s coastal aquaculture production can still be expected to come from the supply and availability of capture-based juveniles.
A particularly attractive feature of aquaculture based on captured juveniles is that many of the environmental concerns associated with the grow-out of juveniles produced in hatcheries (e.g. the transfer of diseases and the “genetic pollution” of wild stocks), is not inherent to the process. The collection of juveniles from the wild, however, does not come without its own set of responsibilities.
The highest priority among these is the need to ensure that the increased production from the culture of juveniles more than offsets any losses in the yield from the wild stock. Capture-based aquaculture is not only based on the catching and removal of juveniles, but can also use mature individuals, e.g. giant individuals for bluefin tuna. In any event, capture should not adversely affect recruitment and the stock level of a wild population, or cause disadvantages to other users of the resource.
Economic considerations are the key drivers for capture-based aquaculture. The selection of species for culture reflects their acceptability and demand in local or international markets. Market requirements are determined primarily by people’s tastes and customs. In Japan, domestically caught tunas are considered to be the highest-grade tuna available on the market, because of their excellent colour, freshness and fat content (Ikeda 2003), and the traditional Japanese custom to eat raw fish (sushi and sashimi). Global bluefin tuna farming has caused an important socio-economic impact in Japan. Farmed bluefin tuna from other sources is much cheaper – 30 to 50 percent less than wild varieties, and the same is true for southern bluefin tuna. The abundance of fattened bluefin tuna from farming centres has opened new markets in recent years (Miyake et al. 2003) that have filled the gap between the “top quality” tuna served in the top sushi restaurants and the more “popular” ones. Today, bluefin tuna is available throughout the year in the Kaiten-sushi type restaurants and even in supermarkets.
As capture-based aquaculture potentially generates higher profits than other aquaculture systems, the market demand for the products and species cultured is high and it is likely that efforts to promote this activity will significantly increase. This development will be capable of causing a number of very important and diverse effects, not all of them beneficial. Capture-based aquaculture, being an overlap between fisheries and aquaculture, combines various characteristics of these two sectors: the necessity for species-specific gears, size selective gears (nets, etc.), stock assessments, fishing effort restrictions and regulations (time and space closure), and bycatch, etc., from the fisheries; and the culture system (cages, ponds, etc.), environmental impacts, fish diseases, and the use of pharmaceuticals, etc., from aquaculture.
Other aspects are specific to capture-based aquaculture practices. For example, capture-based aquaculture requires the movement of live fish from the place of capture to the on-growing area. This can lead to the loss or distortion of catch data, which appears to be happening in the bluefin tuna fishery of the Mediterranean. There is an urgent need to develop new regulations or other legislation to control these activities, e.g. catching methods; seasons; sizes; quantity; catch per unit effort; import export of capture-based juveniles; etc.
Thus it can be stated that an immediate consequence of capture-based aquaculture is that it complicates the evaluation of target stock assessment, which forms the basis for designing a rational national and regional fisheries management system. These procedures become more difficult when capture-based farmed species are widely distributed or migratory. Exploitation of the same resources by fleets from different countries reinforces the need for a shared strategy to ensure the Maximum Sustainable Yield (MSY) of the resource. International cooperation is essential, given the difficulties in developing a common policy which safeguards the stock, and the incomes of politically and economically heterogeneous countries.
To develop and apply regional models for sustainable capture-based aquaculture it is imperative to obtain information regarding the life history, characteristics, recruitment dynamics, habitat requirements and fishery activities for each species. For example, large groupers are particularly vulnerable to intensive fishing because of their longevity, slow growth, delayed reproduction, and aggregate spawning. The over fishing of adult groupers would result in a decline in the capture-based juveniles available for farming, while the over fishing of juveniles could have a much more lasting impact, not only on the adult fishery, but to the supply of juveniles for farming.
As capture-based aquaculture is a practice which is constantly developing, countries should create or amend the comprehensive regulatory framework to ensure that the sector develops in a sustainable manner; the inadequacy of existing legislation to control the growth of the industry properly constitutes a common problem.
Besides the economic, social, biological, and management aspects mentioned above, there are various technical aspects (which are also common to other farming systems) that are important for consumer health and food safety. It is necessary to stress that these aspects are effectively common to all aquaculture practices, but in capture-based aquaculture their importance is greater owing to the fact that many of its products are consumed raw. The situation is further complicated where non-formulated diets, e.g. trash fish, are used to feed the fish; this may cause deterioration in feed quality when it is not properly stored. This could result in greater risks to the health of the farmed species, and the consequent requirements to treat the fish for ill health. There is a lack of research studies on the prevention of the risks associated with feed consumed by capture-based farmed species. Trash fish has the potential to introduce diseases and infections, and it is therefore necessary to develop certification systems to guarantee quality and good practices for capture-based aquaculture operations.
The long-term sustainability of the industry depends largely on a reduction of its reliance on bait fish for feeding; problems include fluctuations in bait fish quality and its availability (seasonability) (Nakada 2000; Montague 2003). At the moment information on the environmental impact of almost all capture-based aquaculture is still lacking. Reports focus on the impact of salmon, seabream and seabass aquaculture, but little is known about the effect of capture-based farmed species. Enrichment and degradation of the aquatic ecosystems in the vicinity of fish farms is possible where management does not measure and control outputs from the site. Potential wastes from fish farms include metabolic products (faecal and excretory urinary material) and uneaten food, which directly or indirectly enter the aquatic environment. The level of environmental impact depends upon the intensity of fish culture activities, (i.e. stocking density and feed inputs) and the characteristics of the culture site. Capture-based aquaculture systems which use trash fish for feeding have an enhanced potential to pollute the environment than intensive farming operations that use special low-pollution feeds. The level of sustainable production in each area will vary, depending on the level of environmental impact.
There is an increasing interest in monitoring the environmental discharges and degradation of the area caused by fish farming. In many countries, new legislation has set new criteria for environmental quality and introduced tighter controls. Japan introduced new laws in 1999 for monitoring sediment and water quality in fish farming areas, in order to assess its sustainability (Pawar et al. 2001). Sustainable development of capture-based aquaculture needs careful site selection, pre-assessment of the carrying capacity of sites using bio-modelling, the use of suitable feeding regimes, good health management, stocking density control, and accurate environmental impact assessments. Sustainable development should ensure the conservation of the marine environment for future generations and as well as bring both short-term and long term benefits to the industry.
Capture-based aquaculture has the potential to generate high profits when compared to other aquaculture activities. This has naturally resulted in an increase in this system of aquaculture, which is capable of bringing about a number of very important and diverse socio-economic effects. Capture-based aquaculture can cause significant positive social and economic changes at a regional level, particularly in those regions with depressed and marginal local economies, characterized by high rates of unemployment. New employment opportunities are generated and specialists are required for its different activities, e.g. divers, biologists, quality measurements, “seed” collectors, harvesters, etc. Although it can bring high profits for a few users, however, capture-based aquaculture can also lead to negative impacts when it conflicts with other coastal activities, such as navigation, fisheries, tourism and industry.
It is important to realize that negative impacts are not always predictable, as there is little data yet available, some of their characteristics are species-specific, and it is very difficult to have a complete perspective of the entire socio-economic spectrum. Capture-based aquaculture is a complex issue and it is necessary to make a detailed analysis of every aspect which is directly or indirectly associated with it. There is a need for a better understanding of the problems and advantages that may be associated with this practice.