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Contents:
1 - Introduction; 2 - Wild resource harvesting; 3- Physical changes to the habitat; 4 - The effect of aquaculture wastes on ecological systems; 5 - Diseases and parasites; 6 - Genetic effects on wild fish and invertebrates of accidentally or deliberately introduced cultured organisms; 7 - Interactions with wildlife; 8 - Sustainability of aquaculture.
Review:
Like dams and biological control, aquaculture was, for a long time, considered a win-win situation. The wild species were no longer depleted and people had a source of protein which was needed. Now that we have had a chance to see some schemes in operation it is obvious that many of the early promises about the environmental and ecological effects have not been forthcoming. This slim text is another BES book which aims to highlight the role of ecology and ecological thinking in current environmental issues.
We start with a series of points which comprise an overview of the key issues relating to aquaculture. This provides the reader with some idea of the nature and extent of the problem. In keeping with a balanced overview both positive (the importance of aquaculture to the world's food supply) and negative (40% of introduced species have come from aquaculture) ideas are put forward. From here, the introduction highlights the growth of aquaculture since the 1950s, the commercial value (especially for the developing nations) and the main species involved. From this overview we see how the process starts. Chapter two describes the need for wild seed (the most economical source), the possibility of using 'brood' fish stocks and the impact of fish 'food' (often other aquatic species) on the environment. Aquaculture is not done in isolation - all aspects have their repercussions. Chapter three shows how the environment needs to be modified for intensive production whether by ponds (now seen as part of the UK countryside rather than as a food supply area!) or in marine areas. Like any intensive production system there is the production of wastes. Chapter four explores the ecological impact of waste production. Some might be seen as a benefit to a nutrient-poor ecosystem (although that alters species composition) but excess waste can also produce algal blooms, toxic waste and an increase in fish parasites. This notion of disease and parasites is taken up in chapter five. These might be part of the natural system but intensification creates a far higher concentration for the spread of disease. This is more than bad management. There have been cases (e.g. oysters) where the disease has made the entire stock in a large area inedible. Part of the problem with disease is that it often strikes a modified organism - fish breeding has altered the wild stock in many cases. What happens when this is released? Chapter six looks at the problems of release especially on the genetics of wild populations. The other side of farmed releases is on the other wildlife in the area. Often, wild species cannot compete with the introduced ones with disastrous effects on the ecosystem (chapter 7). Of course, this might not mean just loss of all species. Although competition for food might reduce some species the released species also provides food for other parts of the food chain. As with all aspects of this issue there are several sides to the story. The final chapter considers the sustainability of aquaculture. Again ,there is no simple answer here. Some fish farming e.g. carp needs a completely artificial environment (the pond) whereas some marine systems are far more likely to be productive in the long term.
Overall this is a great text. It is brief enough to be readable by students but detailed enough (especially with references) to provide an excellent overview of the topic. The choice of a balanced view works well and the contribution of ecology is clear (which makes this text good PR as well as ecology!). It is an excellent addition to the BES series and deserves the widest readership.