According to the Watercress Alliance, watercress has been prized for its food values as well as flavour -

Brimming with more than 15 essential vitamins and minerals, its health giving properties has been known since ancient times. Around 400 BC on the Island of Kos, Hippocrates, the father of medicine, is said to have located his first hospital beside a stream so that he could grow a plentiful supply of watercress to help treat his patients, the Greek general Xenophon made his soldiers eat it to increase their vigour before going into battle and Roman emperors said it enabled them to make “bold decisions.”

The annual Alresford Watercress Festival is held in celebration of the health, nutrition, flavour, historic, and economic virtues of watercress. Further exploration of the properties of the watercress includes a research investigation into the potential of watercress as a superfood. It would be just wrong to not mention the pleasures of cooking with watercress as well.

Watercress (Nasturtium microphyllium, Nasturtium officinale) is a species gazetted for land-based aquaculture in New Zealand. The Australian Rural Industries Research and Development Corporation (RIRDC) have published indicating that larger scale watercress production has potential as a vibrant new production industry catering to the demand for new flavours and healthy foods in Australia. The full report Potential for Watercress Production in Australia is available online. This from the media release:

Watercress plants are aquatic members of the brassica (cabbage) family, and are botanically related to garden cress and mustard — characterized by a peppery, tangy flavour. The vegetable is associated with a range of health benefits and contains significant amounts of iron, calcium and folic acid, in addition to vitamins A and C.

The plants are relatively easy to row, and production systems can be hydroponic or gravel based. While gravel-based production offers more cost-effective mechanized harvesting and handling, hydroponic systems offer greater water-use efficiency.

The RIRDC-funded research collates information useful to potential investors in watercress production and marketing in Australia, including new opportunities for its introduction into Australian diets, both as a flavoursome salad or in new cooked recipes.

It seems possible that the domestic or backyard aquaculturalist has a potential to explore watercress farming – here’s an indication of how it might be achieved from Herbs from Wales. A similar approach using watercress is described at Growing Power in Wisconsin, USA, and for another perspective of the use of watercress as a water filter plant in the same development. In contrast, the Independent (UK) reports of environmental issues for the Bourne, a small chalk river, renown for its trout fishing, having been polluted by a watercress farm.

In general, detailed information about the practical husbandry of watercress is quite difficult. Courtesy of the wayback engine, it is possible to examine an article from a 1947 edition of the Herts (Hertfordshire, UK) Countryside by W. G. S. Crook, J.P. – Down to the Cress Beds. From the article –

Cultivation requires about one person per acre for the whole operation of planting, bunching, washing and dispatching, together with the incidental work of maintaining the ditches. The men are supplied with thigh-length wading boots. During the winter months the cress is kept down in the water as far as possible by the use of heather brooms or wooden rollers as a protection against frost. At this time the crop makes its quickest growth close upon the outlet from the artesian wells, where the temperature of the water is most conducive to growth; at the far end of the ditch it may be very retarded because of the drop in temperature.

Transition metals are essential for health, forming integral components of proteins involved in all aspects of biological function. However, in excess these metals are potentially toxic, and to maintain metal homeostasis organisms must tightly coordinate metal acquisition and excretion. The diet is the main source for essential metals, but in aquatic organisms an alternative uptake route is available from the water. This review will assess physiological, pharmacological and recent molecular evidence to outline possible uptake pathways in the gills and intestine of teleost fish involved in the acquisition of three of the most abundant transition metals necessary for life; iron, copper, and zinc.

P. Carriquiriborde (from the Environmental Research Centre, National University of La Plata-CONICET, La Plata, Argentina), R. D. Handy, and S. J. Davies (School of Biological Sciences, University of Plymouth, UK), have published a report entitled: Physiological modulation of iron metabolism in rainbow trout (Oncorhynchus mykiss) fed low and high iron diets. From the abstract:

Iron (Fe) is an essential element, but Fe metabolism is poorly described in fish and the role of ferrireductase and transferrin in iron regulation by teleosts is unknown. The aim of the present study was to provide an overview of the strategy for Fe handling in rainbow trout, Oncorhynchus mykiss.

J. Burke and R. D. Handy (again, from the School of Biological Sciences, University of Plymouth, UK), have published a report entitled: Sodium-sensitive and -insensitive copper accumulation by isolated intestinal cells of rainbow trout Oncorhynchus mykiss. From the abstract:

The pathway for copper (Cu) uptake across the mucosal membrane into intestinal cells has not been elucidated in fish. Copper accumulation in freshly isolated intestinal cells from rainbow trout Oncorhynchus mykiss was measured after exposure to 0–800 µmol l^–1 CuSO₄ for 15 min.

Update (Dec 2010) – sadly, the Native Fish Conservancy seems to have met an untimely end. The above link is via the Internet Archive. If any of the former webmaster/site managers are out there please feel free to make contact.

The Australian Centre for International Agricultural Research (ACIAR) is a statutory authority that operates as part of the Australian Government’s development cooperation programs. The Centre encourages Australia’s agricultural scientists to use their skills for the benefit of developing countries and Australia. Geoff Allan and Don Fielder (from ACIAR) have published a .pdf document for download entitled Mud Crab Aquaculture in Australia and Southeast Asia.

The summary:

Mud crab aquaculture has been practised for many years in Southeast Asia, based primarily on capture and fattening of juvenile crabs from the wild. There is an unmet demand for mud crabs and this has led to over-exploitation in many areas. Difficulties with obtaining wild caught juveniles for farming operations, plus concerns of further over-exploitation, have led to major investments in research into hatchery techniques. To review mud crab aquaculture in Australia and Southeast Asia, ACIAR funded a scoping study, followed by a workshop to review the study and discuss status and problems in different regions. Those results are presented in this report.

A.F. Medina Pizzali has published research via the FAO entitled Low-Cost Fish Retailing Equipment and Facilities in Large Urban Areas of Southeast Asia. Of particular interest from a mangrove crab perspective is a case study from metro Manila.

Four species of crabs are of commercial importance in Metro Manila; these are pelagic swimming crab (Portunus pelagicus), mangrove crab (Scylla serrata), peregrine crab (Varuna litterata) and horned ghost crab (Ocypode spp). Mangrove crabs are considered a delicacy and are always marketed alive. The Metro Manila market is characterised by consumer preference for live mangrove crabs which command high prices; in particular, ripe females fetch premium prices. The domestic market is supplied with mangrove crab the year-round, with a peak season from May to September. During the Christmas period, there is an increased demand and prices of live mangrove crab are relatively higher.

From the introduction:

This work is meant to provide a guide to the freshwater fishes of Iran. There are no modern keys to this fauna, some available books are incomplete or cursory treatments or outdated, and the detailed and diverse scientific literature is widely scattered in time, languages and journals. Iran lies at a region of major zoogeographical interchange and has a diverse and interesting ichthyofauna about which comparatively little is known. An accurate identification is a pre-requisite for further scientific studies and this website aims to serve that purpose and to be an introductory guide to the fishes. The guide is aimed at a mixed audience, including scientists familiar with ichthyology to whom some introductory sections of this work will be superfluous, and those whose knowledge of fishes is embryonic or who may have limited access to literature sources.

This work has been carried out over a period of over 30 years from my first arrival in Iran in January 1976. In that year, 7 articles were published strictly on Iranian fishes (3 on parasites, 1 on pesticides, 1 on fisheries, 1 describing the blind white fish and 1 a summary of the latter; 2 were in Farsi). In 2006, 160 articles on Iranian fishes appeared, along with many relevant works from neighbouring countries, works on the aquatic environment in Iran and works on taxonomy and systematics relevant to Iran. The study of fishes is now a very active field within Iran and the Middle East. Accordingly, 2006 is the last year that this work was updated although some systematic and taxonomic studies may still be incorporated.

Bui Xuan Men, Brian Ogle, and T R Preston have published research findings entitled Use of restricted broken rice in duckweed based diets for fattening Common and Muscovy ducks (Livestock Research for Rural Development, Volume 8, Number 3, September 1996). From the abstract:

A feeding system of restricted levels of broken rice (60 to 80 g/day) with free access to fresh duckweed appears to be appropriate for the Common type of duck typically used for foraging on rice fields throughout Vietnam. More research is needed in order to ascertain if the apparent capacity of Common ducks to eat large quantities of duckweed really is a comparative advantage and, if so, how this can best be used to improve the economic benefits to small scale poor farmers.

The authors have also published Duckweed (Lemna spp) as replacement for roasted soya beans in diets of broken rice for fattening ducks on a small scale farm in the Mekong delta (Livestock Research for Rural Development, Volume 8, Number 3, September 1996). From the abstract:

There was a slight indication (P=0.1 for females and 0.34 for males) that carcass yield was reduced on the duckweed treatments but differences were small. There were no differences in weights of chest and thigh muscle nor in heart and liver weights.

For farmers growing the duckweed there were economic benefits on all duckweed diets with best results from the complete substitution of the soya beans.

Paul Skillicorn, William Spira, and William Journey have published an extensive report entitled Duckweed Aquaculture – A new aquatic system for developing countries (The World Bank – Emena Technical Department, Agricultural Division). From the foreword:

Although duckweed species are familiar to most people who have seen the tiny aquatic plants covering stagnant water bodies, few people realize their potential. Until a few years ago, man made little use of duckweed species. Their unique properties, such as their phenomenal growth rate, high protein content, ability to clean wastewater and thrive in fresh as well as brackish water, were only recognized by a few scientists.

Prior to 1988 duckweed had been used only in commercial applications to treat wastewater in North America. In 1989 staff of a non-governmental organization based in Columbia, Maryland, The PRISM Group, initiated a pilot project in Bangladesh to develop farming systems for duckweed and to test its value as a fish feed. An earlier project in Peru investigated the nutritional value of dried duckweed meal in poultry rations.

The results of the pilot operations were extremely promising; production of duckweed-fed carp far exceeded expectations, and dried duckweed meal provided an excellent substitute for soy and fish meals in poultry feeds. Duckweed could be grown using wastewater for nutrients, or alternatively using commercial fertilizers.

During start-up of the pilot operations it also became apparent how little is known about the agronomic aspects of producing various species of the duckweed family, and exactly why it is so effective as a single nutritional input for carp and other fish.

Although these pilot operations were located in South Asia and Latin America, the results suggested that the plant would be important as a source of fish and poultry feed and simultaneously as a wastewater treatment process in selected areas of the Middle East, particularly in Egypt and Pakistan.

Technical and agronomic information about duckweed culture and feed use, and details of farming duckweed and fish in a single system, are not easily available to the general public, let alone to fish farmers in developing countries. The pilot operations in Bangladesh demonstrated that duckweed and fish culture can succeed commercially, although such ventures would initially require technical assistance and information. In many other areas of the world pilot operations linked to applied research may be required to review production parameters before commercial operations should be initiated. This Technical Study was therefore designed to bring together, in one publication, relevant information on duckweed culture and its uses to make people worldwide aware of the potential of this plant, to disseminate the currently available technical and agronomic information, and to list those aspects that require further research, such as duckweed agronomy, genetics and use in animal feeds.

This Technical Study is aimed at the following audiences: (a) established fish farmers who would like to experiment with duckweed as a fish feed, and staff of agricultural extension services involved in fish culture; (b) scientists of aquaculture research institutes who may initiate pilot operations and applied research on duckweed; (c) staff of bilateral and multilateral donor agencies who may promote funding for duckweed research and pilot operations; and (d) wastewater specialists in governments and donor agencies who may promote wastewater treatment plants based on duckweed in conjunction with fish culture.

Ultimately, sustainability may be the aquaculture industry’s ability to adapt on a planet with an ever increasing human population which continues to consume its limited supply of non-renewable resources at an alarming rate.

Although ever increasing costs of resources such as oil and water continue to apply pressure to the development of sustainable models across all spectra of human endeavor, the discussion around sustainable aquaculture is not exactly new. Sustainable Aquaculture Development and the Code of Conduct for Responsible Fisheries was presented by William D. Dar to the FAO, Rome in March 1999.

Sustainability is also not just a concern of aquaculture – the broader concerns of ocean governance has also been considered by George Pararas-Carayannis in Ocean Governance and Sustainability – Present Trends – Future Challenges. From the abstract:

The ability of marine ecosystems to produce the economic and ecological goods and services that are desired and needed, have been substantially reduced. In some instances there has been a significant decline of ocean wildlife and even collapses of ocean ecosystems. It is clearly evident that what we once considered to be inexhaustible and resilient is, in fact, finite and fragile.

Patrick Sorgeloos offers comment regarding Technologies for Sustainable Aquaculture Development. From the introduction:

Risks of major environmental and human-health problems need to be weighed against achieving a more cautious rise in production that is, in the longer term, sustainable. We should all see this not only as a challenge to do it well and responsibly, but also as a commercial opportunity for the industry.

Aquaculture is clearly at a crossroads and can come, in fact, should come of age in the twenty-first century. However, this will require more responsible researchers and more integrated R&D approaches than we apply at present.

Denis Bailly and Rolf Willmann have provided research findings entitled Promoting Sustainable Aquaculture through Economic and other Incentives. From the abstract:

Economic incentives have been widely applied to encourage growth in aquaculture production, especially in the “infant” phase of development where risks are often high and scale economies cannot yet be realized. In recent years, increasing attention has been given to incentives that encourage the use of environmental and natural resources in a sustainable manner. This growing interest is not least due to the frequently disappointing performance of command and control measures. Different kinds of incentives can be developed in isolation or in combination, including tradable use/access rights, taxes/subsidies, codes of conduct, eco-labelling and others. While practical experiences are still very limited in aquaculture, these measures have proven effective in other sectors to induce producers to adopt better and more environmentally friendly production practices.

…leading expert on VHS in the United States, Jim Winton of the US Geological Survey, indicated that the VHS virus exists in four strains, with a single, unique sub-strain occurring in the Great Lakes. The VHS virus has been known in Europe, Japan, and the coasts of the U.S. for many years; how it came to occur in the Great Lakes is not known. Winton speculates that it may have originated in ballast water from ocean-going ships sailing into the Great Lakes, or that it may have hitchhiked in shipments of hatchery-raised fish.

According to the New York State Department of Environmental Conservation (NYSDEC),

Viral hemorrhagic septicemia (VHS) virus is a serious pathogen of fresh and saltwater fish that is causing an emerging disease in the Great Lakes region of the United States and Canada. VHS virus is a rhabdovirus (rod shaped virus) that affects fish of all size and age ranges. It does not pose any threat to human health. VHS can cause hemorrhaging of fish tissue, including internal organs, and can cause the death of infected fish. Once a fish is infected with VHS, there is no known cure. Not all infected fish develop the disease, but they can carry and spread the disease to other fish. VHS has been blamed for fish kills in Lake Huron, Lake St. Clair (MI), Lake Erie, Lake Ontario, the St. Lawrence River and Conesus Lake (Western NY). The World Organization of Animal Health has categorized VHS as a transmissible disease with the potential for profound socio-economic consequences. Because of this, they list VHS as a disease that should be reported to the international community as an exceptional epidemiological (study of diseases in large populations) occurrence.

The NYSDEC has released revised Emergency Regulations Adopted to Prevent Spread of VHS.

Animal and Plant Health Inspection Service (APHIS) note the following species are susceptable: Atlantic cod Gadus morhua, Black crappie Pomoxis nigromaculatus, Bluegill Lepomis macrochirus, Bluntnose minnow Pimephales notatus, Brown bullhead Ictalurus nebulosus, Brown trout Salmo trutta, Burbot Lota lota, Channel catfish Ictalurus punctatus, Chinook salmon Oncorhynchus tshawytscha, Coho salmon Oncorhynchus kisutch, Chum salmon Oncorhynchus keta, Emerald shiner Notropis atherinoides, Freshwater drum Aplodinotus grunniens, Gizzard shad Dorosoma cepedianum, Grayling Thymallus thymallus, Haddock Gadus aeglefinus, Herring Clupea spp, Japanese flounder Paralichthys olivaceus, Largemouth bass Micropterus salmoides, Muskellunge Esox masquinongy, Pacific cod Gadus macrocephalus, Pike Esox lucius, Pink salmon Onchorhynchus gorbuscha, Pumpkinseed Lepomis gibbosus, Rainbow trout Oncorhynchus mykiss, Redhorse sucker Moxostoma spp, Rock bass Ambloplites rupestris, Rockling Onos mustelus, Round goby Neogobius melanostomus, Smallmouth bass Micropterus dolomieu, Sprat Sprattus spp, Turbot Scophthalmus maximus, Walleye Sander vitreus, White bass Morone chrysops, White perch Morone americana, Whitefish Coregonus spp, Yellow perch Perca flavescens.

APHIS has also released the Amended Federal Order Viral Hemorrhagic Septicemia (VHS) dated May 4, 2007. The purpose of this Federal Order is to prevent the spread of viral hemorrhagic septicemia (VHS) into aquaculture facilities. Also refer to the APHIS July 2006 Emerging Disease Notice – Viral Hemorrhagic Septicemia in the Great Lakes for further analysis.

Research reports published from the Scottish Fisheries Research Services may serve to provide management options:
Viral Haemorrhagic Septicaemia (VHS) – from the abstract:

Viral haemorrhagic septicaemia (VHS) was diagnosed inrainbow trout (Oncorhynchus mykiss) at a farm in Englandon 26 May 2006. VHS is a notifiable disease in the UK and a List II disease under European Directive 91/67/EEC. Investigations into the source and potential spread of the disease are being carried out by Centre for Environment, Fisheries and Aquaculture Science (Cefas) in England and Wales, and by Fisheries Research Services (FRS) in Scotland. VHS has occurred once before in the UK, in 1994, affecting a single turbot farm. The disease was successfully eradicated on that occasion. VHS has no implications for human health.

Risks to Wild Freshwater Fisheries from Viral Haemorrhagic Septicaemia (VHS) – from the abstract:

There is a risk of transfer of VHSV from farmed to wild freshwater fish species and vice versa. There is evidence that a reservoir of infection may be created in wild freshwater fish species. This may pose a risk of re-infection of farms (eg rainbow trout). There are no reports of VHSV infection leading to significant disease outbreaks in wild freshwater fish stocks. Based on evidence from outbreaks in farms and experimental evidence, free living rainbow trout, brown trout, whitefish, grayling and pike may be at risk of disease. Available evidence suggests a high infection pressure would be required to initiate a disease outbreak in wild fish (eg shedding of virus from an infected farm).

Disinfection guide version IV: practical steps to prevent the introduction and minimise transmission of diseases of fish – from the abstract:

Emerging diseases have had a significant impact on development of the Scottish aquaculture industry, highlighting the importance of preventing their introduction and minimising their transmission. The risk of disease spread is reduced by the implementation of good sanitary practices by fish farmers, and fisheries and the application of effluent disinfection systems in the processing industry. To maintain healthy fish stocks and minimise the introduction and spread of disease, the aquaculture industry should ensure best practice on farm sites, during transportation of live or dead fish and equipment, at the processing plant and during subsequent effluent and waste disposal. For an assessment of the risks associated with specific tasks, reference should be made to the Final Report of the Joint Government/ Industry Working Group on Infectious Salmon Anaemia (ISA) available from the Fisheries Research Services (FRS) web site, at www.frs-scotland.gov.uk. The protocols described in this guide are based upon current scientific knowledge and practical experience and will continue to be developed as the needs of industry change. This guide is intended for distribution to relevant industry personnel.

From Chapter 1:

Fishing is one of the oldest ways by which people have fed themselves and their families. Except for gathering shellfish by hand and spearing fish, primitive trapping is probably the oldest form of fishing.

In early times, flowing water caused by tidal movement and changes in river and lake levels were probably used to trap fish behind rudimentary barriers, often made from sticks and stones. It is likely that early humans found that fish catches could be improved by driving fish into these barriers. They would have found that catches from these barriers decreased over time, as fish became accustomed to them, and would have had to move the traps to fresh areas where more fish could be caught. It would have been hard work to construct new traps, either by moving stones from the old trap or finding new ones. Primitive fishers probably tried making barriers from lighter, more readily available material such as tree branches, brush and vines. This led to the fishers inventing lighter, movable traps made from brush and nets made from vines which they could carry with them when they moved to new areas. They may even have tried bigger, more complicated corral-type fish traps in lakes, rivers and coastal waters.