EXPERT TOPIC – TROUT

Welcome to Expert Topic, a new feature for International Aquafeed. Each issue will take an in-depth look at a particular species and how its feed is managed. To kick off the first Expert Topic, trout takes centre stage. Over the next pages you’ll find, amongst other things, a feature on the trout value chain in Peru, a glimpse behind the scenes at Bibury Trout Farm in the UK and an overview trout culture and feed in Turkey.  First of all, industry experts from around the world give the inside track feed and management in their country. Enjoy.

Peru
by Anna Pyc, Peruvian Aquaculture Company, Peru
The highest industrial aquaculture center in the world is located in Peru’s central Huancavelica department, 4,600 meters above sea level. Peruvian Aquaculture Company (PACSAC) was founded in 2007 for the development of industrial aquaculture, an activity that is emerging worldwide as the main protein source for the near future.
To meet this goal, PACSAC integrates social and environment care with the use of modern technologies that make possible to provide quality products to international markets. At this stage, PACSAC is raising rainbow trout. As well as beign the higest trout farm in Peru, the company’s facilities are also the largest industrial aquaculture site in the country.
According to an article published by FIS.com, the company uses the same technologies applied in fish farming by the major producers of salmon and trout, like Norway, Chile and the United Kingdom.
However, this technology has been adapted to its unique environment and an individual model has been developed for the high Andes. The natural environment and the purity of the water in this mountain range is the greatest asset of the company, which allows making aquaculture a sustainable activity.
All procedures used by the company are environmentally friendly, and as a result, the Peruvian Aquaculture Company implements norms ISO 14001: 2004. PACSAC also develops regular environmental water monitoring to asses quality and sediment.The fish are fed exclusively with extruded fishmeal specially formulated for trout. After reaching the required market size the trout are harvested and transported to the processing plant.

Turkey
by Prof Dr Belgin Hossu, Faculty of Fisheries, Ege University, Turkey
According to the latest parametres from the Turkish Statistics Office, rainbow trout production is around 85.244 tonnes in Turkey and is increasing each day. Farms are mostly on land and damed lakes with a small amount in sea cages.
Rainbow trout production in Turkey can be divided in to two parts. The reason for this is the continously changing cost of feed due to fishmeal and fish oil prices. Unstable prices of fishmeal and fish oil has forced the farms to produce their feed themselves. As a result, the feed sector has to be seen as commercial feed mills and self-feed producers. Feed production for rainbow trout is done totally in Turkey. Foreign feed mills have built fish feed plants in Turkey because of increasing demand by farms. Trout farms choose feed mills according to their prices and payment ease.
Rainbow trout have differences between them because of geographic conditions of the country. Depending on these changing conditions, FCR is between 0.84- 0.97. The main protein source of feed is fishmeal. Fishmeal sources are foreign countries and sardine and anchovy from Black Sea according to the fishing seasons. Protein rate of feed is around 44 percent at growing ages. In addition to fishmeal, vegetable protein sources have been used to decrease the cost of the feed. These are soybean meal, corn meal and wheat meals. Adding of caroteneids generally happens at salmon breeding or matured fish of trout.
The feed manufacturing system is extruder. To decrease waste, floating feed is prefered.
Generally, the colour of the meat isn’t important because trout is consumed both fresh and frozen. On the other hand, yellow coloured meat isn’t preferable because it indictaes high levels of corn and soybean meal.

Poland
by Anna Py, Aller Aqua, Poland
Trout farming in Poland is situated mainly in the northern part of the country with its main species – rainbow trout. It is relatively young part of the Polish aquaculture reaching 14 thousand tons of annual production in 2010 with a value of approximately €40m. The farms are modern, many using partially recirculated systems and technology reducing environmental impact. Over 200 trout farms employ approximately 1000 people. The location of farms in rural areas makes them important for local employment levels.
Trout farms in Poland use high quality feeds purchased from leading feed producers in Europe. 41.5 percent of the market share belongs to Aller Aqua (2010), in the second place is Biomar (34.6 percent) and third is Skretting (12.3 percent). Aller Aqua is the only fish feed company with a production plant in Poland, which makes the company competitive regarding delivery conditions.
Trout farms in Poland are in most cases well managed and therefore the approximate FCR reaches values of starter feeds at 0.72 and, in fingerlings production 0.88. In recent years there has also been investment in automatic feeding systems to improve feeding effectiveness.
Very strict regulations in Polish law regarding the environmental impact of salmonids production also require that feeds that meet certain standards. According to individual farm water conditions the feed is chosen in respect of its caloric value and other properties. Many of the farms have their own hatcheries, where starter feeds are used. These feeds are especially important for having high survival rate and fish in good condition as a basis for fast growth.
Fish feed is the largest cost component of trout farms, amounting on average to about 34 percent, however it used to reach over 40 percent in previous years. Cost of labour, live raw material and other operational costs amount to 19 percent , 16 percent and 14 percent respectively. Other components costs are relatively small.
Polish trout production faces new challenges in terms of market demands as well as increasing pressure on reducing environmental impact. The Polish Trout Breeders Association faces these challenges and among other activities introduced a four year promotional campaign of trout in Poland. The campaign focuses mainly on promoting trout as a source of healthy nutrition, as well as spreading knowledge about the species.

Denmark
by Brian Thomsen, Director, Danish Aquaculture Organisation
Danish trout farmers almost exclusively use fish feed manufactured in Denmark. The mains reasons are that they view it as being superior and that it is in compliance with national legislation. Danish national legislation also regulates digestibility but most types of feed exceeds the legal requirements.
Key decision parameters when choosing a feed include: low FQR, high growth rates, national regulation, environmental impact – in general ‘price/performance’.
The national average FQR is approximately 0.94, thus we use on average approximately 940g of feed to make 1kg of trout. The protein content is gradually declining but it is typically around 42 percent. The main protein source is fishmeal.
The legislation for freshwater farming was changed this February. One of the key changes is that farms may now choose to be regulated on output (discharge quotas) and not on input (feed quotas). This will probably puts even more emphasis on the ‘price/performance’ ratio.
The fish farmers are well aware of the fact ‘that we are what we eat’. Therefore quality is of the highest importance. We mainly farm white fish but caratenoids are used in fish feeds that are used to make pink trout.
The cost of feed is always a key factor but the cost is judged against performance. The key question is therefore not the price per kg per se but the ‘price/performance’ ratio.
We produce approximately 10,000 tons of trout in marine farming and 25,000 tons in freshwater farming. The gross output (2010) was approximately €45m for marine farming and €80m for freshwater farming. The industry employs approximately 1000 people (including production and feed and processing).

United Kingdom
by David Bassett, British Trout Association
UK trout farming differs to some other countries in that the UK employs a number of different production methods. Trout are farmed in freshwater open net pens, earth ponds and concrete raceways and are also farmed in open net pens in marine water off the west coast of Scotland. UK trout farmers also employ recirculation technology – most commonly as partial recirculation in hatchery facilities rather than the entirely closed recirculation sites as may be seen elsewhere.
The UK primarily produces rainbow trout, although brown trout are farmed too. Both species may be farmed to organic standards, and consequently use organic feeds, although this market remains small, producing only in the hundreds of tonnes. Both brown and rainbow trout are farmed for the restocking market (i.e. sale of live fish for stocking to fisheries) although the majority of fish that are farmed are for the table market.
Production tonnages vary annually, but current official statistics suggest that circa 11,000 tonnes of table trout are farmed each year, with a further circa 3,500 tonnes for restocking. Large trout production, those fish farmed in marine water, is increasing, with 2011 production being estimated at 2,000 tonnes, up from circa 1,600 tonnes in 2010.
Fish feed accounts for approximately 50 percent of production costs, and so is of paramount importance to UK producers. Through both European Union and UK domestic legislation, fish feeds, their composition and their use, are tightly regulated. The vast majority of trout farms source feed from the major commercial suppliers. Skretting has the largest market share, although other suppliers include EWOS, Biomar, Le Gouessant and Aller Aqua. However, whilst costs are high, trout farmers seek value for money and a return in terms of performance and as such would prefer to pay for a top quality feed in that this is a better investment in the long term resulting in a better yield and healthier fish.
Feed compositions vary between manufactures and specific formulations / diets. The major source of protein continues to be fish meal. Increasingly, producers seek to be able to vary the inclusion rates in diets of such ingredients as fish and vegetable oils. With the global commodity index affecting the price of key ingredients, trout farmers support feed manufactures in their attempts to operate using as wide a basket of ingredients as possible, to optimise variations in the commodity market.
With the exception of fish farmed to organic standards, the UK market prefers fish that is “pink” fleshed. As such, astaxanthin on canthaxanthin are included in the formulation of diets.
Most UK feeds for the table market avoid using land animal protein. Although permitted to do so by law, retail buyers seem reluctant to purchase fish fed using such diets. However, research undertaken by industry and other third parties suggests that there is little to no opposition to the inclusion of such protein sources on the part of the consumer / general public, who remain generally unconcerned about the diets fed to farmed fish.
In common with other sectors, ‘sustainability’ is a term that is used increasingly often with regard to fish farming and fish feeds. Whilst a definition of sustainability is always hard to achieve, it would be fair to suggest that much greater emphasis is now being placed upon such issues as Fish In Fish Out (FIFO). As a trade association representing the UK farming industry, the British Trout Association is increasingly liaising with feed companies and NGO organisations over issues relating to the inclusion percentages of fish meal and fish oil in diets, and the origin of the fish meal and fish oil that is used. It is predicted that greater emphasis will be placed upon such issues in the future, with certain certification schemes placing greater emphasis on the sustainability imprint of all aspects of production.  How much importance consumers attach to this has yet to be demonstrated.
UK fish farming is strictly regulated in relation to discharges into the aquatic environment. As such, farmers pay close attention to feed conversions ratios and associated nutrient discharge and suspended solids. Whilst feed conversion ratios vary across the UK, given the wide range in production systems, water temperatures and other variables, feed conversion and feeding protocols have continued to improve in sophistication and understanding with reported ratios varying from under 1:1 (typically 0.95) to 1.2 :1.
UK trout farmers enjoy a close and mutually beneficial working relationship with commercial fish feed manufacturers and as an industry we continue to work together to be at the forefront of trout production.

Buxton Trout and Salmon Farm, Australia
by Mitch MacRae, Secretary of the Australian Trout & Salmon Farmers Association
At Buxton Trout & Salmon Farm we have a general feed conversion rate of 1.1 – 1.2. Protein content of the feed we use is 45 per cent and the percentage of fish meal is not known. There are only 2 feed suppliers in Australia, we chose Skretting as their feed performs better (better FCR) without compromising environmental targets on discharge and is more economical because of freight costs.
The taste of the trout is not affected by the feed, however the colour is depending on how much colour is added to the feed. Costs of feed and FCR are important factors as margins are tight, and fish feed is one of our biggest costs. On average to produce 1kg of trout we will need 1.1 – 1.2kg of feed.
In Australia approximately 1500-2000 tonnes of trout are produced each year, with approximately 85 per cent of Australia’s trout being grown in the Murrindindi region in Victoria. Australia’s trout production has an approximate value of 10-15 million dollars per year and employs approximately 200 people.
Trout culture and feed in Turkey
by Dr Atilla Ozdemir, Central Fisheries Research Institute, Turkey
Although Aquaculture has a relatively short history in Turkey, it began with rainbow trout (Onchorhynchus mykiss) and common carp (Cyprinus carpio) in the late 1960s and developed further with gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax) culture in the mid-1980s. Production reached 167,000 tonnes a year in 2010 of rainbow trout, seabass, seabream, mussel, common carp and other species, produced on nearly 2100 farms.
The rainbow trout has been cultured since the early 1970s and Turkey has become one of the top trout producing countries in Europe with an annual production of over 85,000 tonnes, or almost 50 percent of the country’s total aquaculture production. With the surprising appropriate ecological supply for trout culture in the marine environment thanks to low salinity the Black Sea has an enormous potential. Today there are more than 20 sea-based farms which are situated in the Black Sea. This tends to increase in number of fish farms and production.
Apart from marine and some freshwater cage farms in lakes and reservoirs, the majority of the trout farms employ small concrete raceways mainly using stream waters. In the past ten years, trout cage culture in dams has reached a very important level of production. Over 50 percent of the farms have their own hatcheries with eggs being produced during the natural breeding season (between December and February). Ongrowing in raceways lasts between 12 and 24 months. The majority of fish are sold locally as portion size white trout.  In the Black Sea, fish are reared in cages up to 0.5–1.5 kg and sold as ‘Black Sea salmon’.
Steadily increasing production has accompanied a large volume of fish feed needs. Trout feeds are produced in state-of-the-art facilities using leading-edge quality assurance techniques. There are currently 10 feed mills with the total capacity of over 300,000 tonnes per year. Almost all feed mills produce trout, sea bass and sea bream feeds using extruding technology made after 2000. Since the regulatory standards are high, all fish mills track  raw materials acquisition, handling and storage, production processes and packaging and delivery.
The main protein source is always declared as fish meal. But reliable data on this is hard to obtain. Although Turkey has different zones all around country having various water characteristic features, the feeds are produced regardless ecological differences as implemented in some countries by chosen different protein/lipid/energy ratios.
There is high variation in FCR depending on feed management in farms and location of farms. The lowest rate obtained in cages in Black sea as 0,9 and highest as 1,2 in inland farms. The effect of type of feed on taste and colour of the fish is has not been considered very much so far.
The initial on-farm experience and following demands/complaints from processing units may lead producers to select the best available feed. No carotenoids are incorporated into most trout diets produced in Turkey but in some cases producers in Black Sea demanded pigmented feeds.
The cost and quality are almost equal factors in choosing feed. As production increases, the market competition is getting more stressful for producers. As a consequence of competition between farmers, feed producers are always introduced the best available feeds in order to reach desired size as quickly as possible. So the growth rate is almost primary factor feed driven. The intrabrand competition occurs also among feed producers.
The environmental pressures and impacts caused by the typical production of rainbow trout in Turkey have been taken into consideration particularly in the last decade. After the adoption of new regulations on aquaculture in Environment Law, all aquaculture facilities are under a monitoring programme. Through implementation of a control programme the farmers are directly or indirectly forced to use better quality feeds particularly in low phosporus content. Since the overall production is increasing steadily, this pressure is expected to increase in near future.

Behind the scenes at Bibury Trout Farm – A working trout farm that is attracting new business from tourism
by Kate Marriott, General Manager, Bibury Trout Farm, United Kingdom

Bibury Trout Farm is one of Britain’s oldest, and certainly most attractive, trout farms. Founded in 1902 by the famous naturalist Arthur Severn, the farm was set up to stock the local rivers and streams with the native brown trout. Today, it covers 15 acres in one of the most beautiful valleys in the Cotswolds, the Coln Valley. The Farm has diversified over the years, and the leisure side of the business now plays a very important part.
Situated in the heart of the beautiful village of Bibury, the farm benefits from the large number of tourists who visit the region.The crystal clear waters of the Bibury Spring provide the essential pure water required to run the hatchery which spawns up to six million trout ova every year.
Up to a third of the ova are sold to outlets throughout Britain and occasionally abroad.  The remainder are grown on and sold to supply angling waters throughout the country, approximately 80 tons.  A small proportion (20 tons) are sold to other trout farms to supply the table market and are sold to local hotels, wholesalers and to the public through both the farm shop and farmers markets as fresh gutted trout, fillets or smoked trout, all smoked and packaged on the premises.
On the farm visitors can learn about the rainbow and brown trout while they wander in the beautiful surroundings. There is a chance to see grading in progress when the fish are selected for size and quality before being transported to new homes in oxygenated water in specially made fibre glass tanks.
Information boards give a insight to what goes on in the hatchery and fryary areas and staff are on hand to answer any questions. Feeding is done daily by staff and the water comes to life as the fish vie for the last morsel.
For the more adventurous, or the budding fisherman, Bibury’s Catch Your Own Fishery is an ideal opportunity to catch your supper or get hooked on a new hobby. Open at weekends during March – October, and during the local school holidays, we provide all the equipment and help if required.
In addition to the farm, our recently refurbished fish shop which now houses a wonderful range of wines, deli products, and preserves as well as quality breads, eggs, and milk.
The Trout Farm is situated in the centre of the village of Bibury, next to Arlington Mill. Bibury is between Cirencester and Burford in the United Kingdom
Website: http://www.biburytroutfarm.co.uk
Emerging disease in Mexican trout
by Celene Salgado Miranda, Mexico State University, Mexico
Infectious pancreatic necrosis (IPN) is a disease caused by a birnavirus affecting several wild and commercial aquatic organisms. Salmonid species are the most affected, having an important impact in the salmon and trout culture due to a high rate mortality of fry and fingerling. IPN disease is listed in the fish diseases of the International Health Code, World Organization for Animal Health (OIE). For this reason, any IPN outbreak has to be reported.The epizootiological knowledge of the IPN is relevant for establishing preventive and control strategies against both disease and causative agent.
Distribution
The IPN and the causative agent (IPNV) has been reported in several countries: Australia, Canada, Chile, Denmark, Scotland, Spain, Finland, France, England, Italy, Japan, Norway and Switzerland, among others. Based on these reports, IPN is regarded as a worldwide distributed disease. In Mexico, IPNV was identified in 2001 from US-imported rainbow trout fry. In a recent study, the IPNV was isolated from three rainbow trout breeding farms located at Mexico State, Mexico, regarded as the main producer of this fish species.

Etiology
The causative agent of IPN is a virus belonging to the Birnaviridae family. Other members of this family include infectious bursal disease (IBD) of chickens and X virus of Drosophila melanogaster. This birnavirus is single-shelled icosahedrons with characteristic isometric hexagonal profi les and has a diameter of about 60nm. The genome consists of two segment of double-stranded RNA. Genome segment A encoding two structural proteins (VP2 y VP3) and a nonstructural protease, while segment B encoding for a RNA polymerase. VP2 protein induces the production of specific-type neutralizing monoclonal antibodies. It is thought that VP2 contains all the epitopes recognized by these antibodies.
The serological classification scheme of Hill and Way recognizes nine different IPNV serovars into the serogroup A. Seven of these serotypes have been identified in IPNV rainbow trout isolates. Serogroup B includes a single serotype represented by the TV-1 archetype isolated from brown trout (Salmo trutta) and common carp (Cyprinus carpio). Each serotype includes a number of strains that differ in virulence. This variation complicates the disease which is little understood.

Epizootiology
Natural and experimental hosts Salmonids are the most susceptible species under natural conditions. The brook trout (Salvelinus fontinalis) is the most susceptible one to lethal effects of IPNV, followed by rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). Also, IPNV has been isolated from artic char (Salvelinus alpinus),brown trout (Salmo trutta) and lake trout (Salvelinus namaycush).
The IPNV has been isolated from important non-salmonid species in marine aquaculture: turbot (Scophthalmus maximus), sole (Solea senegalensis) and Atlantic halibut (Hippoglossus hippoglossus).Also has been isolated from some fishs as pike (Esox lucius), goldfish (Carasius auratus), discus fish (Symphysodon discus) and bream (Abramis brama), among others. IPNV was experimentally inoculated and re-isolated from zebra fish eggs (Brachydanio rerio).Some IPNV cases have been reported in American and European eels (Anguilla anguilla). However, the infection in Japanese eel (Anguilla japonica) has a greater economic impact.
In summary, the IPNV has been identified in a number of teleosts family fish: Anguillidae, Atherinidae, Carangidae, Channidae, Cichlidae, Clupeidae, Cobitidae, Cyprinidae, Gadidae, Esocidae, Percichthyidae, Percidae, Pleuronectidae, Poeciliidae, Salmonidae, and Sciaenidae.
Transmission, carriers and vectors
Infected fish can transmit the virus by both horizontal and vertical transmission. These fish shed the virus by urine and faeces, contributing to the horizontal transmission. In breeding fish, it has been demonstrated that the IPNV is vertically transmitted by viral adsorption to the surface of spermatozoids, or it can be present in the follicular fluid, but not in the nonfertilized eggs.
Bebak et al. experimentally determined the IPNV excretion patterns in rainbow trout fry. The time between challenge and excreting, and challenge and signs onset were evaluated.
The authors also estimated the rate of susceptible-excreting fish into a population from inoculated IPNV fry. It was demonstrated that IPNV-infected rainbow trout fry shed the virus two days post-inoculation, and the shedding is increased, and approximately decreased after 12 days post-inoculation. More than 75 percent of the rainbow trout population was infected in less than a week from the beginning of the viral shedding.
In rotifers (Brachionus plicatilis) it has been observed birnavirus lesions associated with an IPNV-like virus. It is likely that invertebrate animals used as living-food for seabream and turbot larvae, could be involved in the viral transmission. Similarly, it has been demonstrated that the freshwater crayfish (Astacus astacus) retains the virus in tissues and hemolymph, constantly shedding the virus to the water. Halder and Ahne suggest that these organisms are infected by the consumption of IPNV-infected trouts.
The following shellfish species are regarded as reservoirs of the IPNV: mussels (Mytilus galloprovincialis), oysters (Crassostrea gigas), periwinkles (Littorina littorea), and wild fish as sand eels (Ammodytes sp), sprat (Sprattus sprattus) and blue whiting (Micromesistius poutasou), among others. IPNV has been also isolated from moist fish pellets and marine sediments. Wild piscivorous birds are regarded as vectors of the IPNV, which can be isolated from faeces samples.
Signs
The IPN is a typical disease in early ages of salmonids, causing up to 100 percent of mortalit y in fi ngerlings and fi rst-feeding fry. An experimental study reported a mean cumulative mortality ranging from 84 percent to 92 percent in challenged Atlantic salmon fry. The fish mortality started seven days post-challenge and peaked at 10-12 days.
Generally affected fish showed anorexia and rotate about their long axis in a whirling motion with lapses of ataxia. In these fish darkening occurs (hyperpigmentation). Mild to moderate exophthalmia and abdominal distention are common. Also, gills are typically pale and hemorrhages are sometimes present in ventral areas, including the ventral fins. Many emaciated fish trail long, thin, whitish, cast-like excretions from the vent.
Macroscopic and microscopic findings
According to necropsy findings, spleen, heart, liver and kidneys of fry are abnormally pale and the digestive tract is almost always devoid of food. Petechiae are observed in some viscera. Sometimes, food residue remains in the gut, the quantity is small and confined to the far distal or rectal portion. Very often the body cavity may contain ascitic fluid. The stomach and anterior intestine contains a clear to milky cohesive mucus, among other findings.
Main lesions found at the histopathology study include: focal coagulative necrosis in pancreas, kidney and intestine. The pancreatic tissue showed degenerative changes, including acinar cell areas, and zymogen granules freeing. Nuclear pyknosis of different sizes are observed. In many cases, inflamatory cell infiltration is not evident. In fish that suffered the disease up to two years before the histology study, hypertrophy of Langerhans’ islets with abundant fibrosis were found.
In cases of pancreatic lesions, also acute enteritis featured by necrosis and sloughing of the epithelium are observed. In the intestinal lumen, catarrhal whitish exudate is associated with the disease. Inclusion bodies are not observed in affected cells. In many cases, the renal tissue has small focal degenerative changes. In fish that were infected during early ages, abundant rounding up of epithelial cells with karyorhectic nuclei was found. This finding suggest that they can be viral replication sites in carrier fish; however, it has not been confimed.
Diagnosis
The procedure for IPN diagnosis, recommended by the OIE, is based on the isolation of IPNV in susceptible cell lines (Figure 1), and further identification by serological techniques by immunofluorescent test, neutralization test and ELISA.
Diagnosis of clinical outbreaks is based on histology and immunological ev idence of the IPNV in infected tissues. These cases are confirmed by the IPNV isolation and immunological identification of the virus. Due to insufficient knowledge of the serological responses of fish to IPNV infection, the detection of fish antibodies to IPNV has not been accepted by the OIE (2003) as routine tests.
Detection of IPNV in cell lines is consistent and simple, particularly in cell lines from homologous species. It is due to: 1) the virus is present in high level titers in the tissues; 2) viral isolation could be positive from non-diseased fish 3) viral isolation could be positive from any viral phase; 4) two to three weeks are required for isolation and identification of the agent, which is not a critical issue for presentation of a epizootic outbreak, and 5) high sensitivity and easy observable cytopathic effect. Cell lines used for the IPNV isolation include: RTG-2 (rainbow trout gonad), CHSE-214 (chinook salmon embryo) and BF-2 (bluegill fry).
Currently, some methods have been developed for detecting IPNV by reverse transcriptase-polymerase chain reaction (RT-PCR) technique. However, sensitivity of this technique has not been greater than the cell culture. Hence, viral isolation and serological confirmation of the virus are regarded as the choice procedures for the IPNV identification.

Prevention and control
Current preventive methods are based on the onset of control and hygiene practices during rearing of salmonids, avoiding introduction or importation of fertilized eggs or fish from IPNV-infected breeding trouts. Also, the use of fish-free freshwater (for example, spring water), particularly IPNV-carrier fish, reduces the risk of infection. However, in Mexican trout farms, this condition is not always possible. As mentioned above, Salgado-Miranda carried out the IPNV isolation from three rainbow trout breeding farms located at Mexico State.
Obtained results indicated a possible horizontal transmission throughout the water supply from a farm where a previous IPN outbreak in fry was recorded. In these cases, treatment of supplied water could decrease the risk of an IPN outbreak and other infectious agents. Liltved et al. experimentally exposed live cultures of Aeromonas salmonicida subsp. salmonicida, Vibrio anguillarum, V. salmonicida, Yersinia ruckeri and IPNV to ozone or ultraviolet (UV) irradiation at nine°-12°C. The four bacteria tested were inactivated by 99.99 percent (fourlog reductions in viable count) within 180 seconds at residual ozone concentrations of 0.15-0.20 mg/L.
The IPNV was inactivated within 60 seconds at residual ozone concentrations of 0.10 a 0.20 mg/L.
Similarly, the four bacteria tested were inactivated by 99.9 percent (five log reductions in viable count) at a UV dose of 2.7 m Ws/cm2 at room temperature. IPNV was much more resistant to UV irradiation than the bacteria. An average UV dose of 122 m Ws/cm2 was required for 99.9 percent (three log) reduction in virus titer. However, it has to be considered that ozone low residual levels (0.010 a 0.20 mg/L) have also caused mortalities in trout recirculating systems.
A concentration of 40ppm available chlorine was required to experimentally inactivate 10 TCID50 of IPN V/ml in 30 minutes. Similarly, a concentration of 35ppm of active iodine was required to completely inactivate 10 TCID50 of IPNV/ml in the same time. Other studies, where several disinfectants were tested, 25ppm of iodine was required to inactivate IPNV, infectious haematopoyetic necrosis virus (IHNV) and viral haemorrhagic septicemia (VHS).
It is important to highlight that IHNV and VHS are exotic infectious agents in Mexico. For controlling IPN in breeding farms, infected fish and its offspring (eggs, fingerling and fry) have to be sacrificed. IPNV transmission by fertilized eggs can occur in spite of iodine treatment. Propagation of IPNV-free stocks monitored by viral isolation during several years, has been a good strategy for the control of IPN in breeding farms.
In areas where IPN is enzootic, it is recommended, during an outbreak, to decrease the density of the affected population, reducing the impact on the total mortality. A study showed that interaction between fish density and number of infected fi sh, affected signifi cantly the mortality parameter. However, there are some disagreements about it.
Up to date, highly effective IPNV-inactivated vaccines do not exist. Treatment with formalin or ß-propiolactone for use in vaccines, completely inactivated IPNV, but caused a slight reduction in antigenicity up to 50 percent . An active vaccine containing an IPNV non-pathogenic strain, normal trout serum-sensitive, did not confer protection in experimental challenged fish.
In Norway, both inactivated and recombinant vaccines are widely used. The recombinant vaccine, the first one licensed for using in fish, express the VP2 sequence in Escherichia coli and induce specific IPNV antibodies.
As it happens in other viral diseases, there is no treatment for the IPN. Several antiviral compounds inhibits the in vitro replication in cell culture; for example, ribavirin, pyrazofurin and 5-ethynyl-1-ß-D-ribofuranosylimidazole-4-carboxamide (EICAR),among other compounds. Research on EICAR as an antiviral compound showed good results in experimentally IPNV-infected rainbow trout.
The effect of the administration of lysozyme (KLP-602) in the feed of IPNV experimentally infected rainbow trout, has been also evaluated. Cumulative mortality was lower in fish fed on dietary treatment containing lysozyme (30%), compared with untreated fish (65%). Based on the significant increase of all the immunological parameters, these authors refer that the lyzozyme modulated the cellular and humoral defense mechanisms after suppression induced by IPNV. Also, a selected trout strain resistant to natural infection by this virus has been reported.
As Håstein et al. pointed out, future national and international aquaculture regulations for the establishment of preventive and control strategies of infectious diseases include: adoption of standardized control methods, suitable infrastructures development, and a deeper comprehension of the epizootiology of aquatic organism diseases.

Conclusion
IPNV is a birnavirus affecting mainly salmonid species, being the rainbow trout the most susceptible species. In Mexico, isolation and identification of this infectious agent from rainbow trout was recently reported. Neither a treatment nor totally effective vaccines against this disease are available, being the preventive and control measures of great importance. Introduction into farms of eggs, fish and water supply free of IPNV are the main preventive strategy. These also constitute the most important risk factors in spreading of this disease.
Acknowledgments
The collaboration in structure design and critical review of the manuscript by Dr. Edgardo Soriano Vargas, CIESA-FMVZ-UAEM, is greatly acknowledged.

Struggling Downstream? – The trout value chain in Peru
by Jodie Keane with Alberto Lemma, based on studies by Juana Kuramoto at GRADE, a member of the Consorcio de Investigación Económica y Social (CIES), Peru.
In Peru, the United States Agency International Aid (USAID) project for Poverty Reduction and Alleviation (PRA) has been one of the pioneers of value chain interventions. Under the PRA, value chains of distinct products have been fostered, ranging from agro-industrial products to artisanal goods and small manufacturing, which have then gained placement in international markets.
The chain for trout is one of the successful chains achieved by the PRA. Not only has it combined the natural advantages of raising this fish in Peruvian territory, but also it has managed to consolidate access to foreign markets through a national producer and trader, Piscifactoría Los Andes.
Raising trout has a long history in Peru. The species was introduced in the country in the 1930s, with the import of eggs and fry brought from the US. The development of trout farming occurred extensively, by populating lakes and water sources.
By the 1980s, there was a new effort to propel this activity through the construction of fish farms in various mountainous provinces of the country. However, raising trout did not take off as an economic activity and the infrastructure that was constructed was left underused.
In the 2000s, the Peruvian enterprise Piscifactoría Los Andes made important efforts to begin trout export to foreign markets. These efforts complemented the PRA project, with the development of trout value chains initiated in Junín, Huancavelica and Puno.
Linking producers to exporters
Although the initial investments required for trout production may be low, export of trout to international markets requires a series of sanitary certifications, imposing a high cost on producers and traders. The value chain for trout is divided into three well-determined links: fry production, trout production and marketing. These links define the principal actors in the value chain.
One company in Peru accounts for the majority of trout exports (90 percent as of 2006) and is the largest and oldest within the industry in Peru. Piscifactoría Los Andes recognised that it would need to increase production in order to begin exporting trout. In 2000, the company decided to participate in the PRA project and initiated negotiations with producer organization, SAIS. The company would provide the necessary capital as well as purchasing the fry and balanced food.
SAIS agreed to hand over its production to the company once the trout had reached the optimal size and weight. The PRA financed the contracting of several experts, who provided technical assistance to SAIS.
Despite initial incompliance on the part of SAIS, the interaction allowed for Piscifactoría Los Andes to increase production and sell to the export market. The agreement between SAIS and Los Andes was broken, but the coordination model must have appealed to the company because it continued to participate with the PRA in other regions. In fact, the company has signed an agreement with private company California’s Garden de Oxapampa within the framework of a PRA project.
The experience of Acoria
In this case, the coordination was between the Municipality of Acoria and the Los Andes company. The agreement continues to present day. In 2003, initial production reached 12 metric tones of trout per year and production is expected to reach 72 metric tones in 2008. In 2007, the municipal enterprise attained financial self-sufficiency and managed to generate employment for its community members (including single mothers and widows). The Municipality of Acoria is contemplating initiating trout farming in other locations in its jurisdiction.
There are several lessons to be learnt from this experience. First, coordination agreements need to be put in place to facilitate investments in public infrastructure; management could be realised by a municipal company or by a company under a franchise agreement. Second, it is feasible to replicate coordination models on a small scale, but it is still necessary to include components of technical assistance and financing. Third, expanding the level of production of trout requires significant capital. The financial solvency of large producers and coordinators is vital.
The experience of Puno
In Puno, there are different institutions linked to trout farming, such as strong producer associations like the Association of Trout Producers (APT), which are relatively active in promoting technical assistance projects for the benefit of their associates. However, initiatives have not managed to coordinate the value chain strongly, owing to budget limitations and overemphasis on the provision of basic training to the neglect of other activities. The low prices that are prevalent in the region, lack of credit, high levels of informality, lack of coordination of the actions of state organs and scant knowledge of marketing aspects of trout are the main obstacles to the development of this activity in Puno.
Conclusions
This study showed that value chain interventions should be utilized for programs whose main objective is to increase the dynamism of economic activity in a specific territory, as such programs are not necessarily effective in alleviating poverty.
In general, value chain interventions are targeting foreign markets, which are subject to quality certification and sanitary norms that can present bottlenecks for small local producers. Moreover, coordinating the chain requires significant technical and financial capacity. In the examples discussed, such assistance has been forthcoming from the PRA, but project objectives have not always been achieved.
It is important not only to provide technical assistance, but also to offer access to finance and to facilitate institutional development. Sensitisation programs are recommended in order to promote the formalization of producers and membership in associations, and to engender confidence and respect in the agreements.
Poverty alleviation programs should be designed mainly to elevate basic poverty indicators, and not to coordinate with sophisticated markets. Poor producers generally manage a range of resources and activities in order to support themselves, and often consider focusing on a single economic activity to be a high risk.
In parallel with the promotion of value chains that coordinate with foreign markets, it is necessary to work on the formation of value chains that coordinate with regional markets and the domestic market, in order to prevent prices falling from excess supply. To this end, it is necessary to work on the formation of regional markets and the provision of public goods in the form of physical infrastructure and market information systems.
The focus on demand promoted by the PRA project should be supported by the important activity of market intelligence. Only in this way will we be able to construct stable demand for local producers and ensure that market prices are adequate in order to generate sufficient utility to cover the risk that they face for their specialization.

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