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November 14
Salmon Farming in Chile – Skyrocketing Growth, Disaster, and Recovery
In the past three decades, Chile has become a major player in the aquaculture industry. From 1985 to 2000, its annual production rate increase was nearly double the world average, with an average annual growth in value of 32.2%, over four times the world average. Chile’s primary catches are jack mackerel (1.12 million tons) and anchoveta (1.07 million tons). Small chorito mussels, Northern scallops, and Pacific oysters are also important aquaculture products. By far the most valuable, however, are its salmon and trout exports. Chile’s salmonids (salmon and trout) account for nearly 100% of its farmed fish. In 2005, the production of Atlantic salmon was nearly 385,000 tons, rainbow trout nearly 123,000 tons, and Coho salmon just over 102,000 tons. In 2007, exports were worth $2.7 billion and accounted for nearly 40% of the world’s total salmonid production.
But in 2008 an epidemic of infection salmon anemia (ISA) blindsided the Chilean aquaculture industry. Despite Chile’s heavy investment in aquaculture research and development (0.68% of GDP) and the economic significance of the aquaculture industry, Chile was unprepared to handle the outbreak of ISA. The devastating virus was likely imported in salmon eggs, and spread throughout the nation’s fish farms largely unrestrained. The disease emptied entire fish farms and bankrupted the industry. Millions of salmonids perished, and millions more were prematurely harvested to prevent them from contracting the viral disease. The industry went $1.8 billion into debt.
The industry was forced to press the restart button and, despite the difficulty obtaining capital due to the global financial downturn in 2008, many empty ponds were eventually restocked with fresh fish eggs. On the legislative side, Chile has looked to Norway, Canada, Scotland, and the Faroe Islands for lessons on how to beat the infectious virus. New biosecurity measures were introduced, as well as tighter industrial regulations, such as halving the maximum allowed density at previously overcrowded pens. With industry support, these regulations improved the environmental conditions in which salmon are raised and will help prevent another disease outbreak.
Due to premature harvesting, many experts expected that it would take four years to recover to production levels that peaked at 650,000 metric tons in 2008, just before ISA hit. In 2012, the industry toppled expectations, projecting salmonid production of 700,000 metric tons. Additional good news is that the current production is more evenly divided between Atlantic salmon, rainbow trout, and Coho salmon, the latter two of which are less susceptible to ISA.   
The Chilean aquaculture industry has been able to carve itself a place in the global aquaculture market, but its rapid growth may have also contributed to the disastrous disease outbreak it faced in 2008. Thanks to the commitment of individual farmers, industry leaders, and the Chilean government, production is now back on track and stronger than ever.
November 14
Determining the UV Dose Necessary to Inactivate Fish Pathogens
Imagine checking your fish pens to find fish gulping for air, with bulging, blood-shot eyes and swollen abdomens. Some fish swim lethargically and others sink to the bottom of the pen. A few fish appear healthy, but they will soon die. There is nothing you can to do stop the spread of this devestating pathogen in your fish stocks.
Fortunately, there are techniques you can use to prevent fish pathogens from contaminating the water that enters your fish pens. One of these techniques is to use a machine that produces ultraviolet light to irradiate influent water and inactivate pathogens. What intensity of UV light should be applied to inactivate the pathogens that have the potential to threaten your fish stocks? How long should the light be applied? There are a number of scientists dedicated to finding the answers to these questions.
In 2001, two scientists, Ann Kristin Oye and Espen Rimstad, conducted a study to determine the UV dose (UV intensity x length of time UV applied) required to inactivate 99.9% of three different fish viruses: viral haemorrhageic septiceamia (VHS) virus, infectious salmon anemia (ISA) virus, and infectious pancreatic necrosis (IPN) virus. They found that VHS and ISA viruses were much more sensitive to UV radiation than the IPN virus. 99.9% (3 log) of  ISA and VHS viruses in freshwater were inactivated at doses of 7.9 ± 1.5 J/m2, 33 ± 3.5, respectively, whereas the dose required to inactivate the IPN virus was over 30 times higher (1188 ± 57 J/m2).
Applying the appropriate UV dose is important so that the target organisms are inactivated cost-effectively. For example, applying a dose of 10 J/m2, would inactivate VHS virus, but be not inactivate ISA virus by 99.9% and therefore there may be enough viable virons enough to cause a disease outbreak among your fish.  On the other hand, applying a dose of 1300 J/m2 would inactivate all three virus types, but at a cost much higher than the dose required to inactivate only the VHS and ISA viruses.
It is important to note that the UV doses found apply to freshwater; a higher or lower UV dose may be required to achieve log 3 (99.9%) viral inactivation in seawater, freshwater with high turbidity, or effluent water.
If you are interested in applying UV disinfection at your aquaculture facility, or have other questions concerning disinfection science, please contact 914-323-5700.