Chilean Salmon Farming on the Horizon of Sustainability: Review of the Development of a Highly Intensive Production, the ISA Crisis and Implemented Actions to Reconstruct a More Sustainable Aquaculture Industry - Aquaculture and the Environment: A Shared Destiny - page 228

approximately 10,000 gross tons in the early 1990s to over 545,000 tons exported in 2008
(TechnoPress, 2010). Mortalities caused by infectious diseases increased over the years and
dropped after the sanitary crisis as less salmon where transferred for grow-out purposes.
In the early 1990´s, the main diseases present in Chilean salmon farming were the Bacterial
Kidney Disease (BKD), affecting rainbow trout, Atlantic salmon and Coho salmon,
throughout their entire production cycle. Piscirickettsiosis (Fryer et al., 1992) or Salmonid
Rickettsial Septicemia (SRS), a disease detected for the first time in the world, endangered at
that time mainly Coho salmon during grow-out phase (Bravo & Campos, 1989a, 1989b;
Fryer et al., 1990). The etiological agent was first described in southern Chile (Cvitanich et
al., 1991; Fryer et al., 1990). The pathogen was extremely aggressive, and farms in the
southern part of the country were devastated over a very short period (Branson & Diaz-
Muñoz, 1991). Until now, piscirickettsiosis caused by the facultative intracellular bacteria,
Piscirickettsia salmonis , is one of the diseases most threatening to the sustainability of the
Chilean salmon industry (Olivares & Marshall, 2009). Piscirickettsiosis affects all salmonid
species farmed in Chile, causing up to 90% mortality in some sites. First calculations
estimated mortality of 1,5 million of Coho salmon, which represented an estimated loss of
USD 10 million for year 1989 (Larenas et al., 2000). According to further calculations, the
industry attributes annual losses of USD 50 million to piscirickettsiosis (Smith et al., 1997).
Currently data from SalmonChile estimate losses of USD 19 million considering direct costs
due to mortalities but not considering indirect costs i.e. treatment, decreased performance,
and other costs related to the disease. Global losses have been estimated to USD 120 million
for each year (InnovaChile, 2008). Different factors contribute to the occurrence of a
persistent clinical course, much more as a chronic presentation of the disease with abscess
observation (Godoy, 2010). Today, piscirickettsiosis represents 90% of the infectious-disease-
caused mortalities (Intesal pers. comm., 2011) and is the pathogen agent mostly diagnosed
in SW (Subpesca, 2010). In addition to the appearance of BKD and SRS, the first intensive
productions of eggs and fries were visibly affected by diseases caused by funguses
( Saprolegnia sp.) and flavobacteria (mainly Flavobacterium columnare and F. psycrophilum ) in
hatcheries and fry farming sites located in lakes. These infections are considered the major
problems in FW, where infections with flavobacteria can result in 5% to 70% mortality rate
of fingerlings (Valdebenito & Avendaño-Herrera, 2009). In 2008, Saprolegnia showed a
monthly average mortality in Coho salmon of 0.06%, in Atlantic salmon of 0.02% and in
rainbow trout of <0.01% (Intesal, 2009). The first clinical case of enteric redmouth disease
(ERM, caused by Yersinia ruckeri ) in Atlantic salmon fries and smolts in FW net pens was
described at the end of 1992 (Troncoso et al., 1994). This case was related to increasing water
temperature during the spring and summer seasons. Concurrently, during the same season
a fresh water Rickettsia (Unidentified Agent-2, UA2) was confirmed to have caused
mortalities of Atlantic salmon in lakes (Cvitanich et al., 1995). Subsequently, in June 2006 the
gram-negative bacteria Francisella was confirmed as the agent responsible for UA2, which
caused severe mortalities in Atlantic salmon farms located in Lake Llanquihue (Birkbeck et
al., 2007). Francisella philomiragia presented high rates of morbidity and outbreaks with
cumulative mortality ranging from 5% to 20% (Bohle et al., 2009). This bacterium presented
100% homology with F. philomirhagia subsp. noatunensis , currently denominated F.
noatunensis comb. nov (Mikalsen & Colquhoun, 2010; Ottem et al., 2009).
Sea lice infestations in salmonids were first reported in Chile in 1982 (Reyes & Bravo, 1983)
caused by the ectoparasite Caligus sp. Historically in Chile the most problematic parasite