Aquaculture Magazine

Octuber-Novembrer 2016

The harmful algal bloom last summer had a major impact on the Chilean salmon industry

By Asbjørn Bergheim

A mass mortality of salmon and trout in cage farms in Chile during last February – March was frequently described in international media. Some sources wrongly called the incident a ‘red tide’ – it was actually blooming of so-called ichthyotoxic algae that caused the huge mortality (German Merino, pers. comm.)

By Asbjørn Bergheim*

A group of algae, Pseudochattonella spp., affected all salmon farms around Pt. Mont. The bloom of Dinoflagellates, often described as ‘red tide,’ arrived later on in another zone along the coast of Chiloe Island and affected primarily mollusks.
According to German Merino at Universidad Católica del Norte, this algae (Pseudochattonella) was not typically seen before in Chile and its provenance is unknown. This species has formerly been identified in China, and it can remain dormant for a long time in sediments (up to 70 years). Mass blooming of Pseudochattonella does not color the ocean red – it looks more like turbid water. In the most affected areas, these algae totally dominated the phytoplankton at 5 – 15 m depth. A density exceeding 10 cells per mL becomes critical for fish.
Scientist are still trying to understand the exact mechanisms by which the algae species in the bloom in Chile kills fish. Three possible and combined mechanisms are involved: critical oxygen deficit, toxic effects from algae-produced neurotoxins, and/or suffocation due to accumulation of mucus on the salmon’s gills.
Altogether, about 100,000 MT were lost in the algal bloom, including Atlantic salmon, Coho and trout. The death of nearly 23 million fish represents 15 % of Chile’s total production and is equivalent to an export value of some US$800 million. Consequently, the formerly predicted growth of the industry is no longer achievable for the next couple of years.
The algal bloom has been described as the country’s worst environmental crisis in recent years, affecting hundreds of miles along the coastline of Patagonia and further north to Region X, the Chiloe Island – Puerto Mont area where the salmon industry dominates. Dozens of people were poisoned by the algae-produced neurotoxin, seafood became toxic and the bloom “deprived thousands of fishermen of a living.”
Scientists are considering the high seawater temperature during the last summer, 2 – 4 ºC above normal levels, to be the major reason for the toxic algae outbreak along the southern coast of Chile. Unusually high temperatures are a direct consequence of the weather phenomenon El Niño, which was especially strong in late 2015. CCN reported that the last El Niño was one of the three strongest ever (Figure 5). The last comparable temperature peak happened almost 20 years ago (1997-98). Normally, such warm conditions last for 9 – 10 months (La Niña is the cold phase) and each phase is supposed to occur every two to seven years. 
Recently, climate experts at NOAA (US National Oceanic and Atmospheric Administration) report that there are now signs of a developing La Niña with weakly falling temperatures in the tropical Pacific Ocean.

Dr. AsbjØrn Bergheim is a senior researcher in the Dept. of Marine Environment at the International Research Institute of Stavanger. His fields of interest within aquaculture are primarily water quality vs. technology and management in tanks, cages and ponds, among others.

Asbjørn Bergheim

Asbjørn Bergheim

Dr. A. Bergheim is a senior researcher in the Dept. of Marine Environment at IRIS – International Research Institute of Stavanger ( Prior to the present position, he worked at NINA – Norwegian Institute for Nature Research for ten years and he has also been at a private Norwegian consultancy company, Aqua Consult, for two years. He stayed one year as a visiting researcher at Institute of Aquaculture, Univ. of Stirling. Dr. Bergheim holds a PhD from The Norwegian Agricultural College (since 2005 Nor. Univ. of Life Science). He is a former President of AES – Aquacultural Engineering Society (2011). He has been a member of the editorial board of Aquacultural Engineering since 1996, of Aquaculture Research (since 2007) and of The Open Fish Science Journal (since 2007). Besides, he is the Norwegian representative of the Nordic Network on RAS (2010 - ).

Dr. Bergheim’s fields of interest within aquaculture are primarily water quality vs. technology and management in tanks, cages and ponds, effluent loading and treatment, recirculation systems, and intensification of farming systems. He has been involved in many research and consultancy projects in Norway (land and cage based systems for salmonids), Scotland, Asia (mainly brackish water shrimp culture in Bangladesh, India, Sri Lanka, Thailand), and in some other parts of the world. Some of the achieved results are published in Aquaculture and Aquacultural Engineering, and Dr. Bergheim has been a permanent columnist in the UK based magazine, Fish Farmer (2000 – 2003). He has published more than 50 articles in peer-review journals.

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