- The study suggests that stress in fish may be causing economic losses for the country due to its impact on the production of salmon farming industry.
According to the Chilean Undersecretariat for Fishing and Aquaculture’s report of October 2015, exports last August reached 93 different countries, likes USA, Japan, Brazil, Rusia, China and others.
The importance of this strategic productive sector to Chile's economy, led Dr Claudio Acuña Castillo, Head of the Department of Biology and researcher at the Aquaculture Biotechnology Center (CBA, in Spanish) and his colleagues at Universidad de Santiago and other institutions, to conduct a literature review to understand the stress-generating mechanisms in fish, in comparison to mammals.
The analysis entitled Neuroendocrine mechanisms for immune system regulation during stress in fish was published on the Fish and Shellfish Immunology journal. The article has had a high impact on the scientific community and has been cited in other scientific works, allowing to go deeper in an insufficiently studied subject. “It has contributed to understand some aspects of stress in fish and to help other researchers who are interested in the same subject,” Dr Acuña said.
According to the researcher, major causes of stress among farmed fish are overcrowding, relocation, vaccines and transitions between freshwater and saltwater. The latter process happens normally in nature, but in productive contexts, it causes stress and affects the immune system of fish.
Chronic stress and acute stress
When analyzing stress in fish, Dr Acuña emphasizes that we must consider that fish are not mammals, therefore, they have a different behavior. They have different regulation mechanisms, different anatomy and a lonely life, as they are not gregarious animals.
All living organisms need some stress to develop. “Chronic stress is dangerous and harmful. When it becomes permanent, it affects the immune system. However, acute stress is necessary and useful, as it contributes to decision-making in conflict situations,” he explained.
When stress becomes chronic, it can be perceived in different ways. “Fish show physiological and behavioral changes, aggressiveness, and, sometimes, loss of appetite and increased susceptibility to contagious diseases,” he said.
Impact on aquaculture production
According to Dr Acuña, “It is highly probable that stress in fish may be having an impact on the production losses of salmon farming industry. When stress is too much, fish become susceptible to sea lice, for example. So, when all the produced fish die, as it is happening now, maybe there are not only genetic causes but stress-related factors.”
The researcher is also very worried about the side effects of production losses: lack of jobs and unemployment. He thinks that, if we begin to understand the process, we will be able to provide solutions.
Besides, Dr Acuña expects to reduce the stress effects in fish by using natural solutions, like plants or natural elements.
The article was also led by Dr Ricardo Fernández, researcher at the Faculty of Biological Sciences and the Faculty of Medicine of Universidad Andrés Bello. Dr Gino Nardocci, Dr Cristina Navarro and Dr Paula P. Cortes, of Universidad Andrés Bello, and Dr Mónica Imarai, Dr Margarita Montoya, Dr Beatriz Valenzuela and Dr Pablo Jara, researchers at the Faculty of Chemistry and Biology and the CBA of Universidad de Santiago, collaborated with the study.
Translated by Marcela Contreras
