The seawater temperature impact: One of the biggest aquaculture challenges

Top view of the white ice floes on the shore and in the blue sea water. Aerial view of melting ice on the sea coast. Climate change in the Arctic. Northern nature. Beautiful wide panoramic background.
Top view of the white ice floes on the shore and in the blue sea water. Aerial view of melting ice on the sea coast. Climate change in the Arctic. Northern nature. Beautiful wide panoramic background.

Farmed salmon is mainly produced in Norway, Chile, Scotland, the Faroe Islands, Ireland, Iceland, Canada, the USA, Tasmania, and New Zealand. This is due to biological limitations, seawater temperature requirements, and other natural limitations.

One of the great enemies of salmon growth is changes in seawater temperature. In winter and spring salmon grow more slowly as the water is colder. Therefore, production normally peaks around the end of the year and gets to its lower limits in mid-summer.

Indistinctly, with high sea temperatures the risk of disease increases, and with temperatures below zero degrees, mass mortality becomes more likely.

The World Meteorological Organization (WMO) predicts that the annual global temperature has a 20% chance to exceed 1.5°C in at least one year.

"The speed at which temperatures are rising is alarming," said Pascal Peduzzi, director of GRID-Geneva at the United Nations Environment Program (UNEP).

Climate change effects

The Norwegian food research institute Nofima, aware of the dreaded consequences, work on raising awareness and alert about this matter.

Thereby, a study carried out by the company advises how high-temperature scenarios will affect salmon farming in the 13 regions from today to 2070.

One of the scientists that collaborated in the study, Elisabeth Ytteborg, indicated: "Even under the mildest scenario we see that rising ocean temperatures may pose a challenge for salmon".

"We still don't know enough about how the farmed salmon will react to higher temperatures, increased ocean acidification, and reduced oxygen. Our research has revealed major knowledge gaps in terms of both available datasets and the biology of salmon," she added.

Regarding the measures to be implemented, Ytteborg noted: "New technologies, breeding for improved temperature tolerance and alternative farming locations are some of the solutions that could help maintain healthy fish."

Nofima, SalmoBreed AS, Akvaforsk Genetics Center AS, Danish Salmon, SalMar Farming, and Aller Aqua A/S, among other companies, take part in the FutureEUAqua project. The aim is to promote sustainable growth of resilience to climate change. Also, environmentally friendly organic and conventional aquaculture of major fish species.

FutureEUAqua looks for innovations in the whole value chain. Including genetic selection, ingredients and feeds, non-invasive monitoring technologies, innovative fish products, and packaging methods, and optimal production systems.

FutureEUAqua brochure

Chile's privileged location

Compared to other countries, Chile has an important natural competitive advantage. The more constant water temperature allows the farms of the country to release smolts. Throughout the year and use in a more uniform way all the facilities.

Mowi echoes this fact. Moreover, it recalls that direct employment in Chilean aquaculture (including processing) was estimated at around 30,000 people in 2014.

In addition, the company indicates that Chile has the highest relative feeding. This is measured by feed sold or fed during a month relative to the incoming biomass.

Salmon Farming Industry Handbook 2019 – Mowi

How to predict the growth rate

It makes sense we can only estimate the salmon growth rate as its natural environment is always changing. But, according to the Alaska Department of Fish and Game, we can predict it. Through a controlled environment by monitoring the temperature of the water.

To clarify, this daily measurement can describe the cumulative effect of temperature over time. Also, noted in a unit of measure known as the Accumulated Thermal Unit (ATU).

Moreover, Alaskan fish farmers can issue a Classroom Incubation Permit (CIP) from the Department. Without this, it is illegal in Alaska to move eggs or fish from one place to another.

The worst scenario

Unfortunately, several studies confirm that warming trends will be much more severe in the coming decades than those experienced in the past.

According to UK Environment Agency, even in a "low emissions" scenario, the future rate of global warming during this century may be about four times greater than experienced during the 20th century.

On the other side, if we reach a "high emissions" scenario, the future rate of warming may be about eight times that of the 20th century.

Although the agency confirms that warming could be extremely detrimental to both species, it may be more detrimental to freshwater trout than salmon. Because trout have lower temperature tolerance.

Moreover, it advises that sublethal temperature consequences are much harder to predict. Those, influence too in processes such as growth and maturation.

In other words, more complexity is required to identify the generic effects of temperature on the ecosystem and the implications for fish populations.

The physiological issue

Likewise, Atlantic salmon physiology can be affected by the rise of ocean temperatures. A study carried out by the Institute for Marine and Antarctic Studies (IMAS) which depends on The University of Tasmania talks about this.

"By studying changes in the salmon liver proteome after exposure to prolonged elevated temperatures, we were able to identify that the main way the salmon met the need for extra energy was to suppress liver functions that synthesize and degrade proteins," Professor Chris Carter indicated.

Furthermore, the Co-author of the IMAS study explained: "This research is part of an ongoing program. It aims to understand how salmon and other aquaculture animals manage the increased temperature. Besides, we build a picture about a sequence of physiological changes that occur over periods of exposure to elevated temperature."

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