Reports

Stress of salmonid fish during pumping

Published:

30/06/2022

Authors:

Gunnar Þórðarson - Matís, Agnar Steinarsson - Marine Research Institute, Ásgeir Bjarnason - Stjörnu-Oddi, Ína B. Össurardóttir - Skaginn 3X

Supported by:

Matvælasjóður

contact

Gunnar Þórðarson

Regional Manager

gunnar.thordarson@matis.is

Minimizing the stress of salmonids during fire handling can be crucial in ensuring the welfare, growth and survival of the fish, as well as the quality and shelf life of closed products. Stress during treatment, eg against lice, can reduce the resistance of fish to infections and colds as well as reduce growth; because it may take the salmon some time to recover and start feeding again. If the pumping of fish for slaughter causes a great deal of stress that can affect the quality of the products. It is also important to meet animal welfare requirements in aquaculture along with increased pressure from consumers. 

Vacuum pumps, which are most commonly used in aquaculture today, are known to cause considerable stress, depletion and poorer quality, as pumping involves a lot where the air space with fish is evacuated and then fired to pump the fish. Therefore, manufacturers of pumping equipment have been looking for new ways of pumping salmonids and the Icelandic company Skaginn 3X has been developing a so-called spiral pump (Archimedes pump) as a solution to this problem. The pump has been named ValuePump.

In this project, a prototype of the pump was built and then comparative experiments were made with it and a traditional vacuum pump, where the stress in the fish during the pumping was measured with heart rate sensors, as well as measurements of the production of stress hormones in the blood.

Experiments were carried out in the facilities of the Marine Research Institute in Reykjanes under the direction of specialists in aquaculture and in the use of heart rate sensors. During a four-week period, 100 salmon (about 1 kg average weight) were pumped once a week with each pump, of which 20 salmon had an internal heart rate sensor from Stjörna-Oddi. 

The results showed a significant difference between groups following pumping. Heart rate rose sharply during pumping, but the ValuePump group was quicker to recover and regain baseline. Pumping with a vacuum pump had a much greater long-term stress effect than experimenting with maximum stimuli where the fish crackled on dry land. There was also a large visual difference between the groups according to the type of pump, as fish pumped with a vacuum pump often came injured or even dead from the pump, swam sideways or upside down hours after pumping. Fish that were pumped with ValuePump, however, did not experience any visible damage during the pumping and seemed to be doing well after it. 

The results of the comparative experiments must be considered very positive, but further research is needed to definitively determine the advantages of ValuePump over conventional vacuum pumps. It seems clear from the results of the project that salmon that are pumped with ValuePump are quicker to recover after pumping and then start feeding again. The results regarding pumping for slaughter are not as obvious and require further research, especially since fish that have reached slaughter size need to be examined under real conditions. 
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Minimizing the stress of salmonids during handling and before slaughtering can be extremely important for welfare, survival and growth, as well as to ensure overall quality and shelf-life of the final products. Stress during treatment, eg, against lice, can reduce the resistance of fish to infections and cold seawater as well as reduce growth which may take the salmon some time to recover from stress and start feeding again. If the pumping of fish for slaughter causes a lot of stress, it can affect the quality of the products. Animal welfare is also becoming more important in aquaculture with increased welfare demands from the consumers.

It is known that vacuum pumps, that are most commonly used in the aquaculture industry today, cause considerable stress, loss and poor quality, as pumping causes a lot of discomfort for the fish. Companies have therefore been searching for an alternative to vacuum pumping for some time. The Icelandic company Skaginn 3X has for some time been developing a so-called Archimedes pump to replace vacuum pumps. 

In this project, a prototype of the Archimedes pump (called ValuePump) was made, and then compared to a conventional vacuum pump. The pumping stress of fish was measured by cardiac sensors along with the measurement of a stress hormone Over a 4-week period, 100 salmons (1 kg average weight) were pumped once weekly with either pump, including 20 salmons implanted with heart rate loggers from Star-Oddi.

Experiments were carried out in the facilities of the Marine and Freshwater Research Institute in Reykjanes under the supervision of specialists in aquaculture and the use of cardiac sensors.

The results showed a significant difference in heart rate recovery between the two groups. There was a large increase in heart rate immediately after pumping but the ValuePump group recovered more quickly to pre-pumping levels. Pumping with the vacuum pump caused a larger and longer stress effect then an applied max stress chase protocol. There was also a considerable visible difference between the two groups, where the vacuum pump fish were injured or even dead after pumping, swimming on the side or upside down for hours after pumping. The ValuePump fish, however, received no visible physical damage from the pumping and seemed fit. 

The results of the comparative studies indicate very positive results, but further studies are however needed to validate the results. It is apparent that salmon pumped with ValuePump is faster to recover than when pumped with vacuum pumps and is as results faster to start feeding again after handling. Results regarding pumping of fish for slaughtering are not as comprehensive and need to be studied further, particularly by analyzing fish that has reached slaughter size and preferably in real industry setting. 

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