Animal welfare in modern production systems for fish

Last changed: 15 June 2021
Photo: Fish swimming in the water.

FRESH – Fish REaring and Stress Hazards.

Illustration: The logotype of SLU and The University of Gothenburg in one picture.

Researchers: Bo Algers (SLU), Michael Axelsson (GU), Lotta Berg (SLU, co-ordinator), Jeroen Brijs (GU, not in photo), Albin Gräns (SLU), David Huyben (SLU, not in photo), Anders Kiessling (SLU), Torbjörn Lundh (SLU, not in photo) Erik Sandblom (GU), Kristina Sundell (GU) and Henrik Sundh (GU) .

Photo: A group of people, all of them in the FRESH project research group.

Contact the FRESH group here!


New publications:

 General aim of the project

  • Establishing a world class fish welfare platform.

Specific aims

  • Obtain physiological data enabling identification of cause and effect,
  • Establish quantitative comparison of critical situations for farmed fish,
  • Develop specific recommendations and basis for legislation to ensure animal welfare and improve future production and management systems.

What are the problems in fish welfare research?

  • Fish lack discernible facial expression and most farmed species also lack vocal abilities.
  • Fish in a production environment has a very limited behavioural repertoire and is hard to observe visually.

Hence, it is difficult for a human caretaker to perceive fish expressions of distress.

Possible stressors in commercial fish farming

Capture and handling procedures such as netting pumping, sorting, vaccination, treatment, transport, nutritional disorders as well as aggression and inability to hide from threat and infections. Several of these stressors will be evaluated within the project.

Physiological stress indicators for fish in general After perceiving stress, a primary stress response, i.e. increased circulating levels of catecholamines (CAT) and cortisol, is initiated through the hypothalamic-pituitary-interrenal axis. This elicits secondary stress responses, in fish documented as cellular, osmoregulatory, hematological, barrier or immunological changes. This may create tertiary stress responses, affecting performance and manifested as decreased growth, swimming capacity, disease resistance, feeding activity and altered behaviour.

Stress indicators currently used at fish farms

  • Flight attempts in direct conjugation with the stressor,
  • Reduced feed intake over days and even weeks after a stressful event,
  • Reduced growth and increased mortality and/or increased diseases occurrence is a more long term and multi‐cause response.

Methods to be used in this project

To understand the causality and severity of different farming practises, physiological responses in vivo and in vitro will be studied in the fish at site.

  • A telemetric dual-channel Doppler blood flow system, measures total cardiac output flow, gut blood flow, heart rate and body temperature.
  • Using chamber techniques, evaluates the integrity of the intestinal primary barrier, a well-established secondary stress response and welfare indicator.
  • Primary stress responses will be measured using non-invasive and invasive methods. Use of permanent cannula in in order to obtain repeated blood samples in normally feeding and behaving fish.
  • Non-invasive techniques ensures representative baseline and stress values of the secondary stress responses, heart and respiration frequency, in non‐experimentally influenced fish.
  • Controlled laboratory experiments on instrumented fish under mimicked farming situations will study the mechanisms of specific physiological responses.

Illustration showing modern fish farming system in western Norway (out in the water)
Figur 1. Modern fish farming system in western Norway. Such an enclosure can have a circumference of up to 120 meters and house more than 100,000 animals. To study the individual animals in such systems is almost impossible today, but nevertheless crucial when aiming at ensuring not only the welfare of the fish but also at developing rational and well-functioning production systems. (Photo: Anders Kiessling)

Illustration: Stress response systems in fish.
Figure 2. Stress response systems in fish.

The project has 4 sub-projects, please see links below:

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