Fish Health and Animal Welfare

Making stress and deficiencies detectable — validation of testing methods for detecting welfare and health parameters of fish

This research area is very diverse and includes studies on fish in aquaculture and in the environment.

Aquaculture is the sustainable and animal-welfare-friendly production of fish for food. Because of restrictions on the use of surface waters due to nature-conservation, environmental and water laws, aquaculture systems with a high degree of process water recycling are considered to be extremely promising for the future. However, production in recirculating systems in particular faces special challenges because several factors can negatively affect fish welfare (e.g., water parameters such as oxygen content, pH, nitrite or ammonium/ammonia or the total live germ count). The complex concept of animal welfare can only be ensured through good management, which requires the availability of valid process data. Environmental parameters can be collected with specific sensors, but further correlations to the effects on fish health are lacking. Linking to animal welfare parameters is still a challenge, and as a result problems are only detected when limit violations may have already caused damage to animals and animal welfare. A system that reliably detects problems at an early stage does not yet exist. We are trying to remedy this by using different approaches to find detection methods for different stressors.

On the one hand, we are working on molecular stress markers that can be isolated from the blood or other organs and mRNA-based markers that can be detected in the process water. The focus here is on the effects of different feeds or stress caused by temperature fluctuations or high stocking densities, e.g., before slaughter.

The development of animal welfare indicators for fish provides us with a tool to assess the welfare status of a farm at a higher level. By assessing fish (externally and histologically) and using our veterinary expertise, we can make a sound assessment of external damage in terms of disease and animal welfare. This is further enhanced by molecular biology test methods (expression of stress and immune markers).

Holistic welfare and health monitoring of aquaculture and ornamental fish

• Harm counts
• Blood analyses
• Molecular biology tests

General health issues

• Blood analyses
• Fish pathology investigations (macroscopy, histology)
• Veterinary expertise on fish health

Fish welfare in a general context 

• Committee work
• Animal welfare support for the construction of fish-friendly pumps
• Vital marking methods for stocking fish
• Health monitoring of wild fish stocks

Application of welfare and health parameters “Knowledge creates animal welfare — Science!”​

After detection, we go to practical application and use our experience to improve animal welfare and fish health in specific cases. For example, we investigate the influence of different fish feed ingredients on the health and immune system of fish and evaluate the impact of the farming environment on the stress axis and health of fish. We relate this to the feed, among other things. Optimal farming conditions, healthy animals and innovative raw materials are prerequisites for sustainable aquaculture of animal organisms, the production of quality products, and profitable sales. Although fish in aquaculture grow successfully from a human point of view, knowledge of animal welfare itself is rudimentary and production success may be reduced as a result. Biochip-based molecular indicators can be used to measure the stress, health and welfare of aquatic organisms at different stages of production, from hatching to reaching market weight, in order to certify farming conditions and aquaculture facilities and thus optimize fish production methods up to the slaughtering process. The main focus of our work at Fraunhofer IMTE is on detecting and reducing negative influences in aquaculture.

At Fraunhofer IMTE, we use established molecular biology methods to determine parameters from blood and other organic samples or to investigate questions in cell culture models. We also investigate the influence of environmental parameters on the health of fish in natural waters and help to assess the fish-friendliness of pumps for inland drainage and flood protection in coastal and river pumping stations. We have developed a welfare index and scoring scheme for trout and specialize in the study of welfare parameters, including ethograms. ​

Holistic welfare and health monitoring of aquaculture and ornamental fish

• Harm counts
• Blood analyses
• Molecular biology tests

General health issues

• Blood analyses
• Fish pathology investigations (macroscopy, histology)
• Veterinary expertise on fish health

Fish welfare in a general context 

• Committee work
• Animal welfare support for the construction of fish-friendly pumps
• Vital marking methods for stocking fish
• Health monitoring of wild fish stocks

Like almost no other technology, ultrasound provides non-invasive, real-time imaging with resolutions down to the submillimeter ranges. This scalability, combined with other attributes such as freedom from ionizing radiation and comparatively low acquisition and operating costs, makes ultrasound the most widely used diagnostic imaging method in the world. The Aquaculture@Fraunhofer community uses this technology for fish diagnostics.

• Monitoring of health and reproduction
• Development of special systems for ultrasound diagnostics of farmed fish
• Swim-through ultrasound tomograph for non-contact examination of internal organs