Fish health and welfare

In the research field of fish cell technology, we use cell cultures of various organs for in vitro studies on the topic of fish health. We are pursuing various research approaches and focal points.

The BMBF-funded SALHEARTCELL project is concerned with piscine orthoreoviruses, which can trigger cardiovascular disorders in the popular edible fish salmon and trout and thus threaten the sustainable development of aquaculture. As a prerequisite for the study of fish viruses and, in the long term, the development of a vaccine, cell cultures of the respective fish species are needed in which the virus can be propagated and cultivated in the laboratory. Together with the Department of Fish Diseases of the University of Veterinary Medicine Hanover Foundation, new permanent and primary cell cultures from heart tissue are being established and further developed. The main focus is on the fish species Atlantic salmon, brown trout and rainbow trout. The developed cell cultures are to be used to detect the piscine orthoreoviruses 1 and 3 and, if virus propagation is successful, represent the first step towards vaccine development.

In projects already completed, the Fraunhofer IMTE has been able to successfully provide established fish cell cultures as a tool for virology in vaccine development. One example is the project "KHV-Vacc", which dealt with the establishment of cell cultures from carp to combat the koi herpes virus.

Cell cultures make it possible to test various substances for their harmful potential on fish without actually having to carry out animal experiments. They offer the possibility of in vitro experiments of all kinds and are thus an important means of implementing the 3Rs principle.

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

Aquaculture serves the sustainable and animal welfare-friendly production of fish as a foodstuff. Due to nature, environmental and water law restrictions on the use of surface waters, aquaculture systems with a high level of recycling of the process water are considered extremely promising for the future. However, especially in recirculating systems, production faces special challenges because various influencing variables can have a negative impact on 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. The collection of environmental parameters is possible with specific sensors, but there is a lack of further correlations to the effects on fish health. The link with animal welfare parameters is still a challenge, so that problems are only detected when limit value transgressions may have already caused damage to the animal 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, which are isolated from the blood or other organs, and mRNA-based markers, which are to be detected in the process water. The focus here is on influences caused by various feedstuffs or stress caused by temperature fluctuations or high stocking densities, e.g. before slaughter.

Through the development of animal welfare indicators for fish, we have a tool at hand with which we can evaluate the welfare status of a farm on 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 assessed in more depth by molecular biological examination methods (expression of stress and immune markers). 

With detection, we go into practical application and use our experience to improve animal welfare and fish health in concrete cases in practice. For example, we investigate the influence of different ingredients in fish feed on the health and immune system of fish and evaluate what influence the husbandry environment has on the stress axis and health of fish. We relate this to the feeds, among other things. Optimal husbandry 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 grow up successfully in aquaculture from a human point of view, knowledge about animal welfare itself is rudimentary and, as a result, production success may be reduced. Biochip-based molecular indicators can be used to measure the stress, health and animal welfare of aquatic organisms at different stages of production from hatching to when the animals reach market weight, to certify husbandry conditions and aquaculture facilities, and thus to optimise fish production methods right through to the slaughter process. The main focus of our work at the IMTE is the recording and reduction of negative influences in aquafarming.

To determine parameters from blood and other organic samples or to investigate questions in cell culture models, we use established molecular biological methods at the IMTE. We also investigate the influence of environmental parameters on the health of fish in natural waters and help to assess how fish-friendly pumps are that provide inland drainage and flood protection in pumping stations along coasts and in rivers. We have developed a Welfare Index and Bonit Scheme for trout and specialise in the study of welfare parameters, including ethograms.