Forms of aquaculture

Fish farming has a long tradition in the form of carp and trout ponds. And it has a future. An interdisciplinary working group in the Cluster of Excellence »The Future Ocean« is pursuing the optimisation of marine aquaculture in terms of sustainability.

Fish farms do not have the best reputation. They are regarded as intensive animal farming (or »factory farming«) in the water, which is detrimental to the environment and animal welfare. According to Profes­sor Konrad Ott, this is largely related to the beginnings of the industrial development of aquaculture, 30 to 40 years ago.

»Back then, fish farming required a very high input. You had to catch fish in order to feed them to the farmed fish, large quantities of antibiotics were used, and mangrove forests were destroyed for shrimp breeding,« said the Kiel Professor of Environmental Philosophy and Ethics. »That was first-generation technology, which can certainly be optimised, so that even a demanding sustainability theorist would find it acceptable.« This optimisation of marine aquaculture is the focus of a working group at Kiel University.

The aquaculture of fish, shellfish, crustaceans and algae is extremely important to feed the global population. The market has sharply rising growth rates. »By now, every second fish that is consumed comes from aquaculture,« emphasised Carsten Schulz. The Professor of Marine Aquaculture at Kiel University, and scientific director of the Gesellschaft für Marine Aquakultur mbH (GMA, Society for Marine Aquaculture) in Büsum, researches innovative solutions, such as feeding using as little fish meal and fish oil as possible. According to Schulz, examples of inherently resource-saving production include traditional, extensively farmed carp ponds or mussel beds.

Professor Schulz tackles four problem areas of aquaculture in his research: feeding, animal welfare, pollution of water and intervention in ecosystems. »Feeding requires significant resources, but these are not utilised one hundred percent, so that nutrient residues and fish excretion can pollute the waters,« explained Carsten Schulz. Fish farming is also challenging from the point of view of animal welfare. »We try to quantify animal health and welfare in order to better understand the reaction of the fish to varying environmental conditions and, in the long-term, to minimise the use of medication.«

The problem of water pollution can be solved using new plant systems, such as the so-called multi-trophic aquaculture system. Simultaneously rearing different organisms balances nutrient inputs and can avoid water pollution. For example, you combine the aquaculture of algae with fish farming. »The algae need the nutrients that the fish leave uneaten or excrete,« explained Professor Rüdiger Schulz, algae expert at the Botanical Institute at Kiel University. »Algae are an important part of aquaculture systems, since they absorb nutrients just like mussels, and thus reduce nutrient levels in the waters.«

Afterwards the algae itself can be used for various purposes, as it provides valuable ingredients. These include, for example, the red-orange pigment astaxanthin. As a feed additive in salmon farming, it ensures that the salmon gain their typical pink colour. Micro-algae are also a good source of omega-3 fatty acids. Fish which consume these micro-algae store their valuable fatty acids in the fish oils. Rüdiger Schulz is convinced: »By cleverly combining, we could achieve emission-free aquaculture, not only in closed systems, but also in the Kiel Fjord.«

In light of fish meal problems, it is also worth considering rearing more fish on vegetarian diets. The mullet, which has populated the Kiel Fjord has a vegetarian diet, and according to Schulz is satisfied living in a cage and nibbling the algae which grow on it.

»In Kiel, we can investigate and research new models for aquaculture systems, both land-based systems, i.e. artificial, as well as those in marine systems. In this way, we want to show what is possible today, and at the same time deal with old prejudices,« said the environmental ethicist Konrad Ott. The Cluster of Excellence »The Future Ocean« will highlight various possibilities for sustainable aquaculture in a series of lectures during the summer semester.

Author: Kerstin Nees