EUROFISH Magazine 2 2020

Page 49

ESTONIA

Feed based on local raw materials can contribute to the sustainable development of marine aquaculture

Achieving Blue Growth in the Baltic Sea

Primary production is the supporting pillar of the marine ecosystem and is most affected by the availability of light and the nutrients, nitrogen and phosphorus, which limit plant growth. Excessive inflow of nutrients causes eutrophication of the sea. Currently, nutrients are too readily available in the Baltic Sea and restrictions on the amount of nitrogen and phosphorous compounds reaching the sea are recommended to improve the quality of the aquatic environment. Intensification of agriculture is, however, increasing the nutrient burden on the Baltic Sea. Based on the above, methods are sought for developing sustainable aquaculture.

Algae and bivalves can remove nutrients from the water While fish farms in natural waterbodies increase the environmental burden, farming algae and bivalves is a form of aquaculture which leads nutrients out of the marine environment and is considered the flagship of environment-friendly management. In 2014, the European Commission adopted the Sustainable Blue Growth Agenda for the Baltic Sea Region. Aquaculture is currently

one of the best opportunities for increasing blue growth in the European Union, which is aimed at achieving both economic and environmental goals. In the spring of 2019, researchers from the Estonian Marine Institute of the University of Tartu drew up an analysis in which they highlighted the potential compensation measures for neutralisation of the inflow of nutrients which accompanies fish farming. The analysis is narrowly focused on the measures which can be applied to remove excessive nutrients from the marine environment. The aspects which are related to other human activity or other negative impacts, such as sources of pollution or changes in the flora or fauna, were not analysed.

Several potential compensation measures studied Within the framework of the project, cultivation of filtrating invertebrates with removal of biomass from the aquatic environment, cultivation of algae with removal of biomass from the aquatic environment, removal of the natural biomass of algae from the aquatic environment, collection of coastal deposits from the beach, the possibilities for removal of nitrogen and phosphorus from the seawater provided by coastal and pelagic fishing, and additional fishing (e.g. non-commercial species and foreign species) were analysed as compensation

Interreg project Baltic Blue Growth

S

cientists at the Estonian Marine Institute of the University of Tartu show ways of compensating for nutrients generated by fish farming in the Baltic Sea.

Growing mussels in the Baltic Sea and using the biomass as fish feed can compensate for the nutrients released by farming fish in the sea.

measures. As a result of the analysis, two scenarios were presented with the alleviation measures for fish farming calculated for both. In the case of one of the scenarios, the calculation included using feed made of local raw material.

farming. It would, however, be necessary to implement alleviation measures to compensate for the additional nitrogen.

According to the analysis, if local raw material-based feed was used in fish farming, it would only enrich the marine environment with nitrogen and to a considerably lower extent compared to using traditional feed. With respect to phosphorus, the marine environment would be cleaned of excessive nutrients. Species such as the Baltic herring, the zebra mussel, the blue mussel, the round goby, the Prussian carp, and the three-spined stickleback are considered local raw material. If local fishing could cover the demands of the production of fish feed, this would be the most efficient and costeffective measure of alleviation of the environmental impacts of fish

In addition to the above, it was highlighted that the peculiarities of each farm must also be taken into consideration in determining compensation measures applied to fish farms. For example, in the case of coastal net cage farming, it is important to focus on local impacts; in the case of deeper-sea farms, however, large-scale processes should be taken into consideration. Measures which have a direct effect on the availability of nutrients in the water column are suitable for the alleviation of local measures, while it is important to take into consideration transportation of nutrients and water between the pools and the water column and the bottom of the sea in the large scale.

Fish farms respond differently to compensation measures

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EUROFISH Magazine 2 2020 by Eurofish - Issuu