Ongoing research projects

The roots of the Baltic herring research project are in a project where it was studied if the increased ship traffic in the Airisto Inlet (Archipelago Sea) was having negative impact on local fish stocks. Since this first study, the project has continued and expanded to map out herring spawning areas in the inner archipelago, to study factors influencing the spawning biology of herring, and most recently, to estimate climate-induced effects on e.g. herring biochemical quality and reproduction as well as how the climate change is affecting the pelagic ecosystem as a whole. The research utilizes unique sets of environmental and biological data, collected by the research team since the 1980s.

The variation and significance of iodine in the Baltic Sea ecosystem

Iodine is an essential trace element for health as it is needed in the production of thyroid hormones thyroxine (T4) and triiodothyronine (T3), which are required throughout life for e.g. normal growth, development and metabolism.

The aim of the project is to study the temporal (long-term and seasonal) and spatial variation of iodine in the brackish ecosystem of the Baltic Sea and how its availability (e.g. iodine deficiency) affects key species such as the Baltic herring and bladderwrack (Fucus vesiculosus).

The project is conducted in close collaboration with Ruuskanen Group (Dep. of Biological and Environmental Science, JYU) and Anttila Lab (Dep. of Biology, UTU). Nationally our collaborators also include the Geology division (UTU), Laboratory of Industrial Physics (Department of Physics and Astronomy,UTU), Pyhäjärvi-Institute, and the Finnish Food Authority. Internationally we also collaborate with Dr. Patrick Polte and his colleagues at the Johann Heinrich von Thünen-Institute (Rostock, Germany) and with Prof. Karin Limburg from the department of Environmental and Forest Biology at SUNY-ESF (New York, USA).

The project started in summer 2020. The work is supported by Sakari Alhopuro Foundation (PI Katja Mäkinen) and Turku University Foundation (to K. Mäkinen).

Contact person: Katja Mäkinen

Seasonal and spatial variation of herring quality characteristics in the Archipelago Sea

The aim of the project is to study seasonal and spatial variation of herring quality characteristics (e.g. muscle fat content and quality) in the Archipelago Sea, northern Baltic Sea. A major aim is to produce useful information for both consumers and fish industry.

The project conducted in collaboration with the department of Life Technologies (Food Chemistry and Food Development; Adj. Prof. Jukka-Pekka Suomela).

The project is funded by The Finnish Operational Program for the European Maritime and Fisheries Fund (EMFF) (via Archipelago Sea Fisheries Action Group, Saaristomeren kalatalouden toimintaryhmä) (PI Jari Hänninen).

Final research report:

Rajasilta, M., Hänninen, J., Karpela, T., Mäkinen, K., Ollennu-Chuasam, P., Sahlstén, J. & Suomela, J-P. 2022. Silakan rasvapitoisuuden ja rasvojen laadun ajallinen ja alueellinen vaihtelu Saaristomerellä. Tutkimusraportti Hankeno: 93977. [Temporal and regional variation of the Baltic herring fat content and quality in the Archipelago Sea]. Final research report no 93977]. SEILI Archipelago Research Institute Publications 9. 26 s. + 8 liit. [in Finnish with Swedish and English abstracts]. ISSN 1456-4548. Turun yliopisto. Pdf-julkaisu. 10.13140/RG.2.2.34332.77449/1.

Contact person: Marjut Rajasilta

The prevalence of Corynosoma-worms in the Baltic herring and Great Cormorants at the northern Baltic Archipelago Sea

The project aims to study the distribution and occurrence of Corynosoma worms in Baltic herring and Great cormorant populations in the northern Baltic Sea.

The project has received funding from the European Maritime and Fisheries Fund (EMFF), Archipelago Sea Fisheries Action Group (Saaristomeren kalatalouden toimintaryhmä), and Southwest Finland ELY-centre. The research is carried out together with the Joensuu Molecular Ecology Group of the University of Eastern Finland.

Contact person: Jari Hänninen

Corynosoma worms on a petri dish. Photo: Johannes Sahlsten.

More information:

Related theses and reports:

  • Johannes Sahlsten & Jari Hänninen (2020) “Silakan loismatojen esiintyminen, isäntälajit ja vaikutus Saaristomeren elinkeinokalatalouteen” Hankkeen loppuraportti. Study report (in Finnish) (Pdf).
  • Sahlsten, Johannes. 2019. Corynosoma-suvun väkäkärsämatojen esiintyminen Saaristomeren ja Selkämeren silakoissa. University of Turku, Turku. Bachelor’s thesis.

Past research projects

Trap net project

Photo: Johannes Sahlsten

The herring data set has been largely collected in close collaboration with local fishermen, from who we have annually received samples of spawning herring. However, in the recent years, traditional method of fishing spawning herring has largely been abandoned and the trap net catch of herring has decreased as a consequence of this.

The aim of the project is to continue to collect spawning herring samples from the Archipelago Sea as well as to transfer knowledge and skills from professional fishermen to students.

The project has been funded by the Southwestern Finland ELY-centre and European Maritime and Fisheries Fund (EMFF), Archipelago Sea Fisheries Action Group (Saaristomeren kalatalouden toimintaryhmä). The project is conducted in collaboration with local fishermen and Livia college.

Contact person: Jari Hänninen

Project reports:

The future of the Baltic Sea and us: the effects of climate change to the Baltic Sea pelagic ecosystem

The purpose of the project was to provide information on the key changes that can be expected in the Baltic Sea pelagic ecosystem if the current sea stagnation continues and/or climate change is progressing to increased precipitation in the Baltic watershed area. Besides ecological changes our aim was to deepen the analysis to include occurring biochemical changes in the ecosystem, especially in the phytoplankton – zooplankton – herring food chain. The food chain analysis will define whether the herring’s nutritional value for human consumption (e.g., fat types) has changed resulting from the Bothnian Sea zooplankton community change making it less favorable diet for herring.

Limnocalanus macrurus, C: Marjut Rajasilta

The project was conducted in collaboration with the department of Life Technologies (Food Chemistry and Food Development; Adj. Prof. Jukka-Pekka Suomela).

The research was supported by the Finnish Cultural Foundation, Jenny and Antti Wihuri Foundation and Turku University Foundation.

Contact person: Katja Mäkinen & Jari Hänninen

Related publications and theses:

  • Mäkinen, Katja. 2019. Climate-induced Variability in Northern Baltic Sea Zooplankton – Assessing Driving Forces and Effects on Higher Trophic Levels. Annales Universitatis Turkuensis Ser 358. University of Turku, Turku. PhD dissertation. Pdf.
  • Mäkinen K, Vuorinen I, Hänninen J (2017). Climate-induced hydrography change favors small-bodied zooplankton in a coastal ecosystem. Hydrobiologia. 792:83–96.
  • Mäkinen, K., Elfving, M., Hänninen, J., Laaksonen, L., Rajasilta, M., Vuorinen, I., & Suomela, J. P. (2017). Fatty acid composition and lipid content in the copepod Limnocalanus macrurus during summer in the southern Bothnian Sea. Helgoland Marine Research71(1), 11.
  • Rajasilta, M., Hänninen, J., Laaksonen, L., Laine, P., Suomela, J. P., Vuorinen, I., & Mäkinen, K. (2018). Influence of environmental conditions, population density, and prey type on the lipid content in Baltic herring (Clupea harengus membras) from the northern Baltic Sea. Canadian Journal of Fisheries and Aquatic Sciences, (999), 1-10.
  • Laaksonen, L. (2014) Itämeren makeutumisen vaikutus silakan ja silakan ravinnon rasvahappokoostumukseen. Opinnäytetyö (AMK). Bio- ja elintarviketekniikka. Biotekniikka.