TRONDHJEM BIOLOGICAL STATION MARINE DATA SERIES

1. TRONDHJEM BIOLOGICAL STATION MARINE DATA SERIES TBS anno 1990

2. A brief history of time … • The Biological Station was founded in the year 1900 • Plaice hatching and stock reinforcement important activity up to the 1960ies • Systematic and detailed hydrographical data series initiated in 1963, monthly on fixed stations • From 1970 marine zoology, botany, physiology, fisheries biology and population genetics series • After 2000, also marine biodiversity in focus (ROV)

3. RESEARCH VESSELS Through the years, TBS has owned a series of research vessels on its own. However, from ~ 2006 NTNU established a joint vessel, the R/V ”Gunnerus”, which is now the platform for maintaining the marine data series at NTNU. R/V ”Gunnerus” (~ 90 feet)

4. F/F "Gunnerus" (Trawling) Minerva (ROV) LVPP Secchi disk Lightweight Video Profiling Platform (LVPP) constructed by Prof. Ulf Båmstedt, Umeå University, Sweden

5. EXISTING MARINE DATA SERIES • Already from the start in 1900, TBS started collecting information about the marine milieu and fauna in the Trondheimsfjord, although not in the same systematic way as from the 1960ies. • The entire collection spans a multitude of data types: • hydrographical profiles of temperature, salinity, O2 • fish species composition in beach seine catches • species composition in plankton samples • yearclass strengts fluctuations of the plaice • photobiology and plant nutrient dynamics

6. marine fish series • From ~ 1973, extensive series of genetic and biologic data in fish from trawl and beach seine catches have been collected. This time series has two main focuses: • A close monitoring of biology and genetics of cod • Monitoring fish species composition on fixed locations

7. marine fish during climate change Species composition change: The possibility to compare species composition in catches from the same locations and taken with the same gear over a period of more than 100 years is extremely valuable and informative with respect to the actual geographical distribution of fishes, and how it might be affected by e.g. temperature changes. Boreal-Arctic transition area: The Trondheimsfjord has traditionally represented the northern distribution limit for many boreal species, and as the southern distribution limit for many arctic species. This also applies to fish, for which the Trondheimsfjord is among the most species-rich waters in Norway (> 100 fish species). Monitoring ecosystem changes: In the case of a general warming of the ocean in this region, the species composition of fish in this transition region can be a sensitive instrument for monitoring the ecological effects of a climate shift.

8. marine fish abundance series

9. hydrography series Mean bottom temperatures at three stations in the Trondheimsfjord in the period 1963-2007

10. hydrography series Temperature St Røberg 400meter

11. Oxygen saturation on 3 stations and various depths hydrography series

12. CLIMATE CHANGE AND SPECIES COMPOSITION

13. WHAT ARE THE GATEWAYS TO THE TRONDHEIMSFJORD AND OTHER NORWEGIAN FJORDS AND COASTAL WATERS? Answer: The Norwegian coastal current and the Gulf Stream

14. The Trondheimsfjord, depths and bottom topography The Trondheimsfjord has 3 main basins which are separated by thresholds at Agdenes, Tautra and Skarnsundet. 600 m Atlantic water regularly (ca April each year) flows over the thresholds in the ford. This water is salt and heavy and renews the fjord bottom water. It brings with it organisms which in this way get a chance to establish themselves in the fjord.

15. The Trondheimsfjord, depths and bottom topography SPECIES INTERCHANGE WITH COASTAL WATERS There are 2 main inflows to the Trondheimsfjord each year: ~ April: A large inflow of water of atlantic origin ~ September: A smaller inflow of water from the Norwegian coastal current Together with tidal currents, these inflows stand for the interchange of plankton and nekton between the coast and the fjord. Species which are becoming increasingly abundant outside the fjord will eventually enter the fjord as ”new” species, permanently or as temporal ”guests”. See next slide

16. … ONE SUCH UNINVITED GUEST IS THE CORONATE JELLYFISH Periphylla periphylla

17. SYSTEMATIC POSITION Rike : Dyreriket Rekke :Cnidaria (nesledyr) Klasse :Scyphozoa (stormaneter (500 MY): gresk skyphos = drikkebeger Orden :Coronatae (kronemaneter (ringmaneter) - 8 familier) Familier (8): Atollidae Atorellidae Collaspididae Linuchidae Nausithoidae Paraphyllinidae Tetraplatidae Periphyllidae Species:Periphylla periphylla --->

18. History of the invasion … After its first detection in a small fjord south of Bergen (Lurefjorden), P. periphyllahas spread northwards along the Norwegian coast. During the last 10 years, this jelly has increased dramatically in abundance in the inner Trondheimsfjord, to the degree that it must now be regarded as a real threat to the traditional ecosystem of the fjord. Like in other Norwegian fjords earlier, it rapidly established itself as a top predator in the inner Trondheimsfjord, and is now reproducing intensively in the two inner of the three fjord basins. This is typical; it establishes itself in the inner parts of fjords with marked thresholds. The biomass of the Trondheimsfjord jellyfish stock was estimated at > 20.000 tonnes in 2007, telling that it is a real contender for food with the traditional fish species.

19. Example in 2007: The codend of ”Gunnerus” is filled with P. periphylla after a 40 min hawl in Verrasundet (6 tonnes) Foto: TBS

20. Example ct’d: The 6 tonnes of jelly filled the aft deck of ”Gunnerus” completely Foto: TBS

21. What does this jelly eat? • Mesopelagic species: small fishes, squids • Pelagic larvae and small codfish, flatfish and clupeoids • Shrimps, copepods, krill (meaning it competes for food with cod, whiting, • saithe o.a.) Copepods (Calanus sp.) Krill Pandalus sp. Shrimps Codlings Squid Myctophidae – Lantern fish Gonostomatidae Small herring, sprat Light fishes

22. … a serious predator on herring and sprat … A serous threat: Fishing for jellies with a pelagic trawl revealed new information about the diet of P. periphylla. In 2007, hard evidence of predation on small clupeoids was obtained. Half-digested sprat was found in the stomach contents of jellies caught in the ”scattering layer” in the inner Trondheimsfjord. ”Smoking gun"

23. … powerful local reproduction capacity … In the inner Trondheimsfjord, P. periphylla of all sized are found, indicating a self- sustaining and reproducing population

24. The effects of this jellyfish invasion for the ecosystem of the Trondheimsfjord is currently under monitoring and assessment.

25. THANK YOU FOR YOUR ATTENTION

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