Transcript marine fish abundance series

TRONDHJEM BIOLOGICAL STATION
MARINE DATA SERIES
TBS anno 1990
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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)
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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)
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F/F "Gunnerus"
(Trawling)
Minerva (ROV)
LVPP
Secchi disk
Lightweight Video Profiling Platform
(LVPP) constructed by Prof. Ulf
Båmstedt, Umeå University, Sweden
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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
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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:
1. A close monitoring of biology and genetics of cod
2. Monitoring fish species composition on fixed locations
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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.
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marine fish abundance series
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hydrography series
Mean bottom temperatures at three stations in the Trondheimsfjord in the period 1963-2007
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hydrography series
Temperature St Røberg 400meter
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hydrography series
Oxygen saturation on 3 stations and various depths
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CLIMATE CHANGE AND
SPECIES COMPOSITION
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WHAT ARE THE GATEWAYS TO THE TRONDHEIMSFJORD AND OTHER
NORWEGIAN FJORDS AND COASTAL WATERS?
Answer: The Norwegian coastal current and the Gulf Stream
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The Trondheimsfjord, depths and bottom topography
600 m
The Trondheimsfjord
has 3 main basins which
are separated by
thresholds at Agdenes,
Tautra and Skarnsundet.
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.
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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
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… ONE SUCH UNINVITED GUEST IS THE
CORONATE JELLYFISH
Periphylla periphylla
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SYSTEMATIC POSITION
Rike :
Rekke :
Klasse :
Orden :
Dyreriket
Cnidaria (nesledyr)
Scyphozoa (stormaneter (500 MY): gresk skyphos = drikkebeger
Coronatae (kronemaneter (ringmaneter) - 8 familier)
Familier (8):
Atollidae
Atorellidae
Collaspididae
Linuchidae
Nausithoidae
Paraphyllinidae
Tetraplatidae
Periphyllidae
Species: Periphylla periphylla --->
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History of the invasion …
After its first detection in a small fjord south of Bergen
(Lurefjorden), P. periphylla has 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.
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Example in 2007: The codend of ”Gunnerus” is filled with
P. periphylla after a 40 min hawl in Verrasundet (6 tonnes)
Foto: TBS
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Example ct’d: The 6 tonnes of jelly filled
the aft deck of ”Gunnerus” completely
Foto: TBS
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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.)
Krill
Pandalus sp.
Shrimps
Copepods (Calanus sp.)
Codlings
Squid
Myctophidae – Lantern fish
Small herring, sprat
Gonostomatidae
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Light fishes
… 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"
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… powerful local reproduction capacity …
In the inner Trondheimsfjord,
P. periphylla of all sized are
found, indicating a selfsustaining and reproducing
population
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The effects of this jellyfish invasion for the ecosystem
of the Trondheimsfjord is currently under monitoring
and assessment.
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THANK YOU FOR
YOUR ATTENTION
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