Investigating coastal ecosystem structure and
dynamics using Ecopath/Ecosim ecosystem
models and stable isotope data
Torstein Pedersen
Einar M. Nilssen
Silje Ramsvatn, PhD student
Trond Ivarjord, vit. Ass.
Fredrikke Museæus, tech.
Marianne Nilsen, IRIS
Lyne Morissette, ISMER, Canada
Anita Maurstad, TMU
Håvard Fause, master student
Ina Kolsum, master student
Christer Michalsen, master student
Geir Helge Systad, NINA
Background
• Main objective: which biotic and abiotic
factors affect dynamics and structure of
coastal ecosystems in northern areas?
• Is it possible to advocate management
regimes that enhance fishery yield,
resilience, resistance and biodiversity ?
• Use models that integrate data from
classical sampling methods and stable
isotope data?
Comparative ecosystem approach; local
(Sørfjord vs Ullsfjord), regional, intercontinental
scale
•General large decline in costal cod after 1995
•Cascade effects of decline in cod?
•Ullsfjord warmer and more diverse than
Sørfjord
•Reference ecosystem for king crab effect
studies
Barents Sea
Ullsfjord & Sørfjord
Norwegian Sea
Russia
Sweden
Finland
Norway
•Ullsfjord, a deep, outer and relatively
warm fjord (400 km2), and Sørfjord
which is shallower and colder (55 km2)
•Ullsfjord has higher biodiversity
• Mass-balance approach
• Ecological groups (n = 40 in Ullsfjord)
• Input data are Biomass, P/B, Q/B,
Ecotrophic efficiency (need 3 of 4),
catches and diet
• Diet data input are essential
• Ecopath -> Ecosim -> Ecospace
6 Combine with 5
Unique approach;
uses Ecopath-model structure as framework
for strategic sampling of groups that are
necessary and important to estimate
ecosystem model
Structure in Ullsfjord 40 group model, ”new groups” shown in bold,
multistanza groups in colour
Gr. No.
Gr. No.
1
Mammals
21
Heterotrophic nanoflagellates
2
Pisciivore benthic bird
22
Schypomedusae
3
Pelag diving birds
23
Chaetognaths
4
Surface feeding birds
24
Other shrimps
5
Benthic invertebrate f. birds
25
Pelagic shrimps
6
Large cod
26
Other large zooplankton
7
Small cod
27
Large crustacea
8
Large saithe
28
Predatory benthos
9
Small saithe
29
Detrivore polychaetes
30
Small benthic crustacea
birds &
mammals
(5)
10
Large haddock
11
Small haddock
31
Small molluscs
12
Small gadoids
32
Large bivalves
13
Large other fish
33
Detrivore echinoderms
14
Small other fish
34
Herbivore echinoids
15
Small pelagic fish
35
Other benthic invertebrates
16
Herring
36
Bacteria
17
Small krill
37
Phytoplankton
18
Large krill
38
Macroalgae
19
Small zooplankton
39
Discard and offal
20
Microzooplankton
40
Detritus
Fish (10)
zooplankton/
crustaceans
zooplankton/
cr.nekton
(10)
benthos (9)
Field/Survey
Literature
”data”
Commercial
catch data
Diet analysis
Large sampling effort,
challenge to sample
all groups and diets
representatively
How to represent; top-predators, fish and
pelagic groups (WP1), benthic invertebrate
groups (WP2) ?
How to assess and incorporate data from
stable isotopes into an Ecopath model (WP3) ?
How to evaluate effects of trophic control
mechanisms and exploitation regimes using
Ecopath/Ecosim modelling (WP4) ?
Stable isotopes (SI)
Trophic
level (TL)
Carbon
δ13C= 13C / 12C
Primary
source of
carbon
• SI can be used to
investigate
ontogenetic diet
shifts
• Haddock less than
20 cm in length
feed pelagic and
then change to a
more benthic
signature/diet at
larger size
Ullsfjord
Small haddock
(< 20 cm)
How to compare Ecopath models with diet
data input from gut content analysis (GCA)
and stable isotopes (SI)?
Use MIXSIR, a bayesian source mixing
model, to estimate diet prey proportions for
a predator from the SI of the predator, SI of
potential prey groups and trophic
enrichment factors for delta13C and
delta15N. Uses individual data.
GCA Ecopath
Comparison of trophic levels estimated directly from SI data and
Ecopath model based on stomach/literature data input
1:1 line
regression
SI data
SI Ecopath
Comparison of trophic levels directly from SI data and
Ecopath model based stable isotope data diet input
Trophic level increased
with new diet data
SI data
Fish species
Invertebrate
bentic predators
Invertebrate
benthos
Detrivore
echinoderms
whiting
long rough dab
Trophic
redundancy
(fish with length 20-40
cm)
witch
haddock
Fish species
Invertebrate
bentic predators
Invertebrate
benthos
Detrivore
echinoderms
Conclusions SI
•SI can be used to estimate diet input to
Ecopath models
•More local data can be used
•SI can be also used to improve diet data
from benthic invertebrates, need sufficient
diversity of groups
Comparative Ecosystem approach
Fish and shrimp
Pelagic shrimp
Shrimps
Herring
Small pelagic fish
Group
Small other fis
Large other fis
Small gadoids
Small haddock
Large haddock
Small saithe
Large saithe
Sørfjord
Small cod
Ullsfjord
Large cod
0.00
0.05
0.10
0.15
0.20
Biomass (g C m -2)
0.25
0.30
Benthic invertebrate groups
P/B
Other benthic i
Other benthic i
Herbivore echin
Herbivore echin
Detrivore echin
Detrivore echin
Large bivalves
Large bivalves
Group
Group
Biomass
Small molluscs
Small benthic c
Ullsfjord
Detrivore polyc
Predatory benth
Predatory benth
Large crustacea
Large crustacea
0.0
1.0
2.0
3.0
4.0
-2
Biomass (g C m )
Ullsfjord
Small molluscs
Small benthic c
Sørfjord
Detrivore polyc
Sørfjord
5.0
0.0
0.5
1.0
P/B (per year)
1.5
2.0
Regional comparison
Norwegian Sea/Barents Sea
Sørfjord
Ullsfjord
Mammals
North Sea
Seabird
Cod
Haddock
Saithe
Prawns
Small gadoids
Small pelagic fishes and
herring
0.00
0.00
0.01
0.10
Biomass g C m
-2
1.00
10.00
Intercontinental: Sørfjord versus Northern Gulf of St Lawrence, Canada
Who are the main predators? Morissette
et al. 2009
In Sørfjord, fishing mortality is minimal, and cod is the
dominant predator
In the Gulf of St. Lawrence, fishing is 10X higher, and since
cod is collapsed, marine mammals became the main
predators
Fishery regimes. Annual catches of deep sea shrimp in
Ullsfjord and Lyngen (source Råfisklaget)
600
Fangst Ullsfjord
500
per fatøy)
(kg(tons)
per fartøy
Fangst
catch
Annual
Fangst Lyngen
400
300
200
100
0
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
20
01
20
00
20
99
19
98
19
97
19
96
19
År