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Individual based modeling of
growth and survival of Atlantic Cod
(Gadus morhua) and Lesser Sandeel
(Ammodytes marinus) larval stages
Zeren Gürkan, Asbjørn Christensen, Henrik Mosegaard
DTU Aqua, Charlottenlund Castle, Denmark
Summer course 2009
5/7/2017
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My background
• BSc in Biology, METU, Turkey
• MScE in Env. Engr., DTU, Denmark
• Grad. study in Env. Engr., METU & PhD for 1 year
in Bio.&Agr. Engr., UGA, USA
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Contents of presentation
• SUNFISH project summary
• PhD research contents
• Results from literature review
• Prey field for fish models – Feeding conditions
• Existing bioenergetic models
• Initial bioenergetic Individual-Based Model
(IBM) formulations
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My PhD research objectives
• They are embedded in and address several tasks in SUNFISH
• Main objectives are identifying and modeling key biological
processes that affect growth and survival of larval and
juvenile cod and sandeel by giving emphasis to responses to
local physical and feeding conditions
• Existing bioenergetic individual-based models (IBMs) will be
developed and coupled to biogeochemical models of the
North Sea together with other SUNFISH partners
• The coupled models will be used to simulate responses of
biological processes of drift, growth and survival to climate
change effects as conditions of physical and biogeochemical
spatio-temporal fields, and formulate future sustainable
ecosystem management strategies
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SUNFISH - “Sustainable fisheries, climate change and
the North Sea ecosystem”
• Global climate change will challenge fisheries and ecosystem
management in the seas
• Primary and secondary production and distribution, feeding,
growth, and survival of fish will be affected by changes in
temperature, wind conditions, river runoff, currents
• It will be more difficult to separate effects of fishing from
those of environmental changes, to identify biological
reference points, and to develop management strategies for
sustainable fisheries
• Well-founded assessment of the population dynamics of the
North Sea fish stocks is necessary
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• SUNFISH is a collaborative project of several Danish and
international institutes
• It aims to improve the scientific basis and predictions of
effects of climate change on the North Sea ecosystem and
the sustainable fisheries management in the North Sea
• It will provide an integrated modeling framework for
developing optimal and sustainable fisheries management
strategies, based on description of mechanisms of processes
instead of extrapolations of observed trends, to predict the
outcomes of climate change on the North Sea ecosystem
• It focuses on cod and sandeel, which are key species in the
North Sea ecosystem and economically important to the
Danish fishery
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SUNFISH tasks from work packages I contribute to :
 Formulation of a model describing food intake of larvae based on
literature & growth of cod larvae
 IBM model of larval cod growth based on biological process models of
growth
 IBM model of larval cod survival
 Predictions of the spatio-temporal distribution of larvae based on IBM
models
 Comparison of predicted larval distribution and size with survey
observations
 Identification of processes limiting survival of early life stages
 Comparison of predicted distribution of settled cod with distribution
observed in surveys
 Spatio-temporal analysis of the predicted probability of survival to
settling of eggs spawned in different areas
 Estimation of sandeel growth in relation to biophysical conditions
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• Methods include the use of predictions of conditions
in the North Sea in past and future accounting for
climate change scenarios by BSHcmod and HYCOM
hydrodynamic models, which are coupled to 3-D
biogeochemical model, ERGOM, as basis of analyses
of spatio-temporal variation in growth and survival
of the fish early life stages
• Survival will be modeled using Letcher type IBM and
hydrographic approach. Estimates of energy intake
and expenditure will produce model of growth.
Effects of local physical conditions and behavioral
aspects will be included
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Marine Ecological Modeling Center workshop
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Initial bioenergetic IBM formulations
• Sandeel Population Analysis Model (SPAM) assumes von
Bertalanffy temperature modulated growth model
(Christensen)
• I develop this to a detailed model based on Letcher et al.
(1996) formulation
• Energy intake and expenditure are combined
• Function of temperature, food abundance and quality
• Includes explicit descriptions of physiological processes and
behavioral aspects
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SPAM (SLAM - Christensen et al., 2008)
Growth
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SPAM (SLAM - Christensen et al., 2008)
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SPAM (SLAM - Christensen et al., 2008)
Sandeel
Suitable
sandeel banks
Av.
Spatial SD (bank variability)
Interbank exchanges
of sandeel larvae
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Year
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Generic larval IBM - Letcher et al. (1996)
Flow diagram - All functions are dependent
on larval size. 5 submodels determine prey
encounter, foraging, bioenergetics-growth,
starvation, and predation rates. Major
processes affecting each submodel are in the
pointed boxes. Characteristics of the larvae’s
environment (food and predators) are in the
boxes with horizontal arrows. The model
calculates growth rates for each larva every
time step. Each simulation may start with a
certain number of larvae all with a specified
length.
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Growth submodel
Ingestion, I
(Assimilation efficiency)
(Total costs) Specific dynamic action, SDA & egestion, E
(Routine metabolism) Weight, W
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Foraging submodel : Applies optimal foraging model
(Charnov, 1976)
Maximum consumption,
total mass eaten, and
masses of four prey
types eaten under
nominal conditions and
optimal foraging model
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Foraging submodel varying ingestion
0.05
0.12
0.045
0.1
Prey rank / Profitability
0.04
Profitability
0.035
0.03
0.025
0.02
0.08
0.06
0.04
0.015
0.02
0.01
0.005
0
9.5
9.5
9
9
4
8.5
8
3
7.5
7
4
8.5
2 preys
8
7
2
6.5
Fish length, mm
3
7.5
2
6.5
6
1
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Prey types
Fish length, mm
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1
Prey types
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Hypothesis - Bottom-up cascade.
Recent statement by Beaugrand et al.
(2003) says recruitment failure of many
species in the North Sea is linked to the
change in distribution and composition
of warm (Calanus helgolandicus) and
cold (C. finmarchicus) water
zooplankton, which is potentially
driven by regional warming. It will be
analyzed further with the bioenergetic
IBMs developed using zooplankton
model outputs from SUNFISH partners
and ‘Continuous Plankton Recorder’
(CPR) time series data.
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• Sir Alister Hardy
Foundation for Ocean
Science (SAHFOS)
provided the CPR data for
NS area of several taxa of
plankton included in diets
of cod and sandeel
• One use of this database
will be to realize the prey
conditions as input to the
model
• Calibration & validation
of model results
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Thank you.
Questions & feedback?
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PhD project contents - Hypotheses
• Climate change effects. Recent progress by SUNFISH partners
allows improved description of water turbidity, turbulence,
and light penetration in relation to meteorological forcing
factors. These three factors strongly affect feeding success
and efficiency as well as predation risk. Future climate
scenarios anticipate stronger winds on average and
therefore, it is highly relevant to explore the biological
impacts on early life stages using the developed bioenergetic
IBMs.
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PhD project contents - Hypotheses
• Optimal life history analysis. The ecological fitness of a
species depends on the traits characterizing its entire life
history. Traits in early life stages and of individuals including
behavioral aspects may matter in determining the ecological
fitness of a species. Evolutionary mechanisms have optimized
these traits for each species in its ecosystem niche. The
fitness of alternative life histories may shift relative to each
other due to direct and indirect climate change effects, which
may mean a regime shift in the ecosystem. The project can
explore these aspects for cod and sandeel early life stages.
Optimal life history analysis also constitutes a useful
consistency check of the developed bioenergetic IBMs.
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PhD project contents - Hypotheses
• The physical and biogeochemical fields with sufficient spatial
resolution will be available within the SUNFISH project to
explore biological consequences. The processes on which
climatic effects are quantified include drift, growth and
survival of zooplankton and fish. The bioenergetic IBMs
developed will be coupled to operational biogeochemical
models for North Sea with other members of the SUNFISH
project simulating climatic effects on total biomass and on
spatio-temporal distribution, composition and nutritional
value of zooplankton.
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PhD project contents - Hypotheses
• The distribution and composition of warm (C. helgolandicus) and
cold (C. finmarchicus) water zooplankton has a distinct spatial and
seasonal pattern. How the spatial and temporal heterogeneity and
composition of the zooplankton community, which may include
species with different nutritional values, affect recruitment
predictions of cod and sandeel will be examined.
• Operational biogeochemical models most often assume a constant
or otherwise simplified grazing rate from planktivorous biomass
while elementary estimates suggest the grazing rate is highly
variable over the seasonal cycle. Possibility of improving the
performance of current operational biogeochemical models by
implementing a feedback loop of fish grazing on zooplankton to
demonstrate the importance of grazing dominated either by cod or
sandeel larvae at a locality will be examined.
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