171
3
From Spatial Analyses
to Modelling Ecosystem
Compartments
3.1
The Common Sole ( Solea
solea ) Population and Fishery,
from Ecology Along the Life
Cycle to Population Dynamics
Common sole is an abundant species in the
Eastern Channel and sustains important fi sheries
(4,000–5,000 t per year). The common sole has a
complex life cycle (Rochette et al. 2013 ); after
the eggs have hatched, the larvae spend several
weeks drifting in open water. Survivors go on to
metamorphosis into benthic fi sh. Juveniles of
common sole spend the fi rst 2 years of their life
in coastal nurseries before migrating to deeper
areas, where they reproduce. To investigate the
drivers of common sole abundance in the Eastern
Channel, an integrated approach was developed,
coupling different models describing the different life stages, to estimate the different sources of
mortality throughout the whole life cycle.
3.1.1 Young Stages (Larval Stages
and Nursery Habitat
Dependence)
An individual-based model (IBM) coupled to a
hydrodynamic model was used to simulate common sole larval supply from spawning areas to
coastal and estuarine nursery grounds at the population scale on a 3-decade time series.
Hydroclimate is the main driver of abundance
patterns during early stages of the life cycle. As
mortality (~1/1,000 survival) is particularly high
at these stages (eggs and larvae), hydroclimate
drives the year class strength of juvenile abundance, without viewable relation with the spawning biomass (Rochette et al. 2012 ).
3.1.2 Integrated Life Cycle Model
Accounting for Various
Pressures
Essential fi sh habitat suitability (EFHS) models
and geographic information system were combined to describe nursery habitats for sole, using
parameters known to infl uence juvenile fl atfi sh
spatial distribution (i.e. bathymetry, sediment,
estuarine infl uence and wave exposure). Juveniles
strongly depend on shallow soft-bottom sheltered
coastal and estuarine nursery grounds and host a
large proportion of total juvenile common sole,
suggesting that these restricted habitats should be
considered as essential habitats for sole (Rochette
et al. 2010 ).
A hierarchical Bayesian framework was
developed for modelling the life cycle of
marine exploited fi sh with a spatial perspective. The approach combined within an integrated framework: (1) outputs of the model for
larval drift and survival that provided yearly
estimates of the dispersion and mortality of
eggs and larvae, from spawning grounds to
settlement in coastal nurseries (Rochette et al.
2012 ); (2) a habitat suitability model based on
juvenile trawl surveys coupled with a geographic information system, to estimate juvenile densities and surface areas of suitable
juvenile habitat in each nursery sector
(Rochette et al. 2010 ) and (3) a statistical
catch-at- age model for the estimation of the
numbers at age and the fi shing mortality on
subadults and adults. Successive modelling
approaches allowed to demonstrate that juvenile mortality on nursery grounds is high
(~1/100 survival) and strongly limits the population size (Rochette et al. 2013 ), fi shing pressure is a main source of mortality at subadult
and adult stages (Rochette et al. 2013 ) and spatial segregation at the successive life stages
(i.e. eggs/larvae, juveniles, adults) along the
life cycle limits the connectivity between different subparts of the population. Perspectives
include further development of the modelling
framework on the common sole and applications to other fi sh species to disentangle the
effects of multiple interacting stress factors
(e.g. estuarine and coastal nursery habitat degradation, fi shing pressure) on population
renewal and to develop risk analysis in the context of marine spatial planning for sustainable
management of fi sh resources.
From Data to End-to-End Models: 15 Years of Research to Describe the Dynamics…
3
From Spatial Analyses
to Modelling Ecosystem
Compartments
3.1
The Common Sole ( Solea
solea ) Population and Fishery,
from Ecology Along the Life
Cycle to Population Dynamics
Common sole is an abundant species in the
Eastern Channel and sustains important fi sheries
(4,000–5,000 t per year). The common sole has a
complex life cycle (Rochette et al. 2013 ); after
the eggs have hatched, the larvae spend several
weeks drifting in open water. Survivors go on to
metamorphosis into benthic fi sh. Juveniles of
common sole spend the fi rst 2 years of their life
in coastal nurseries before migrating to deeper
areas, where they reproduce. To investigate the
drivers of common sole abundance in the Eastern
Channel, an integrated approach was developed,
coupling different models describing the different life stages, to estimate the different sources of
mortality throughout the whole life cycle.
3.1.1 Young Stages (Larval Stages
and Nursery Habitat
Dependence)
An individual-based model (IBM) coupled to a
hydrodynamic model was used to simulate common sole larval supply from spawning areas to
coastal and estuarine nursery grounds at the population scale on a 3-decade time series.
Hydroclimate is the main driver of abundance
patterns during early stages of the life cycle. As
mortality (~1/1,000 survival) is particularly high
at these stages (eggs and larvae), hydroclimate
drives the year class strength of juvenile abundance, without viewable relation with the spawning biomass (Rochette et al. 2012 ).
3.1.2 Integrated Life Cycle Model
Accounting for Various
Pressures
Essential fi sh habitat suitability (EFHS) models
and geographic information system were combined to describe nursery habitats for sole, using
parameters known to infl uence juvenile fl atfi sh
spatial distribution (i.e. bathymetry, sediment,
estuarine infl uence and wave exposure). Juveniles
strongly depend on shallow soft-bottom sheltered
coastal and estuarine nursery grounds and host a
large proportion of total juvenile common sole,
suggesting that these restricted habitats should be
considered as essential habitats for sole (Rochette
et al. 2010 ).
A hierarchical Bayesian framework was
developed for modelling the life cycle of
marine exploited fi sh with a spatial perspective. The approach combined within an integrated framework: (1) outputs of the model for
larval drift and survival that provided yearly
estimates of the dispersion and mortality of
eggs and larvae, from spawning grounds to
settlement in coastal nurseries (Rochette et al.
2012 ); (2) a habitat suitability model based on
juvenile trawl surveys coupled with a geographic information system, to estimate juvenile densities and surface areas of suitable
juvenile habitat in each nursery sector
(Rochette et al. 2010 ) and (3) a statistical
catch-at- age model for the estimation of the
numbers at age and the fi shing mortality on
subadults and adults. Successive modelling
approaches allowed to demonstrate that juvenile mortality on nursery grounds is high
(~1/100 survival) and strongly limits the population size (Rochette et al. 2013 ), fi shing pressure is a main source of mortality at subadult
and adult stages (Rochette et al. 2013 ) and spatial segregation at the successive life stages
(i.e. eggs/larvae, juveniles, adults) along the
life cycle limits the connectivity between different subparts of the population. Perspectives
include further development of the modelling
framework on the common sole and applications to other fi sh species to disentangle the
effects of multiple interacting stress factors
(e.g. estuarine and coastal nursery habitat degradation, fi shing pressure) on population
renewal and to develop risk analysis in the context of marine spatial planning for sustainable
management of fi sh resources.
From Data to End-to-End Models: 15 Years of Research to Describe the Dynamics…