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Task 1: Atlantic cod in Iceland
Cod is one of the main pillars
supporting Icelandic fisheries, both at present and historically. The
age at 50% maturity for
Icelandic cod has declined over the last few decades, but it is not known
whether these changes can to some extent be attributed to fisheries-induced
genetic changes. Furthermore, the stock offers interesting possibilities
to investigate fisheries-induced adaptation in a stock that has a complex
population structure and has been subject to spatially varying exploitation
pressure: historically, fishing pressure has greatly varied over large
geographical areas as well as between adjacent spawning grounds within
the main spawning area along the south coast. The overarching objective
here is to document and understand the changes that have occurred in the
maturation and growth of Icelandic cod during the second half of the 20th
century. Large amount of data on size, age, and maturity of cod sampled
throughout the last century, as well as data from fishing vessel log-books
and commercial catch records exist. Analyses will be conducted at different
geographical scales. The delineation of the areas will be guided by information
on subunits as well as knowledge on areas with contrasting exploitation
levels. The main question to be addressed include the following:
- Description of changes
in growth and maturity in various stock components over long time
spans.
- Analysis of reaction
norms for age and size at maturation to disentangle phenotypically
plastic and potentially genetic changes in maturation in various
stock components.
- Relating the results
on Icelandic cod to fisheries-induced adaptive changes in other cod
stocks on both sides of the Atlantic.
- Management implications of fisheries-induced
selection of a geographically heterogeneous fish stock.
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Task
2: Arctic charr in Iceland
Arctic charr is an exceptionally
polymorphic fish, and one of the very few species inhabiting freshwaters
in Iceland. The evolution of morphs is known to result from adaptations
to local ecological conditions, which may lead to population segregation
and even to the formation of new species. However, the potential effects
of exploitation (mainly gillnetting targeting the largest morphs) and
management measures (e.g., efforts aimed at improving the growth rates
of individuals by ‘thinning’ the population) on immediate
and longer-term genetic and phenotypic diversity have hardly been studied.
An important novel aspect and likely breakthrough that this study aims
at is to comprehensively test whether exploitation of a rapidly diverging
species of fish can have significant effects on evolutionary patterns.
A multidisciplinary approach using available databases for ecological,
genetic, and phenotypic diversity of a number of charr populations
in Iceland will be applied. Between 1992 and 1998, a comprehensive
survey was conducted on the ecology of Icelandic lakes resulting in
vast amounts of information that can be used in the current study.
Otoliths have been collected from several populations. This will allow
for age determination and for the establishment of individual growth
trajectories. A special field effort will be invested on target populations
by examining their ecological, phenotypic, and genetic structures.
The objectives for this task can be outlined as follows:
- Summarising available
data on the potential effects of fishing from databases, papers, and
reports.
- Examining apparent
short-term and longer-term effects of fishing on life-history patterns
such as growth and maturation patterns using reaction norm methods.
- Investigating
the hypotheses that exploitation has affected evolution in arctic
charr by (1) changing the ecological conditions potentially causing
evolutionary divergence; (2) reducing or even eliminating particular
morphs through overfishing; and (3) influencing levels of gene flow
among morphs by, e.g., size-selective fishing affecting size-dependent
mate choice.
- Communicating all scientific
findings effectively to both the scientific community and stakeholders.
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Task 3:
Pacific oysters on the French Atlantic coast
Following the decline of the
indigenous oyster in the 1960s, Pacific oysters from Japan were massively
introduced to the French coastlines in order to sustain production.
Nowadays Pacific oysters form the basis of oyster farming in France.
This is an attractive case for studying exploitation-induced adaptations
because of three particularities. First, exploitation is strongly
size-selective: oysters are harvested once they reach market size.
Second, oyster farming still relies on recruitment in the natural environment.
Third, since farmed oysters represent 95% of the total oyster biomass,
recruited juveniles are mostly produced by farmed stocks, such that
selective exploitation can readily affect subsequent generations. Data
on farmed oysters show a significant decrease in growth rate and a
significant delay in spawning timing since the introduction. Three
hypothesized causes for these changes are: (1) Phenotypically plastic
response to reduced food abundance caused by a strong increase of oyster
biomass; (2) Local adaptation of the species to its new environment;
(3) Exploitation-induced evolution caused by the size-selective harvest.
The main aim of this research task is to disentangle the three potential
components of phenotypic changes by the mutually illuminating use of
data analysis and modelling. In addition to potentially being the first
demonstration of exploitation-induced evolution in mollusks, major
advances towards realistic life-history theory by developing models
including genetics, energy allocation, and ecological feedback are
expected. Salient research actions for these purposes are:
- Disentangling plastic
and evolutionary components of changes in growth, timing and length
of the reproduction period, and reproductive effort.
- Developing theoretical
models integrating genetics, energy allocation, and ecology for understanding
life-history evolution in farmed oyster stocks and assessing the
respective likelihoods of evolutionary local adaptation and exploitation-induced
evolution.
- Investigating
potential management strategies to minimize evolutionary changes
due to selective farming and maximize long-term sustainable yield.
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Task 4: Sole and plaice in
the North Sea and the eastern English Channel
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Substantial changes in growth, maturation, and reproductive
investment have been documented in sole and plaice during the 20th century.
Plaice became heavily exploited at the beginning of the 20th century,
whereas sole only became heavily exploited in the early 1960s. In plaice,
the changes in maturation and reproductive investment were shown to be
partly due to fisheries-induced adaptive change. In sole, the changes
have so far been interpreted to be related to density-dependent effects
and an increase in food availability, but the possibility of fisheries-induced
adaptations has not been rigorously considered. As growth, maturation,
and reproductive investment are interdependent aspects of the energy allocation
schedule, the scope for fisheries-induced evolution will depend on the
covariance between these traits. In this project, the observed changes
in growth, maturation and reproductive investment of sole will be analysed
using the biological monitoring data collected monthly since 1958. The
possibility for supporting tank experiments is being explored. A major
step forward will be achieved by the analysis of the covariance between
growth, maturation, and reproduction by estimating the growth history,
the onset of sexual maturity, together with the reproductive investment
of individual fish. The main components of this task are:
- Determination
of individual energy allocation schedules from changes in the proportion
of the various allocation schedules in the population by sampling
cohorts at successive ages.
- Relating changes
in allocation schedules to the demographic structure of the population
and the demographic impact of the exploitation.
- Comparisons
between fisheries-induced adaptations in sole and plaice in relation
to their species-specific characteristics.
- Integration of flatfish
results with the energy allocation and management tasks (Tasks 8 and
9).
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Task 5: Atlantic cod, Atlantic
herring, and sprat in the baltic
The Baltic Sea ecosystem is dominated by three closely
interacting fish species: cod, herring, and sprat, which also are
the
major targets of the commercial fisheries. This gives an exceptional
opportunity to address the evolutionary effect of fishing in a multi-species
context.
The objectives will be approached by parallel statistical analyses of
existing data (including reaction norm analyses) and the development
of
three-species models reflecting the biological interactions in the Baltic
Sea. Important insights are expected to originate from clarifying
(1)
whether observed changes in the maturation of Baltic cod is a result
of fisheries-induced adaptive changes, (2) whether there are significant
maturation changes also in sprat and herring populations, and, if so,
(3) whether these changes are fisheries-induced adaptive changes,
and
(4) how any adaptive changes in maturation relate to changes in relative
abundance of the three interacting species. By combining empirical
analyses
of the biological information with development of general evolutionary
models, reflecting the types of interactions among the three species,
we will generate knowledge of both fisheries-induced adaptive changes
in the Baltic sea community, and foster a general understanding of
evolutionary
effects of fishing on interacting species. Furthermore, exploring the
development and variability of biological characteristics will improve
the interpretation of fish assessment models in the Baltic. Anticipated
major breakthroughs from the modelling are answers to (1) how mixed
and
single-species fishing affects adaptation in target and non-target species
subject to multi-species interactions, (2) how fisheries-induced adaptive
changes in multi-species communities depend on the strength and type
of species-interactions, and (3) to what extent fisheries-induced
adaptive changes may influence community dynamics. The major objectives
of this
task are thus threefold:
- Describing
changes in biological characteristics in cod, herring, and sprat.
- Investigating and
predicting potential fisheries-induced adaptive change in the Baltic
Sea fish community through integrated empirical and theoretical analyses.
- Understanding
how fishing in general affects adaptation and resulting long-term
population dynamics in closely interacting species.
The following three additional
research tasks are designed to improve our conceptual or theoretical
understanding of fisheries-induced adaptive change, to be developed
in close contact with the previously described empirical studies:
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Task 6:
Eco-genetic models
Adequately dealing
with fisheries-induced adaptive change requires a new generation
of models be developed. These models have to do justice both to the
ecological and the genetic intricacies involved in the dynamics of
a particular stock. At the same time, these models must remain computationally
tractable, be parameterised with routinely collected data, and accurately
predict expected rates of evolutionary change. First steps in this
direction have already been taken by merging age- and size-structured
population models that capture a reasonable amount of ecological
detail with modern dynamical models of quantitative genetics, resulting
in models referred to as ‘eco-genetic’. A breakthrough
is expected from the fact that, for a first time, quantitative medium-term
predictions on fisheries-induced evolutionary change in exploited
stocks will become available. Evidently, such models have much wider
utility. The main questions to be addressed in this task include
the following:
- Comparisons of predictions
to results obtained with traditional evolutionary models.
- Applications to concrete
empirical systems (in close interaction with other FishACE teams)
in order to gain better understanding of the particular strengths
and limitations of eco-genetic modelling.
- Increasing computational
efficiency of eco-genetic models.
- Investigating strategies
for incorporating data obtained with the help of genetic markers.
- Evaluation of management
strategies with explicit considerations of short- and long-term
costs and benefits.
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Task 7:
Evolutionary responses of food webs to harvesting
All species are embedded in food webs. The harvesting of one species
invariably changes the environment for the other species, since many
of the latter experience the harvested species as a resource, predator,
or competitor. Even though the ecological dimensions of this so-called ‘ecosystem
embedding’ have received increasing attention over the past
few years, the corresponding evolutionary dimensions remain virtually
unexplored. The problem is that ecological interactions between species
may result in completely unexpected evolutionary responses to exploitation.
How much of the complexity of real food webs needs to be considered
in order to properly understand and predict the evolutionary implications
of fisheries therefore is an open question of critical importance.
In order to address this question in a tractable and systematic manner,
we have to scale up from the most basic models of interaction, involving
only two species, to small food-web modules of three or four species,
to eventually gain insight into the evolutionary response of larger
assemblages of species. A major promise of this research is to better
understand under which ecological conditions single-species predictions
of evolutionary responses to harvesting are bound to be reliable.
The main components of this task are:
- Obtaining
a full overview of evolutionary responses to harvesting in two-species
models of all three fundamental types of ecological
interaction (predation, competition, and mutualism).
- Extending
this understanding to food web modules involving mixed interactions
of predatory and competitive type (resulting in cannibalism,
omnivory, or intra-guild predation).
- Investigation
of evolutionary responses in food webs of larger size in dependence
on the historical route and the biological mechanisms
(immigration, speciation) through which the food web has been assembled.
- Broadening
these investigations to include implications of size-dependence
in the rates of predation, harvesting, and competition.
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Task
8: Evolutionary energy allocation models
The primary objective here
is to investigate evolution of growth rates under size-selective harvesting.
It is often taken for granted that fishing, by selectively removing
large, fast-growing fish, results in evolution towards slower growth.
Two caveats must be acknowledged. First, reduced growth may incur fitness
costs in terms of reduced fecundity, and it may increase death rate
due to natural predators. Second, growth rate may decrease as a secondary
response to a change in energy allocation between growth and other
needs, or directly, when intrinsic growth capacity is reduced. Understanding
whether the benefits of reduced growth offset the costs, and whether
direct or indirect reduction is more likely to happen, requires carefully
calibrated models tailored to a specific fish stock. Energy allocation
models, with their strong mechanistic underpinning, offer a powerful
approach for addressing these questions. Links will also be built with
other FishACE modelling tasks, as well as with the oyster and flatfish
case studies (Tasks 3 and 4). The specific goals for this task are
as follows:
- Investigating the conditions
under which size-selective fishing can result in genetic reductions
in growth, compared to conditions under which that is not expected
to happen.
- Investigating
the relative likelihoods of evolutionary responses in growth rate
through direct and indirect evolutionary effects.
- Understanding
the consequences of fisheries-induced changes in growth rates on
population dynamics and sustainable yield.
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Studying the possibilities to influence fisheries-induced evolution
of growth rate by management measures, including technical measures
that directly change the size-selectivity of fishing gear.
The final task below is focused
on the management implication of fisheries-induced adaptive change,
merging the results and insights gained in all other eight tasks:
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Task 9: Management of fisheries-induced
adaptive changes
The principal aim for this task concerns the
design of innovative and practically valuable management tools that
take into account fisheries-induced adaptive changes, on top of the
traditional ecological considerations. In order to guide the development
of appropriate management tools, it is recognised that, as a first
step, the objectives of management need to be as explicit and carefully
articulated as possible. Once such management objectives have been
identified, management tools to achieve specific objectives can be
devised. Crucial goals include identifying metrics that can suggest
when specific, evolutionarily enlightened management actions are called
for, and identifying the most cost-effective actions. Model-assisted
evaluations of various management tools are indispensable throughout
this task. The major output from the task is expected to be new methodologies
for advising on the sustainable management of fisheries. In essence,
all other FishACE tasks will be linked to this task, and provide information
on the scope and consequences of fisheries-induced selection on particular
stocks. Predictions on future evolutionary trajectories, either under
prevailing exploitation regimes or after managerial interventions,
are generated with the help of models. New information arising from
other tasks within the FishACE project will be synthesised, and as
a next step, applied within the routine advisory process with which
ICES is charged. The main questions to be addressed in the work on
this task include the following:
- Establishing objectives for managing
fisheries-induced adaptive changes, including considerations from
both utilitarian and ethical perspectives, and taking explicitly
into account the trade-offs and compromises between short-term and
long-term goals.
- Evaluation of evolutionary vulnerability
in light of exploitation patterns and species-specific characteristics.
- Evaluating the utility of different management
tools and options, including technical management measures like minimum
mesh sizes and minimum landing sizes, in light of the inherent uncertainty
of the information on which decisions have to be based.
- Influence of evolutionary changes in
growth, maturity, fecundity, and survival of offspring on a stock’s
viability in general, and on the relationship between spawning stock
biomass and recruitment in particular.
- Formulation of management advice in the
modern regime of the Precautionary Approach, e.g., through the specification
of suitable reference points.
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Responsible for this page: Melanie
Wenighofer
Last updated:
10 Mar 2006
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