Research
Project summary
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Human-induced ecosystem change can occur in only a few years and can be detected at different levels of biological complexity. Fishing in particular can cause rapid phenotypic change by affecting size-dependent mortality at the individual level, altering population structure, species interactions and eventually community dynamics. Because of these cascading effects, an eco-evolutionary perspective is needed to understand the ecosystem effects of fisheries. However, to achieve such understanding, we need to compare human-impacted areas with others that remain undisturbed.
In this project we will examine the ecosystem effects of the Atlantic cod fishery in Skagerrak (Norway), with the aim to generate robust evidence-based knowledge for a sustainable management of coastal ecosystems. Several Marine Protected Areas (MPAs), offering full to partial protection from fisheries to Atlantic cod, were established in Skagerrak between 2006-2012 and will be used here as reference sites to investigate the eco-evolutionary effects of cod fishing. Scientific monitoring of these MPAs and adjacent harvested areas has generated a unique collection of data on both cod and associated species that we will analyze in this project to fill knowledge gaps on different processes at the individual, population and community levels, using novel and flexible modelling tools. This approach will allow us to obtain urgently needed demographic quantities (i.e. natural mortality, home range size, population growth rates under different harvest scenarios) and knowledge of predictor-response relationships (i.e. body size effects on cod mortality, cod population effects on community composition) for multiple cod populations and associated biological communities within MPAs and harvested areas. These expected results will enhance both marine biodiversity conservation and the evidence-based management of MPAs and coastal cod fisheries in Norway.
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Objectives
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The main objective of this project is to determine what are the broader ecological and evolutionary consequences of Atlantic cod fishing across levels of biological organisation, to achieve better predictions of biological responses to changes in harvest pressure in coastal systems. Areas with partial or full restriction to fishing provide the ideal control sites to examine the ecosystem-effects of fisheries because they release patches of the ocean from fishing pressures. Therefore, in CodChange, we will analyse extensive data sets collected inside and outside MPAs in Skagerrak, southern Norway.
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The specific objectives of CodChange are described in the following Work Packages (WP):
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a) Location of the Skagerrak sea; b) Location of MPAs; c) Map of Tvedestrand fjord, where a No-take MPA for Atlantic cod is located. Red dots show the location of acoustic receivers; d) Map showing the placement and size of Flødevigen MPA and Gjervoldsøy control area, where multi-year data on tagged cod has been collected.
WP1: Phenotypic selection
In WP1, we will quantify changes in phenotypic diversity between MPAs and harvested areas by focusing on the selection of individual traits within a fjord containing areas with varying fishing restrictions.
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Key questions:
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Does phenotypic trait distribution in cod populations change after full protection?
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Does phenotypic selection operate differently between cod ecotypes?
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Methodology:
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We will quantify temporal changes in body size and space use of Atlantic cod using both mark-recapture and acoustic telemetry data on Atlantic cod available from Tvedestrand fjord, in Agder county (Norway)
WP2: Population dynamics
In WP2 we will quantify the size-dependence of cause-specific mortality rates under different harvest contexts and how it translates into long-term population growth.
Key questions:
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How much do fishing and natural mortality depend on cod phenotypes in areas under different modes of management?
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What is the expected population growth rate of Skagerrak cod under different management scenarios?
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Methodology:
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We will quantify mortality hazard rates from mark-recapture data on Atlantic cod collected along the Skagerrak coast and build Integral Projection Models (IPMs) to generate population trajectories under different modes of management.
WP3: Community change
In WP3 we will quantify the impacts of cod fishing on coastal biological communities by linking local species’ occupancy dynamics to spatio-temporal changes in both environmental factors and cod population status.
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Key questions:
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How do coastal biological communities change once fishing is removed?
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Can changes in local fish communities be driven by Atlantic cod population status?
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Methodology:
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Long-term presence–absence data of cod and other species of fish and invertebrates collected at different sites along the Skagerrak coastline will be analyzed using Dynamic Occupancy Models, to examine spatiotemporal changes in species’ assemblages.
Overview of the different biological processes (1,2,3) and levels of organization (Individuals, Populations and Communities) that will be examined in CODCHANGE. Grey and black fish represent divergent phenotypic traits (i.e. different body sizes or behavioural strategies). Blue arrows represent the direction of potential cascading effects.