Modelling recruitment and abundance of Atlantic cod, Gadus morhua, in the eastern Skagerrak–Kattegat (North Sea): evidence of severe depletion due to a prolonged period of high fishing pressure

Cardinale, Massimiliano; Svedäng, Henrik

doi:10.1016/j.fishres.2004.04.001

Cited by 59 publications

(66 citation statements)

References 42 publications

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“…Many fisheries whose profits are substantially influenced by the stock effect (Hannesson 2007) are still able to profitably exploit populations to <10-20% the original stock (Lipcius and Stockhausen 2002;Cardinale and Svedang 2004;Worm et al 2006), corresponding with θ<10-20. To represent density dependent harvest costs experienced among these fisheries, I focused the bulk of my analysis on the range of stock effect conditions 0≤θ≤20.…”

Section: Methodsmentioning

confidence: 99%

Density dependence and the economic efficacy of marine reserves

White

2009

Theor Ecol

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Predictions on the efficacy of marine reserves for benefiting fisheries differ in large part due to considerations of models of either intra-or inter-cohort population density regulating fish recruitment. Here, I consider both processes acting on recruitment and show using a bioeconomic model how for many fisheries density dependent recruitment dynamics interact with harvest costs to influence fishery profit with reserves. Reserves consolidate fishing effort, favoring fisheries that can profitably harvest low-density stocks of species where adult density mediates recruitment. Conversely, proportion coastline in reserves that maximizes profit, and relative improvement in profit from reserves over conventional management, decline with increasing harvest costs and the relative importance of intra-cohort density dependence. Reserves never increase profit when harvest cost is high, regardless of density dependent recruitment dynamics. I quantitatively synthesize diverse results in the literature, show disproportionate effects on the economic performance of reserves from considering only inter-or intra-cohort density dependence, and highlight fish population and fishery dynamics predicted to be complementary to reserve management.

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Section: Methodsmentioning

confidence: 99%

Density dependence and the economic efficacy of marine reserves

White

2009

Theor Ecol

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“…An almost total eradication of locally spawning cod aggregations along the Swedish Skagerrak coast has, in some years, resulted in the apparent anomaly of low adult cod abundance coinciding with high juvenile abundance (Svedäng 2003, Svedäng & Svenson 2006. Svedäng (2003) and Cardinale & Svedäng (2004) hypothesised that most juvenile cod along the eastern Skagerrak coast had been passively transported from offshore spawning areas (Munk et al 1999), and the following (unexpected) low abundance of adult cod was due to return migration of juvenile and/or maturing fish which had reached a certain size or age (Pihl & Ulmestrand 1993). This theory was supported by the fact that strong year classes of juvenile cod along both the Norwegian and Swedish Skagerrak coast have been genetically assigned to eastern North Sea cod populations (Knutsen et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Migratory behaviour of Atlantic cod Gadus morhua: natal homing is the prime stock-separating mechanism

Svedäng¹,

Righton²,

Jönsson³

2007

Mar. Ecol. Prog. Ser.

143

118

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“…1). There are, however, close interlinkages between these management units, both ecologically (Garrod 1977; see also Cardinale & Svedäng 2004) and genetically (Nielsen et al 2001, 2003, Knutsen et al 2003. However, such interlinkages have generally not been quantified, particularly not within a population dynamic setting; we attempt this in the present paper.…”

Section: Cod Managementmentioning

confidence: 95%

“…Following Knutsen et al (2004) and N. C. Stenseth et al (unpubl. data) we assume that North Sea larvae may be transported from spawning grounds in the North Sea into the Skagerrak where they mix with natively produced larvae (see also Munk et al 1995, Cardinale & Svedäng 2004 The overall purpose of this study is to develop coupled statistical models of the dynamics of the 3 areas -the North Sea, the Skagerrak and the Kattegat -explicitly including the effect of potential transportation of spawning products and of migration of mature cod between the areas.…”

Section: The North Sea-skagerrak-kattegat Systemmentioning

confidence: 99%

Population dynamics of cod Gadus morhua in the North Sea region: biological density-dependent and climatic density-independent effects

Chen¹,

Chan²,

Lekve³

et al. 2005

Mar. Ecol. Prog. Ser.

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Through the statistical modeling of monitoring data, we assess the ecological interlinkages between cod Gadus morhua L. in the North Sea, Skagerrak and Kattegat -regions which typically have been considered separate management units. The model includes both within-population density dependence (within and between age classes), as well as density-dependent effects of migration between the North Sea, Skagerrak and Kattegat. Further, the model incorporates the effects of environmental features (such as temperature and the North Atlantic Oscillation). The obtained results are discussed, both with reference to general ecological principles as well as with respect to management implication. Altogether our analysis suggests a unified management regime for the entire region including the North Sea, the open Skagerrak and Kattegat.KEY WORDS: GAM · NAO · North Sea-Skagerrak-Kattegat system · Time-series modeling · Transport effect Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 302: [219][220][221][222][223][224][225][226][227][228][229][230][231][232] 2005 density dependence within and between cohorts) and extrinsic processes (such as climate dependence). We apply a time-series approach to deduce the underlying forms of dynamics and interactions of the populations. We analyze data on cod Gadus morhua L. from the International Bottom Trawl Survey (IBTS) monitoring surveys coordinated by the ICES, together with environmental data, in order to arrive at a joint model for the North Sea, Skagerrak and Kattegat populations. Using this approach we are able to demonstrate the effect of transport between the areas, and show that almost identical models can be used to represent the dynamics of the cod populations in the 3 areas.The overall perspective of our study is a general one focusing on the density-dependent and densityindependent structure of populations (see, e.g., Stenseth et al. 2002), where climate is seen as the main density-dependent factor. A key focus of our paper is the interlinkage of various sub-units of the overall population (North Sea, Kattegat and Skagerrak), where each of these sub-units may affect each other in a density-dependent manner. As a platform for our analyses, we provide in the following section a synoptic account of the Skagerrak system with its neighboring waters. The North Sea-Skagerrak-Kattegat systemCurrents in the North Sea, as in any continental shelf sea, occur in response to forcing by tides, winds, density gradients (arising from freshwater input) and pressure gradients. For most of the North Sea the dominant motion is tidal, with the next most significant motion generator being wind forcing (Howarth 2001). About 70% of the water entering the North Sea is assumed to pass through the Skagerrak before leaving for the North Sea again (Danielssen et al. 1996). The general circulation pattern in the Skagerrak is counterclockwise. After passing by the northern tip of Denmark, the highly saline North Atlantic water (entering from the ...

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Modelling recruitment and abundance of Atlantic cod, Gadus morhua, in the eastern Skagerrak–Kattegat (North Sea): evidence of severe depletion due to a prolonged period of high fishing pressure

Cited by 59 publications

References 42 publications

Density dependence and the economic efficacy of marine reserves

Density dependence and the economic efficacy of marine reserves

Migratory behaviour of Atlantic cod Gadus morhua: natal homing is the prime stock-separating mechanism

Population dynamics of cod Gadus morhua in the North Sea region: biological density-dependent and climatic density-independent effects

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