scholarly journals Spatial and temporal shift in the factors affecting the population dynamics of Calanus copepods in the North Sea

2020 ◽  
Vol 27 (3) ◽  
pp. 576-586
Author(s):  
José T. Montero ◽  
Mauricio Lima ◽  
Sergio A. Estay ◽  
Enrico L. Rezende
Keyword(s):  
Population Dynamics ◽  
North Sea ◽  
Temporal Shift ◽  
Factors Affecting ◽  
The North ◽  
The North Sea

Offshore North Sea Pipeline and Riser Loss of Containment Study (PARLOC)—Applications and Limitations in the Assessment of Operating Risks

1996 ◽  
Vol 118 (2) ◽  
pp. 115-120 ◽  
Author(s):  
J. L. M. Robertson ◽  
D. Smart ◽  
T. Al-Hassan
Keyword(s):  
North Sea ◽  
Risk Control ◽  
Management Program ◽  
Comparative Risk Assessment ◽  
Factors Affecting ◽  
Safety Standards ◽  
The North ◽  
Risk Management Program ◽  
Comparative Risk ◽  
The North Sea

Since the Piper Alpha disaster in 1988, there has been an urgent requirement to prevent such tragedies occurring by the introduction of higher safety standards and by improving the confidence in the statistical information available for the assessment of the risks of loss of containment associated with operation of North Sea pipelines. In order to achieve the latter, two databases have been compiled: 1) a pipeline database containing details of pipelines and risers installed in the North Sea; 2) an incident database containing details of reported “occurrences” (covering the period from 1975 to end 1993), which directly resulted or threatened to result in loss of containment from a pipeline or riser. The data has been compiled from information obtained from: U.K., Norwegian, Dutch and Danish Regulatory Authorities; Operators in the U.K., Dutch and Danish Sectors; reports from previous studies made available to the study; published sources. The databases have been used to perform assessments of factors affecting the frequency of incidents, such as: incident cause; part of pipeline or riser affected; pipeline or riser diameter, length, contents, age, type; whether the line is trenched or buried, piggy-backed or not; hydrotest pressure; location of pipeline or riser in the North Sea. The PARLOC study identifies potential hazards and provides an indication of likely loss of containment frequency associated with the operation of North Sea pipelines and risers. Furthermore, PARLOC provides a continually updated key reference for comparative risk assessment and ultimately for the implementation of risk control as part of an overall risk management program.

scholarly journals Exit and entry of fishing vessels: an evaluation of factors affecting investment decisions in the North Sea English beam trawl fleet

2011 ◽  
Vol 68 (5) ◽  
pp. 961-971 ◽  
Author(s):  
Alex N. Tidd ◽  
Trevor Hutton ◽  
Laurence T. Kell ◽  
Gurpreet Padda
Keyword(s):  
North Sea ◽  
Choice Model ◽  
Investment Decisions ◽  
Strategic Decision ◽  
Beam Trawl ◽  
Factors Affecting ◽  
The North ◽  
Fishing Vessels ◽  
The North Sea ◽  
The Impact

Abstract Tidd, A. N., Hutton, T., Kell, L. T., and Padda, G. 2011. Exit and entry of fishing vessels: an evaluation of factors affecting investment decisions in the North Sea English beam trawl fleet. – ICES Journal of Marine Science, 68: 961–971. A profitable fishery attracts additional effort (vessels enter), eventually leading to overcapacity and less profit. Similarly, fishing vessels exit depending on their economic viability (or reduced expectations of future benefits) or encouraged by schemes such as decommissioning grants and/or when there is consolidation of fishing effort within a tradable rights-based quota system (e.g. individual transferable quotas). The strategic decision-making behaviour of fishers in entering or exiting the English North Sea beam trawl fishery is analysed using a discrete choice model by integrating data on vessel characteristics with available cost data, decommissioning grant information, and other factors that potentially influence anticipated benefits or future risks. It is then possible to predict whether operators choose to enter, stay, exit, or decommission. Important factors affecting investment include vessel age and size, future revenues, operating costs (e.g. fuel), stock status of the main target species, and the impact of management measures (e.g. total allowable catches) and total fleet size (a proxy for congestion). Based on the results, the predicted marginal effects of each factor are presented and the impact of each is discussed in the context of policies developed to align fleet capacity with fishing opportunities.

scholarly journals Integrating stochastic age-structured population dynamics into complex fisheries economic models for management evaluations: the North Sea saithe fishery as a case study

2014 ◽  
Vol 71 (7) ◽  
pp. 1638-1652 ◽  
Author(s):  
Sarah Laura Simons ◽  
Heleen Bartelings ◽  
Katell Gaelle Hamon ◽  
Alexander Johannes Kempf ◽  
Ralf Döring ◽  
...  
Keyword(s):  
Population Dynamics ◽  
North Sea ◽  
The North ◽  
Control Rules ◽  
Structured Population ◽  
Structured Population Dynamics ◽  
The North Sea ◽  
Age Structured ◽  
Age Structured Population ◽  
Harvest Control Rules

There is growing interest in bioeconomic models as tools for understanding pathways of fishery behaviour in order to assess the impact of alternative policies on natural resources. A model system is presented that combines stochastic age-structured population dynamics with complex fisheries economics. Explicitly, the economic response of fleet segments to changes in stock development is analysed by applying observed values and stochastic recruitment. The optimization of net profits determines the fishing effort and the investment and disinvestment behaviour of fleet segments, which, in turn, affect the level of catch rates and discards. This tool was applied to the North Sea saithe fishery, where ICES re-evaluated the existing EU–Norway management plan, focusing on biological reference points only. Two scenarios were tested with alternative harvest control rules and then contrasted with one unregulated scenario with no quotas and driven by optimizing the net profit of the whole fleet. The model showed the success of both harvest control rules in rebuilding the stock and the associated costs to the fleets in terms of maximal 21% reduction in net profits, 21% reduction in crew wages and 11% reduction in fleet size in the midterm (2007–2015). In the long term (2022), successful stock recovery coincided with net profits almost equalling that of the unrestricted fishery. The model is highly sensitive to the parameter values but can be used strategically, providing a qualitative understanding of the anticipated relative changes.

scholarly journals The proportion of flatfish recruitment in the North Sea potentially affected by offshore windfarms

2019 ◽  
Vol 77 (3) ◽  
pp. 1227-1237 ◽  
Author(s):  
Léo Barbut ◽  
Berthe Vastenhoud ◽  
Laurence Vigin ◽  
Steven Degraer ◽  
Filip A M Volckaert ◽  
...  
Keyword(s):  
Population Dynamics ◽  
North Sea ◽  
Wind Farms ◽  
Offshore Wind ◽  
Spawning Grounds ◽  
Spatial Overlap ◽  
Flatfish Species ◽  
The North ◽  
The North Sea ◽  
Tracking Model

Abstract Understanding the influence of man-made infrastructures on fish population dynamics is an important issue for fisheries management. This is particularly the case because of the steady proliferation of offshore wind farms (OWFs). Several flatfish species are likely to be affected because areas with OWFs in place or planned for show a spatial overlap with their spawning grounds. This study focuses on six commercially important flatfish species in the North Sea: common sole (Solea solea), European plaice (Pleuronectes platessa), turbot (Scophthalmus maximus), brill (Scophtalmus rhombus), European flounder (Platichthys flesus), and common dab (Limanda limanda). We used a particle-tracking model (Larvae&Co) coupled to a 3D hydrodynamic model to assess the effects of spatial overlap of OWFs with the species’ spawning grounds on the larval fluxes to known nursery grounds. An important overlap between planned areas of OWFs and flatfish spawning grounds was detected, with a resulting proportion of settlers originating from those areas varying from 2% to 16%. Our study suggests that European plaice, common dab, and brill could be the most affected flatfish species, yet with some important local disparities across the North Sea. Consequently, the study represents a first step to quantify the potential impact of OWFs on flatfish settlement, and hence on their population dynamics.

scholarly journals Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat

2009 ◽  
Vol 66 (9) ◽  
pp. 1899-1914 ◽  
Author(s):  
Gwladys Lambert ◽  
J. Rasmus Nielsen ◽  
Lena I. Larsen ◽  
Henrik Sparholt
Keyword(s):  
Population Dynamics ◽  
North Sea ◽  
Stock Assessment ◽  
Age Group ◽  
Commercial Catch ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The North Sea ◽  
Immature Fish

Abstract Lambert, G., Nielsen, J. R., Larsen, L. I., and Sparholt, H. 2009. Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat. – ICES Journal of Marine Science, 66: 1899–1914. The population dynamics of the Norway pout stock in the North Sea are investigated by statistical analyses, and GIS of ICES International Bottom Trawl Surveys (IBTS) and Danish commercial catch data from 1983 to 2006. The stock spawns mainly around mid-February along the northeastern English and Scottish coasts and between Shetland and Norway. Sex ratios indicate that males, which mature younger than females (age-at-50%-maturity, respectively, 1.2 and 1.5 years), migrate out of the Skagerrak–Kattegat to the spawning grounds before females. There is a decrease in the 2+-group maturity ratios as well as in weight and female length from before to after spawning. The results indicate spawning mortality. Only some 20% of the 1-group reaches maturity in the first quarter, which is higher than assumed in the stock assessment. Although the maturity ogives are variable over time, this difference should be taken into account when estimating spawning-stock biomass in routine assessments. Growth is also variable, with a tendency for male maximum length to be smaller than that of females, and immature fish to be smaller than mature ones in each age group. The juvenile growth rate is higher when the stock density is low and results in a reduced age-at-50%-maturity. Besides these intraspecific patterns, the growth rates show interspecific links to stock sizes of the important predators: cod, haddock, and whiting.

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