scholarly journals Bayesian survey-based assessment of North Sea plaice (Pleuronectes platessa): extracting integrated signals from multiple surveys

2009 ◽  
Vol 66 (4) ◽  
pp. 665-679 ◽  
Author(s):  
Johannes A. Bogaards ◽  
Sarah B. M. Kraak ◽  
Adriaan D. Rijnsdorp
Keyword(s):  
North Sea ◽  
Small Sample Size ◽  
Small Sample ◽  
Distribution Area ◽  
Parameter Estimates ◽  
Model Parameters ◽  
Fishing Mortality ◽  
Pleuronectes Platessa ◽  
The North ◽  
Spawning Stock

Abstract Bogaards, J. A., Kraak, S. B. M., and Rijnsdorp, A. D. 2009. Bayesian survey-based assessment of North Sea plaice (Pleuronectes platessa): extracting integrated signals from multiple surveys. – ICES Journal of Marine Science, 66: 665–679. Dependence on a relatively small sample size is generally viewed as a big disadvantage for survey-based assessments. We propose an integrated catch-at-age model for research vessel data derived from multiple surveys, and illustrate its utility in estimating trends in North Sea plaice abundance and fishing mortality. Parameter estimates were obtained by Bayesian analysis, which allows for estimation of uncertainty in model parameters attributable to measurement error. Model results indicated constant fishing selectivity over the distribution area of the North Sea plaice stock, with decreased selectivity at older age. Whereas separate analyses of survey datasets suggested different biomass trends in the southeast than in the western and central North Sea, a combined analysis demonstrated that the observations in both subareas were compatible and that spawning-stock biomass has been increasing over the period 1996–2005. The annual proportion of fish that dispersed in a northwesterly direction was estimated to increase from about 10% at age 2 to 33% at age 5 and older. We also found higher fishing mortality rates than reported in ICES assessments, which could be the consequence of inadequate specification of catchability-at-age in this study or underestimated fishing mortality by the conventional ICES assessment, which relies on official landings figures.

scholarly journals Genotyping an <i>Emiliania huxleyi</i> (Prymnesiophyceae) bloom event in the North Sea reveals evidence of asexual reproduction

2014 ◽  
Vol 11 (3) ◽  
pp. 4359-4408 ◽  
Author(s):  
S. A. Krueger-Hadfield ◽  
C. Balestreri ◽  
J. Schroeder ◽  
A. Highfield ◽  
P. Helaouët ◽  
...  
Keyword(s):  
North Sea ◽  
Asexual Reproduction ◽  
Small Sample Size ◽  
Large Population ◽  
Emiliania Huxleyi ◽  
Small Sample ◽  
Phytoplankton Species ◽  
The North ◽  
Generation Times ◽  
The North Sea

Abstract. Due to the unprecedented rate at which our climate is changing, the ultimate consequence for many species is likely to be either extinction or migration to an alternate habitat. Certain species might, however, evolve at a rate that could make them resilient to the effects of a rapidly changing environment. This scenario is most likely to apply to species that have large population sizes and rapid generation times, such that the genetic variation required for adaptive evolution can be readily supplied. Emiliania huxleyi (Lohm.) Hay and Mohler (Prymnesiophyceae) is likely to be such a species as it is the most conspicuous extant calcareous phytoplankton species in our oceans with generation times of 1 day−1. Here we report on a validated set of microsatellites, in conjunction with the coccolithophore morphology motif genetic marker, to genotype 93 clonal isolates collected from across the world. Of these, 52 came from a single bloom event in the North Sea collected on the D366 UK Ocean Acidification cruise in June-July 2011. There were 26 multilocus genotypes (MLGs) encountered only once in the North Sea bloom and 8 MLGs encountered twice or up to six times. Each of these repeated MLGs exhibited Psex values of less than 0.05 indicating each repeated MLG was the product of asexual reproduction and not separate meiotic events. In addition, we show that the two most polymorphic microsatellite loci, EHMS37 and P01E05, are reporting on regions likely undergoing rapid genetic drift during asexual reproduction. Despite the small sample size, there were many more repeated genotypes than previously reported for other bloom-forming phytoplankton species, including a previously genotyped E. huxleyi bloom event. This study challenges our current assumption that sex is the predominant mode of reproduction during bloom events. Whilst genetic diversity is high amongst extant populations of E. huxleyi, the root cause for this diversity and ultimate fate of these populations still requires further examination. Nonetheless, we show that certain CMM genotypes are found everywhere; while others appear to have a regional bias.

scholarly journals Evaluation of the quality of the North Sea herring assessment

2009 ◽  
Vol 66 (8) ◽  
pp. 1814-1822 ◽  
Author(s):  
E. John Simmonds
Keyword(s):  
North Sea ◽  
Management Strategy ◽  
Fishing Mortality ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The North Sea ◽  
Acoustic Surveys ◽  
One Year

Abstract Simmonds, E. J. 2009. Evaluation of the quality of the North Sea herring assessment. – ICES Journal of Marine Science, 66: 1814–1822. The assessment of North Sea herring has been used to give advice on catch quota for more than 20 years. The data sources comprise acoustic surveys, International Bottom Trawl Surveys, Methot Isaacs–Kidd net post-larval surveys, larval surveys, and catch-at-age data. These sources and their uses are briefly reviewed, and the changes in the weighting attached to each index in the assessment over time are discussed. The performance of the assessment is examined both in historical and analytical retrospectives of spawning–stock biomass and fishing mortality, and in retrospective assessments of numbers by cohort. Increased length of the time-series, the use of a statistical model with appropriate weighting, and a more consistent management strategy have all contributed to the assessment becoming highly stable from one year to the next. The results presented lead to the conclusion that the assessments provide an excellent basis for the management of this stock.

scholarly journals Genotyping an <i>Emiliania huxleyi</i> (prymnesiophyceae) bloom event in the North Sea reveals evidence of asexual reproduction

2014 ◽  
Vol 11 (18) ◽  
pp. 5215-5234 ◽  
Author(s):  
S. A. Krueger-Hadfield ◽  
C. Balestreri ◽  
J. Schroeder ◽  
A. Highfield ◽  
P. Helaouët ◽  
...  
Keyword(s):  
North Sea ◽  
Asexual Reproduction ◽  
Small Sample Size ◽  
Large Population ◽  
Emiliania Huxleyi ◽  
Small Sample ◽  
Phytoplankton Species ◽  
The North ◽  
The North Sea ◽  
June July

Abstract. Due to the unprecedented rate at which our climate is changing, the ultimate consequence for many species is likely to be either extinction or migration to an alternate habitat. Certain species might, however, evolve at a rate that could make them resilient to the effects of a rapidly changing environment. This scenario is most likely to apply to species that have large population sizes and rapid generation times, such that the genetic variation required for adaptive evolution can be readily supplied. Emiliania huxleyi (Lohm.) Hay and Mohler (Prymnesiophyceae) is likely to be such a species, as it is the most conspicuous extant calcareous phytoplankton species in our oceans with growth rates of 1 day−1. Here we report on a validated set of microsatellites, in conjunction with the coccolithophore morphology motif genetic marker, to genotype 93 clonal isolates collected from across the world. Of these, 52 came from a single bloom event in the North Sea collected on the D366 United Kingdom Ocean Acidification cruise in June–July 2011. There were 26 multilocus genotypes (MLGs) encountered only once in the North Sea bloom and 8 MLGs encountered twice or up to six times. Each of these repeated MLGs exhibited Psex values of less than 0.05, indicating each repeated MLG was the product of asexual reproduction and not separate meiotic events. In addition, we show that the two most polymorphic microsatellite loci, EHMS37 and P01E05, are reporting on regions likely undergoing rapid genetic drift during asexual reproduction. Despite the small sample size, there were many more repeated genotypes than previously reported for other bloom-forming phytoplankton species, including a previously genotyped E. huxleyi bloom event. This study challenges the current assumption that sexual reproduction predominates during bloom events. Whilst genetic diversity is high amongst extant populations of E. huxleyi, the root cause for this diversity and ultimate fate of these populations still requires further examination. Nonetheless, we show that certain CMM genotypes are found everywhere, while others appear to have a regional bias.

scholarly journals Gadoid dynamics: differing perceptions when contrasting stock vs. population trends and its implications to management

2014 ◽  
Vol 71 (6) ◽  
pp. 1433-1442 ◽  
Author(s):  
Steven J. Holmes ◽  
Colin P. Millar ◽  
Robert J. Fryer ◽  
Peter J. Wright
Keyword(s):  
North Sea ◽  
Stock Assessment ◽  
Research Vessel ◽  
Vital Rates ◽  
The North ◽  
Depth Contour ◽  
Spawning Stock ◽  
Population Structures ◽  
The North Sea ◽  
Local Pressures

Recent research suggests that ICES stock definitions for cod, haddock, and whiting of “west of Scotland” and “North Sea”, do not reflect underlying population structures. As population responses to different vital rates and local pressures would be expected to lead to asynchrony in dynamics, we examined trends in local spawning-stock biomass (SSB) among putative subpopulations of the three species. Delineation of subpopulation boundaries around spawning time was made based on genetic, tagging, and otolith microchemistry studies together with density distributions of species based on research vessel survey data. Subpopulation specific indices of SSB were derived using numbers-at-age and maturity observations from the same research vessel data and asynchrony was assessed by fitting a smoother to log SSB for each subpopulation and testing whether the smooths were parallel. Results for cod support the hypothesis of distinct inshore and larger offshore subpopulations and for whiting for northern and southern North Sea subpopulations with a boundary associated with the 50 m depth contour. In haddock, no difference in SSB trends between the North Sea and west of Scotland was found. For cod and whiting, subpopulation SSB trends differed substantially within current stock assessment units, implying reported stock-based SSB time-series have masked underlying subpopulation trends.

Otolith increments in European plaice (Pleuronectes platessa) reveal temperature and density-dependent effects on growth

2018 ◽  
Vol 75 (5) ◽  
pp. 1655-1663 ◽  
Author(s):  
Peter van der Sleen ◽  
Christoph Stransky ◽  
John R Morrongiello ◽  
Holger Haslob ◽  
Melita Peharda ◽  
...  
Keyword(s):  
Environmental Factors ◽  
North Sea ◽  
Bottom Temperature ◽  
Growth Data ◽  
Mixed Effect ◽  
Pleuronectes Platessa ◽  
Growing Season Length ◽  
The North ◽  
Growth Variation ◽  
The North Sea

Abstract European plaice (Pleuronectes platessa) is a commercially important flatfish species in the North Sea. Yet, the environmental factors that affect the growth of plaice remain unresolved. Here we examine the drivers of plaice growth variation by using a large archive of otoliths from female plaice collected in the northeastern part of the North Sea from 1993 to 2015, providing growth data over the period 1985–2014. We developed a series of increasingly complex mixed-effect models to explore intrinsic (within individual) and extrinsic (environmental factors: bottom temperature and plaice density) sources of growth variation. We analysed juvenile (0 and 1 year) and (sub)adult (≥2 years) growth separately due to different habitat utilization across life stages. Juvenile growth was positively correlated with bottom temperature, whereas growth of adults was negatively correlated with bottom temperature. Correlations for both were strongest during autumn (September to October). For juveniles, the temperature–growth relationship likely reflects a response to growing season length while for adults it could reflect temperature-dependent changes to metabolic rate or food availability. For both juveniles and adults, we also found inverse relationship between population density and growth. We suggest that the approach used in this study can find a much wider application in European waters.

scholarly journals Inaccuracies in routinely collected Atlantic herring (Clupea harengus) maturity data and correction using a gonadosomatic index model

2011 ◽  
Vol 91 (7) ◽  
pp. 1477-1487 ◽  
Author(s):  
Lindsay R. McPherson ◽  
Konstantinos Ganias ◽  
C. Tara Marshall
Keyword(s):  
North Sea ◽  
Low Cost ◽  
Gonadosomatic Index ◽  
Clupea Harengus ◽  
Implicit Assumption ◽  
Multinomial Regression ◽  
Index Model ◽  
The North ◽  
Spawning Stock ◽  
The North Sea

Macroscopic maturity staging data are widely used to distinguish between reproductive and non-reproductive individuals. The implicit assumption is that these data are accurate. The accuracy of macroscopic maturity staging of North Sea herring (Clupea harengus) has not been checked since the macroscopic scale was produced in 1961. The aim of this study was to assess the accuracy of macroscopic maturity staging of female North Sea herring by comparison to histological staging and the gonadosomatic index (GSI). Ovary samples were collected during the North Sea Herring Acoustic Survey in 2006 on-board FRV ‘Scotia’ (Scotland) and in 2007 on-board FRV ‘Scotia’ and RV ‘Johan Hjort’ (Norway). Commercial samples were also collected by Marine Scotland, Aberdeen in both years. The maturity staging error was relatively low in 2006 (21% error) but was much higher on-board FRV ‘Scotia’ (57%) and RV ‘Johan Hjort’ (47%) in 2007. There was estimated to be a 27% under-estimation of the spawning stock biomass (SSB) in 2007 due to the differences in the proportion mature but no change in SSB estimates in 2006. GSI cut-off scores, estimated by means of multinomial regression models were successfully able to separate immature females from both mature-active and recovering females; however, there was some overlap between the mature-active and recovering individuals. We conclude that an effective and low-cost means of reducing error in herring maturity studies is the combined use of a four-point macroscopic maturity scale with routinely collected GSI data, the latter acting to validate and fine tune macroscopic staging.

Social Allocation Models of Intelligence: A Methodological Inquiry

1969 ◽  
Vol 39 (3) ◽  
pp. 484-510 ◽  
Author(s):  
Richard Light ◽  
Paul Smith
Keyword(s):  
Statistical Model ◽  
Sample Size ◽  
Racial Differences ◽  
Small Sample Size ◽  
Twin Studies ◽  
Feedback Loops ◽  
Small Sample ◽  
Social Differentiation ◽  
Parameter Estimates ◽  
Statistical Procedures

The authors consider Professor Jensen's hypothesis that inherited factors may be"implicated" in observed racial differences in measured intelligence. They argue that even if one chooses to accept Professor Jensen's estimates of the proportion of variance in intelligence accounted for by heredity, environment, and their interaction,his hypothesis is not substantiated by his own data. They go on to say that the parameter estimates are highly suspect, given the small sample size of the twin studies and the way disparate studies were combined. The authors simulated, on a computer, the process of studying twins and found that the statistical procedures employed in these studies of intelligence yield quite unstable estimates. In particular,the estimate of the interaction effect is quite unreliable, both because of sample size, and because Jensen chose a statistical model which would attribute some interaction to the main variables—heredity and environment. Finally, the authors propose that the studies of intelligence reported by Professor Jensen ignore the reality of feedback loops, initiated by physical differences, and enhanced by processes of social differentiation in our society.

Hierarchical Bayesian lithology/fluid prediction: A North Sea case study

Geophysics ◽  
2012 ◽  
Vol 77 (2) ◽  
pp. B69-B85 ◽  
Author(s):  
Kjartan Rimstad ◽  
Per Avseth ◽  
Henning Omre
Keyword(s):  
North Sea ◽  
Rock Physics ◽  
Model Parameters ◽  
Gas Oil ◽  
Clear Fluid ◽  
Prior Model ◽  
Spatial Coupling ◽  
The North ◽  
Likelihood Model ◽  
Physics Model

Seismic 3D amplitude variation with offset (AVO) data from the Alvheim field in the North Sea are inverted into lithology/fluid classes, elastic properties, and porosity. Lithology/fluid maps over hydrocarbon prospects provide more reliable estimates of gas/oil volumes and improve the decision concerning further reservoir assessments. The Alvheim field is of turbidite origin with complex sand-lobe geometry and appears without clear fluid contacts across the field. The inversion is phrased in a Bayesian setting. The likelihood model contains a convolutional, linearized seismic model and a rock-physics model that capture vertical trends due to increased sand compaction and possible cementation. The likelihood model contains several global model parameters that are considered to be stochastic to adapt the model to the field under study and to include model uncertainty in the uncertainty assessments. The prior model on the lithology/fluid classes is a Markov random field that captures local vertical/horizontal continuity and vertical sorting of fluids. The predictions based on the posterior model are validated by observations in five wells used as blind tests. Hydrocarbon volumes with reliable gas/oil distributions are predicted. The spatial coupling provided by the prior model is crucial for reliable predictions; without the coupling, hydrocarbon volumes are severely underestimated. Depth trends in the rock-physics likelihood model improve the gas versus oil predictions. The porosity predictions reproduce contrasts observed in the wells, and mean square error is reduced by one-third compared to Gauss-linear predictions.

A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method

2009 ◽  
Vol 66 (9) ◽  
pp. 1999-2011 ◽  
Author(s):  
Cindy J. G. van Damme ◽  
Loes J. Bolle ◽  
Clive J. Fox ◽  
Petter Fossum ◽  
Gerd Kraus ◽  
...  
Keyword(s):  
North Sea ◽  
Egg Production ◽  
Stock Assessment ◽  
Population Analysis ◽  
Spatial Dynamics ◽  
Production Method ◽  
Southern Bight ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock

Abstract van Damme, C. J. G., Bolle, L. J., Fox, C. J., Fossum, P., Kraus, G., Munk, P., Rohlf, N., Witthames, P. R., and Dickey-Collas, M. 2009. A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method. – ICES Journal of Marine Science, 66: 1999–2011. Uncertainty about the quality of current virtual population analysis-based stock assessment for North Sea plaice (Pleuronectes platessa) has led to various abundance indices. We compared biomass estimates from the annual egg production (AEP) method with current stock assessments based on catch-at-age to validate the current and historical perception of exploitation. The AEP method was also used to investigate the dynamics of the spatial components of plaice in the North Sea. We corrected for fecundity down-regulation and changes in sex ratio. Estimates from both methods were similar in trend and absolute biomass. On the Dogger Bank, there was a dramatic decline in biomass from 1948 and 1950 to 2004, and in the Southern Bight, the stock appeared to increase from 1987 and 1988 to 2004, although not reaching the historically high levels of 1948 or 1950. The timing of spawning of North Sea plaice does not appear to have changed throughout the period of high exploitation. We conclude that the AEP method is a useful way to hindcast the spatial dynamics of heavily exploited flatfish stocks.

scholarly journals Haddock on the Porcupine Bank, September 1944

1946 ◽  
Vol 26 (3) ◽  
pp. 398-407 ◽  
Author(s):  
C. F. Hickling
Keyword(s):  
Growth Rate ◽  
North Sea ◽  
Growing Up ◽  
Fishing Mortality ◽  
Rate Of Growth ◽  
The North ◽  
The North Sea

1. It is suggested that the population of haddock (Gadus aeglefinus L.) on the Porcupine Bank is largely a self-contained stock.2. This stock had complete immunity from trawling from December 1940, to September 1944.3. In 1939 and 1940 there was an abundance of small haddock in this stock, due to the good brood of 1938. In 1944, this brood was still very abundant, and was then joined by the good brood of 1942.4. These two good broods, growing up immune from fishing mortality, caused the Porcupine Bank to carry, in 1944, the densest stock of haddock ever experienced there.5. The average number of sclerites in the first zone of the scales of these fish is the highest recorded in any region. It is still high in the second zone, but in the later zones falls below that found in the scales of haddock from other regions.6. The growth rate was faster, in the first four years of life, than even that of Iceland and Faroe haddock, but in the later years it fell behind these, though still superior to the growth rate of the North Sea haddock.7. The expectation that this greatly increased stock of haddock, due to the war-time cessation of fishing, would show a slowing in its rate of growth, due to intensified competition for the available food, is not supported by the facts.

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