A general framework for integrating the standardization of catch per unit of effort into stock assessment models

2001 ◽  
Vol 58 (4) ◽  
pp. 795-803 ◽  
Author(s):  
Mark N Maunder
Keyword(s):  
Confidence Intervals ◽  
General Framework ◽  
Simulation Analysis ◽  
Stock Assessment ◽  
Integrated Approach ◽  
Assessment Model ◽  
The Other ◽  
Parameter Estimates ◽  
Explanatory Variables ◽  
Point Estimates

A general framework is presented for integrating the standardization of catch per unit of effort (CPUE) into stock assessment models. Catchability is modeled using both continuous and categorical explanatory variables. The likelihood for the CPUE data is combined with the other likelihoods from the stock assessment model; the parameters used to model catchability are estimated simultaneously with the other parameters of the stock assessment model. The method is applied to a New Zealand rock lobster (Jasus edwardsii) stock, and the results are compared with those obtained using a generalized linear model. The point estimates are similar for both methods, but the confidence intervals from the integrated framework are much narrower. Simulation analysis supports the findings that the integrated approach gives narrower confidence intervals that more accurately represent the uncertainty in the parameter estimates, provided the model is correct.

A Bayesian hierarchical formulation of the De Lury stock assessment model for abundance estimation of Falkland Islands' squid (Loligo gahi)

2004 ◽  
Vol 61 (6) ◽  
pp. 1048-1059 ◽  
Author(s):  
Murdoch K McAllister ◽  
Simeon L Hill ◽  
David J Agnew ◽  
Geoffrey P Kirkwood ◽  
John R Beddington
Keyword(s):  
Sampling Error ◽  
Stock Assessment ◽  
Assessment Model ◽  
Abundance Estimation ◽  
Falkland Islands ◽  
Parameter Estimates ◽  
Bayesian Hierarchical ◽  
Stock Assessments ◽  
Catch Rates ◽  
Using Data

In stock assessments of short-lived species, De Lury depletion models are commonly applied in which commercial catches and changing catch rates are used to estimate resource abundance. These methods are applied within fishing seasons to decide when to close the fishery and can be reliable if the data show a distinct decline in response to the catch removals. However, this is not always the case, particularly when sampling error variation masks trends in abundance. This paper presents a Bayesian hierarchical formulation of the De Lury model in which data from previous years are combined hierarchically in the same stock assessment model to improve parameter estimation for future stock assessments. The improved precision in parameter estimates is demonstrated using data for the Falkland Islands' Loligo gahi squid fishery.

scholarly journals Incorporating Stakeholder Knowledge Into a Complex Stock Assessment Model, the Case of Eel Recruitment

2021 ◽  
Author(s):  
Hilaire Drouineau ◽  
Vanacker Marie ◽  
Estibaliz Diaz ◽  
Mateo Santos Maria ◽  
Korta Maria ◽  
...  
Keyword(s):  
Western Europe ◽  
Fishery Management ◽  
Stock Assessment ◽  
Assessment Model ◽  
The Other ◽  
Complex Life Cycle ◽  
European Eel ◽  
Complex Models ◽  
Prior Construction ◽  
Multiple Actors

Mistrust between scientists and non-scientist stakeholders is a key challenge in fishery management. This problem is exacerbated with the use of complex models to support management: these models suffer from difficulties in communicating their results and a lack of confidence from end users. The European eel is an illustrative example; its complex life cycle raises problems of coordination and discussion among the multiple actors involved in the management of the species. The GEREM model has been proposed as a tool for estimating recruitment, but its complexity, which is essential for addressing the characteristics of the species, makes it difficult to understand and accept by all stakeholders. In the context of the SUDOANG project, we proposed a co-parametrization of this assessment model to tackle this mistrust. Through the use of various questionnaires and appropriate statistical analyses, stakeholders were involved in two important choices for the model (zone definition and prior construction). Regular workshops and presentations were organised to explain the model rationales and to gather feedback and expectations. The results show that stakeholders have very similar perceptions of the potential definitions of sub-areas of recruitment in south-western Europe, and these perceptions are consistent with the underlying environmental conditions. On the other hand, the stakeholders have contrasting opinions about the exploitation rates of fisheries in different river basins, and the use of their knowledge currently has little effect on GEREM estimates. More importantly, the overall approach of this study is thought to have reconstructed the trust and confidence among participants.

Testing the performance of a spatially explicit tag-integrated stock assessment model of yellowtail flounder (Limanda ferruginea) through simulation analysis

2015 ◽  
Vol 72 (4) ◽  
pp. 582-601 ◽  
Author(s):  
Daniel R. Goethel ◽  
Christopher M. Legault ◽  
Steven X. Cadrin
Keyword(s):  
Stock Assessment ◽  
Population Models ◽  
Assessment Model ◽  
Spatially Explicit ◽  
Parameter Estimates ◽  
Integrated Models ◽  
Closed Population ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Wide Range

In any stock assessment application, the implicit assumptions regarding spatial population structure must be carefully evaluated. Tag-integrated models offer a promising approach for incorporating spatial structure and movement patterns in stock assessments, but the complexity of the framework makes implementation challenging and the appraisal of performance difficult. A flounder-like fishery was simulated to emulate the metapopulation dynamics of the three yellowtail flounder (Limanda ferruginea) stocks off New England, and the robustness of spatially explicit tag-integrated models were compared with closed population assessments. Different movement parametrizations and data uncertainty scenarios were simulated, while the ability of the tag-integrated model to estimate reporting rate and time-varying movement were also evaluated. Results indicated that the tag-integrated framework was robust for the simulated fishery across a wide range of connectivity levels and that tag reporting rates were accurately estimated. Closed population models also demonstrated limited error. Therefore, spatially explicit approaches may not always be warranted even when regional connectivity is occurring, but tag-integrated models can provide improved parameter estimates when reliable tagging data are available. Tag-integrated models also serve as valuable tools for informing spatially explicit operating models, which can then be used to evaluate the assumptions and performance of closed population models.

scholarly journals Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa

2010 ◽  
Vol 67 (6) ◽  
pp. 1185-1197 ◽  
Author(s):  
C. Fernández ◽  
S. Cerviño ◽  
N. Pérez ◽  
E. Jardim
Keyword(s):  
Time Series ◽  
Stock Assessment ◽  
Reference Points ◽  
Assessment Model ◽  
Marine Science ◽  
Fishing Mortality ◽  
Change Over Time ◽  
Age Structured ◽  
Available Information ◽  
Over Time

Abstract Fernández, C., Cerviño, S., Pérez, N., and Jardim, E. 2010. Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa. – ICES Journal of Marine Science, 67: 1185–1197. A Bayesian age-structured stock assessment model is developed to take into account available information on discards and to handle gaps in the time-series of discard estimates. The model incorporates mortality attributable to discarding, and appropriate assumptions about how this mortality may change over time are made. The result is a stock assessment that accounts for information on discards while, at the same time, producing a complete time-series of discard estimates. The method is applied to the hake stock in ICES Divisions VIIIc and IXa, for which the available data indicate that some 60% of the individuals caught are discarded. The stock is fished by Spain and Portugal, and for each country, there are discard estimates for recent years only. Moreover, the years for which Portuguese estimates are available are only a subset of those with Spanish estimates. Two runs of the model are performed; one assuming zero discards and another incorporating discards. When discards are incorporated, estimated recruitment and fishing mortality for young (discarded) ages increase, resulting in lower values of the biological reference points Fmax and F0.1 and, generally, more optimistic future stock trajectories under F-reduction scenarios.

scholarly journals Correcting density-dependent effects in abundance estimates from bottom-trawl surveys

2014 ◽  
Vol 71 (5) ◽  
pp. 1107-1116 ◽  
Author(s):  
Stan Kotwicki ◽  
James N. Ianelli ◽  
André E. Punt
Keyword(s):  
Stock Assessment ◽  
Dead Zone ◽  
Walleye Pollock ◽  
Assessment Model ◽  
Bottom Trawl ◽  
Trawl Survey ◽  
Negative Consequences ◽  
Catch Per Unit Effort ◽  
Density Dependent ◽  
Index Of Abundance

Abstract Indices of abundance are important for estimating population trends in stock assessment and ideally should be based on fishery-independent surveys to avoid problems associated with the hyperstability of the commercial catch per unit effort (cpue) data. However, recent studies indicate that the efficiency of the survey bottom trawl (BT) for some species can be density-dependent, which could affect the reliability of survey-derived indices of abundance. A function qe∼f(u), where qe is the BT efficiency and u the catch rate, was derived using experimentally derived acoustic dead-zone correction and BT efficiency parameters obtained from combining a subset of BT catch data with synchronously collected acoustic data from walleye pollock (Theragra chalcogramma) in the eastern Bering Sea (EBS). We found that qe decreased with increasing BT catches resulting in hyperstability of the index of abundance derived from BT survey. Density-dependent qe resulted in spatially and temporarily variable bias in survey cpue and biased population age structure derived from survey data. We used the relationship qe∼f(u) to correct the EBS trawl survey index of abundance for density-dependence. We also obtained a variance–covariance matrix for a new index that accounted for sampling variability and the uncertainty associated with the qe. We found that incorporating estimates of the new index of abundance changed outputs from the walleye pollock stock assessment model. Although changes were minor, we advocate incorporating estimates of density-dependent qe into the walleye pollock stock assessment as a precautionary measure that should be undertaken to avoid negative consequences of the density-dependent qe.

Studying Political Leadership: The Case of François Mitterrand

1994 ◽  
Vol 42 (3) ◽  
pp. 453-468 ◽  
Author(s):  
Alistair Cole
Keyword(s):  
General Framework ◽  
Political Leadership ◽  
The Other ◽  
The Political ◽  
Environmental Constraints ◽  
Liberal Democratic ◽  
The One

The study of political leadership, in France and elsewhere, must be appreciated in terms of the interaction between leadership resources (personal and positional) on the one hand, and environmental constraints and opportunities on the other. This article proposes a general framework for appraising comparative liberal democratic political leaderships. It illustrates the possibilities of the framework by evaluating the political leadership of the French President François Mitterrand.

Towards a Lexically Oriented Automatic Parsing

1991 ◽  
Vol 15 (1) ◽  
pp. 1-40
Author(s):  
Lucio Costa
Keyword(s):  
Artificial Intelligence ◽  
Distributed Control ◽  
Data Structures ◽  
General Framework ◽  
Computational Models ◽  
The Other ◽  
Sono Stati ◽  
Use Context ◽  
And Linguistics ◽  
Context Free

RIASSUNTO La ricerca sul linguaggio naturale condotta in Intelligenza Artificiale si è sviluppata, malgrado le apparenze, in modo alquanto indipendente dal la-voro dei linguisti. Da un lato sono stati elaborati modelli computazionali delle facoltà di lunguaggio che si configurano come largamente autonomi rispetto a quelli sviluppati in linguistica. D'altro lato, l'implementazione dei sistemi è stata influenzata da soluzioni pragmatiche connesse all'efficacia computazionale delle regole indipendenti dal contesto, alla necessità di evitare componenti trasformazionali inversi e ad una concezione rappresenta-zionale del significato. Il presente articolo propone l'interesse dei lavori lin-guistici di Z. S. Harris e M. Gross ai fini dello sviluppo di un'analisi sintat-tica automatica che sia a controllo diffuso e incentrata sul comportamento idiosincratico delle unità lessicali. Essa è anche inquadrata nel tentativo di gettare luce sulla natura del processo denotazionale. SUMMARY In spite of the claim on the interactions between artificial intelligence (AI) and linguistics, AI research on natural language has developed independently from the work of linguists. On one hand, computational models of the faculties of language which are independent from the models developed in linguistics have been worked out. On the other hand, the AI system design has been oriented towards practical solutions, whose main motivations where to use context-free rules, to avoid an inverse transformational component, and to represent meanings by some data structures. This paper is about the linguistic works of Z.S. Harris and M. Gross to develop automatic distributed control parsing which takes seriously into account the indiosyncratic behaviour of the lexical items. The general framework for the discussion is the procedural nature of the denotational process.

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