scholarly journals Contemporary fisheries stock assessment: many issues still remain

2014 ◽  
Vol 72 (1) ◽  
pp. 7-18 ◽  
Author(s):  
Mark N. Maunder ◽  
Kevin R. Piner
Keyword(s):  
Information Content ◽  
Relative Abundance ◽  
Stock Assessment ◽  
Diagnostic Methods ◽  
Natural Mortality ◽  
Absolute Abundance ◽  
Substantial Impact ◽  
Composition Data ◽  
The Absolute ◽  
Management Advice

Abstract Interpretation of data used in fisheries assessment and management requires knowledge of population (e.g. growth, natural mortality, and recruitment), fisheries (e.g. selectivity), and sampling processes. Without this knowledge, assumptions need to be made, either implicitly or explicitly based on the methods used. Incorrect assumptions can have a substantial impact on stock assessment results and management advice. Unfortunately, there is a lack of understanding of these processes for most, if not all, stocks and even for processes that have traditionally been assumed to be well understood (e.g. growth and selectivity). We use information content of typical fisheries data that is informative about absolute abundance to illustrate some of the main issues in fisheries stock assessment. We concentrate on information about absolute abundance from indices of relative abundance combined with catch, and age and length-composition data and how the information depends on knowledge of population, fishing, and sampling processes. We also illustrate two recently developed diagnostic methods that can be used to evaluate the absolute abundance information content of the data. Finally, we discuss some of the reasons for the slowness of progress in fisheries stock assessment.

Reducing retrospective patterns in stock assessment and impacts on management performance

2017 ◽  
Vol 75 (2) ◽  
pp. 596-609 ◽  
Author(s):  
Cody S Szuwalski ◽  
James N Ianelli ◽  
André E Punt
Keyword(s):  
Stock Assessment ◽  
Reference Points ◽  
Natural Mortality ◽  
Time Varying ◽  
Management Performance ◽  
Population Processes ◽  
True Time ◽  
Management Advice ◽  
Spawning Biomass ◽  
Over Time

Abstract Retrospective patterns are consistent directional changes in assessment estimates of biomass in a given year when additional years of data are added to an assessment, and have been identified for a number of exploited marine stocks. Retrospective patterns are sometimes reduced by allowing population processes to vary over time in an assessment, but it is unclear how this practice influences management performance. We simulated stocks in which retrospective patterns were induced by forcing natural mortality, selectivity, or growth to vary over time. We then evaluated the impacts of reducing retrospective patterns by allowing population processes to vary in the assessment. In general, allowing selectivity, natural mortality, and growth to vary in the assessment decreased the magnitude of retrospective patterns in estimated spawning biomass, regardless of whether the true time-varying process was allowed to vary. However, the resulting reference points and management advice were sometimes drastically in error when a process other than the true time-varying process was allowed to vary, and these errors resulted in under-utilizing or over-exploiting the stock. Given the potential for error, identifying the important population processes that vary over time when addressing retrospective patterns should be a priority when providing management advice and may require increased longitudinal life history studies.

scholarly journals Interpreting catch per unit effort data to assess the status of individual stocks and communities

2006 ◽  
Vol 63 (8) ◽  
pp. 1373-1385 ◽  
Author(s):  
Mark N. Maunder ◽  
John R. Sibert ◽  
Alain Fonteneau ◽  
John Hampton ◽  
Pierre Kleiber ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Stock Assessment ◽  
Limited Information ◽  
Catch Per Unit Effort ◽  
Fish Stocks ◽  
Unit Effort ◽  
Strategy Evaluation ◽  
The Status ◽  
Catch Rates ◽  
Management Advice

AbstractDespite being one of the most common pieces of information used in assessing the status of fish stocks, relative abundance indices based on catch per unit effort (cpue) data are notoriously problematic. Raw cpue is seldom proportional to abundance over a whole exploitation history and an entire geographic range, because numerous factors affect catch rates. One of the most commonly applied fisheries analyses is standardization of cpue data to remove the effect of factors that bias cpue as an index of abundance. Even if cpue is standardized appropriately, the resulting index of relative abundance, in isolation, provides limited information for management advice or about the effect of fishing. In addition, cpue data generally cannot provide information needed to assess and manage communities or ecosystems. We discuss some of the problems associated with the use of cpue data and some methods to assess and provide management advice about fish populations that can help overcome these problems, including integrated stock assessment models, management strategy evaluation, and adaptive management. We also discuss the inappropriateness of using cpue data to evaluate the status of communities. We use tuna stocks in the Pacific Ocean as examples.

scholarly journals A multi-view model for relative and absolute microbial abundances

2019 ◽  
Author(s):  
Brian D. Williamson ◽  
James P. Hughes ◽  
Amy D. Willis
Keyword(s):  
Relative Abundance ◽  
Estimation Error ◽  
Bacterial Species ◽  
Critical Role ◽  
Sensitivity Study ◽  
Universal Primers ◽  
Rrna Gene ◽  
Absolute Abundance ◽  
Abundance Data ◽  
The Absolute

AbstractThe absolute abundance of bacterial taxa in human host-associated environments play a critical role in reproductive and gastrointestinal health. However, obtaining the absolute abundance of many bacterial species is typically prohibitively expensive. In contrast, relative abundance data for many species is comparatively cheap and easy to collect (e.g., with universal primers for the 16S rRNA gene). In this paper, we propose a method to jointly model relative abundance data for many taxa and absolute abundance data for a subset of taxa. Our method provides point and interval estimates for the absolute abundance of all taxa. Crucially, our proposal accounts for differences in the efficiency of taxon detection in the relative and absolute abundance data. We show that modeling taxon-specific efficiencies substantially reduces the estimation error for absolute abundance, and controls the coverage of interval estimators. We demonstrate the performance of our proposed method via a simulation study, a sensitivity study where we jackknife the taxa with observed absolute abundances, and a study of women with bacterial vaginosis.

Ecological impact of Eurasian beaver (Castor fiber) activity on macroinvertebrate communities in Lithuanian trout streams

2012 ◽  
Vol 7 (1) ◽  
pp. 101-114 ◽  
Author(s):  
Virginija Pliūraitė ◽  
Vytautas Kesminas
Keyword(s):  
Relative Abundance ◽  
Ecological Impact ◽  
Macroinvertebrate Communities ◽  
Beaver Pond ◽  
Absolute Abundance ◽  
Habitat Types ◽  
Percentage Composition ◽  
Beaver Ponds ◽  
Eurasian Beaver ◽  
The Absolute

AbstractOur study found that beaver activity affects macroinvertebrate assemblages of both beaver ponds and downstream sites. The percentage composition of the invertebrate faunae of beaver ponds was strikingly different from the invertebrate faunae of upstream forested and downstream sites. The number of EPT (ephemeropteran, plecopteran, trichopteran) taxa in the upstream forested sites in all streams was higher than in beaver pond and downstream sites. Statistically significant differences were found in absolute and relative abundances of EPT and Chironomidae between different streams sites. The absolute and relative abundance of pollution-sensitive EPT was significantly higher in forested sites than in beaver pond and downstream sites in all measured streams. Beaver ponds had a significantly higher absolute and relative abundance of Chironomidae compared with upstream forested and downstream sites. We found that Plecoptera and Coleoptera were absent from beaver pond sites. The absolute abundance of Plecoptera was significantly higher in upstream forested sites than in downstream sites in all three streams. Gatherers were the dominant functional feeding group in relative abundance in all three habitat types. The percentage of gatherers was higher in beaver ponds than in forested and downstream sites.

Natural mortality diagnostics for state-space stock assessment models

2021 ◽  
Vol 243 ◽  
pp. 106062
Author(s):  
Andrea M.J. Perreault ◽  
Noel G. Cadigan
Keyword(s):  
State Space ◽  
Stock Assessment ◽  
Natural Mortality

scholarly journals Integrating spatial synchrony/asynchrony of population distribution into stock assessment models: a spatial hierarchical Bayesian statistical catch-at-age approach

2016 ◽  
Vol 73 (7) ◽  
pp. 1725-1738 ◽  
Author(s):  
Yan Jiao ◽  
Rob O'Reilly ◽  
Eric Smith ◽  
Don Orth ◽  
Keyword(s):  
Relative Abundance ◽  
Bayesian Model ◽  
Population Distribution ◽  
Stock Assessment ◽  
Spatial Models ◽  
Reference Points ◽  
Hierarchical Bayesian ◽  
Hierarchical Bayesian Model ◽  
Spatial Synchrony ◽  
Abundance Indices

Abstract In many marine fisheries assessments, population abundance indices from surveys collected by different states and agencies do not always agree with each other. This phenomenon is often due to the spatial synchrony/asynchrony. Those indices that are asynchronous may result in discrepancies in the assessment of temporal trends. In addition, commonly employed stock assessment models, such as the statistical catch-at-age (SCA) models, do not account for spatial synchrony/asynchrony associated with spatial autocorrelation, dispersal, and environmental noise. This limits the value of statistical inference on key parameters associated with population dynamics and management reference points. To address this problem, a set of geospatial analyses of relative abundance indices is proposed to model the indices from different surveys using spatial hierarchical Bayesian models. This approach allows better integration of different surveys with spatial synchrony and asynchrony. We used Atlantic weakfish (Cynoscion regalis) as an example for which there are state-wide surveys and expansive coastal surveys. We further compared the performance of the proposed spatially structured hierarchical Bayesian SCA models with a commonly used Bayesian SCA model that assumes relative abundance indices are spatially independent. Three spatial models developed to mimic different potential spatial patterns were compared. The random effect spatially structured hierarchical Bayesian model was found to be better than the commonly used SCA model and the other two spatial models. A simulation study was conducted to evaluate the uncertainty resulting from model selection and the robustness of the recommended model. The spatially structured hierarchical Bayesian model was shown to be able to integrate different survey indices with/without spatial synchrony. It is suggested as a useful tool when there are surveys with different spatial characteristics that need to be combined in a fisheries stock assessment.

Abundance of Boeckella gracilis (Daday, 1902) (Copepoda, Calanoida) in seasonal coastal pools in the Araucania region (38°S, Chile)

Crustaceana ◽  
2018 ◽  
Vol 91 (10) ◽  
pp. 1211-1217
Author(s):  
Patricio De los Ríos
Keyword(s):  
Correlation Analysis ◽  
Environmental Stress ◽  
Relative Abundance ◽  
Calanoid Copepod ◽  
Inverse Correlation ◽  
Inland Waters ◽  
Absolute Abundance ◽  
Significant Inverse Correlation

Abstract The presence of the calanoid copepod Boeckella gracilis (Daday, 1902) in Chilean seasonal pools has been only poorly studied as yet. The aim of the present study thus is to investigate the role of conductivity and temperature on the relative and absolute abundance of B. gracilis in seasonal coastal pools in the Araucania region (38°S, Chile). The results of correlation analysis revealed the presence of a significant inverse correlation between conductivity and relative abundance, whereas no significant correlations were found between conductivity and absolute abundance, between temperature and absolute abundance, and between temperature and relative abundance. These results agree partially with similar observations for mountain pools in the same region, but they would not agree with observations for calanoids of saline and subsaline inland waters in the northern and southern extremes of Chile. Considering this scenario, the species would show different populational responses to environmental stress in different situations, which phenomenon deserves to be studied more extensively and in more detail.

Understanding historical summer flounder (Paralichthys dentatus) abundance patterns through the incorporation of oceanography-dependent vital rates in Bayesian hierarchical models

2019 ◽  
Vol 76 (8) ◽  
pp. 1275-1294 ◽  
Author(s):  
Cecilia A. O’Leary ◽  
Timothy J. Miller ◽  
James T. Thorson ◽  
Janet A. Nye
Keyword(s):  
Population Dynamics ◽  
Gulf Stream ◽  
Stock Assessment ◽  
Deviance Information Criterion ◽  
Information Criterion ◽  
Natural Mortality ◽  
Vital Rates ◽  
Summer Flounder ◽  
Paralichthys Dentatus ◽  
Abundance Patterns

Climate can impact fish population dynamics through changes in productivity and shifts in distribution, and both responses have been observed for many fish species. However, few studies have incorporated climate into population dynamics or stock assessment models. This study aimed to uncover how past variations in population vital rates and fishing pressure account for observed abundance variation in summer flounder (Paralichthys dentatus). The influences of the Gulf Stream Index, an index of climate variability in the Northwest Atlantic, on abundance were explored through natural mortality and stock–recruitment relationships in age-structured hierarchical Bayesian models. Posterior predictive loss and deviance information criterion indicated that out of tested models, the best estimates of summer flounder abundances resulted from the climate-dependent natural mortality model that included log-quadratic responses to the Gulf Stream Index. This climate-linked population model demonstrates the role of climate responses in observed abundance patterns and emphasizes the complexities of environmental effects on populations beyond simple correlations. This approach highlights the importance of modeling the combined effect of fishing and climate simultaneously to understand population dynamics.

Sign in / Sign up

Export Citation Format

Share Document