scholarly journals Embedding stock assessment within an integrated hierarchical Bayesian life cycle modelling framework: an application to Atlantic salmon in the Northeast Atlantic

2014 ◽  
Vol 71 (7) ◽  
pp. 1653-1670 ◽  
Author(s):  
Félix Massiot-Granier ◽  
Etienne Prévost ◽  
Gérald Chaput ◽  
Ted Potter ◽  
Gordon Smith ◽  
...  
Keyword(s):  
Life Cycle ◽  
Atlantic Salmon ◽  
Density Dependence ◽  
Temporal Dynamics ◽  
Stock Assessment ◽  
Assessment Method ◽  
Hierarchical Bayesian ◽  
Return Rates ◽  
Modelling Framework ◽  
Marine Survival

Abstract We developed a hierarchical Bayesian integrated life cycle model for Atlantic salmon that improves on the stock assessment approach currently used by ICES and provides some interesting insights about the population dynamics of a stock assemblage. The model is applied to the salmon stocks in eastern Scotland. It assimilates a 40-year (1971–2010) time-series of data compiled by ICES, including the catches in the distant water fisheries at Faroes and West Greenland and estimates of returning fish abundance. Our model offers major improvements in terms of statistical methodology for A. salmon stock assessment. Uncertainty about inferences is readily quantified in the form of Bayesian posterior distributions for parameters and abundance at all life stages, and the model could be adapted to provide projections based on the uncertainty derived from the estimation phase. The approach offers flexibility to improve the ecological realism of the model. It allows the introduction of density dependence in the egg-to-smolt transition, which is not considered in the current ICES assessment method. The results show that this modifies the inferences on the temporal dynamics of the post-smolt marine survival. In particular, the overall decrease in the marine survival between 1971 and 2010 and the sharp decline around 1988–1990 are dampened when density dependence is considered. The return rates of smolts as two-sea-winter (2SW) fish has declined in a higher proportion than return rates as one-sea-winter (1SW) fish. Our results indicate that this can be explained either by an increase in the proportion maturing as 1SW fish or by an increase in the mortality rate at sea of 2SW fish, but the data used in our analyses do not allow the likelihood of these two hypotheses to be gauged.

scholarly journals Retrospective analysis of marine growth and relationships to return rates of Penobscot River Atlantic salmon

2021 ◽  
Author(s):  
Miguel Fillion Barajas ◽  
Timothy F Sheehan ◽  
Ruth Haas-Castro ◽  
Brandon Ellingson ◽  
Katherine Mills
Keyword(s):  
Atlantic Salmon ◽  
North American ◽  
Principal Component ◽  
Growth Increment ◽  
Growth Time ◽  
Seasonal Growth ◽  
Return Rates ◽  
Growth Increments ◽  
Penobscot River ◽  
Marine Survival

Beginning in the 1980s, return rates of Atlantic salmon to the Penobscot River, Maine U.S.A. declined and have persisted at low levels. This downturn coincided with similar declines in North American and European Atlantic salmon stocks and with changes in the Northwest Atlantic ecosystem. Previous studies investigated whether early marine growth explained the declines, but results varied, with decreased growth associated with declines in European stocks but not North American stocks. In this study, we evaluate whether growth over the entire marine stage is related to Atlantic salmon marine survival. We constructed a growth time series from scales of returned Penobscot River Atlantic salmon spanning periods of varying marine survival. We used ANOVA and post-hoc tests to quantify seasonal growth increment differences and principal component analysis to characterize variability among the suite of growth increments. We observed reduced growth during the second winter and second marine year starting in the 1990s, with compensatory seasonal growth relationships. These results indicate that diminished growth during late marine stages is associated with low return rates in this population.

scholarly journals Atlantic salmon return rate increases with smolt length

2019 ◽  
Vol 76 (6) ◽  
pp. 1702-1712 ◽  
Author(s):  
Stephen D Gregory ◽  
Anton T Ibbotson ◽  
William D Riley ◽  
Marie Nevoux ◽  
Rasmus B Lauridsen ◽  
...  
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
Survival Rates ◽  
Empirical Support ◽  
Return Rate ◽  
Imperfect Detection ◽  
Factors Affecting ◽  
Return Rates ◽  
Life Phase ◽  
Marine Survival

Abstract Recent declines in Atlantic salmon Salmo salar populations are generally attributed to factors in their marine life-phase. However, it is postulated that factors affecting their freshwater life-phase might impact their marine survival, such as the influence of body size. While larger smolts are widely hypothesized to have higher marine survival rates, empirical support remains scant, in part due to inadequate data and ambiguous statistical analyses. Here, we test the influence of smolt body size on marine return rates, a proxy for marine survival, using a 12-year dataset of 3688 smolts tagged with passive integrated transponders in the River Frome, Southern England. State-space models describe the probability of smolts surviving their marine phase to return as 1 sea-winter (1SW) or multi-sea-winter adults as a function of their length, while accounting for imperfect detection and missing data. Models predicted that larger smolts had higher return rates; the most parsimonious model included the effect of length on 1SW return rate. This prediction is concerning, as freshwater juvenile salmon are decreasing in size on the River Frome, and elsewhere. Thus, to maximize adult returns, restoration efforts should focus on freshwater life-stages, and maximize both the number and the size of emigrating smolts.

scholarly journals Environmental assessment of the Tung cultivation through life cycle analysis

2014 ◽  
Vol 3 (1) ◽  
pp. 70 ◽  
Author(s):  
Marcelo Bern�l ◽  
Rosana Schneider ◽  
�nio Machado
Keyword(s):  
Life Cycle ◽  
Production Systems ◽  
Life Cycle Management ◽  
Assessment Method ◽  
Agroforestry Systems ◽  
Family Farms ◽  
Conventional Agriculture ◽  
The Past ◽  
Ecosystem Changes ◽  
Poor Soil

Over the past few decades, conventional agriculture has been facing serious crises caused by numerous factors, including poor soil management and the excessive application of pesticides. Thus, alternative production systems have been developed, including agroforestry systems, especially those that produce both energy and food. The objective of this study was to environmentally evaluate the culture of Aleurites fordii Hemls. (Tung) using the Life Cycle Assessment method with the SimaPro 7.3.2 software. The results revealed that in family farms that use less mechanization to harvest crops, the primary category of environmental impact was land use, which included the removal of animal and vegetable species and ecosystem changes. The full impact of this category was 1741.21 m2yr PDF (potentially disappeared fraction). Subsequently, prognostics were established for the reduction of such impacts, and we conclude that Tung has a high potential for agricultural installation with high responsibility to the environment. Keywords: Environmental factors, Aleurites fordii Hemls, Life Cycle Management, Tung.

scholarly journals Attributional & Consequential Life Cycle Assessment: Definitions, Conceptual Characteristics and Modelling Restrictions

2021 ◽  
Vol 13 (13) ◽  
pp. 7386
Author(s):  
Thomas Schaubroeck ◽  
Simon Schaubroeck ◽  
Reinout Heijungs ◽  
Alessandra Zamagni ◽  
Miguel Brandão ◽  
...  
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Environmental Impact ◽  
Product Life Cycle ◽  
Sustainability Assessment ◽  
Consequential Life Cycle Assessment ◽  
Modelling Framework ◽  
Potential Environmental Impact ◽  
Reference Environment ◽  
The Impact

To assess the potential environmental impact of human/industrial systems, life cycle assessment (LCA) is a very common method. There are two prominent types of LCA, namely attributional (ALCA) and consequential (CLCA). A lot of literature covers these approaches, but a general consensus on what they represent and an overview of all their differences seems lacking, nor has every prominent feature been fully explored. The two main objectives of this article are: (1) to argue for and select definitions for each concept and (2) specify all conceptual characteristics (including translation into modelling restrictions), re-evaluating and going beyond findings in the state of the art. For the first objective, mainly because the validity of interpretation of a term is also a matter of consensus, we argue the selection of definitions present in the 2011 UNEP-SETAC report. ALCA attributes a share of the potential environmental impact of the world to a product life cycle, while CLCA assesses the environmental consequences of a decision (e.g., increase of product demand). Regarding the second objective, the product system in ALCA constitutes all processes that are linked by physical, energy flows or services. Because of the requirement of additivity for ALCA, a double-counting check needs to be executed, modelling is restricted (e.g., guaranteed through linearity) and partitioning of multifunctional processes is systematically needed (for evaluation per single product). The latter matters also hold in a similar manner for the impact assessment, which is commonly overlooked. CLCA, is completely consequential and there is no limitation regarding what a modelling framework should entail, with the coverage of co-products through substitution being just one approach and not the only one (e.g., additional consumption is possible). Both ALCA and CLCA can be considered over any time span (past, present & future) and either using a reference environment or different scenarios. Furthermore, both ALCA and CLCA could be specific for average or marginal (small) products or decisions, and further datasets. These findings also hold for life cycle sustainability assessment.

Multiple Haemoglobins of the Atlantic Salmon (Salmo salar)

1968 ◽  
Vol 25 (12) ◽  
pp. 2651-2663 ◽  
Author(s):  
N. P. Wilkins
Keyword(s):  
Life Cycle ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Gel Electrophoresis ◽  
Initial Increase ◽  
Small Fish ◽  
Starch Gel Electrophoresis ◽  
Complete Development ◽  
Starch Gel ◽  
The Individual

The haemoglobins of over 500 salmon of different lengths, from Scotland, Greenland, and Canada have been analysed by vertical starch–gel electrophoresis at pH 8.1. Complex ontogenetic variations, involving an initial increase and later reduction in the number of fractions evident, have been observed among the anodally migrating haemoglobins. The variations observed have been correlated with changes in length, and the complete development of the anodal haemoglobin complex from the single fraction of small fish to the nine-fraction pattern of adults is outlined. The individual haemoglobin fractions appear to represent structurally distinct molecules whose regulated occurrence at different phases of the life cycle is discussed at the individual and population levels.

A CIRCLE MAP FOR A PHYTOPLANKTONIC LIFE CYCLE

2000 ◽  
Vol 10 (02) ◽  
pp. 325-344 ◽  
Author(s):  
ERIC P. M. GRIST
Keyword(s):  
Dynamical System ◽  
Life Cycle ◽  
Seasonal Change ◽  
West Coast ◽  
Temporal Dynamics ◽  
Piecewise Linear ◽  
Circle Map ◽  
Development Data ◽  
Linear Sections ◽  
Successive Generations

I focus on the temporal dynamics generated by a life cycle consisting of two contiguous stages developing under the influence of a stimulus which pulsates between on and off. I ask: under what general conditions does a population held in exposure to this kind of periodic stimulus achieve life cycle synchrony? The situation is represented by a dynamical system consisting of a nondecreasing circle map whose plot is made up of 45° and horizontal piecewise-linear sections. These features permit the iterative dynamics (itineraries) followed by successive generations to be derived and algebraic conditions for high-ordered synchronization to be derived. Using development data obtained for the phytoplankton Thalassiorira pseudonana and mean daily irradiation intensities recorded over different months at the latitude of Oban (west coast of Scotland), I apply the model to investigate how seasonal change in daily irradiance may directly influence the synchronous dynamics of such populations.

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.

scholarly journals Direct Survival Analysis: a new stock assessment method

2007 ◽  
Vol 71 (1) ◽  
pp. 175-185 ◽  
Author(s):  
Eduardo Ferrandis ◽  
Pilar Hernández
Keyword(s):  
Survival Analysis ◽  
Stock Assessment ◽  
Assessment Method
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