A selection of nonparametric statistical methods for assessing trends in trawl survey indicators as part of an ecosystem approach to fisheries management (EAFM)

Cotter, John

doi:10.1051/alr/2009019

Cited by 16 publications

(6 citation statements)

References 30 publications

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“…Spearman's rho is the product-moment correlation between the ranks of paired data. To test for trend, one member of the pair is the time of observation, the other is the observed variable 83 Trends in the annual means of environmental variables (i.e., SST, UW, and SSC) were assessed in the north and south of Cap Blanc using Spearman tests, which are valid for supplementing linear models with a non-parametric models, such as the Spearman correlation. Diel changes to PA in the sCCLME were first analyzed by comparing PA (log 10 transformed) for day vs night in the vertical dimension (i.e., the mean value for each 1-m depth step over the whole period study).…”

Section: Methodsmentioning

confidence: 99%

On the robustness of an eastern boundary upwelling ecosystem exposed to multiple stressors

Diogoul

Brehmer

Demarcq

et al. 2021

Sci Rep

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The resistance of an east border upwelling system was investigated using relative index of marine pelagic biomass estimates under a changing environment spanning 20-years in the strongly exploited southern Canary Current Large marine Ecosystem (sCCLME). We divided the sCCLME in two parts (north and south of Cap Blanc), based on oceanographic regimes. We delineated two size-based groups (“plankton” and “pelagic fish”) corresponding to lower and higher trophic levels, respectively. Over the 20-year period, all spatial remote sensing environmental variables increased significantly, except in the area south of Cap Blanc where sea surface Chlorophyll-a concentrations declined and the upwelling favorable wind was stable. Relative index of marine pelagic abundance was higher in the south area compared to the north area of Cap Blanc. No significant latitudinal shift to the mass center was detected, regardless of trophic level. Relative pelagic abundance did not change, suggesting sCCLME pelagic organisms were able to adapt to changing environmental conditions. Despite strong annual variability and the presence of major stressors (overfishing, climate change), the marine pelagic ressources, mainly fish and plankton remained relatively stable over the two decades, advancing our understanding on the resistance of this east border upwelling system.

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Section: Methodsmentioning

confidence: 99%

On the robustness of an eastern boundary upwelling ecosystem exposed to multiple stressors

Diogoul

Brehmer

Demarcq

et al. 2021

Sci Rep

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“…Lastly, although not formally as rigorous, by solving for the σ L required for the observed trend to have a nominal confidence level of 95%, the expression for a statistic can be used to roughly gauge the significance of a trend and so circumvent the need for a comprehensive simulation of the natural variability. Nonparameteric tests that do not rely on the glacier adhering to a particular theoretical PDF might be applied for trend detection (Morell and Fried, 2008; Cotter, 2009). Such tests are more flexible (although typically less powerful) than parametric tests, and care is needed to account for serial correlations.…”

Section: Summary and Discussionmentioning

confidence: 99%

What do glaciers tell us about climate variability and climate change?

Roe¹

2011

J. Glaciol.

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ABSTRACT. Glaciers respond to long-term climate changes and also to the year-to-year fluctuations inherent in a constant climate. Differentiating between these factors is critical for the correct interpretation of past glacier fluctuations and for the correct attribution of current changes. Previous work has established that century-scale, kilometre-scale fluctuations can occur in a constant climate. This study asks two further questions of practical significance: how likely is an excursion of a given magnitude in a given amount of time, and how large a trend in length is statistically significant? A linear model permits analytical answers wherein the dependencies on glacier geometry and climate setting can be clearly understood. The expressions are validated with a flowline glacier model. The likelihood of glacier excursions is well characterized by extreme-value statistics, although probabilities are acutely sensitive to some poorly known glacier properties. Conventional statistical tests can be used for establishing the significance of an observed glacier trend. However, it is important to determine the independent information in the observations which can be effectively estimated from the glacier geometry. Finally, the retreat of glaciers around Mount Baker, Washington State, USA, is consistent with, but not independent proof of, the regional climate warming that is established from the instrumental record.

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“…The net-based method, on the other hand, is likely to underestimate the mesopelagic biomass through escapement (e.g., large trawls and large meshes) or avoidance (e.g., small nets and fine meshes) phenomena (Davison et al, 2015;Escobar-Flores et al, 2020). Yet, this method is still the most used and informative (e.g., providing coordinates and exact number of specimens) and provides a ground-truth of size and species composition of the sampled fish (Cotter, 2009;Davison et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Spatial Distribution and Abundance of Mesopelagic Fish Biomass in the Mediterranean Sea

et al. 2020

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Mesopelagic fish, being in the middle of the trophic web, are important key species for the marine environment; yet limited knowledge exists about their biology and abundance. This is particularly true in the Mediterranean Sea where no regional assessment is currently undertaken regarding their biomass and/or distribution. This study evaluates spatial and temporal patterns of mesopelagic fish biomass in the 1994–2011 period. We do that for the whole Mediterranean Sea using two well-established statistical models, the Generalized Additive Model (GAM) and Random Forest (RF). Results indicate that the bathymetry played an important role in the estimation of mesopelagic fish biomass and in its temporal and spatial distribution. The average biomass over the whole time period reached 1.08 and 0.10 t/km2, depending on the model considered. The Western Mediterranean and Ionian Seas were the sub-regions with the highest biomass, while the Adriatic was the area with the lowest. Temporal trends showed different trajectories with steep decrease and a fluctuation, using respectively RF and GAM. This study constitutes the first attempt to estimate the biomass and the spatial temporal patterns of mesopelagic fish using environmental variables as predictors. Given the growing interest in mesopelagic fish, our study sets a baseline to further develop mesopelagic fish biomass assessments in the region. Our results stress the need to improve data collection and quality in the region while identifying appropriate tools to better understand and assess the processes behind mesopelagic fish dynamics in the basin.

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A selection of nonparametric statistical methods for assessing trends in trawl survey indicators as part of an ecosystem approach to fisheries management (EAFM)

Cited by 16 publications

References 30 publications

On the robustness of an eastern boundary upwelling ecosystem exposed to multiple stressors

On the robustness of an eastern boundary upwelling ecosystem exposed to multiple stressors

What do glaciers tell us about climate variability and climate change?

Spatial Distribution and Abundance of Mesopelagic Fish Biomass in the Mediterranean Sea

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