Statistical evaluation and modelling of the stomach contents of Icelandic cod (Gadus morhua)

1997 ◽  
Vol 54 (1) ◽  
pp. 169-181 ◽  
Author(s):  
G Stefansson ◽  
O K Palsson
Keyword(s):  
Degrees Of Freedom ◽  
Gadus Morhua ◽  
Present Model ◽  
Generalized Additive Models ◽  
Stomach Contents ◽  
Additive Models ◽  
Data Set ◽  
Proposed Model ◽  
Sampling Procedures ◽  
Combine Information

A model is proposed for investigating the statistical properties inherent in data on fish stomach contents of cod (Gadus morhua) taken on board Icelandic research vessels. The model explicitly incorporates components to describe the spatial distribution of prey species. It is found that combined delta-gamma (a presence-absence model and an abundance where present model, respectively) generalized additive models are useful in the analysis and explain a considerable portion of the variability in this type of data set, but a fairly large number of degrees of freedom is required to describe the behaviour of the data. A feature of the proposed model is the ability to combine information on the stomach contents from several predator length groups into a single analysis. Analytical results indicate that sampling procedures that base the analysis on the contents of individual stomachs are preferable to those based on combining the contents of several stomachs into aggregate samples.

Diel variation of stomach contents of North Sea cod (Gadus morhua) during a 24-h fishing survey: an analysis using generalized additive models

2000 ◽  
Vol 57 (12) ◽  
pp. 2363-2367 ◽  
Author(s):  
Sara A Adlerstein ◽  
Henny C Welleman
Keyword(s):  
North Sea ◽  
Stomach Content ◽  
Gadus Morhua ◽  
Generalized Additive Models ◽  
Stomach Contents ◽  
Additive Models ◽  
Large Prey ◽  
Diel Variation ◽  
The North ◽  
The North Sea

Results show that the weight of cod (Gadus morhua) stomach contents sampled in the North Sea varies significantly within 24 h. To determine whether feeding varied with time, over 1100 cod stomachs were collected around the clock between 7 and 18 May 1984 in two areas in the central North Sea thought to be representative for feeding studies. Here we investigate temporal feeding patterns based on the analysis of stomach-content data, using generalized additive models (GAMs). Results show significant variation of content weight and indicate morning and evening peaks. The relative peak importance differed between and within areas. We propose that differences are due to diet composition, namely, prey size and diel availability. Cod fed primarily on molluscs, mainly ocean quahog (Cyprina islandica), crustaceans, sandeels (Ammodytes spp.), haddock (Melanogrammus aeglefinus), herring (Clupea harrengus), and several flatfish species. In one area, the diet was dominated by fish, relatively large prey that perform diel vertical migration, and in the other by invertebrates, smaller prey that are digested faster. The diel pattern was more pronounced where invertebrate prey were dominant. Generalisation of results and implications for predation-mortality estimates based on data from the North Sea Stomach Content Database, used to implement multispecies models in the region, are discussed.

Statistical modelling reveals spatial, temporal, and environmental preferences for white sharks at an oceanic aggregation site

2020 ◽  
Vol 655 ◽  
pp. 171-183
Author(s):  
EE Becerril-García ◽  
RO Martínez-Rincón ◽  
F Galván-Magaña ◽  
O Santana-Morales ◽  
EM Hoyos-Padilla
Keyword(s):  
Feeding Habits ◽  
Generalized Additive Models ◽  
Statistical Modelling ◽  
Time Of Day ◽  
White Shark ◽  
Additive Models ◽  
Environmental Preferences ◽  
Data Set ◽  
Aggregation Site ◽  
Guadalupe Island

Guadalupe Island, Mexico, is one of the most important white shark (Carcharodon carcharias) aggregation sites in the Eastern Pacific. In the waters surrounding Guadalupe Island, cage diving has been carried out since 2001 during August-November; however, there is scarce information regarding the factors associated with this seasonal aggregation. The purpose of this study was to describe the probability of occurrence of white sharks relative to spatial, temporal, and environmental factors in Guadalupe Island. Generalized additive models (GAMs) were used to describe the effect of sea surface temperature, water visibility, tide, moon phase, cloud cover, time of day, and location on white shark occurrence. GAMs were generated from a data set of 6266 sightings of white sharks, classified as immature males, mature males, immature females, and mature females. A sexual segregation related to month was observed, where females arrived after males during late September. GAMs evidenced a segregation of white sharks according to the analysed variables, which is consistent with previous observations in this locality. Environmental preferences for each white shark category are potentially influenced by feeding habits, sexual maturation, and reproduction. This study constitutes a baseline of the effect of the environment on the occurrence of white sharks in Guadalupe Island, which can be used in further studies regarding management and conservation in future climatic and anthropogenic scenarios. Its relevance is related to the understanding of its ecology in oceanic environments and the presence of this threatened species during the ecotourism season.

Using local ecological knowledge to inform fisheries assessment: measuring agreement among Polish fishermen about the abundance and condition of Baltic cod (Gadus morhua)

2017 ◽  
Vol 74 (8) ◽  
pp. 2213-2222 ◽  
Author(s):  
Elizabeth Figus ◽  
Courtney Carothers ◽  
Anne H Beaudreau
Keyword(s):  
Body Condition ◽  
Gadus Morhua ◽  
Local Ecological Knowledge ◽  
Generalized Additive Models ◽  
Additive Models ◽  
Ecological Knowledge ◽  
Consensus Analysis ◽  
Cultural Consensus Analysis ◽  
Biological Assessments ◽  
Baltic Cod

Abstract Although fisheries managers often attempt to incorporate stakeholders’ views into development of policy options, integration of fishermen’s local ecological knowledge into biological assessments remains uncommon. Using the case of the eastern Baltic cod (Gadus morhua) resource, this article documented local ecological knowledge about a managed fishery stock. In 2012 and 2013, local media reported that fishermen were observing increased occurrences of cod with poor body condition (“skinny” cod) in their catches from waters off Poland. Polish cod fishermen were interviewed (n = 31) to quantify the strength of their agreement about the abundance and body condition of cod. Agreement among fishermen was assessed about trends in abundance and occurrence of “skinny” cod, as well as the mechanisms explaining those patterns. Cultural consensus analysis showed strong agreement among Polish fishermen that “skinny” cod may be attributed to overfishing on sprat, a key prey species. Fishermen and scientists observed similar declines in the abundance and condition of cod along the Polish coastline; however, they may perceive causes of those changes differently. Generalized additive models were used to show that trends in fishermen’s observations of abundance and “skinny” cod occurrence may be partially explained by variation in temperature, salinity, and sprat abundance.

scholarly journals Home range and elevated egg densities within an inshore spawning ground of coastal cod

2007 ◽  
Vol 64 (5) ◽  
pp. 920-928 ◽  
Author(s):  
Sigurd Heiberg Espeland ◽  
Ailin Fernløf Gundersen ◽  
Esben Moland Olsen ◽  
Halvor Knutsen ◽  
Jakob Gjøsæter ◽  
...  
Keyword(s):  
Home Range ◽  
Site Fidelity ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Generalized Additive Models ◽  
Spatial Dynamics ◽  
Additive Models ◽  
Spawning Season ◽  
Spawning Ground ◽  
Spawning Site

Abstract Espeland, S. H., Gundersen, A. F., Olsen, E. M., Knutsen, H., Gjøsæter, J., and Stenseth, N. C. 2007. Home range and elevated egg densities within an inshore spawning ground of coastal cod. – ICES Journal of Marine Science, 64: 920–928. Atlantic cod (Gadus morhua) along the Norwegian Skagerrak coast are structured into genetically distinct local populations. Mechanisms contributing to this genetic structure may include spawning site fidelity of adult cod as well as retention of pelagic early life stages close to the spawning grounds. Spawning in sheltered inshore localities is likely to favour retention of eggs and larvae, the opposite situation to offshore spawning. A combined study was made of area utilization by adult cod and the distribution of cod eggs within an inshore locality of the Norwegian Skagerrak coast. The behaviour of adult cod was studied using acoustic telemetry and kernel modelling, and eggs were sampled throughout the spawning season. Generalized additive models were applied to test hypotheses about the spatial dynamics of the eggs, and the best model described a central spawning area that retained its integrity through time. Adult cod were confined to small parts of the study area and remained there throughout the spawning season. The average home range of the adult cod was 27 ha. Overall, the study demonstrated two mechanisms by which coastal (i.e. inshore) cod maintain their population structure: spawning site fidelity and the spatial dynamics of their eggs.

scholarly journals A tutorial on regression-based norming of psychological tests with GAMLSS (version 3)

2019 ◽  
Author(s):  
Marieke Timmerman ◽  
Lieke Voncken ◽  
Casper J Albers
Keyword(s):  
Generalized Additive Models ◽  
Reference Population ◽  
Psychological Tests ◽  
Additive Models ◽  
Normative Study ◽  
Data Set ◽  
Composite Scale ◽  
Sample Data ◽  
Proper Interpretation ◽  
Multiple Reference

A norm-referenced score expresses the position of an individual test taker in the reference population, thereby enabling a proper interpretation of the test score. Such normed scores are derived from test scores obtained from a sample of the reference population. Typically, multiple reference populations exist for a test, namely when the norm-referenced scores depend on individual characteristic(s), as age (and sex). To derive normed scores, regression-based norming has gained large popularity. The advantages of this method over traditional norming are its flexible nature, yielding potentially more realistic norms, and its efficiency, requiring potentially smaller sample sizes to achieve the same precision. In this tutorial, we introduce the reader to regression-based norming, using the generalized additive models for location, scale, and shape (GAMLSS). This approach has been useful in norm estimation of various psychological tests. We discuss the rationale of regression-based norming, theoretical properties of GAMLSS, and their relationships to other regression-based norming models. Based on six steps, we describe how to: a) design a normative study to gather proper normative sample data; b) select a proper GAMLSS model for an empirical scale; c) derive the desired normed scores for the scale from the fitted model, including those for a composite scale; and d) visualize the results to achieve insight into the properties of the scale. Following these steps yields regression-based norms with GAMLSS for a psychological test, as we illustrate with normative data of the intelligence test IDS-2. The complete R code and data set is provided as supplemental material.

Structure in a sea of sand: fish abundance in relation to man-made structures in the North Sea

2018 ◽  
Vol 77 (3) ◽  
pp. 1206-1218 ◽  
Author(s):  
Serena R Wright ◽  
Christopher P Lynam ◽  
David A Righton ◽  
Julian Metcalfe ◽  
Ewan Hunter ◽  
...  
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Oil And Gas ◽  
Generalized Additive Models ◽  
Strong Association ◽  
Additive Models ◽  
Artificial Structures ◽  
Habitat Alterations ◽  
The North ◽  
The North Sea

Abstract Artificial structures in the marine environment may have direct and/or indirect impact on the behaviour and space use of mobile foragers. This study explores whether environmental and physical features in the North Sea—including artificial structures (wrecks, wind turbines, cables, and oil and gas structures) were associated with local abundance of three fish species: cod (Gadus morhua), plaice (Pleuronectes platessa), and thornback ray (Raja clavata). Generalized additive models (GAMs) were used to compare distributions between data collected by fisheries surveys and electronic tags. Distributions of cod, plaice, and ray were correlated with environmental variables including temperature, depth, and substrate, matching findings from previous studies. All species showed seasonal increases in their abundance in areas with high densities of artificial structures, including oil and gas platforms and wrecks. Independent of whether fish purposefully associate with these features or whether structures happen to coincide with locations frequented by these populations, the strong association suggests that greater consideration needs to be given to regulation of habitat alterations, including decommissioning.

How flood risk impacts residential rents and property prices

2018 ◽  
Vol 36 (1) ◽  
pp. 50-67 ◽  
Author(s):  
Jens Hirsch ◽  
Jonas Hahn
Keyword(s):  
Flood Risk ◽  
Generalized Additive Models ◽  
Additive Models ◽  
Data Set ◽  
Content Type ◽  
Real Estate Markets ◽  
Property Price ◽  
The Usa ◽  
Rental Markets ◽  
The Impact

Purpose The purpose of this paper is to quantify the impact of 100-year flood risk on both property rents and values in Germany, exemplified by the market of the historic city of Regensburg, and therefore supports investors in understanding market behavior patterns in both rental and investment context. Design/methodology/approach The authors construct two generalized additive models for rents and purchasing prices with spatial components and under inclusion of both typical property characteristics (as control variables) and a 100-year flood risk parameter in order to estimate its effect on the rents and property price structure. The authors apply the methodology to a four-year data set of more than 16,500 observations. Findings The analysis shows that flood risk is a highly significant parameter when estimating both the rent as well as the sales price model. The authors also find that purchase prices for one square meter of living area are, on average, EUR299 lower if the property is located in the flood risk zone. In addition, also rental markets come with a respective, but rather low, discount. Practical implications The authors provide transparency to investors in terms of the impact that a flood risk location has on property rents as well as purchasing prices. The study supports investors by providing evidence on reaction patterns in German real estate markets and helps quantifying the financial impact that comes with flood risk in Germany. Originality/value This is the first study that aims to empirically test and to quantify the impact of flood risk on property rents and purchasing prices in Germany. Related research has been performed for the USA, Ireland and New Zealand and largely refers to event-driven work or rather conceptual in the context of property valuation.

Recruitment of North Sea cod (Gadus morhua) and Norway pout (Trisopterus esmarkii) between 1992 and 2006: the interplay between climate influence and predation

2009 ◽  
Vol 66 (4) ◽  
pp. 633-648 ◽  
Author(s):  
Alexander Kempf ◽  
Jens Floeter ◽  
Axel Temming
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Generalized Additive Models ◽  
Additive Models ◽  
The North ◽  
Time Period ◽  
Spawning Stock ◽  
The Status ◽  
Temperature Ranges ◽  
The North Sea

The interplay between temperature-related processes and predation in determining age-1 recruitment strength between 1992 and 2006 was analysed for North Sea cod ( Gadus morhua ) and Norway pout ( Trisopterus esmarkii ). For this purpose, an predation impact index (PI) was calculated out of survey data. PI was assumed to depend on the abundance of the predators and on the spatial overlap between predator and prey populations. Generalized additive models (GAMs) were created with spawning stock biomass (SSB) and sea surface temperature (SST) in the respective spawning and nursery areas and PI as explaining variables. SSB had no significant impact on recruitment during this time period for both species. SSTs during spring and PI explained the interannual variability in recruitment strength to a large extent (88% of the total variance for cod and 68% for Norway pout). The SST during spring determined the overall level of recruitment. At SSTs above a certain level, however, the effect on recruitment was no longer significant. In these temperature ranges, predation was the dominant effect. Therefore, the fate of North Sea cod and Norway pout stocks under global-warming conditions will be strongly influenced by the status of the North Sea food web.

scholarly journals Does Tokyo Stock Exchange Appreciate Corporate Innovations? Role of Patents’ Quality and Research Productivity.

2020 ◽  
Author(s):  
Kostiantyn Ovsiannikov
Keyword(s):  
Stock Exchange ◽  
Manufacturing Sector ◽  
Dominant Role ◽  
Research Question ◽  
Generalized Additive Models ◽  
Additive Models ◽  
Data Set ◽  
Empirical Measures ◽  
Tokyo Stock Exchange

This paper examines the market perception of corporate innovations in Japan. It follows the research question formulated by Hall, Jaffe, and Trajtenberg (2005): "how does innovative activity translate into market value, and what aspects of the underlying process are captured by the empirical measures available?". The novelty of my study is twofold. First, it embraces the longitudinal innovation- and finance-related corporate records to come up with the largest ever combined data-set for Japan that encompasses 632 companies listed at the Tokyo Stock Exchange over the period of 19 years. Second, in addition to linear regressions, it applies the generalized additive models (GAMs). The latter technique allows for realistically capturing nonlinear patterns present in the data while at the same time retaining predictive features of a model. The main finding of the article is following. Amid the dominant role of research and development (R&D), especially for the Pharmaceutical and Chemical industries, market consistently rewards influential patents in the manufacturing sector.

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