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On population dynamics of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Adriatic Sea: from an analytical to an ecological perspective
No full textAlici Engraulis encrasicolus e sardine Sardina pilchardus sono due delle più importanti specie
commerciali dell’Adriatico centro-settentrionale e sostengono la pesca più produttiva dell’intero
Mar Mediterraneo. Lo stock assessment di queste specie, così come la comprensione dei
fattori ambientali che ne influenzano le popolazioni, sono estremamente importanti a fini gestionali.
Questa tesi copre diversi aspetti della dinamica di popolazione dei piccoli pelagici nel
Mar Adriatico ed è organizzata in 3 capitoli, da un approccio puramente analitico ad uno più
ecologico.
Nel primo capitolo, per lo stock assessment delle alici, sono state usate due diverse stime
di mortalità naturale (i.e. Prodbiom e Gislason’s), ed è stato applicato un modello di analisi
chiamato Integrated Catch-at-age Analysis (ICA), le cui prestazioni sono state messe a confronto
con una Virtual Population Analysis (VPA) tradizionale. I risultati hanno mostrato che la stima
di mortalità naturale fornita dal metodo di Gislason è più adatto per la popolazione di alici.
Inoltre, nonostante le stime di biomassa e di mortalità per pesca siano risultate similari tra i
due modelli di dinamica di popolazione (VPA e ICA), tuttavia l’ICA ha permesso una maggiore
flessibilità nelle impostazioni iniziali del modello e ne ha migliorato i risultati diagnostici.
Nel secondo capitolo, un modello statistico più sofisticato che permette la suddivisione delle
catture per flotta peschereccia (Age Structured Assessment Program - ASAP), è stato usato per
le sardine e confrontato con l’ICA. Di nuovo, le stime di biomassa e mortalità per pesca non sono
cambiate troppo tra i due modelli, ma l’ASAP permette di tenere in considerazione la possibile
eterogeneità tra le diverse flotte. Inoltre, l’ASAP ha permesso l’inclusione di una variabile
ambientale, nello specifico la temperatura superficiale del mare (SST), nella funzione statistica:
l’inclusione della SST, anche se non ha modificato la prospettiva generale, ha migliorato il fitting
della relazione stock-reclutamento di Beverton-Holt, confermando come l’ambiente possa aiutare
a spiegare le ampie fluttuazioni osservate nei piccoli pelagici.
Nell’ultima parte di questa tesi, l’ammontare di alici catturate è stata messa in relazione
con alcune variabili ambientali. Per relazionare i dati di cattura provenienti da un sistema di
osservazione sulla pesca (FOS) a dati oceanografici provenienti da modello idrodinamico (ROMS)
sono stati usati Generalized Additive Mixed Models (GAMM). Dati settimanali di cattura georeferenziati
di Engraulis encrasicolus sono stati suddivisi in celle di 0:2 x 0:2 in latitudine e
longitudine ed associati ai rispettivi parametri ambientali da ROMS. Le variabili oceanografiche
che sono risultate più significative e quindi considerate nel GAMM finale sono state l’interazione
tra temperatura e profondità in situ, la profondità in situ, la temperatura superficiale, il gradiente
della componente U (est-ovest) della corrente e il gradiente di salinità sul fondo. I risultati
suggeriscono che l’abbondanza nelle catture di alici nel Mar Adriatico è positivamente correlata
a basse temperature, upwelling localizzati e fronti di salinità. Inoltre, le conclusioni di questo
capitolo hanno dimostrato che i GAMM sono degli strumenti molto utili per combinare dati
di cattura geo-referenziati con variabili oceanografiche, e che l’inclusione di effetti random è un
modo utile per meglio comprendere la distribuzione spaziale di specie marine.
Nel complesso, questo studio fornisce un’analisi completa delle dinamiche di popolazione dei
piccoli pelagici nel Mar Adriatico. Inoltre, fornisce alcuni miglioramenti metodologici allo studio delle popolazioni ittiche, tenendo anche in considerazione effetti dell'ambiente.Anchovy Engraulis encrasicolus and sardine Sardina pilchardus are two of the most important
commercial species of the northern and central Adriatic Sea and support two of the most productive
fisheries in the whole Mediterranean. The stock assessment of these species, as well
as the understanding of the environmental-driven mechanism that influences their populations,
are really important for management purposes. The present study covers several aspects of the
population dynamics of small pelagics in the Adriatic Sea and it is organized in 3 chapters that
move from an analytical approach to a more integrated ecological one.
In the first chapter of this thesis, the stock assessment of anchovy has been carried out
applying two methods for the estimation of natural mortality (i.e. Prodbiom and Gislason’s),
and applying a Virtual Population Analysis (VPA)-like model, namely Integrated Catch-at-age
Analysis (ICA), whose performances were compared with a traditional VPA model. The results
showed a better performance of the former model using the Gislason’s estimation for natural
mortality: despite the fact that the general trend in biomass and fishing mortality was similar
between VPA and ICA, nevertheless ICA allowed a higher flexibility in the model settings and
improved the model diagnostics.
In the second chapter, a more advanced statistical-at-age fleet based approach (i.e. Age
Structure Assessment Program) was used for sardine and compared to the ICA approach. The
general trend in biomass and fishing mortality was similar between the two models but the
fleet-based assessment accounts for potential heterogeneity across differently operating fisheries.
Besides, the ASAP model allowed the inclusion of an environmental variable, namely the Sea
Surface Temperature (SST), into the calculation: the inclusion of SST, despite not changing the
overall perspective, improved the fitting of the Beverton-Holt stock-recruitment relationship and
somehow confirmed the expectation that environmental conditions can help explaining the wide
fluctuations observed in small pelagic species.
In the last part of this thesis, the amount of anchovy caught was related to some environmental
variables. Generalized Additive Mixed Models (GAMM) were used to couple a Fishery
Observing System (FOS) to an oceanographic model (ROMS). Weekly geo-referenced catch data
of Engraulis encrasicolus were divided into cells of 0:2 x 0:2 in latitude and longitude and
associated to the weekly environmental parameters described for each cell by the ROMS hydrodynamic
model. The more significant oceanographic variables and therefore included in the
final GAMM model were in situ temperature- depth interactions, depth, surface temperature,
gradient of the U (eastern-western) component of the current, and gradient of salinity at the
bottom. The results suggested that catch abundance of anchovy in the Adriatic Sea is positively
related to lower temperature, local upwelling and salinity fronts. Moreover, the outcomes of this
paper demonstrated that GAMM are a useful tool to combine geo-referenced catch data with
oceanographic variables and that the inclusions of random effects is a reasonable way to better
understand the spatial distribution of marine species.
On the whole, this study provides a comprehensive analysis of the stock dynamics of small
pelagics in the Adriatic Sea. Besides, it provides some methodological improvements to the study
of fish populations, also taking into account environmental effects
Coupling an oceanographic model to a Fishery Observing System through mixed models: The importance of fronts for anchovy in the Adriatic Sea
No full textAnchovy, Engraulis encrasicolus, forms the basis of Italian small pelagic fisheries in the Adriatic Sea. The strong dependence of this stock on environmental factors and the consequent high variability makes the dynamics of this species particularly complicated to model. Weekly geo-referenced catch data of anchovy obtained by means of a Fishery Observing System (FOS) from 2005 to 2011 were referred to a 0.2 × 0.2 degree grid (about 20 km2) and associated with the environmental parameters calculated by a Regional Ocean Modelling System, AdriaROMS. Generalized Additive Mixed Models (GAMM) with and without random effects were used to identify a relationship between abundance in the catch and oceanographic conditions. The outcomes of models with no random effects, with random vessel effects and with the random vessel and random week-of-the-year effects were examined. The GAMM incorporating a random vessel and week-of-the-year effect were selected as the best model on the basis of the Akaike information criteria (AIC). This model indicated that catches (abundance) of anchovy in the Adriatic Sea correlate well with low temperatures, salinity fronts and sea surface height, and allowed the identification of areas where high concentrations of this species are most likely to occur. The results of this study demonstrate that GAMM are a useful tool to combine geo-referenced catch data with oceanographic variables and that the use of a mixed-model approach with spatial and temporal random effects is an effective way to depict the dynamics of marine species
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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