1,720,984 research outputs found
Improving the selectivity of bottom trawls in the Adriatic and Tyrrhenian sea
Full text linkU prvom eksperimentu ispitala se selektivnost vreća pridnene povlačne mreže ko će izrađenih od 50 milimetarskog romboidnog i 40 milimetarskog kvadratnog oka. Razlika u selektivnosti između dviju navedenih konfiguracija uočena je kod vrsta Nephrops norvegicus, Galeus melastomus i Trisopterus minutus u korist kvadratnog oka. U drugom eksperimentu ispitana je razlika u selektivnosti vreća izrađenih od 40 mm kvadratnog mrežnog tega, sa razli čitim brojem oka u opsegu, gdje je uočeno da se povećanjem opsega smanjuje vrijednost parametra L50 za vrstu Mullus barbatus. Trećim eksperimentom ispitana je selektivnost pridnene povlačne mreže ko će kojoj je u zadnjem segmentu grla postavljena 90 milimetarska selektivna rešetka . Rezultati su pokazali kako se upotrebom selektivne rešetke može smanjiti koli čina prilova u ulovu, bez značajnog gubitka ulova gospodarski važnih vrsta. U četvrtom eksperimentu ispitala se selektivnost pridnene povlačne mreže ko će kojoj je u posljednjem segmentu grla postavljen selektivni panel izrađen od 50 milimetarskog kvadratnog oka. Rezultati su pokazali da prisutnost selektivnog panela, zbog malog broja riba koje su uopće došle u kontakt s njim, nema značajnog efekta na selektivnost testirane mreže. Temel jem dosadašnjih istraživanja selektivnosti pridnene povla čne mreže ko će na Mediteranu, dati su odnosi između selekcijskih parametara (L50, SR) i različitih tehničkih parametara koće za koje je poznato da utječu na selektivnost.The first experiment was set up to investigate selectivity of 40 mm square and 50 mm diamond mesh codend. The difference in selectivity between two indicated configurations was evident for Nephrops norvegicus, Galeus melastomus and Trisopterus minutus, favouring square mesh codend. The second experiment was set up to investigate the effect of changing the codend circumference made up entirely of 40 mm square mesh netting. The negative effect of increasing the codend circumference was evident only in case of Mullus barbatus, where parameter L50 was significantly reduced. Third experiment was set up to investigate the selectivity of trawl with a selective grid of 90 mm bar spacing in front of the size-selective codend made of 50 mm diamond mesh. The presence of grid proved to be good in bycatch reduction, without affecting commercial catches. Fourth experiment was set up to investigate the selectivity of trawl with the selective panel made of 50 mm square mesh, positioned in front of the size-selective codend made of 50 mm diamond mesh. The results showed no significant effect of panel on the overall selectivity. Finally, by critically reviewing existing literature on bottom trawl selectivity, general relationships between selectivity parameters (L50 and SR) and different codend technical parameters known to affect selectivity are given
Underwater visual census cove Martinska transect
No full textKlimatske promjene i antropogeni utjecaj uvelike su narušile stanje morskog ekosustava. Zbog izričite važnosti u globalnim procesima te gospodarstvu općenito nužno je vršiti stalna ispitivanja kako bi utvrdili stanje i što ranije uočili promjene morskog ekosustava. Moguće su različite tehnike ispitivanja i uzorkovanja mora koje dijelimo u tri glavne kategorije: ulovne, neulovne i kombinirane. Mnoge metode mogu biti vrlo destruktivne te je iz tog razloga metoda podvodnog vizualnog cenzusa (Underwater Visual Census - UVC) najčešće korištena metoda koja spada u kategoriju neulovnih metoda. U našem istraživanju u uvali Martinska ispred Zavoda za istraživanje mora i okoliša Instituta Ruđer Bošković provedena je tehnika podvodnog vizualnog cenzusa metodom transekta. Ukupno je determinirano 47 organizama od kojih 14 čine riblje vrste, 22 beskralježnjaci bentosa i 11 vrsta algi. U sva četiri provedena vizualna cenzusa zabilježene su vrste fratar (Diplodus vulgaris), gavun (Atherina hepsetus), pirka (Serranus scriba), glavoč (Gobius auratus) i vučić (Serranus hepatus). Najbrojnija riblja vrsta bila je gavun (Atherina hepsetus), zatim slijedi salpa (Sarpa salpa) i cipli (Chelon auratus, Chelon ramada). Sve tri vrste čine plove. U daljnjim istraživanjima potrebno je provoditi dugoročni monitoring kako bi utvrdili rasprostranjenost, odnosno istražiti interakcije ribljih vrsta sa staništem.Climate change and anthropogenic impact have greatly disrupted the state of the marine ecosystem. Because of their explicit importance in global economic processes, it is generally necessary to conduct ongoing surveys to determine the status and early detection of changes in the marine ecosystem. Different sea testing and sampling techniques are possible, which are divided into three main categories: destructive (using fishing gear), non-destructive and combined methods. Many methods can be very destructive, for these reasons the underwater visual census (UVC) method is the most used method that falls into the category of non-destructive methods. In our research in the Martinska Bay in front of the Department for Marine and Environmental Research of the Ruđer Bošković Institute, the underwater visual census technique was chosen using the transect method. A total of 47 organisms were identified, of which 14 are fish species, 22 invertebrates and 11 algae. In all four conducted visual censuses, the species common two-banded seabream (Diplodus vulgaris), Mediterranean sand smelt (Atherina hepsetus), painted comber (Serranus scriba), golden goby (Gobius auratus) and brown comber (Serranus hepatus) were recorded. The most numerous fish species was Mediterranean sand smelt (Atherina hepsetus), followed by the salema porgy (Sarpa salpa) and the mullets (Chelon auratus, Chelon ramada). All three species make schools. In further research, it is necessary to perform long-term monitoring to determine the distribution and to investigate the interactions of fish species with the habitat
Fishing boats for hunting small and large blue fish
No full textU ovom završenom radu govori se o raznolikosti brodova za lov male i krupne plave ribe. U tu grupu plovila spadaju parangalaši, koćari i plivaričari pri čemu je poseban naglasak stavljen na karakteristike plivaričara. Ulov plivaričara čini oko 25% svjetskog ulova plave ribe. Plivaričari mogu osigurati veliki ulov na jedinici ribolovnog napora i minimalnu potrošnju goriva po toni ulovljene ribe. Ovisno o rasporedu palubno – ribolovne opreme izdvajaju se različiti tipovi plivaričara: plivaričar sjeverno – američkog tipa, plivaričar tunolovac, plivaričar europskog tipa, plivaričar – koćar i plivaričar sa bubnjem. Plivaričar tunolovac cilja tunu i njene srodnike, dok se ostali plivaričari bave lovom male plave ribe kao što su srdela i inćun. Način pronalaska jata plivaričare čini drugačijim od ostalih ribolovnih brodova jer koriste sonare.In this thesis, we talk about the variety of boats for fishing small and large pelagic fish. This group of vessels includes longliners, trawlers and purse seiner, while the primary focus in this thesis is on purse seiners.. The catch of purse seiners accounts for about 25% of the world´s catch of the fish. Purse seiners can ensure a large catch per unit fishing effort and minimum fuel consumption per ton of fish caught. Depending on the arrangement of deck-fishing equipment, different types of purse seiners are distinguished: north-American type, tuna purse seiner, purse seiner of the European type, purse seiner – trawler and purse seiner with drum. Tuna purse seiner targets tuna and species similar to tuna, while other boat are engaged in hunting small pelagic fish such as sardines and anchovies. Method of finding fish stocks is what makes purse seines different from other fishing boats as they use sonar
Fishing boats for hunting small and large blue fish
No full textU ovom završenom radu govori se o raznolikosti brodova za lov male i krupne plave ribe. U tu grupu plovila spadaju parangalaši, koćari i plivaričari pri čemu je poseban naglasak stavljen na karakteristike plivaričara. Ulov plivaričara čini oko 25% svjetskog ulova plave ribe. Plivaričari mogu osigurati veliki ulov na jedinici ribolovnog napora i minimalnu potrošnju goriva po toni ulovljene ribe. Ovisno o rasporedu palubno – ribolovne opreme izdvajaju se različiti tipovi plivaričara: plivaričar sjeverno – američkog tipa, plivaričar tunolovac, plivaričar europskog tipa, plivaričar – koćar i plivaričar sa bubnjem. Plivaričar tunolovac cilja tunu i njene srodnike, dok se ostali plivaričari bave lovom male plave ribe kao što su srdela i inćun. Način pronalaska jata plivaričare čini drugačijim od ostalih ribolovnih brodova jer koriste sonare.In this thesis, we talk about the variety of boats for fishing small and large pelagic fish. This group of vessels includes longliners, trawlers and purse seiner, while the primary focus in this thesis is on purse seiners.. The catch of purse seiners accounts for about 25% of the world´s catch of the fish. Purse seiners can ensure a large catch per unit fishing effort and minimum fuel consumption per ton of fish caught. Depending on the arrangement of deck-fishing equipment, different types of purse seiners are distinguished: north-American type, tuna purse seiner, purse seiner of the European type, purse seiner – trawler and purse seiner with drum. Tuna purse seiner targets tuna and species similar to tuna, while other boat are engaged in hunting small pelagic fish such as sardines and anchovies. Method of finding fish stocks is what makes purse seines different from other fishing boats as they use sonar
Structure of fish communities on vertical coralligenous habitats in the Hvar channel
No full textOva disertacija se sastoji od pet objedinjenih radova i zasniva se na istraživanjima ribljih naselja na podvodnim vertikalnim koraligenim grebenima tehnikom podvodnog vizualnog cenzusa (metoda kvadrata i metoda transekta) i ulovnim neribolovnim tehnikama. Podaci su se prikupljali na četiri lokacije u Hvarskom kanalu tijekom razdoblja od pet godina. Najveća dubina ronjenja prilikom istraživanja je bila 65 m, a uz korištenje tehnike dubokih dekompresijskih zastanaka osim komprimiranog zraka za disanje korišteni su i Nitrox50 i Trimix mješavine plinova. Prvi rad obuhvaća kvantitativno uzorkovanje metodom kvadrata od površine do 45 m dubine te je prikupljeno 220 kriptobentoskih i 61 epibentoska jedinki. Kriptobentoskim naseljima riba dominirala je obitelj glavoča, kako po biološkoj raznolikosti (> 60% svih vrsta) tako i po brojnosti (> 90% svih primjeraka). Vrste koje su se ranije smatrale rijetkim bile su prisutne, neke čak i brojne u ovom istraţivanju. Drugi rad opisuje prvi put korištenu kvantitativnu metodu uzorkovanja za duboku kriptobentosku i epibentosku ihtiofaunu pomoću Trimix mješavina plinova koja je provedena na dubini od 57 do 62 m. Prikupljeno je 16 primjeraka iz četiri vrste riba, tj. tri vrste glavoča i jedna babica. Dvije od sakupljenih vrsta, Thorogobius macrolepis i Vanneaugobius dollfusi su do tada smatrane rijetkima, usljed veoma malo zabiljeţenih nalaza u svijetu. U trećem radu testirane su dnevne razlike u sastavu naselja epibentoskih i kriptobentoskih riba. Ukupno je zabiljeţeno 27 kriptobentoskih i epibentoskih vrsta riba. Kombinirani rezultati sugeriraju da su kriptobentoska riblja naselja većinom sastavljena od stalnih stanovnika skrivenih prostora s veoma malim dnevnim promjenama. Četvrti rad opisuje novu metodu podvodnog vizualnog cenzusa prikladnu za dublje vertikalne podvodne grebene.
Nazvana je Deep Vertical Transect (DVT) i rađena je na dubinama od površine mora do 50 m. U istraživanju je ukupno zabilježena 51 vrsta riba, pri čemu je 41 vrsta kategorizirana kao stalni stanovnik koraligenog grebena, dok se 10 vrsta smatra povremenim stanovnicima. U transektima ispod termokline opaţen je najmanji broj vrsta što ukazuje na temperaturu kao jedan od najvažnijih parametara koji utječe na dubinsku raspodjelu ribljih naselja u ljetnom razdoblju. Peti rad opisuje metodu podvodnog vizualnog cenzusa zasnovanu na korištenju transekta te podvodnog skutera uz uporabu ronilačkih aparata zatvorenog kruga disanja. Tri varijable okoliša, dubina, životinjski pokrov i istočni položaj grebena, identificirane su kao vrlo značajne za pojavljivanje vrsta, ali značajne varijable bile su i nagib, morsko dno s pukotinama i šupljinama (prostorna heterogenost) te podloga s više ili manje glatkom površinom.This dissertation consists of 5 combined papers and is based on research of fish communities on underwater vertical coralligenous reefs using the underwater visual census technique (square method and vertical transect method) and catching non - fishing techniques. Data were collected at 4 locations in the Hvar Channel over a five years period. The maximum diving depth during the research was 65 m, and with the use of the technique of deep decompression stops, in addition to compressed breathing air, Nitrox50 and Trimix gas mixtures were also used. The first paper includes quantitative sampling by the method of squares from the surface to a depth of 45 m, and 220 cryptobenthic and 61 epibenthic individuals were collected. Cryptobenthic fish communities were dominated by the gobiid family, both in terms of biological diversity (> 60% of all species) and in terms of abundance (> 90% of all samples). Species previously considered as rare were present, some of them even numerous in this locality. The second paper describes the first-used quantitative sampling method for deep cryptobenthic and epibenthic ichthyofauna using Trimix gas mixtures conducted at a depth of 57 to 62 m. Two of the collected species, Thorogobius macrolepis and Vanneaugobius dollfusi, were previusly considered rare in the Mediteranean, due to the very few reported records. In the third paper, daily differences in the composition of cryptobenthic and epibenthic fish populations were tested. A total of 27 cryptobenthic and epibenthic fish species were recorded. The results suggest that cryptobenthic fish settlements are mostly composed of permanent residents with very little daily change. The fourth paper describes a new method of underwater visual census suitable for deeper vertical underwater reefs. We named it as Deep Vertical Transect (DVT) and we performed it at depths of up to 50 m. The study recorded a total of 51 fish species, with 41 species categorized as permanent inhabitant of the coralligenous reef, while 10 species are considered occasional residents. In the transects below the thermocline, the smallest number of species was observed, which indicates temperature as one of the most important parameters influencing the depth distribution of fish settlements in the summer period. The fifth paper describes the method of underwater visual census based on the use of a transect and an underwater scooter with the use of closed-circuit diving apparatus - CCR rebreather. Three environmental variables, depth, zoocover and eastern reef position, were identified as very significant for species occurrence, but significant variables were also slope, seabed with cracks and cavities, and substrate with more or less smooth surface
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
Dužinsko-maseni odnos pedeset litoralnih i obalnih riba u istočnom Jadranu
Full text linkThe length–weight relationship parameters are reported for the fifty littoral and coastal marine fish species from the Eastern Adriatic. Captures were made between the years 2004 and 2017 during sport fishing competitions. The parameters a and b of the equation W = aLb were estimated. The b values ranged from 2.1972 for Spicara smaris (Linnaeus, 1758) to 3.7044 for Salaria pavo (Risso, 1810). The L-W relation for Scyliorhinus stellaris (Linnaeus, 1758), Gobius bucchichi Steindachner 1870, Gobius geniporus Valenciennes 1837 and Lipophrys trigloides (Valenciennes, 1836) are not available in FishBase and presents new data for these species. For some other species, such as Labrus mixtus Linnaeus 1758, there are only two relationships, but none from the Mediterranean, for Gobius paganellus Linnaeus 1758 only four relationships and none from Central and Eastern Mediterranean, while for Labrus merula Linnaeus 1758, Symphodus mediterraneus (Linnaeus, 1758), Symphodus roissali (Risso, 1810), Gobius cobitis Pallas 1814, Gobius cruentatus Gmelin 1789, Gobius niger Linnaeus 1758, Parablennius gatorugine (Linnaeus, 1758), Parablennius sanguinolentus (Pallas, 1814), Salaria pavo (Risso, 1810), and Bothus podas (Delaroche, 1809) very low number of relationships are presented and none from the Adriatic Sea.Parametri dužinsko-masenog odnosa su prijavljeni za 50 litoralnih i obalnih rba iz istočnog Jadrana. Svi primjerci su ulovljeni u periodu 2004-2017 za vrijeme natjecanja u sportskom ribolovu. Parameteri a i b od jednadžbe W = aLb su prezentirani. Vrijednosti b parametra su varirale od2.1972za Spicara smaris (Linnaeus, 1758) do3.7044 za Salaria pavo (Risso, 1810). Dužinsko-maseni odnosi za Scyliorhinus stellaris (Linnaeus, 1758), Gobius bucchichi Steindachner 1870, Gobius geniporus Valenciennes 1837 i Lipophrys trigloides (Valenciennes, 1836) dosad nisu bili dostupni u FishBase. Za neke druge vrste, primjerice Labrus mixtus Linnaeus 1758, postoje samo dva prijavljena odnosa, pri čemu niti jedan nije iz Mediterana, za Gobius paganellus Linnaeus 1758 postoje samo 4 odnosa i nijedan iz središnjeg i istočnog Mediterana, dok za Labrus merula Linnaeus 1758, Sym-phodus mediterraneus (Linnaeus, 1758), Symphodus roissali (Risso, 1810), Gobius cobitis Pallas 1814, Gobius cruentatus Gmelin 1789, Gobius niger Linnaeus 1758, Parablennius gatorugine (Linnaeus, 1758), Parablennius sanguinolentus (Pallas, 1814), Salaria pavo (Risso, 1810) i Bothus podas (Delaroche, 1809) postoji veoma mali broj dužinsko-masenih odnosa, pri čemu niti jedan nije prijavljen za Jadransko more, osim za T. radiates
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
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