Title Struktura ribljih naselja na okomitim koraligenim staništima u Hvarskom kanalu Title (english) Structure of fish communities on vertical coralligenous habitats in the Hvar channel Author Igor Glavičić Mentor Alen Soldo (mentor)Mentor Marcelo Kovačić (komentor)Committee member Gorana Jelić Mrčelić (predsjednik povjerenstva)Committee member Damir Valić (član povjerenstva)Committee member Lovrenc Lipej Granter University of Split Defense date and country 2021-02, Croatia Scientific / art field, BIOTECHNICAL SCIENCES Universal decimal classificationUDC ) 59 - Zoology Abstract Ova 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.
Abstract (english) 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.
Keywords
podvodni vizualni cenzus
metoda vertikalnog transekta
metoda kvadrata
riblja naselja
koraligeni grebeni
kriptobentoske vrste
Keywords (english)
underwater visual census
vertical transect method
square method
fish communities
coralligenous reefs
cryptobenthic species
Language croatian URN:NBN urn:nbn:hr:226:382899 Promotion 2021 Study programme Title: Applied Marine Sciences Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2021-05-12 06:48:05
