| Sažetak | Invazivni ponto-kaspijski glavoči: riječni glavočić (Neogobius fluviatilis), glavočić okrugljak
(Neogobius melanostomus), keslerov glavočić (Ponticola kessleri) nedavno su uzrokovali
dramatične promjene struktura ribljih zajednica diljem europskih riječnih sustava. Iako je
njihova prisutnost u hrvatskom dijelu dunavskog slijeva primjećena i distribucija izučena,
njihova ishrana, utjecaj na autohtone populacije riba, kondicija, dob i rast, zastupljenost
haplotipova i porijeklo, do sada su bili nepoznati. Analiza sadržaja probavnog trakta
riječnog glavočića (Neogobius fluviatilis) ukazuje da mu je ishrana vrlo raznolika, ali
prevladavaju Trichoptera, Chironomidae, Bivalvia i Odonata. Ishrana mu se u znatnoj
mjeri preklapa s ishranom glavočića okrugljaka (Neogobius melanostomus), kojem u
ishrani prevladava Gastropoda. Mala riba i Gammarus sp. prevladavaju u ishrani
keslerova glavočića (Ponticola kessleri). Usporedba sadržaja probavnog trakta s plijenom
dostupnim u okolini ukazuje da riječni glavočić i glavočić okrugljak preferiraju Trichoptera,
Megaloptera i Coleoptera, a keslerov glavočić Trichoptera, Gammarus sp. i Pisces.
Analize ukazuju na potencijalno pozitivan utjecaj prisustva ponto-kaspijskih glavoča na
neke populacije riba: glavočića okrugljaka i keslerova glavočića na zlatnog vijuna
(Sabanejewia balcanica), riječnog glavočića na šarana (Cyprinus carpio), karasa
(Carassius carassius), manjića (Lota lota) i velikog vijuna (Cobitis elongata). Međutim,
postoje i naznake da keslerov glavočić negativno utječe na klena (Squalius cephalus), a
glavočić okrugljak na malog vretenca (Zingel streber). Pozitivan alometrijski rast utvrđen
je za sve tri analizirane vrste ponto-kaspijskih glavoča upućujući na vremenski duže
prisutne populacije. Kondicijski faktor najveći je za glavočića okrugljaka, a najmanji za
riječnog glavočića. Za riječnog glavočića je utvrđena dob I, II i III, a za glavočića
okrugljaka i keslerova glavočića I, II, III i IV, s tim da najveću brzinu rasta ima riječni
glavočić, a najmanju glavočić okrugljak. Za svaku od analiziranih vrsta ponto-kaspijskih
glavoča utvrđen je jedan crnomorski haplotip. Malen broj haplotipova upućuje na relativno
malobrojne populacije ponto-kaspijskih glavoča što potencijalno smanjuje visinu njihova
invazivnog potencijala u savskom slijevu. |
| Sažetak (engleski) | Invasive Ponto-Caspian gobies have recently caused dramatic changes in fish
assemblage structures throughout the Danube basin. While their presence in the Croatian
part of the basin has been noted and distribution studied, their dietary habits, impact on
native fish communities, condition, age and growth, presence of haplotypes and origin,
until now, have been unknown. In 2011, 17 locations in the Sava River Basin were
sampled for fish and 15 for benthic invertebrates. Fish population monitoring data,
available for nine seasons (2003-2006 and 2010-2014) and 12 locations, were used to
analyse the impacts of Ponto-Caspian gobies on benthic fish abundance. Gut content
analysis indicates that the monkey goby (Neogobius fluviatilis) diet is very diverse, but
dominated by Trichoptera, Chironomidae, Bivalvia and Odonata. The diet overlaps
considerably with the round goby (Neogobius melanostomus) diet, although Gastropoda
are dominant in the latter's diet. Small fish and Gammarus sp. dominate the bighead goby
(Ponticola kessleri) diet. Comparison of gut content with the prey available in the
environment indicates that monkey and round gobies exhibit preference for Trichoptera,
Megaloptera and Coleoptera, and bighead goby for Trichoptera, Gammarus sp. and
Pisces. Ponto-Caspian gobies in the Sava River are spreading upstream, towards the
reaches with lower fish diversity. Analyses indicate potentially positive impacts of PontoCaspian
gobies presence on some fish populations: round and bighead goby on Balkan
golden loach (Sabanejewia balcanica) and monkey goby on common carp (Cyprinus
carpio), crucian carp (Carassius carassius), burbot (Lota lota) and Balkan loach (Cobitis
elongata). However, there are also indications that bighead and round goby could
adversely impact the native chub (Squalius cephalus) and zingel (Zingel streber)
populations, respectively. Positive allometric growth has been determined for all three
analyzed Ponto-Caspian goby species, suggesting that they have been present for a
longer period of time. Condition factor, as a function of available energy resources, is the
largest for the round goby and the lowest for the monkey goby. Age I, II, III have been
determined for the monkey goby and age I, II, III, IV for the round and bighead goby, with
the highest growth rate determined for the monkey goby and the lowest for the round
goby. For each of the analyzed Ponto-Caspian goby species only one haplotype,
originated from native Black Sea populations, has been found. Determined monkey goby
haplotype has also been found in Ukraine and Slovakia and determined round goby
haplotype in Ukraine, Bulgaria, Slovakia, Serbia, Poland and Belgium. Determined
bighead goby haplotype has also been found only in Ukraine. A small number of
haplotypes indicates a relatively small number of Ponto-Caspian goby populations and
potentially reduces their invasive potential in the Sava River Basin. Although the PontoCaspian
goby caused significant disruptions in some areas of the Danube basin, density
of its population and impacts are relatively limited in the Sava River and its tributaries. As
Ponto-Caspian gobies are still in the expansionary period of invasion and the ecosystem
still adapting to new circumstances, continued monitoring of fish population dynamics in
the Sava basin is needed to determine the outcome and impacts of this invasion. |
