The invasion of fish and invertebrate species of Ponto-Caspian origin is in the forefront of fres... more The invasion of fish and invertebrate species of Ponto-Caspian origin is in the forefront of freshwater research due to the extremely fast range expansion of many species and their radical effects on the structure and functioning of ecosystems in their non-native habitat. This study provides the first assessment of the offshore distribution of invasive Ponto-Caspian gobies along the longitudinal profile of the Danube River using the data of the Joint Danube Survey 3 research expedition. Six goby species were collected, the round goby Neogobius melanostomus, the monkey goby N. fluviatilis, the Kessler goby Ponticola kessleri, the racer goby Babka gymnotrachelus, the stellate tadpole-goby Benthophilus stellatus, and the tubenose goby Proterorhinus semilunaris, which showed large differences in their offshore distribution along the river. N. fluviatilis was found for the first time as a new species in Austria, which shows the slow spread of this species upstream in the Danube River or alternatively, its introduction by ships. Offshore trawling confirmed the use of deep channel habitats by gobies, and is suggested as a useful tool for monitoring spatial and temporal trends in the dynamics of invasive benthic species for riverine fish biological research.
The organization of fish assemblages in offshore, deep channel habitats is poorly known in very l... more The organization of fish assemblages in offshore, deep channel habitats is poorly known in very large rivers compared with shoreline, littoral areas. We report on the parameters and testing of an electrified benthic frame trawl (EBFT), developed for monitoring the distribution and abundance of benthic fishes in the Danube River, Hungary. We also compare the results of the benthic main channel survey with a shoreline electrofishing (SE) data set. Altogether 33 species were collected offshore during the 175 trawling paths (500 m long each). Both sample based and individual based rarefaction showed that night time SE detected significantly more species with increasing sampling effort than day time trawling of offshore areas. However, offshore surveys detected sterlet Acipenser ruthenus, which could not be detected by SE, even using extreme high sampling effort. Offshore trawling also proved the common occurrence and high abundance of the strictly protected endemic Danube streber Zingel streber in the river, which proved to be extremely rare in SE catches. The EBFT caught larger/older individuals of many species than SE, and indicated diverse size/age structure for many species offshore. Our survey revealed that offshore areas are intensively used by a variety of species, which occur relatively even, but with variable abundance in the Danube River. We suggest that even a relatively small (i.e. 2 m wide 1 m high) EBFT can be a very useful device for monitoring offshore fish assemblages in very large rivers and provide important data for bioassessment and conservation purposes.
We examined whether gillnetting and hydroacoustics provide comparable relative fish density and f... more We examined whether gillnetting and hydroacoustics provide comparable relative fish density and fish size distribution estimates in the uppermost water layer of a shallow turbid lake and whether the inclusion of environmental and stock parameters could improve comparability of data between different gears. According to gillnetting, most fish shorter than 14 cm in total length were Alburnus alburnus, and most fish longer than 14 cm were Pelecus cultratus. Size distributions and median sizes obtained from gillnetting and acoustics differed. Pure acoustics-derived density estimates accounted for only <8.8% of the variation in the gillnet catch by number and no correlation was found in biomass indices. Most variances observed in the gillnet catch-per-unit-effort data were associated with water transparency, none of the other investigated variables had significant explanatory power. We conclude that the feasibility of establishing a powerful model describing the relationship between fish density estimates of gillnetting and acoustics is low in shallow and turbid habitats, and it might be successful only if the crucial sampling and environmental parameters affecting catch efficiency of gillnets and post-processing of acoustic data are considered. This study cautions again that gillnetting should be used carefully to analyse trends of fish abundance.
Abstract: A food web manipulation experiment was conducted in the small, shallow, eutrophic Lake ... more Abstract: A food web manipulation experiment was conducted in the small, shallow, eutrophic Lake Major, part of the Kis-Balaton Water Protection System (KBWPS) wetland area. Several factors affected the development of turbid water during the fish manipulation period (FMP) ...
Cambridge Journals Online (CJO) is the e-publishing service for over 270 journals published by Ca... more Cambridge Journals Online (CJO) is the e-publishing service for over 270 journals published by Cambridge University Press and is entirely developed and hosted in-house. The platform&amp;amp;#x27;s powerful capacity and reliable performance are maintained by a combination of our own expertise ...
... DOI: 10.1002/iroh.200811090 GERGELY BOROS*, 1, 3, ISTVÁN TÁTRAI 1, ÁGNES IRMA GYÖRGY 1, 2, ÁG... more ... DOI: 10.1002/iroh.200811090 GERGELY BOROS*, 1, 3, ISTVÁN TÁTRAI 1, ÁGNES IRMA GYÖRGY 1, 2, ÁGNES VÁRI 2 and ALEX SÁNDOR NAGY 3 ... SEREDA, JM, JJ HUDSON, WD TAYLOR and E. DEMERS, 2008: Fish as sources and sinks of nutri-ents in
The invasion of fish and invertebrate species of Ponto-Caspian origin is in the forefront of fres... more The invasion of fish and invertebrate species of Ponto-Caspian origin is in the forefront of freshwater research due to the extremely fast range expansion of many species and their radical effects on the structure and functioning of ecosystems in their non-native habitat. This study provides the first assessment of the offshore distribution of invasive Ponto-Caspian gobies along the longitudinal profile of the Danube River using the data of the Joint Danube Survey 3 research expedition. Six goby species were collected, the round goby Neogobius melanostomus, the monkey goby N. fluviatilis, the Kessler goby Ponticola kessleri, the racer goby Babka gymnotrachelus, the stellate tadpole-goby Benthophilus stellatus, and the tubenose goby Proterorhinus semilunaris, which showed large differences in their offshore distribution along the river. N. fluviatilis was found for the first time as a new species in Austria, which shows the slow spread of this species upstream in the Danube River or alternatively, its introduction by ships. Offshore trawling confirmed the use of deep channel habitats by gobies, and is suggested as a useful tool for monitoring spatial and temporal trends in the dynamics of invasive benthic species for riverine fish biological research.
The organization of fish assemblages in offshore, deep channel habitats is poorly known in very l... more The organization of fish assemblages in offshore, deep channel habitats is poorly known in very large rivers compared with shoreline, littoral areas. We report on the parameters and testing of an electrified benthic frame trawl (EBFT), developed for monitoring the distribution and abundance of benthic fishes in the Danube River, Hungary. We also compare the results of the benthic main channel survey with a shoreline electrofishing (SE) data set. Altogether 33 species were collected offshore during the 175 trawling paths (500 m long each). Both sample based and individual based rarefaction showed that night time SE detected significantly more species with increasing sampling effort than day time trawling of offshore areas. However, offshore surveys detected sterlet Acipenser ruthenus, which could not be detected by SE, even using extreme high sampling effort. Offshore trawling also proved the common occurrence and high abundance of the strictly protected endemic Danube streber Zingel streber in the river, which proved to be extremely rare in SE catches. The EBFT caught larger/older individuals of many species than SE, and indicated diverse size/age structure for many species offshore. Our survey revealed that offshore areas are intensively used by a variety of species, which occur relatively even, but with variable abundance in the Danube River. We suggest that even a relatively small (i.e. 2 m wide 1 m high) EBFT can be a very useful device for monitoring offshore fish assemblages in very large rivers and provide important data for bioassessment and conservation purposes.
We examined whether gillnetting and hydroacoustics provide comparable relative fish density and f... more We examined whether gillnetting and hydroacoustics provide comparable relative fish density and fish size distribution estimates in the uppermost water layer of a shallow turbid lake and whether the inclusion of environmental and stock parameters could improve comparability of data between different gears. According to gillnetting, most fish shorter than 14 cm in total length were Alburnus alburnus, and most fish longer than 14 cm were Pelecus cultratus. Size distributions and median sizes obtained from gillnetting and acoustics differed. Pure acoustics-derived density estimates accounted for only <8.8% of the variation in the gillnet catch by number and no correlation was found in biomass indices. Most variances observed in the gillnet catch-per-unit-effort data were associated with water transparency, none of the other investigated variables had significant explanatory power. We conclude that the feasibility of establishing a powerful model describing the relationship between fish density estimates of gillnetting and acoustics is low in shallow and turbid habitats, and it might be successful only if the crucial sampling and environmental parameters affecting catch efficiency of gillnets and post-processing of acoustic data are considered. This study cautions again that gillnetting should be used carefully to analyse trends of fish abundance.
Abstract: A food web manipulation experiment was conducted in the small, shallow, eutrophic Lake ... more Abstract: A food web manipulation experiment was conducted in the small, shallow, eutrophic Lake Major, part of the Kis-Balaton Water Protection System (KBWPS) wetland area. Several factors affected the development of turbid water during the fish manipulation period (FMP) ...
Cambridge Journals Online (CJO) is the e-publishing service for over 270 journals published by Ca... more Cambridge Journals Online (CJO) is the e-publishing service for over 270 journals published by Cambridge University Press and is entirely developed and hosted in-house. The platform&amp;amp;#x27;s powerful capacity and reliable performance are maintained by a combination of our own expertise ...
... DOI: 10.1002/iroh.200811090 GERGELY BOROS*, 1, 3, ISTVÁN TÁTRAI 1, ÁGNES IRMA GYÖRGY 1, 2, ÁG... more ... DOI: 10.1002/iroh.200811090 GERGELY BOROS*, 1, 3, ISTVÁN TÁTRAI 1, ÁGNES IRMA GYÖRGY 1, 2, ÁGNES VÁRI 2 and ALEX SÁNDOR NAGY 3 ... SEREDA, JM, JJ HUDSON, WD TAYLOR and E. DEMERS, 2008: Fish as sources and sinks of nutri-ents in
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Papers by Ágnes Irma György
research due to the extremely fast range expansion of many species and their radical effects on the structure and
functioning of ecosystems in their non-native habitat. This study provides the first assessment of the offshore distribution
of invasive Ponto-Caspian gobies along the longitudinal profile of the Danube River using the data of the
Joint Danube Survey 3 research expedition. Six goby species were collected, the round goby Neogobius melanostomus,
the monkey goby N. fluviatilis, the Kessler goby Ponticola kessleri, the racer goby Babka gymnotrachelus,
the stellate tadpole-goby Benthophilus stellatus, and the tubenose goby Proterorhinus semilunaris, which showed
large differences in their offshore distribution along the river. N. fluviatilis was found for the first time as a new
species in Austria, which shows the slow spread of this species upstream in the Danube River or alternatively, its
introduction by ships. Offshore trawling confirmed the use of deep channel habitats by gobies, and is suggested
as a useful tool for monitoring spatial and temporal trends in the dynamics of invasive benthic species for riverine
fish biological research.
research due to the extremely fast range expansion of many species and their radical effects on the structure and
functioning of ecosystems in their non-native habitat. This study provides the first assessment of the offshore distribution
of invasive Ponto-Caspian gobies along the longitudinal profile of the Danube River using the data of the
Joint Danube Survey 3 research expedition. Six goby species were collected, the round goby Neogobius melanostomus,
the monkey goby N. fluviatilis, the Kessler goby Ponticola kessleri, the racer goby Babka gymnotrachelus,
the stellate tadpole-goby Benthophilus stellatus, and the tubenose goby Proterorhinus semilunaris, which showed
large differences in their offshore distribution along the river. N. fluviatilis was found for the first time as a new
species in Austria, which shows the slow spread of this species upstream in the Danube River or alternatively, its
introduction by ships. Offshore trawling confirmed the use of deep channel habitats by gobies, and is suggested
as a useful tool for monitoring spatial and temporal trends in the dynamics of invasive benthic species for riverine
fish biological research.