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The Razim Lake is a great part of the Danube Delta Biosphere Reserve (DDBR), with a surface of 54,000 ha. Fish fauna from Razim lake include pike-perch (Sander lucioperca) as one of the main top predators of fish community, however ecological significance indicates accessory species, recedent as dominance, sometimes been subrecedent species like in 2011 and 2012 sampling, but constant species regarding frequency in sampling. Otherwise, pike-perch is an important value DDBR fishery species with an average of 5% in total catch, range 2-10%, from what Razim lake contributes with average 71%, range 41-95% in the 1960-2015 period. Razim Lake has been in average 13%, range 1-40% from total Razim lake catch, in the same period of time. Since in RBDD has been fishing up to 2000 fisherman, in Razim lake activated up to 500 fishermen, however nowadays number of fishermen was regulated at lower range. Catch data series shows a continuous stock decline trend, considered to be a consequences of habitat degradation and over-exploitation. Fish stock estimation in last 15 years (2001-2016) support the hypothesis of over-exploitation. Based on length frequency structure of landings, the growth and exploitation parameters have been estimated as well as the average biomass and the maximum sustainable yields for the Razim lake pike-perch stock. Recommendation concerning fisheries management towards sustainable fishing of pike-perch stock, as increasing of cod-end seine mesh size and decreasing of fishing effort regulation are outlined.

The genus Alosa is present only in the northern hemisphere of the earth with four species living in North America and others five in Europe, from which Pontic shad (Alosa immaculata) is subject of present study. Migration of shad depends of the environmental drivers such as increasing spring water temperature and river flooding. In 2016, both factors favoured an earlier start of shad migration in February with peak of spawning run in April, and ended in mid of May. Afterwards the size of catches and market demands no longer motivated fishermen to fish and sell Pontic shads. The 2016 catch of 386 t fitted in the multiannual 10-11 years cyclical catches. Reproduction success was estimated by Larval Abundance Index (LAI) standardized as Catch per Unit Effort (CPUE) by number of larvae per 100 m3 filtered water volume. Relative abundance of drifting larvae in 2016 compared with other 6 previously years showed that average LAI varied widely (2-1,252 larvae per 100 m3) with an average of 84 larvae/100 m3 which was ranked in regular reproductive success.

Danube shad is a fish with high economic and socio-cultural value for the human communities established in the Danubian-Pontic space. In Romania, shad fishery has a market value of about 1.5 million euro, with average annual catches of 200-500 tonnes. Biological material was collected during research surveys organized along the Black Sea coast, in 2012-2013, in spring season (March, April), summer (June, July) and autumn (September). Experimental fishing was done with fishing gillnets. Demographic structure of Alosa immaculata consists of generations of 2-5 years, dominated by generations of 3 to 4 years. The aim of this paper is to provide recent data regarding Alosa immaculata population along the Black Sea Coast considering that its biology is less known.

The Danube Delta is one of Earth's biodiversity hotspots and includes many endemic, rare, and important species of both major conservation and economic value. This unique complex of ecosystems also plays a key role for Danube River and Black Sea fish fauna through its role as a natural safe buffer, shelter, feeding, reproduction, and smooth transitional area for a large number of fish species. Climate change is inducing a progressive sea level rise in the Black Sea, a fact that is expected to impact the delta's key complex and dynamic habitats, biocoenoses, and associated biota, and last but not least the key taxonomic group, namely, fish. Around one-third of the fish species of this delta will be greatly affected, sometimes negatively, by this climate change scenario, another one-third to a lesser extent, and the final one-third not at all. The ecological positive feedback of fish can stimulate environmental change and is expected to be responsible for changes within Danube Delta ecosystems, and also for the near Danube River and Black Sea diverse matrix of aquatic and semi-aquatic ecosystems. Sea level rise in the Black Sea is considered to have been one of the main stress factors of the Danube Delta fish fauna in the past, and is likely to be the case in the future. In this spatio-temporal dynamic context, for the fish species under threat and risk, in situ-adapted management measures are highly required. The current work brings for the first time such a prospective knowledge about the potential impact on Danube River–Danube Delta–Black Sea coast fish diversity in the potential climate change–sea level rise scenario. [ABSTRACT FROM AUTHOR]

The investigation aimed to find out local knowledge on biodiversity conservation through sustainable use and the willingness of the local community Sfântu Gheorghe, Danube Delta, to be involved in the decision making process regarding the sustainable use of the natural resources. In obtaining the necessary information, structuredinterviews and focus group were conducted with the local population and stakeholders in order to achieve a clearer picture of all aspects of sustainable use of natural resources within the area. The results highlighted the unwillingness of local people to exploit the alternative natural resources, other than fish, available in the area and the lack of a strategy to inform and support the local community to realize projects pursuing the recovery of these resources.

The real figure of fish fauna and fishery of the Danube delta is difficult to be estimated due to the limitation in fish sampling and underreporting of catch. This paper proposes to compare output of fish sampling with commercial catch statistics. Fish fauna from Danube delta complex lakes was sampled in 2006-2008 period and catchstatistics represent a long time series data recording. For fish sampling was used two complementary methods: electric fishing for shallow border zone and Nordic gillnet fishing for deep open water. The frequency of occurrence and the dominance in abundance analysis was based on 267 samples including 57158 individuals from both sampling methods since the dominance in biomass was based on 640 kg of fish only from gillnet sampling. In total was sampled 40 fish species, while catch statistics recorded 10 commercial species plus more 3 categories that include more other different species. In the sampling analysis, the most frequent species (very frequent) were perch, bleak, roach, rudd and white bream. The most abundant(eudominant and dominant) species were bleak, roach, rudd, perch, and white bream. In biomass dominate (eudominant and dominant) roach, rudd, perch, white bream, bleak, gibel carp and pike. This analysis shows that Danube delta lakes are dominate by small eurytopic and opportunistic species, favoured by eutrophication of lakes. However, this figure is expression of sampling methods that are limited in estimation of real fish population status. Nevertheless, when this structure is compared to commercial statistics, it is noticed completely other figure. The difference in fish structure may be explained by targeting fishing to large size and high market value fish species. It is not neglected that commercial statistics is deformed by unreported catch sold on black market. According with recorded statistics from 1920 until 2010 the catch trend continuously decrease and species composition was well balanced before 1972 and starting from 1972 until 2010, gibel carp become the dominant commercial species, followed by roach + rudd and bream + white bream. Since, fish estimation based on sampling gives valuable data on actual status of fish structure, catch statistics describe fish evolution and changes in time due to environmental pressure, both analyses are valuable tools in sustainable management of fish resources and for promoting conservation of fish diversity inDanube delta.

Ichthyofauna from Matita-Merhei and Rosu-Puiu lake-complexes was studied in 2008, using two complementary methods of sampling: electric fishing for shallow border zone and gillnet fishing for deep open water. The paper presents the actual status of the fish communities for two lake-complex from Danube Delta (Romania). InMatita-Merhei lake-complex were captured 31 fish species (3 exotic species and 28 native species). For this complex the most abundant fish species are: Alburnus alburnus, Rhodeus amarus, Rutilus rutilus, Scardinius erythrophthalmus, Perca fluviatilis and Carassius gibelio with differences depending on the sampling methods. In Rosu-Puiu lake-complex were caught 31 fish species, with 4 exotic and 27 native. In this complex the most abundant fish species are Alburnus alburnus, Rutilus rutilus, Rhodeus amarus, Perca fluviatilis, Scardinius erythrophthalmus, Blicca bjoerkna and Gymnocephalus cernuus, with differences depending on the sampling methods. The largest biomass percentage had Carassius gibelio and Blicca bjoerkna for both complexes, but with differences depending on the sampling methods. The biodiversity indices show stable ecosystems and stable ichthyocoenosis, little a more bit stable nerby the shoreline than open water.

The study of ichthyofauna from riverine delta, two lakes complexes Gorgova-Uzlina and Sontea- Furtuna was sampled in September 2007, using two complementary methods of sampling: electric fishing forshoreline and Nordic gillnet fishing for open water. Rich species of ichthyofauna from Gorgova-Uzlina is 29 species, with 3 exotic and 26 native species, but in Sontea-Furtuna are 30 fish species, 5 exotic species and 25 native species. The most abundant fish species are Rhodeus amarus (bitterling), Alburnus alburnus (bleak), Carassius gibelio (gibel carp), Perca fluviatilis (perch) Rutilus rutilus (roach) and Scardinius erythrophthalmus (rudd) with slight differences for two complexes and for those two complementary methods of sampling. In biomass are dominating Carassius gibelio, Esox lucius (pike) Cyprinus carpio (carp) and Perca fluviatilis with slight differences for two complexes and for those two complementary methods of sampling. The lakes complexes has a very stableecosystem regarding fish fauna, with shoreline (0,683 equitability indices in Gorgova-Uzlina respectively 0.562 in Sontea-Furtuna) more stables than open water (0,605 equitability indices in Gorgova-Uzlina respectively 0.496 in Sontea-Furtuna).

aspects of fish communities from Danube delta lakes are related in this work paper. The ichthyofauna from complexes lakes of Danube Delta was studied in 3 years (2003-2005), using twocomplementary methods of sampling: electric fishing and gillnet fishing. The species richness included 34 fish species (1/2 from total are commercial species) in Danube delta lakes: 20 fish species in Somova-Parches complex lakes, 24 species in Sontea-Furtuna, also 24 species in Matita-Merhei, 27 species in Gorgova-Uzlina and 29 species in Rosu-Puiu. Regard to richness fish species we can see that the fish richness increase from top Danube delta to theBlack Sea area. For both methods of fish sampling and in all Danube delta studied lakes, the most abundant species is Alburnus alburnus, following by Rutilus rutilus, Carassius gibelio, Scardinius erythrophthalmus, Rhodeus amarus, Blicca bjoerkna and Perca fluviatilis some of these species having small size in total length. Rare species are Hypophthalmichthyes molitrix, Acipenser stellatus, Vimba vimba and Atherina boyeri. Ecological significance (W):leading species is A. alburnus, follow by characteristic species R. rutilus and accompanying species S. erythrophthalmus, R. amarus and C. gibelio. Majority of fish species are included in associated and accessory species categories and some species are accidentally in Danube delta lakes, like: A. stellatus, V. vimba, H. molitrix and A.boyeri. For whole Danube delta Shannon-Wiener indices are more than1.5 and Evenness indices are more than 0.5 indicated a medium stable unto stable ecosystem, with differences between both sampling methods.

The “Gârla Pasarea” was a former flood plane watercourse in connection with Vedea River discharged in Danube River. The floodplane was embanked for agriculture polder, Vedea River was redirected to discharge direct into Danube River and Gârla Pasarea was cut in several sectors, connected through underground tubes. Fish fauna inventory of Gârla Pasarea was performed in august 2007, using for shallow water backpack electrofisher and deep large water by Nordic gillnets. The species richness includes 15 fish species with a gradient of increasing from upstream to downstream. The most frequent species (very abundant) are two exotic respectively, Pseudorasbora parva and Carassius gibelio that survive in extreme condition. Four species are included in Annexes of Emergency Order of Romanian Govern No.57/2007, concerning regime of natural protected area,conservation of natural habitats and wild flora and fauna, respectively Aspius aspius, Cobitis danubialis (elangoides) and Misgurnus fossilis are included in Annex 3 that need designate of Special Protected Area for conservation (SPA), andProterorhinus marmoratus (semilunaris) is included in Annex 4B, for species of national interest that need strict protection. Recovering and conservation of fish fauna need ecological restoration based on rebuilding of longitudinal connectivity of Gârla Pasarea sectors, reconnect with Vedea River and lateral connectivity of Danube River with it former floodplane.

The study of ichthyofauna from Rosu-Puiu lake-complex was undertaken in May 2005, using two complementary methods of sampling: electric fishing for shoreline and gillnet fishing for deep water zone. Thepaper presents the actual situation of the fish communities from the Rosu-Puiu lake-complex, part of “marine delta” from Danube delta. In this lake-complex there were catched 29 species of fish (5 exotic species and 24 native species. The most abundant fish species are Alburnus alburnus (bleak), Abramis bjoerkna (silver bream),Clupeonella cultriventris (Black Sea sprat), Carassius gibelio (Prussian carp) and Rutilus rutilus (roach) with slight differences for those two complementary methods of sampling. The biodiversity index and equitability indices were calculated per lake and methods.The lake-complex has a stable ecosystem, with shoreline (1.155 Shanon-Wiener index and 0.437 equitability indices) less stables than open water (1.878 Shanon-Wiener index and 0.576 equitability indices).

Ichthyofauna from Matita-Merhei lake-comple was studied in 2005, using two complementary methods of sampling: electric fishing for border zone and gillnet fishing for deep open water zone. The paperpresents the actual situation of the fish communities from the Matita-Merhei lake-complex, part of “fluvial delta” of the Danube delta. In these lake complexes there were catched 24 species of fish (4 exotic species and 20 native species). The most abundant fish species are Alburnus alburnus, Proterorhinus marmoratus, Clupeonella cultriventris and Leucaspius delineatus with differences for those two complementary methods of sampling. The biodiversity index andequitability indicies were calculated per lake and methods. The complex lake has a stable ecosystem, with shoreline(1.604 Shanon-Wiener index and 0.607 equitability indices) much more stable than open water (0.957 Shanon-Wiener index and 0.319 equitability indices).

The average commercial fish catch decreased from about 12000 tons (1967 year), in Danube Delta lakes to around 3000 tons in the last years. In this period piscivorous species like pike, wels catfish, european perch declined and the non-piscivorous species like gibel carp, bream, roach and white bream became dominant. According with the last years state of the fish stocks its estimated that in Danube Delta lakes a sustainable yield of about 6000 tons could be fished. The administration of the stocks on the durable principles and implementation of the correct strategy it decisively depends on the quality data concerning the catch size. The lack or unreliable records led to the underestimation or overestimation of some parameters with negative results about the current state and theexploitation of the stocks. The essential error source in stock estimation of lake Complexes is represented by the unrecorded catches of the legal family subsistence quota, black markets and poaching. The real data is very important for accurate assessment of the fish stock. Improvement of the quality of the catch statistics and monitoring of fishing effort are required for sustainable management of Danube delta fisheries.

The average commercial fish catch decreased from 1,379 tons, in Matita-Merhei complex of lakes and 787 tones in Rosu-Puiu complex of lakes (average catch of 1963-1974 period), to 307 tons, respectively 401 tons average catch of 1992 – 2004 period. In this period piscivorous species like pike, wels catfish, European perch declined and the non-piscivorous species like gibel carp, bream, roach and white bream became dominant. According with the last years state of the fish stocks its estimated that in Rosu-Puiu lakes a sustainable yield of 350 tons could be fished while in Matita – Merhei lakes, approximately 270 tons. The administration of the stocks on the durable principles and implementation of the correct strategy it decisively depends on the quality data concerning the catch size. The lack or unreliable records led to the underestimation or overestimation of some parameters with negative results on the current state and the exploitation of the stocks. The essential error source in stock estimation of both lake complexes is represented by the unrecorded catches of the legal family subsistence quota, black markets and poaching. The real data is very important for accurate assessment of the fish stock. Improvement of the quality of the catch statistics and monitoring of fishing effort are required for sustainable management of Danube delta fisheries.

The aim of this study was to determine the ecological status of fish fauna of Razim Lake under the conditions of the water salinity changing from brackish, almost 70 years ago, into freshwater nowadays. The natural processes of siltation and organic deposits, characteristic of Danube Delta lake complexes, intensified in the last decades and included also Razim Lake. The presently reported study of Razim Lake and the adjacent area was undertaken in 2020 with intention to cover fish fauna collected with three different sampling methods (electrofishing, gillnetting, and seining). For each sampling method, Catch per Unit Effort (CPUE), relative abundance, and biomass were determined, as well as selected ecological parameters to determine ecological status of richness species in the area. Published data included 55 fish species, mainly marine and euryhaline, but in 2020 only 43 species were reported. Also, the species composition shifted from marine ones to freshwater or euryhaline ones. Of those 43 species captured in 2020 from Razim Lake and neighboring areas, 39 were native and four were non-native, including a newcomer, the Chinese sleeper, Perccottus glenii Dybowski, 1877. Few species were migratory, reophilous, or reophilous-stagnophilous which rarely enter Razim Lake, but the majority were limnophilous or stagnophilous-reophilous species. Four species were dominant in terms of the abundance; Blicca bjoerkna (Linnaeus, 1758); Rutilus rutilus (Linnaeus, 1758); Alburnus alburnus (Linnaeus, 1758); and Carassius gibelio (Bloch, 1782). In terms of the biomass the dominants were: Cyprinus carpio Linnaeus, 1758; Carassius gibelio; Sander lucioperca (Linnaeus, 1758); Pelecus cultratus (Linnaeus, 1758); and Blicca bjoerkna. Some differences between sampling methods used were observed. Eudominant, euconstant, and main species were Blicca bjoerkna and the majority of fish species were accessories, with differences amongst sampling methods used. Fish diversity parameters indicate a stable ichthyocoenosis, more stable along the lake shoreline. Ecological indicators of fish fauna from Razim Lake in 2020 grade the water lake quality as a moderate ecological class according to the Water Framework Directive of the European Union. [ABSTRACT FROM AUTHOR]

Researches and analysis of heavy metals concentrations in the fish species exploited as a food source are of great interest due to long term toxic effects on human health even at very low concentrations. Therefore, we have conducted this study in an area of great interest in terms of aquatic biodiversity, but also of tourism and trade. Depending on the degree of toxicity in delta aquatic ichtyofauna, five heavy metals (Cr, Cu, Hg, Ni, Pb) and a metalloid (As) concentrations were measured in the muscle tissue of fifteen commercial value fish species in order to assess their impact on human health. Samples were collected seasonally (twice a year) between 2013-2014 from Somova-Parches aquatic complex (situated near Tulcea - Romania industrial area in predeltaic area) and four representative aquatic complexes for Danube Delta, respectively Sontea-Fortuna, Matita-Merhei, Gorgova-Uzlina and Rosu-Puiu. The determination of elements from collected samples was done differently, mercury was analysed by cold vapor atomic absorption, while the other five elements (arsenic, chromium, copper, nickel and lead) were determined using mass spectrometry with inductively coupled plasma. The investigations of heavy metals revealed interspecific differences, important not only because of each specie particularities and food chain, but also for intraspecific variation caused by geographical location. The statistical analysis of the 4800 measurements in correlation with the analysis of the bioaccumulation factor (BCF) reflected the degree of contamination on the exploited Danube Delta Biosphere Reserve fish resources and also showed an irregular distribution of heavy metals and metalloids depending on anthropogenic pollutants. [ABSTRACT FROM AUTHOR]