J. Wetlands Biodiversity (2014) 4: 113-120

CHANGES IN SPECIES RATIOS FROM ICHTHYOFAUNA AND STRUCTURE OF THEIR AREAS IN THE PROCESS OF ECOLOGICAL SUCCESSION OF CUCIURGAN RESERVOIR

Marin Usatîi, Oleg Crepis, Adrian Usatîi, Nicolae Șaptefrați, Piotr Dermenji and Nadejda Usatîi

Received: 16.07.2014 / Accepted: 10.11.2014

Abstract: Cuciurgan estuary, before the regulation of its flow, was a part of the ancient estuary of the and served as spawning area and feeding pond for phytophilic fishes of the river (common bream, roach, common carp, European pikeperch, northern pike etc). Construction of the dam contributed to its ecological succession and natural estuary turned into an artificial pond with inlet recycling water supply of MGRES (Moldavian State Regional Electric Station). The purpose of this study was to investigate changes in the ratios of species from ichthyofauna and the structure of their areas in the process of ecological succession in Cuciurgan reservoir.

Keywords: Cuciurgan reservoir, diversity ecosystem, ecological succession, fish, ichthyofauna, population density, storage reservoir, structure areas, thermal and hydrological regimes.

Introduction:1 of the river (common bream, roach, common carp, European pikeperch, northern pike etc). Cuciurgan estuary, before the regulation of In addition, food migration of such rheophils its flow, was a part of the ancient estuary of as beluga, stellate sturgeon, sterlet, herring, the Dniester and served as a spawning area roach, ide, asp, barb, vimba, and feeding pond for the phytophilic fishes common nase has occurred in Cuciurgan estuary. There were 46 species and subspecies of fish belonging to 13 families Marin Usatîi Oleg Crepis prior to the flow regulation in the pond, Adrian Usatîi (Egherman 1926; Zambriborsci 1960; Nicolae Șaptefrați and Cepurnov and Kubrak 1965). The Piotr Dermenji: construction of the dam contributed to its Institute of Zoology ecological succession and the natural estuary Academy of Sciences of turned into an artificial pond with inlet Str. Academiei 1, Chisinau recycling water supply of MGRES MD-2028, Republic of Moldova (Moldavian State Regional Electric Station). e-mail: [email protected] MGRES exploitation has influenced the environmental conditions of Cuciurgan Nadejda Usatîi: High School “Traian” reservoir, further contributed to its ecological Bd. Cuza-Voda 36, Chisinau succession and was accompanied by a MD-2060, Republic of Moldova, change in the number of different fish e-mail: [email protected] ecological groups.

Istros – Museum of Braila 114 J. Wetlands Biodiversity (2014) 4: 113-120

The purpose of this study was to %), chub (0.1 %), vimba, sabre fish, Black investigate the changes in the ratios of Sea roach (single individuals) and others species from ichthyofauna and the structure (Tab. 1, Annexes). Limnophilic species of their areas in the process of ecological population maintained or increased their succession in Cuciurgan reservoir. number - roach (18.3 %), silver bream (11.3 %), crucian carp (9.1 %), perch (11.0 %). Materials and methods: During the weak thermofication of the reservoir in 1969-1970 were observed an Investigations regarding major fish species’ increase in food base for fish, which ratios and their spatial distribution in the contributed to an increase in the population ichthyofauna of Cuciurgan reservoirs were density of such species as bream (14.0 %), conducted in 2012-2013. There was analyzed roach (30.1 %) and smartweed (16.2 %). information from the specialty literature over However, the number of other species many years. A collection of ichthyological dwindled significantly – European pikeperch material was carried out on control fishing (1.0 %), tench (0.2 %), crucian carp (0.2 %), catches using fishing nets of differents sizes pike (0.6 %), common carp (0.1 %). Despite (218 occasion), fish traps and fishing lifts the large amounts of small fish, a reduction (10 occasion) and dragnet for whitebait 40м in the number of predators was observed, (39 occasion) in different parts of the owing to the location of its main spawning reservoir, as well as on catches of fishermen. areas in front of water intakes and for pike The volume of the collected ichthyological due to the modification of the sexual material amounted to 14 thousand product’s quality under the influence of individuals of different species, sex and age. higher temperatures. For 1421 fish individuals there were Changes in the environmental determined the age, gender and linear- conditions, which occurred due to the weighted indices. Ichthyologic analysis of reservoir’s intensive thermofication in 1981- the collected material was performed using 1985, led to a decrease in primary conventional standard methods in bioproduction and had negative influence on ichthyology (Tipovye metodik 1974-1976; the populations of some native fish species. Metodika prognozirovania 1982). The bream population depleted to 2.2 %, Identification of fish species was done using roach - tо 9.3 %, perch - tо 2.2 %. However, determinators (Koblitskaya 1981; Kottelat in general, changes in environmental and Freyhof 2007). Systematics and conditions in Cuciurgan reservoir in a period nomenclature of fishes used in these work of station intense work had positive impact have taxonomic status, which is considered on its ichthyofauna. Rapid water exchange valid at the present stage of ichthyological and increase of the average water research (Bogutschaia and Naseka 2004; temperature contributed to the extension of California Academy of Sciences. the period of intensive growth to 2 months, Ichthyology 2008: inhabitation of the reservoir with new fish www.calacademy.org/research/ichthyology). species (silver carp, bighead, grass carp and black carp) and allowed to form a new ichthyocomplex with high bioproduction. Results and discussion: Silver carp (29.0 %) and bighead (10.0 %) took the leading position in the fish fauna, At the beginning of the exploitation of and accounted for over 90 % from the MGRES (1964-1965), sturgeons disappeared fishery reserve of the pond. Any significant from ichthyofauna and there was a fast change in its ichthyofauna had not been depletion in the population density of observed until mid-90s. Silver carp and reophilus species - asp (0.4 %), ide (0.1 %), bighead (26 %) still dominated by number. herring (0.1 %), nase (0.1 %), minnow (0.1 The number of perch (10.9 %) and gobies

Istros – Museum of Braila J. Wetlands Biodiversity (2014) 4: 113-120 115

(9.1 %) was increased. Other species (roach, (3.7 %) and sunfish (1.6 %) populations bream, silver roach, European pikeperch, increased significantly. pike) showed a tendency to decrease the Currently, regarding fish fauna the number. In the period of 1991-1995 in the highest population density was observed for pond, new invasive noncommercial species – bleak (12.9 %), rudd (11.6 %), perch (9.0 Black Sea silverside appeared. Its population %), crucian carp (8.3 %), belica (7.8 %) and became numerous (14.2 %) due to silver bream (7.1 %). Over the past three euribiontic characteristics and high rate of years the number of sunfish (13.5 %) reproduction. increased significantly and it represents Since the mid-1990s, as a result of serious competition to native species now. MGRES work intensity reduction, in the However, it was a marked tendency to Cuciurgan reservoir occurred disturbance in restore populations of Azov roach (0.7 %), regulation of abiotic and biotic European pikeperch, chub, asp, catfish (0.1 environmental conditions. This led to a % each) and a number of other valuable further reduction in the number of species that indicates the beginning of the commercial fish populations. Vimba, normalization of the reservoir environmental herring, Black Sea roach, sabre fish, crucian conditions. carp, gobio and needlefish, completely According to the purpose of this research disappeared from the catches. Catfish, asp, there were studied particularities of spatial tench, grass carp were found in single copies distribution changes and the structure of the in catches, and populations density of other population ranges of the main species from species such as – silver carp (0.8 %), Azov Cuciurgan reservoir during its ecological roach (0.5 %), bighead (0.3 %), bream, pike, succession. Analysis of the literature showed European pikeperch (0.1 % each) decreased that before the regulation of Cuciurgan significantly. Conversely, silverside (21.2 estuary water flow and in the first years after %), bleak (20.1 %), gobies (16.4 %), perch the construction of the dam, the population (11.7 %) were the most adapted species to areas of major fish species had been changing environmental conditions. uniformly distributed, and the numerical Further changes in thermal and density would vary during the spawning and hydrological regimes of the reservoir in feeding migrations from the Dniester river 2004-2006 led to mass overgrowing of (Yaroshenko 1973; Karlov and Krepis 1988). macrophytes. As a result, there occurred After the start of the active exploitation another ecological succession and the pond of the MGRES, in the reservoir were noted turned into an overgrown lake with poor specific changes in the spatial distribution of water exchange. During this period, there some fish species and the structure of their was observed successful reproduction of pike areas. For example, bream, European (2.1 %), perch (16.9 %), crucian carp (13.2 pikeperch, crucian carp and silver bream %), rudd (13.8 %), tench (2.9 %) concentrated in the middle section, which populations. In catches appeared isolated seems to create for them a more comfortable specimens of rare fish species – herring, environment (Tab. 2, Annexes). mudminnow, sunfish. On the other hand, it However, their ranges still covered the was noted a further decline in populations of entire area of the pond. The numerical roach (1.8 %) and bighead and silver carp density of the common carp and bleak (0.1%). The European pikeperch and Azov increased in the lower section but maintained roach were represented in catches single the same areas structure. Azov roach copies. In 2007-2009, under the influence of migrated in mass from upper to lower changing environmental conditions, section, where there was marked an ichthyofauna has continued its alteration in overwarming and areas of its population the reservoir. The number of sprat (8.0 %), have been reduced to the waters of lower and belica (7.6 %), rudd (17.4 %), common ruff middle sections now. On the other hand,

Istros – Museum of Braila 116 J. Wetlands Biodiversity (2014) 4: 113-120 species such as pike, tench, rudd, south small Currently, the ongoing biomelioration stickleback were focused in the upper work on the reservoir and the improvement portion of the reservoir, although a small of its hydrological regime triggered marked number of these was also observed in other positive changes in the ecological conditions parts of pond. For belica and Acerina rossica of the reservoir. This is evidenced by the were marked an almost complete shift of the increase in concentration in the upper section areas in upper section. of such fish species as pike, tench, common After the reduction of the carp, silver bream, bitterling. Stickleback thermofication’s intensity in 90s, it began the population areas still cover the upper part, redistribution in numerical density of some but it is noted the extension of these to the species due to changed environmental side of the reservoir middle section. Belica conditions. For example, the populations of and Acerina rossica significantly expanded breams and Crucian carp are relatively their areas due to the massive reservoir evenly distributed throughout the water area. overgrowing. The highest number density of Azov roach extended ranges for all water these species is observed in the upper part areas with the largest density in the middle now. Recently there has been established an section of the pond. The highest invasion of the Dniester River with concentration of European pikeperch, noncommercial sunfish, which has high bitterling, silver bream and perch was also adaptive capacity and reproduction intensity, noticed in the middle section. Pike, tench, and which spreads in the pond and becomes, rudd maintained most part of the population though, a massive species harmful for native in the upper portion and have begun to fish fauna. increase the numerical density at other sites. Stickleback area continued to shift towards the upper section, belica and Acerina rossica Conclusions: populations remained stable in the upper part of the pond. During this period, invasive In this work there were studied peculiarities species – Black Sea silverside formed a of changes in the species’ ratios in fish numerous population, which was fauna, as well as their spatial distribution and concentrated in the lower area, but already structure of the areas in the process of began to spread to the middle site. ecological succession of Cuciurgan reservoir. During the reservoir’s mass It was established that after the overgrowing with water plants, organic transformation of Cuciurgan estuary in an water pollution with products of their inlet artificial pond with recycling water decomposition and disturbance of reservoir supply of MGRES from fish fauna sturgeons self-cleaning process, another distribution of disappeared and the number of populations the numerical density of some species and of rheophilous fish species (asp, ide, herring, the structure of their areas was observed. The common nase, chub, vimba, sabre fish and most polluted site was left by most part of Black Sea roach) was reduced. The bream, Azov roach, common carp, which populations of limnophilic species (roach, were focused on other areas. For the same Azov roach, silver bream, crucian carp, reason numerical density of pike, tench, perch) maintained or increased their crucian carp, perch, silver bream, rudd numbers. decreased significantly as a result of their Improvement of food base for fish in migration to the upper and middle zones. conditions of pond weak thermofication The highest adaptive capacity to unfavorable determined an increase in the population environmental changes was proper to South density of bream, Azov roach and roach, but small stickleback, belica and Acerina rossica a number of other species decreased populations, although they have expanded significantly. It was observed a dwindling in their areas for the entire pond. the number of predators, despite the large

Istros – Museum of Braila J. Wetlands Biodiversity (2014) 4: 113-120 117 amounts of small fish. For the European Azov roach, European pikeperch, chub, asp, pikeperch it was due to the location of its catfish and several other valuable species, main spawning areas in front of water indicating that positive changes have intakes and for pike as a result of disturbance occurred in the reservoir ecosystem. of the sexual products’ quality under the It was established that after the influence of elevated temperature. beginning of active MGRES exploitation in Changing environmental conditions had the reservoir occurred specific changes in the a negative impact on populations of some spatial distribution of some fish species and native fish species during the intensive the structure of their areas. For example, thermofication of the reservoir. However, the bream, European pikeperch, crucian carp and rapid water exchange and increase of the silver bream concentrated in the middle part, average water, the temperature contributed to which apparently found a more comfortable the extension of the fishes’ intensive growth environment. Azov roach migrated in mass period and inhabitation of new fish species in from the upper to the lower area of the pond the reservoir. All these allowed to form a which is warmer. Species such as pike, highly productive ichthyocomplex. Bighead tench, rudd, south small stickleback were and silver carp took the leading position a spotted in the upper site of the reservoir. number of individuals from fish fauna and Redistribution of species’ numerical accounted for more than 90 % of the fishery density occurred in the reservoir after the reserve of the pond. reduction of thermofication intensity. For Reduced work intensity of MGRES led example, the populations of bream and to a disturbance in the regulation of abiotic crucian carp are relatively evenly distributed and biotic environmental conditions and to across the pond. Azov roach expanded its major changes in the ichthyofauna of the areas all over the reservoir with the highest pond. Some species occurred in single copies numerical density in the middle section. The (catfish, asp, tench, grass carp), and others – highest number of European pikeperch, had significantly depleted their numbers bitterling, bleak, silver bream and perch was (bighead and silver carp, Azov roach, bream, also observed in the middle stretch. Pike, pike, European pikeperch). The most adapted tench, rudd, while maintaining most of the ones to changing environmental conditions population in the upper stretch, have begun were silverside, bleak, gobies and perch. to increase their numerical density at other As a result of the mass development of sites of the reservoir. macrophytes and filamentous algae, the Bream, Azov roach, common carp left reservoir turned into an overgrown lake with the most polluted upper sector during the poor water exchange. During this period, it mass overgrowing of reservoirs. For the was noted the successful reproduction of same reason there is a significant decrease in pike, perch, Crucian carp and tench the numerical density of pike, tench, crucian populations. The number of sprat, belica, carp, perch, silver bream, rudd. The highest rudd, common ruff and sunfish soared. On adaptive capacity to environmental changes the other hand, it was observed a further showed south small stickleback, belica and decline in the number of roach, European Acerina rossica populations, although they pikeperch and Azov roach. have expanded their areas throughout the Recently the highest populations number entire pond. in ichthyofauna was observed for non-target Currently, as a result of the ongoing (bleak, belica) and low value (rudd, perch, activity on MGRES and the reservoir crucian carp) fish species. Over the past biomelioration works and improvement of three years the number of sunfish (up to 13.5 hydrological regime, there have been marked %) has soared and it is a serious competitor positive changes in the ecological conditions to native species now. However, there was a of the reservoir, as evidenced by the increase trend to an increase in the populations of in concentration of pike, tench, common carp

Istros – Museum of Braila 118 J. Wetlands Biodiversity (2014) 4: 113-120 and others valuable species in the upper California Academy of Sciences. Ichthyology section. (2008): www.calacademy.org/research/ichthyology. CHEPURNOV V.S., KUBRAK I.F. (1965), O Rezumat: proshlom, nastoyaschem i buduschem ihtiofaunyi Kuchurganskogo limana, Materialyi zoolog. soveschaniya, Kishinev: MODIFICĂRI ÎN RAPORTUL Stiinta. SPECIILOR DE PEȘTI ȘI A EGHERMAN F.F. (1926), Materialyi po STRUCTURII ARIILOR LOR DE ihtiofaune Kuchurganskogo limana (basseyn RĂSPÂNDIRE ÎN PROCESUL DE r. Dnestr) po sboram 1922-1925 g.g., Trudyi SUCCESIUNE ECOLOGICĂ A Vseukr. Gos. Chernomorsko-Azovskoy BAZINULUI CUCIURGAN nauchno-prom. opyitnoy stantsii, T.II, vyip.1, S. 473-489. Estuarul Cuciurgan, înainte de regularizare, a KARLOV V.I., KREPIS O.I. (1988), Perestroyka făcut parte din vechiul estuar al râului ihtiofaunyi, raspredelenie i struktura populyatsiy promyislovo-tsennyih vidov, Dniester, servind ca arie de depunere a Bioproduktsionnyie protsessyi v icrelor și de hrănire pentru peștii fitofagi din vodohranilischah – ohladitelyah TES, râu (plătică, babușcă, crap, șalău, știucă etc.). Kishinev: Stiinta, pp. 165-180. Construirea barajului a contribuit la KOBLITSKAYA A.F. (1981), Opredelitel succesiunea ecologică, estuarul molodi presnovodnyih ryib, M.: Nauka, 208 transformându-se într-un lac artificial cu un pp. sistem de alimentare a apei prin recirculare KOTTELAT M., FREYHOF J. (2007), asigurat de SERSM (Stația Electrică Handbook of European freshwater fishes, Regională a Statului Moldova). Scopul Berlin, 646 pp. acestui studiu a fost să investigheze Metodika Prognozirovaniya Vyilova Ryibyi V Ozerah, Rekah I Vodohranilischah (1982), modificările survenite în raportul speciilor de M.: VNIIPRH, 46 pp. pești și a structurilor ariilor lor de răspândire Tipovyie Metodiki Issledovaniya Produktivnosti în procesul de succesiune ecologică din Vidov Ryib V Predelah Ih Arealov (1974- bazinul acvatic Cuciurgan. 1976), M.: Nauka, T.1 & T.2. YAROSHENKO M.F. (1973), Kuchurganskiy –ohladitel Moldavskoy GRES, References: Kishinev: Stiinta, 208 p. ZAMBRIBORSCI F.S. (1960), Ihtiofauna BOGUTHAIA N.G., NASEKA A.M. (2004), limanov severo-zapadnogo Prichernomorya, Katalog beschelyustnyih i ryib presnyih i Ihtiologicheskaya konferentsii po izucheniyu solonovatyih vod Rossii s nomenklaturnyimi i morskih limanov severo-zapadnoy chasti taksonomicheskimi kommentariyami, Chernogo morya, Tr.1, Kiev: Naukova Moskva: Tovarischestvo nauchnyih izdaniy dumka, pp. 95-103. KMK, 389 p.

Annexes:

Istros – Museum of Braila J. Wetlands Biodiversity (2014) 4: 113-120 119

Table no. 1 Dynamics of fish species ratios changes in the ichthyofauna of Cuciurgan reservoir.

Years 1964- 1969- 1981- 1991- 1997- 2004- 2007- 2012- Fishspecies 1965 1970 1985 1995 2000 2006 2009 2013 Black Sea herring 0.1 - si - - si - - Danubeshad 0.5 si - 0.7 0.1 0.1 0.2 0.2 Sprat 3.5 0.6 - 0.5 0.1 1 8.0 3.6 Pike 8.5 0.6 0.6 0.2 0.1 2.1 1.2 1.2 Mudminnow - - - - - si si - Roach 18.3 30.1 14.0 5.7 4.0 1.8 1.2 1.3 Azovroach 18.3 30.1 9.3 1.7 0.5 si si 0.7 Black Sea roach si - - - - - si - Dace 0.1 - si si si - 0.1 si Chub 0.1 si 0.2 0.2 0.5 - si 0.1 Ide 0.1 0.1 si si - - - - Acerina rossica ------0.2 0.4 Rudd 3.8 2.4 4.5 6.2 9.7 13.8 17.4 11.6 Asp 0.4 0.1 0.3 0.1 si si si 0.1 Tench 1.9 0.2 si 0.1 si 2.9 1.0 0.7 Belica 2.4 1.8 - si - si 7.6 7.8 Bleak 3.4 6.5 11.0 11.7 20.1 19.2 12.3 12.9 Silverbream 11.3 12.7 14.1 3.9 4.0 2.8 1.9 7.1 Bream 7.4 14.0 2.2 0.8 0.1 0.7 0.9 0.8 Vimba si si si si - - - - Bitterling 5.7 16.2 - 4.0 5.3 7.0 3.4 3.5 Commoncarp 1.9 0.1 si 0.1 0.1 0.5 0.8 0.5 CrucianCarp 0.2 si si si - - - - Prussiancarp 9.1 0.2 1.0 0.9 0.6 13.2 7.7 8.3 Silvercarp - si 29.0 19.5 0.8 0.1 0.3 0.9 Bighead - si 10.0 6.5 0.3 0.1 si 0.1 Grasscarp - - 0.8 0.3 si si 0.1 0.2 Black carp - - si si - - - - Sabre fish si si ------Nase 0.1 si ------Commongobio 0.1 ------Europeanpikeperch 5.3 1.1 0.6 0.2 0.1 si 0.1 0.1 Perch 11.0 10.3 2.2 10.9 11.7 16.9 15.8 9.0 Commonruff 0.2 si - - si 0.2 3.7 2.5 Gobies 4.2 2.5 - 9.1 16.4 6.9 5.8 5.3 Roundgoby - - - 3.5 5.2 3.5 1.5 1.2 Monkeygoby - - - 3.1 7.8 2.0 3.6 2.0 Goadgoby - - - 2.0 2.8 0.8 0.5 0.9 Mushroomgoby - - - 0.2 0.4 0.5 si 0.7 Tube-nosedgoby - - - 0.3 0.3 0.1 0.2 0.5 Bighead goby - - - si si si si si Bighead nude ------si Gobio caspiosoma - si si si si si - si Gobio of knipovich ------si si Catfish - si 0.2 0.1 si 0.1 si 0.1 Mudfish 0.3 0.1 - si 0.9 0.4 0.3 0.2 Loach si si si si - - - - Stickleback si si si si si 0.1 0.4 0.3 Needlefish 0.1 0.6 - 2.1 2.1 0.6 1.5 0.9 Silverside - - - 14.2 21.2 9.5 5.9 6.8 Sunfish - - - - - si 1.6 13.5

Istros – Museum of Braila 120 J. Wetlands Biodiversity (2014) 4: 113-120

Channel catfish - - - si 0.1 si 0.3 si Note: si-single individuals

Table no. 2 Dynamics of the numerical density in fish populations from different parts of the Cuciurgan reservoir (%).

1981-1982 1991-1992 2001-2003 2011-2013 Fish species us ms ls us ms ls us ms ls us ms ls Bream 33 53 1436 34 30 1 47 52 5 30 55 Azovroach 1 21 78 27 48 25 5 45 50 5 45 50 Pike 80 155 60 12 28 10 40 50 2030 50 Europeanpikeperch 16 52 32 17 53 30 unit unit unit - unit unit Prussiancarp 25 55 16 35 38.5 26.5 10 40 50 10 45 45 Perch 35 20 4532 48 20 10 40 50 1035 55 Tench 70 10 2060 18 22 30 20 50 4515 40 Commoncarp 14 30 56 16 36 48 1 66 33 10 60 30 Rudd 60 13 2750 18 32 15 35 50 1535 50 Silverbream 10 52 38 29.5 42.5 28 5 50 45 15 35 50 Bleak 14 30 56 15 52 33 20 40 40 20 40 40 Bitterling 42 23 35 12 54 34 10 50 40 40 30 30 Stickleback 63 34 3 79 19 2 70 20 10 80 20 0 Silverside 0 0 0 0 5 95 10 40 50 5 55 45 Acerinarossica 100 0 0 100 0 0 95 0 5 40 10 50 Belica 99 1 0 1000 0 80 5 15 2021 59 Sunfish 0 000 0 0 0 0 0 02080 Note: us-the upper section; ms-the middle section; ls-the lower section

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