The backwaters and drainage canals as natural refuges for the lowland rivers fishfauna (Someş, Crişuri, and Mureş Rivers - north-western Romania)

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1 Biharean Biologist (2009) Vol. 3, No.1, Pp.: P-ISSN: , E-ISSN: Article No.: The backwaters and drainage canals as natural refuges for the lowland rivers fishfauna (Someş, Crişuri, and Mureş Rivers - north-western Romania) Ilie C. TELCEAN* and Diana CUPŞA University of Oradea, Faculty of Science, Department of Biology, 1 Universitatii str., , Oradea, Romania * Corresponding author: Telcean, I.C., itelcean@uoradea.ro Abstract. The lowland rivers and adjacent ponds and backwaters represent special habitats and refuges for those fish species that are able to live and spawn in these biotopes. The majority of the fishes caught here are representative for ubiquitous fish category. In the lowland rivers, we define four categories of fishes according to their environmental requirements and biotope. The fish-community from the backwaters comprises approximately 21 fish species, from which 9 species are restricted to these habitats. Among them occur species that belong both to the mainstream fishfauna and to the backwaters. The number of species that usually live in the backwaters is increased in the lower Mures River (29 species) and is decreasing in the Someş and Crişuri Rivers system (22 species), where the riversides are embanked. Some fishes consequently occur in the backwaters and the drainage canals that join the main stream of the river (Carassius gibelio, Carassius carassius, Gobio gobio, G. albipinnatus, Rutilus rutilus Perca fluviatilis and Cobitis elongatoides). The non-native (exotic) fishes that accompany the previous species in these biotopes are Pseudorasbora parva, Lepomis gibbosus and occasionally Ictalurus nebulosus. The juveniles of large sized fishes (Silurus glanis, Esox lucius, Aspius aspius and Sander lucioperca) also occur in the backwaters. The exclusive rheophilic species Zingel zingel, Z. streber and Barbus barbus are not present in these biotopes probably because of the muddy bottoms. The majority of the fishes that live in the lowland rivers use the backwaters, adjacent ponds and canals as natural refuges and optimal biotopes for their spawning. Many typical fishes from the lowland rivers retain their occurrence in these peculiar aquatic biotopes while their population from the proper rivers has registered a numerical decline. This fact is significant to those river stretches that are affected by human activities and have registered a decline in the fish species. Due to the entity of the backwaters, the opportunist large sized Chinese carps Ctenopharyngodon idella Hypophthalmichthys molitrix and Hypophthalmichthys nobilis are increasing their number in the lower Mures. Nearby, the draining canals connected to the rivers have the same significance upon the spreading of many of the species in the lowland rivers. Key words: Fishfauna, lowland rivers, backwaters, drainage canals, ubiquitous fish, natural refuges. Introduction The fish species from the north western Romanian rivers was the subject of multiple studies that were dedicated to the general knowledge of fishfauna and species distribution along these rivers. The first records of fishes refer to the general Transylvanian rivers also including the species from Someş, Crişuri rivers system, and Mureş (Rotarides 1944, Jásfálusi 1941, 1947, Bǎnǎrescu 1954, Bǎnǎrescu et al. 1960). The fishfauna from the Crişuri rivers system (namely Crişul Repede, Crişul Negru and Crişul Alb) was studied by Futó (1942), Müller (1958) and later by Bǎnǎrescu (1953, 1964, 1981) and Bǎnǎrescu et al. (1957, 1959, 1960). More comprehensive data concerning the fishfauna of whole Romania are provided in the monographs of Bǎnǎrescu devoted to the bony fishes (1964) and to the lampreys (1969). Herewith the author makes the taxonomical analysis of fish species and also refers to the fish distribution and frequency. These data are completed by recent investigations that were carried out both on the Romanian and Hungarian sides of the Someş and Crişuri rivers. The results were the subject of several papers (Bǎnǎrescu et al. 1997, 1999, Bǎnǎrescu 2002, Harka 1995, 1997, 1998, 2004a, Telcean & Bǎnǎrescu 2002, Telcean & Cupşa 2007, Wilhelm et al. 2002). The first records of tubenose Protherorhinus marmoratus (P. semilunaris) was done by Harka from the Hungarian stretches of Crişuri Rivers (Hárka 1990, Hárka et al. 2004b). The only recent data concerning the fishfauna of Mureş river was provided by Nalbant (1995) and later Telcean (2001) wrote up about the fish communities from the upper river. The impact of waste waters upon the most common fish species from the lower Mureş was recent studied (Köhler et al. 2007, Triebskorn et al. 2008). There are no data upon the fishaua from the Biharean Biologist, Oradea, Romania, Oradea, Romania

2 38 Telcean, I.C. & Cupşa, D. lowland river and backwaters. The above mentioned studies refer only to the general species distribution, while the significance of the backwaters biotopes concerning the lowland fishfauna diversity remains oversighted. The draining canals and the ponds from the flooding area of the rivers represent optimal habitats for the majority of the lowland fishes. In the last four decades, we have assisted to a strong modification of the river habitats that occurs mainly on the lowland stretches of the rivers. The riversides are levered close to the riverbed and the former river meander was shortened or cut, actions which led to the loss of the majority of riverside standing waters and habitats. Along the lowland Someş, Crişuri and Mureş rivers we identified such backwaters, canals and ponds that are less affected by human activities. Their local biotope differs depending on the river and it determines the diversity of the local fish community. In many such places, we identified some fish species that do not occur in the river main stream. There are no former data regarding the fish associations on these biotopes and their significance related to the lowland fishfauna diversity. According to these scarce data, we intend to put together the outcomes that derive from our investigations. Our purpose is to identify the fish communities from the backwaters, riverside ponds and canals and also to underline the relationship with the mainstream fish population. On the other hand, we try to reveal our conclusions regarding the potential of natural recovering process based on the fish populations from the backwaters and canals' fishfauna in the lowland rivers. Materials and methods The studies were carried out during by repeatedly collecting trips. The aim of these studies were to survey the general fishfauna from the main stream of the rivers from northwestern Romania (Someş, Crişuri and Mureş). It was a good opportunity for us to investigate the fishes from the less studied biotopes like those from the lowland backwaters, draining canals and ponds. The samplings were located as follows: the lowland Someş river 4 sites (downstream the locality Pomi until Satu Mare city); lowland stretch of Crişul Repede river 3 sites (between the localities Sântandrei and Cheresig); lowland Crişul Negru 5 sites (between the localities Tăut and Ant), lowland Crişul Alb 3 sites (between the localities Ineu and Chişneu -Criş) and the Mureş floodplain 4 sites (between the localities Bodrog and Semlac). For the three Criş rivers, the sampling comprises both the canals mouth and backwaters. Supplementary a number of 4 sampling sites were studied on the collector channel of Crişuri (between the localities Tărian and Cefa). The collecting methods were combined using both the fishing nets (mesh size 5mm) and electro-narcosis device (type IUP 12V, 4-10 A, 360W). The electric fishing procedure was according to the CEN directive (EN 14011; CEN, 2003) using pulsed direct current (PDC). The stop nets were not necessary because of the habitats without swift streams. The fish species were identified and recorded directly at the sampling sites and then released. In some cases was used additional information from local competent people and anglers associations. Results A total number of 48 fish species were found in the lowland stretches of the Someş, Crişul Repede, Crişul Negru, Crişul Alb and Mureş rivers. We also included here the species from the canal system that connects the three Crişuri rivers. The species distributions were not the same in all of the studied rivers and also the species occurrence is diversified according to the local biotopes. We define here four categories of fish species distributed relating to their environmental requirements: - Species those are restricted to the main stream of the rivers. These are not present in the backwaters or their presence in these biotopes is incidental. - Species spread both in the main stream and in the backwaters. We consider these ubiquitous fishes having a large distribution in the lowland rivers. - Species those are restricted to the backwaters. In this category, we included the typical inhabitants from slow flowing and still waters. Many of these species frequently occurring in the canals that join the rivers but their presence in the mainstream is incidental. - Species distributed in the ponds and drainage canals. These occur in the shallow waters that can sometimes have dense vegetation. Many of these ponds join the rivers only in the flooding period. In this category are also included the draining canals disjointed by the rivers. The distribution of the fish species according to these categories is as follows: In the lowland Someş River we found a total number of 39 species, amongst them 10 are exclusive inhabitants of the river s mainstream (Tab. 1), 15 species live both in the backwaters and in the main stream of the river, 7 species are restricted in the backwaters and 22 species live in the connected canals and ponds (tab. 2). A special remark is need for those species that live alike in the river s mainstream and the backwaters. It seems that these fishes have a large capacity to acclimatize in various biotopes represented by the running and still waters. The representative species from here are Leuciscus cephalus, Rutius rutilus, Gobio gobio, Rhodeus sericeus Alburnus alburnus and Abramis ballerus. The latter species frequently occurred in moderate flowing

3 The backwaters and drainage canals as natural refuges for the lowland rivers fishfauna (NW Romania) 39 Figure 1. The study area in north-western Romania Table 1. Fish species restricted on the main stream of the Someş, Crişuri and Mureş Rivers. (SOM = Someş River, CR = Crişuri Rivers, MUR = Mureş River, + = present, ++ = numerous, - = absent) Occurrence Current no. Species SOM CR MUR 1 Acipenser ruthenus Chondrostoma nasus Leuciscus leuciscus 4 Alburnoides bipunctatus Vimba vimba Pelecus cultratus Aspius aspius Gobio albipinnatus Gobio kessleri Barbus barbus Sabanejewia balcanica Sabanejewia bulgarica Zingel zingel Zingel streber TOTAL

4 40 Telcean, I.C. & Cupşa, D. Table 2. Fish species and their occurrence in the lowland Someş, Crişuri and Mureş rivers. (SOM = Someş river, CR = Crişuri rivers, MUR = Mureş river, II = main stream and backwaters; III = restricted to backwaters; IV = drainage canals and ponds; + = present, ++ = numerous, - = absent ;? = uncertain). Occurrence Current SOM CR MUR No. Species II III IV II III IV II III IV 1 Esox lucius Umbra krameri Rutilus rutilus Leuciscus cephalus Leuciscus borysthenicus ? 6 Leuciscus idus Scardinius erythrophthalmus Alburnus alburnus Blicca bjöerkna Abramis brama Abramis sapa Abramis ballerus Leucaspius delineatus Rhodeus sericeus Pseudorasbora parva Gobio gobio Cyprinus carpio Carassius carassius Carassius gibelio Tinca tinca Misgurnus fossilis Cobitis elongatoides Silurus glanis Ictalurus nebulosus Ictalurus melas Lota lota Lepomis gibbosus Perca fluviatilis Gymnocephalus cernuus Gymnocephalus baloni Gymnocephalus schraetser Stizostedion (Sander) + lucioperca Stizostedion (Sander)? volgense ? 34 Potherorhinus marmoratus (P. semilunaris) ? TOTAL

5 The backwaters and drainage canals as natural refuges for the lowland rivers fishfauna (NW Romania) 41 waters from the lower Someş. The non-native fishes Pseudorasbora parva, Lepomis gibbosus and Ictalurus nebulosus have proliferated in the backwaters and draining canals. They are however large distributed in the lowland rivers and ponds. Referring to the species that occur only in the main stream of the Someş river and do not reach the backwaters, a special remark is needed upon the rheophilic representatives of the Percidae family. The species Zingel zingel and Gymnocephalus schraetser prefer the running waters with sandy or gravel bottoms from the lowland Someş. The others Gymnocephalus baloni and G. cernuus prefer the muddy bottoms like those from the slowly running stretches of the river, meanders and the backwaters. Accordingly, the species Gymnocephalus baloni was not able to catch in the lower Someş and possibly, it is very rare in the mainstream of the river. Only in a backwater near the locality Pomi was recorded few specimens of Gymnocephalus cernuus. Fishfauna from lowland Crişul Repede, Crişul Negru and Crişul Alb Rivers comprise a number of 46 species including here a number of 12 species, which live in the connected canals that join these rivers in the lowland sector (tab 1 and 2.). Next five species are restricted to the backwaters and canals that connect the river: Blicca bjoerkna, Abramis sapa, Migurnus fossils, Ictalurus nebulosus and Gymnocephalus cernuus. Another four species Tinca tinca, Leucaspius delineatus, Ictalurus melas and Stizostedion (Sander) volgense are restricted in the socalled Collector channel of the Crişuri rivers (tab. 2). The species Stizostedion (Sander) volgense rarely occurred in the Romanian stretches of these rivers. It was recorded first in the Hungarian stretch of the lower Crişuri rivers. Another rare species is the tubenose Potherorhinus marmoratus (P. semilunaris) representative for the Gobiidae family. It is rarely found in the canals from lowland Crişul Repede river and it seems that this species is expanding eastward from Hungary. This fish are not suposed an invader because of its sparseness. The lower stretch of Mureş River comprises a number of 43 fish species. Amongst them, a number of 11 species are restricted to the mainstream of the river and 32 species occur both in the river mainstream and in the backwaters (tab.2). In the river neighboring canals and ponds live many species which are typical inhabitants in the standing waters. Three species of the Abramis genus (A. brama, A.sapa and A. ballerus) and two representatives of Leuciscus genus (L. cephalus and L. idus) occur there. In the Mureş floodplain was recorded (by a single specimen), the species Leuciscus borysthenicus from a channel near the locality Nădlac (Nalbant, 1995). No specimens of this species were find again during the collecting trips. In the last decade, a number of species from the mainstream of Mureş has restored their former abundance. Due to that, many specimens of the Percidae species Zingel zingel and Zingel streber have been collected. In addition, the burbot Lota lota has become more frequent in the lowland river between the localities Pecica and Nădlac. The ponds from the Mureş floodplain are the biotopes in which the crucian carp Carassius carassius maintains his former abundance. Some fishes amongst the southeastern Asian cyprinids Hypophthalmichthys molitrix, H. nobilis and Ctenopharyngodon idella have become frequent in the lower stretch of the Mureş river. They initially escaped from the fishery farms and then expanded in the rivers and canals. Discussions The last studies upon the fishfauna of the rivers Someş, Crişul Repede, Crişul Negru, Crişul Alb and Mureş mention approximately 45 fish species that live in the lowland waters (Nalbant 1995, Bǎnǎrescu et al. 1997, 1999). Except the species that exclusively inhabit the river s mainstream (nine species), the majority of the fishes from the lower rivers occur both in the mainstream and in the neighboring waters (backwaters, meanders, ponds and canals). Frequently, 21 fish species are larger distributed in the lowland rivers. The most representative in these biotopes are Esox lucius, Carassius gibelio, Rutilus rutilus, Leuciscus cephalus, Scardinius erythrophthalmus, Abramis sapa, Blicca bjoerkna, Rhodeus sericeus, Silurus glanis and Perca fluviatilis. Exotic fishes The introduced (exotic) fishes have increased their number in the backwaters and canals: Lepomis gibbosus, Ictalurus nebulosus, Ictalurus melas, Pseudorasbora parva, Ctenopharyngodon idella and Hypophthalmichthys molitrix. The last two species derive from the fishery farms and inhabit the natural waters like the canals and mainstreams of the lower rivers (Bǎnǎrescu et al. 1997, Harka & Sallai 2004). The propagation of these species in the lowland Mureş provides their capacity to spawn in natural conditions. The pumpkinseed fish Lepomis gibbosus is a representative of the Centrarchidae fish family and originates from North America. Bǎnǎrescu (1964) reports this species from the canals in the lower Crisuri drainage area. This species is expanding the area on the rivers mainstream Crişul Repede (Telcean et al. 2007).

6 42 Telcean, I.C. & Cupşa, D. There are some remarks on the other exotic fishes Ictalurus nebulosus and I. melas. Their occurrence in the lowland rivers from northwestern Romania shows more inequality. The spreading of Ictalurus nebulosus is larger than its congener I. melas, which is more frequent in the canals and ponds from the floodplain of Mures and Crisuri. The first records of Ictalurus melas from Romanian freshwaters are relatively recent (Wilhelm, 1998a, 1998b). It seems this species is expanding the area over the lowland rivers and canals on the left side of the Tisa river (Harka & Sallai, 2004). The so-called stone morocco fish Pseudorasbora parva is a small species accidentally introduced together with the juveniles of valuables Chinese carps in 1962 (Bǎnǎrescu, 1964). It is now widely spread in the majority of the natural waters from Romania and Hungary (Harka & Sallai, 2004). The backwaters and rivers neighboring ponds constitute optimal biotopes for this species. Other exotic fishes that are not yet reported from Romanian rivers are: Mylopharyngodon piceus, Ictiobus bubalus, Ictalurus punctatus, Clarias gariepinus, Microptrus salmoides, Percottus glenii and Oreochromis niloticus. The mentions for these species are scarce in the Hungarian rivers and ponds (Harka & Sallai, 2004). Only the African catfish Clarias gariepinus is farmed in several small ponds from the drainage area of Crişul Repede in Romania, but its survival in natural waters was not proved. Rare and endangered fishes One of the most endangered fish species is Umbra krameri an exclusive inhabitant of shallow standing waters and lowland muddy rivulets (see in: Wilhelm 2008). In the Romanian part of the Criş drainage area it is present only in the river Ier (tributary of Barcău river) and in the neighboring canals and ponds in the westernmost area of Romania (Wilhelm 2002, and also see in: Sas et al. 2006). The riverside embankments and moors draining represent his major threats. Other endangered species are Carassius carassius, Tinca tinca and Misgurnus fosslis. These species survive in the lowland canals and the ponds from the Mureş floodplain and several canals from the lowland Crisuri rivers. The crucian carp Carassius carassius, distributed in well-vegetated ponds and canals, was replaced by the most competitive congener species Carassius gibelio during the last decades. The crucian carp Carassius carassius was recently found in large number in the shallow ponds near the locality Bezdin from the Mureş floodplain (Arad County). It seems that Carassius carassius survives only in the neighboring waters from the lowland rivers. The species Tinca tinca is a rare species that lives in standing well-vegetated and clean waters. It was found on the canals connected to the rivers in the lower Crisuri and Mures. The species survives in a moderated number in the so-called Collector canal of Crisuri. During the last decades, this species has registered a numerical decline that pursuant to the water eutrophisation. Another fish species that is under regress is Misgurnus fossilis. Due to the riverbed rectifications and embankments, is drastically reduced the optimal biotope of this species. It survives in the canals and ponds from lowland Crişuri and Mureş, and just in a few backwaters from the lower Someş. Backwaters and canals as natural refuges for the lowland fishfauna The backwaters and neighboring ponds and canals represent optimal biotopes for approximately 21 species that occur both in the river s mainstream and in the backwaters, or are restricted to the backwaters and canals (tab. 2). With the exception of sturgeon species Acipenser ruthenus and Percidae family representatives Zingel streber and Z. Zingel, the majority of the lowland fishes can accommodate in these waters. Even if several fishes do not permanently live in the river meanders and backwaters, they use these habitats for spawning and their juveniles grow here (Telcean et al. 2005). Accordingly, the river neighboring waters are useful natural refuges for the lowland fishfauna. For instance, in the stretches affected by riverbed rectification, meanders cutting or riverside embankments are losing the fishfauna diversity. The species that were formerly frequent on the river mainstream (Leuciscus idus, Scardinius erythrophthalmus, Abramis sapa, A. ballerus, Gymnocephalus schraetser, G. baloni, Gobio albipinnatus, Cobitis elongatoides are accommodated) are now accommodate in the remaining backwaters and canals. Several largely distributed species, which are present along the entire rivers, have also become frequent in these biotopes: Leuciscus cephalus, Rutilus rutilus, Gobio gobio, Alburnus alburnus, Rhodeus sericeus, Carassius gibelio and Perca fluviatilis. This phenomenon has also happened in the river section affected by waste spilling and extraction of mineral aggregates directly on the riverbed. Along all of the studied rivers were identified such of affected stretches. Due to the industrial and urbanization development the human impact increase especially in the lowland rivers. The rivers in the lowland section have a relatively homogeneous biotope along many kilometers so that, the fish communities comprise a constant number of species. If a major ecological change will happen here, it is very harmful for the majority of the fishes that are not able to escape to other river sectors. In

7 The backwaters and drainage canals as natural refuges for the lowland rivers fishfauna (NW Romania) 43 that case, the natural refuges represented by the backwaters and neighboring canals are singular biotopes that allow the species to survive. References Bănărescu, P. (1953): Prezenţa morunaşului (Vimba vimba)în bazinul Crişurilor [Occurrence of the vimba bream (Vimba vimba) in the basin of Crisuri rivers]. Buletinul Institutului de Cercetări Piscicole 12 (4): 73. [in Romanian]. Bănărescu, P. (1954): Contribuţii la cunoaşterea ihtiofaunei României [Contributions to knowledge of the freshwater fish fauna of the Romanian rivers]. Studii si Cercetari Stiintifice, Cluj-Napoca 4 (3-4): [in Romanian]. Bănărescu, P. (1964): Pisces-Osteichthyes. Fauna R.P.R., Vol. 13. Ed. Academiei, Bucharest. [in Romanian]. Bănărescu, P. (1969): Cyclostomata et Chondrichtyes. Fauna R.S.R.,Vol. 12 (1). Ed. Academiei, Bucharest. [in Romanian]. Bănărescu, P. 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