The fishfauna of the Crişul Repede river and its threatening major factors

Abstract

The Crişul Repede River is belonging at Cris (Körös) Rivers system which is a tributary on the left shore of Tisa River. In the last decades the fishfaunaofthenaturalwatershasundergoingadeclineinthespeciesnumber.Theothersuccessiveprocessisthefishspeciesreplacement due by the immigration of some exotically fishesandtheretirementofsomeofthenativespecies.The Crişul Repede fishfaunahasregisteredadeclinecausedmainlybytheriverdamming,waterpollutionandeutrophisation.Ondespite of that negative factors the fishesfromtheupperriverwasmaintainlessaffectedunliketotheotherrivers.Thereaftertheeconomical transition and the industries reorganization process were redounded to diminishing the impact of these harmful factors. The former studies about the Cris fishfaunacitedanumberof48nativespeciesand12exoticones.Duringtheresearchtripscarriedoutsince10yearsago (beginning in 1995) was identifiedanumberof40fishspeciesandthepresenceoftheother8 speciesarestilluncertain.Thesturgeonspecies Acipenser ruthenus and the migratory fishAnguillaanguillahaveascarcepresenceandtheycannotbefoundinthelastdecade.A number of 5 exotically fishesarebehavedasremarkableintrudersinnaturalwaters:Pseudorasboraparva,Carassiusauratusgibelio,Ictalurus nebulosus, Ictalurus melas, and Lepomis gibbosus. Some of the exotically fishesalreadyrecordedintheHungarianstretchesofthe Crisuri (Körös) was not recorded in the Romanian section of the river (Mylopharyngodon piceus, Ictiobus bubalus, Ictalurus punctatus, Clarias gariepinus, Micropterus salmoides, Oreochromis niloticus, Perccottus glenii). The pervading of these species is expecting also in the Romanian section of the rivers.The present major threatening factors concerning the fishfaunaarerepresentedbythehabitatchanges.Theriverdammingandtheriverside levees have a negative influenceonthefishfauna.Theformerphenomenonofwaterpollutionitseemsthatisreplacedbythehabitat changes. The dam lakes caused unregulated fluctuationsonthewaterlevelandtemperaturedownstreamofit.Theembankmentforpreventing the floodingwasperformedthroughshorteningtherivermeander.Thelostmeandersoftheriversarerepresentinganoptimalhabitat for fishspawning.

Alien fish, amphibian and reptile species in Romania and their invasive status: a review with new data

“…In Romania it was introduced in aquaculture/ fishponds together with other Asiatic cyprinids (with the intent of making use of the abundant mollusk resource, as it is an eater of mollusks - Manea,1985) but it does not reproduce unassisted here and only persists in culture, in small numbers (Iacob and Petrescu-Mag 2008;Gavriloaie et al 2015). Apparently, it occurs in the Hungarian stretch of the Crișul Repede/Sebes Körös river (Telcean et al 2005;Telcean and Cupșa 2009), however, it is unclear whether it reproduces there. (Richardson, 1846).…”

“…Apparently no longer present in Romania (Gavriloaie and Berkesy 2013). However, it occurs in the Hungarian stretch of the Crișul Repede/Sebes Körös river (Telcean et al 2005;Telcean and Cupșa 2009). Ictiobus cyprinellus (Valenciennes, 1844).…”

“…comm.). Nowadays C. gariepinus occurs in fishponds in the Crișul Repede/Sebes Körös river drainage; it was found in the Hungarian stretch of the same river, but not free-ranging in Romania (Telcean et al 2005); it is doubtful whether it can survive overwinter (especially in harder winters) in European free waters (Piria et al 2019). The similar, south-central African species Clarias ngamensis Castelnau, 1861 was published as a new introduction record after a single specimen was found dead at the edge of a lake in Bucharest, in November 2004 (Gavriloaie and Chișamera 2005).…”

“…(Iacob and Petrescu-Mag 2008). However, there are mentions of O. niloticus in the Hungarian stretch of the Crișul Repede/Sebes Körös river (Telcean et al 2005;Telcean and Cupșa 2009), without indications of overwinter survival or otherwise. Also, there are introduced populations in the Balkans, but these generally take advantage of thermal waters (Piria et al 2017).…”

“…There are no indications of reproduction so far. Also, it occurs in the Hungarian stretch of the Crișul Repede/Sebes Körös river (Telcean et al 2005;Telcean and Cupșa, 2009). (The record of the similar American species Micropterus dolomieu Lacepède, 1802, from a backwater of the Râul Negru in Covasna County (Hegyeli 2007), needs to be confirmed by further research -Hegyeli, Zs., ap.…”