EXOTIC FISH SPECIES ACCLIMATIZED IN HUNGARIAN NATURAL WATERS

J. Tóth
Hungarian Danube Research Station
Alsógöd, Hungary

and

P. Biró
Biological Research Institute, Hungarian Academy of Sciences
Tihany, Hungary

ABSTRACT

Since the turn of this century, altogether 18 fish species have improved the Hungarian Native fish fauna. Nine of them were systematically introduced into Hungarian waters, five species were introduced by chance, and only four elements immigrated from Ponto-Caspian or northern territories. Now about seven exotic species have more or less economic significance. None of them is endemic to the Carpathian Basin.

RESUME

Depuis le début du siècle, 18 espèces de poisson ont amélioré la faune indigèene hongroise. Neuf d'entre elles ont été systématiquement introduites dans les eaux du pays, cinq l'ont été par hasard et quatre seulement ont immigré de la zone du Pont caspien ou des territoires septentrionaux. Environ sept espèces exotiques ont à présent une importance économique plus ou moins grande. Aucune des ces espèces n'est endémique du bassin des Carpathes.

1. INTRODUCTIONS INTO HUNGARIAN WATERS

Hungary (93 000 km²) lies entirely within the River Danube catchment area of 817 000 km². The first more or less planned introductions of exotic fish species into the catchment area took place early this century when bullhead (Ictalurus nebulosus Le Sueur), pumpkinseed (Lepomis gibbosus L.), largemouth bass (Micropterus salmoides Lacepede) and rainbow trout (Salmo gairdneri L.) appeared in rivers and lakes of the Hungarian reaches of the River water regime (Arvai, 1907; Vutskits, 1914; Unger, 1927; Hankó, 1932). After more than half of a century the status of these species is as follows: The pumpkinseed commonly occurs in all suitable waters in Hungary, although it is never excessively abundant. The bullhead has multiplied enormously and occurs in great quantities especially in the side arms of the Körös and Tisza Rivers, as well as in the side arms of the lower reaches of the Danube itself. In these waters it had altered the composition of native fish stocks but since 1970 the stock density of bullhead has decreased significantly. The occurrence of largemouth bass was relatively sporadic. Its occurrence was regularly reported from the River Drava and the side arm of the Danube, forming the border between Hungary and Yugoslavia. Some specimens also occur at the confluence of the Drava and Danube rivers or in adjacent reaches of the Danube. At the beginning of this century, this species was also recorded from Lake Balaton. Nowadays it can be found especially in those permanent ponds between Lake Balaton and the River Drava, which cannot be drained entirely. Here, the stocks maintain themselves with natural propagation. Presently, it is not actively introduced although in the late fifties some 10 000 specimens were bred in fish farms and stocked into the side arm of the Danube at Soroksár, which is utilized exclusively for sport fisheries as well as into the Baja-Beszdan canal close to Yugoslavia. No recaptures have been reported from these latest stockings.

The rainbow trout was introduced into Hungarian waters because its temperature and oxygen requirement appeared more suitable for the stocking of Hungarian lowland and mountain waters than the native brook trout Salmo trutta m. fario L. The occurrence of rainbow trout has since always been connected basically with trout-breeding stations. Specimens inhabiting cold rivulets originate from these stations as due to its very rare natural spawning, there is no self-maintaining stock. In 1975, kamloops trout (S. gairdneri L.) and speckled trout (Salvelinus fontinalis Mitchill) were introduced into the Viszló stream flowing into Lake Balaton (Biró, 1981).

Because the stockings made at the turn of this century resulted in bad experiences, new non-native fish species were not imported into Hungary for a long period. New stockings were only undertaken later when the Soviet and the Romanian scientific literature reviewed the results of introductions of phytophagous fish species from the Far East. These species were then imported into Hungary from China and from the bigger fish-breeding stations of the southern part of the U.S.S.R. during the early sixties. The grass carp (Ctenopharyngodon idella Valenciennes), silver carp (Hypophthalmichthys molitrix Valenciennes) and bighead (Aristichthys nobilis Richardson) became acclimatized exclusively in fish ponds in Hungary (Antalfi and Tölg, 1972). Their introduction into Hungary was preceded by the Romanian one and thus the first appearance of these phytophagous fish species in the Danube catchment area was in Romanian territory where most of the stockings were from fry imported directly from China. The first Hungarian stocking was also made with fry imported from China. Although later stockings were with homogenous fry of one species originating from Soviet fish-breeding stations, the original stocking material imported from China contained large numbers of fry of other species which were introduced by accident. These were, for example, Pseudorasbora parva Schlegel, Megalobrama terminalis Richardson, Parabramis pekinensis Basilewsky as well as Milopharyngodon piceus Richardson, the interested species. Of these species only Pseudorasbora parva now occurs abundantly in ecologically suitable Hungarian waters (Biró, 1972a; Toth, 1970). The other species have apparently not become established. In addition to the above species which were introduced either accidently or intentionally, other species have appeared in Hungarian waters by natural immigration. These are the three-spine stickleback (Gasterosteus aculeatus L.), the goby (Neogobius fluviatilis Pallas) and above all the crucian carp (Carassius auratus gibelio Block) (Holčik and Zitnan, 1978; Holčik, 1980). The threespine stickleback was recorded in relatively small numbers in the Hungarian Danube above Budapest (Botta et al., 1980). Neogobius fluviatilis was found exclusively in Lake Balaton (Biró, 1972) having arrived there by way of the River Danube and Sio Canal. Not one specimen, however, has been caught in the Hungarian section of the Danube River. In both these species a gradual invasion from the lower regions of the Danube is expected. The crucian carp appears in relatively great quantities in all suitable water bodies (Antalfi and Tölg, 1972; Holčik, 1980) but such mass appearances as have been observed in the Danube delta and in the Yugoslavian tributaries have not yet been recorded in Hungary. Because it achieves high densities of stunted fish through uncontrolled reproduction in certain fish ponds and thence gets into various natural waters of the country by migration or by transportation mixed with carp fry, it is highly probable that its stock density will eventually increase significantly in Hungary. In the mid fifties this species was experimentally introduced into a Hungarian lowland fishpond for commercial culture, thus its appearance in Hungarian waters is not only due to natural immigration from the lower Danube basin.

Whitefish species have appeared temporarily in Hungarian waters through the natural connexions of water systesm. Coregonus lavaretus L. and C. peled Gmelin probably escaped from Czechoslovakian fishponds and only few specimens have appeared in Hungary during a short period of time. Vendace (Coregonus albula L.) was stocked in Lake Balaton to exploit offshore zooplankton during the fifties (Ribiánszky and Woynárovich, 1962) but was unable to withstand high summer temperature.

The eel (Anguilla anguilla L.) is a native member of the Hungarian fish fauna albeit very rare, when its occurrence depended on natural migration. During the last two decades, however, since the mass introductions of juveniles caught in West European river estuaries into Lakes Neusiedl and Balaton and other waters with commercial aim, eels often escape and appear in various other Hungarian waters.

Some of the species described can maintain themselves by natural spawning. These are bullhead (Ictalurus nebulosus), pumpkinseed (Lepomis gibbosus), largemouth bass (Micropterus salmoides), rainbow trout (Salmo gairdneri), crucian carp (Carassius auratus gibelio), Pseudorasbora parva, Neogobius fluviatilis and the three-spined stickleback (Gasterosteus aculeatus). There are no confirmed observations concerning the natural spawning of white amur (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix) and bighead (Aristichthys nobilis). The present frequency of occurrence of these species is primarily due to offspring which are produced in great numbers and stocked into fish farms in various parts of the country. Specimens escape from these ponds and establish themselves in most natural waters excepting Balaton, Velence and some other lakes. Their natural propagation under favourable weather conditions cannot be excluded however and it has been observed already on the River Tisza floodplain. Consequently, these species may be present continuously in the waters of the middle Danube basin.

REFERENCES

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Árvai, S., 1907 Amerikai jövevények. Halászat, 9:139–40

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Tóth, J., 1970 Fish fauna list from the Hungarian section of the River Danube. Ann.Univ.Sci.Budap.Rolando Eötvös Nominatse, (Biol.), 12:277–80

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