Evoked bradycardia as response criterion for the detection of electrical stimuli in catfish

Heart rate deceleration (HRD) after exposure to novel stimuli is part of the orienting reflex, and can be used as a tool to investigate the susceptibility of various organisms to sensory stimuli. HRD as response criterion was used in unrestrained catfish, Ameiurus (Ictalurus) nebulosus (Lesueur, 1819) to investigate its susceptibility to electrical stimuli. HRD in catfish occurs after stimulation with light, mechanical stimuli, and electrical stimuli. HRD shows habituation and correlates with stimulus strength. The response to sinusoidal electrical stimuli from 70 to 700 μV/cm p-p was determined in the range from 0.1 to 1000 Hz. Using HRD as response criterion we found that at 85 μV/cm catfish react to stimuli from 0.1 to 3 Hz. In the absence of stimuli, the heart rate develops an ultradian rhythm with periods of 7 to 15 min. About twice a day cardiac arrest of 1 min occurs. During anaesthesia oscillations with a period of about 1 min are recorded. Comparison of this study with others supports the notion that there exist at least two neural channels for processing electrical stimuli. One channel is involved in predation, namely processing the fast potential changes accompanying the passage of a bioelectric dipole; another is involved in processing uniform DC fields used for navigation.

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

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.

The relationship between silver crucian carp (Carassius auratus gibelio bloch) and fish poulations of natural waters

The fisheries management on inland waters is very complicated. Often the unclear propriety rights make the normal management difficult, and other times the stocking of the waters is problematic. In the last hundred years a lot of new fish species have been introduced to Hungary. Lot of them have found their place in the Hungarian fishfauna, till others have caused big problems for the fish farmers, and the anglers too. The biggest problem was caused by the topmouth gudgeon (Pseudorasbora parva Schlegel, 1842) brown bullhead (Ictalurus nebulosus LeSueur, 1819) and the silver crucian carp (Carassius auratus gibelio Bloch, 1782). In this article I show what kind of problems were caused by the silver crucian carp, because it seems that this fish is the most harmful.The damage caused by silver crucian carpposesa complex question. To get into the ponds and rivers, the crucian carps occupy the territory form the native fishspeciesandthesilvercrucian carp competes with these fishes for food, too.The silver crucian carphasa special reproduction method and because of this the speciesis expand rapidly. The silver crucian carp is able to reproduce with other cyprinids, and because the female silver crucian carps are triploids every fingerlings will be silver crucian carp.This fish is a vectorfora lot of diseases, which can easily spread over for other species.

Results of Brown Bullhead Fingerling Rearing in Recirculating Fish Production Systems

Predator fish species are in great demand, both in fish production and consumption. Because of their rarity and perfect meat quality, these species have considerable economical significance and increasing domestic and foreign demand.The brown bullhead (Ictalurus nebulosus) has been in Hungary for more than 100 years, but not popular because of its early maturation rate, aggressive reproduction and slow growth. Despite of these properties, larger specimens (about 150-200 g) are marketable overseas.Our objective is to ensure the adequacy of the brown bullhead in intensive fish farming and its biological, technological and economic references. The pre-experiments were performed at the Bocskai Fishing Co-operative in Hajdúszoboszló, where we reared the juvenile age class. In our university’s recirculating system we examinated the brown bullhead from the fingerling age class.The black bullhead prefers artificial feed, and produces excellent growth parameters and a specific feed-live weight conversation ratio.

New Possibilities of Brown Bullhead (Ictalurus nebulosus) Farming

The brown bullhead (Ictalurus nebulosus) has been settled in Europe at the end of Century XIX from North America. In Hungary it has been brought in 1902. The naturalization of this species was successful because the brown bullhead found adequate conditions for its life and reproduction in Hungary. But it was unsuccessful because lost its excellent growth.In inland water habitats-and that’s why also fishponds-extraordinarily multiplied, but because of its slight growth this species is undesirable for the native farmers. The brown bullhead is concurrent for domestic fish species, on the other hand its weight not more than 150-200 g. Occasionally it was exterminated, but multiplied again and again.In 1999 we placed out black bullhead offspring in a pool of a new intensive fish farm, in order to breed at least 300-350 g weight for the customers. The accidental trial was surprisingly successful. Consequently, the black bullhead prefers the artificial food, and produces excellent growth parameters and specific feed-live weight conversation ratio.On the 20th of September 1999 there was placed 23 300 pieces of brown bullhead offspring, with 28 g average weight and 625 kg gross weight. When we sold them on the 22nd of February 2000, the gross weight was 3387 and the live weight gain was 2735 kg. The gross weight of the feed was 3041,8 kg, and the feed-live weight conversation ratio was 1,11 kg/kg.Because of this successful trial the managers of the farm wanted to start systematic experiments to work out the details of the intensive farming of brown bullhead. We undertook to help to find the right place of the species in the Hungarian fish processing because of the increasing native and foreign demand.

Dermal Melanoma with Schwannoma-Like Differentiation in a Brown Bullhead Catfish (Ictalurus Nebulosus)

A dermal melanoma with histologic similarities to mammalian melanocytic schwannomas was diagnosed in a wild-caught brown bullhead catfish ( Ictalurus nebulosus). The diagnosis was based on cytologic, histopathologic, immunohistochemical, and ultrastructural findings. The neoplasm protruded from the cutaneous surface of the dorsal midline immediately caudal to the dorsal fin, was diffusely black and focally ulcerated, and was attached to the underlying skin by a broad-based stalk. Cytologically, the tumor was composed of a monomorphic population of melanophores, the melanin-producing and storing cells within the dermis and epidermis of fish that are partially responsible for rapid color changes. Histopathologic examination of the neoplasm revealed an unencapsulated, well-circumscribed, moderately cellular neoplasm composed of 2 distinct cell populations: spindle cells arranged in a “herringbone” pattern and numerous melanophores. The spindle cells had scant bipolar eosinophilic cytoplasm, with small centrally located vesicular nuclei; nucleoli were not seen. The histologic appearance was similar to that described for mammalian melanocytic schwannomas. Immunohistochemically, the spindle cells exhibited positive cytoplasmic staining for S-100 protein but were negative for vimentin, neurofilament protein, and glial fibrillary acidic protein. Ultrastructurally, the tumor consisted of neoplastic spindle cells with rudimentary cell junctions, actin bundles, and few melanosomes and melanophores with abundant intracytoplasmic melanosomes.