No abstract

Since three bullhead catfish species were introduced to Europe in the late 19th century, they have spread to most European countries. In Hungary, the brown bullhead (Ameiurus nebulosus) was more widespread in the 1970s–1980s, but the black bullhead (Ameiurus melas) has gradually supplanted since their second introduction in 1980. The introgressive hybridization of the two species has been presumed based on morphological examinations, but it has not previously been supported by genetic evidence. In this study, 11 different Hungarian habitats were screened with a new species-specific nuclear genetic, duplex PCR based, marker system to distinguish the introduced catfish species, Ameiurus nebulosus, Ameiurus melas, and Ameiurus natalis, as well as the hybrids of the first two. More than 460 specimens were analyzed using the above markers and additional mitochondrial sequence analyses were also conducted on >25% of the individuals from each habitat sampled. The results showed that only 7.9% of the specimens from two habitats belonged to Ameiurus nebulosus, and 92.1% were classified as Ameiurus melas of all habitats, whereas the presence of Ameiurus natalis was not detected. Two specimens (>0.4%) showed the presence of both nuclear genomes and they were identified as hybrids of Ameiurus melas and Ameiurus nebulosus. An additional two individuals showed contradicting results from the nuclear and mitochondrial assays as a sign of a possible footprint of introgressive hybridization that might have happened two or more generations before. Surprisingly, the level of hybridization was much smaller than expected based on the analyses of the North American continent’s indigenous stock from the hybrid zones. This phenomenon has been observed in several invasive fish species and it is regarded as an added level of complexity in the management of their rapid adaptation.

In this study data on successful propagation of zander (Sander lucioperca L.) from several spawning seasons are evaluated. Propagation was based on stripping of spawners after hormonal induction and rearing of fry in artificial ponds. Fish were injected with acetone-dried carp pituitary extract at a dose of 4.0 mg/kg homogenized in a fish physiological saline. When ovulation was detected, the eggs were stripped and weighed. Eggs were collected from each ovulated female and fertilized with milt from the male. Stickiness of zander eggs was removed before transferring them into Zuger jars. Data collected from four consecutive spawning seasons were analyzed statistically calculating individual and group-based pseudogonadosomatic index (PGSI) values. Reproduction capacity assays were grouped on the basis of three aspects: (1) examination of differences between years, (2) within a reproductive season, and (3) examination of the effects of females' size. During the four-year trial period eggs were gained from 121 hormonally treated females, 64.7% of the total 187. Based on the data of the investigated period the mean PGSI was 10.7%. At 95% significance level PGSI data of different years were considered to be similar. There were no significant differences between PGSI data collected from different periods of the reproductive season. Previous findings on the positive correlation between the amount of stripped eggs and body weight of females were confirmed (r 2 =0.103). Correlation was not justified between PGSI and body weight (r 2 =0.002). Advanced rearing of zander fry in a 2.0 hectare pond was carried out in six consecutive years. Before stocking the nutrient level of the pond was increased by organic manuring and the Copepods were eliminated by insecticides. To prevent cannibalism, four weeks after stocking the advanced fry of zander were harvested. On the basis of the results from six consecutive years, after rearing of advanced fry in a shallow, 2.0 hectare rearing pond for four weeks, the mean survival rate was 13.4±4.37% (mean±SD). By considering our results, breeders can calculate their hatchery's and pond's production in advance. These results will also be helpful in calculating the total weight of broodstock which must be held in order to produce a specific number of advanced fry.

Magyarországon a hízott lúdárutermelésnek nemcsak gasztronómiai és kulturális jelentősége van, hanem nemzetgazdasági szempontból is nagyon fontos szerepet tölt be. Magyarország liba előállításban abszolút Európa élmezőnyébe tartozik. A hízott libából készített termékeket a világon igazi különlegességként tartják számon, hazánkban pedig a hízott libamáj hungaricum terméknek számít. Egy alapvető szezonalitás jellemző a liba termék keresletére, főként a májra és a húsra, emellett drága mivolta miatt elsősorban a gasztronómiai szolgáltatók a végfelhasználói a hízott májféléknek (Internet 1). Az elmúlt időszak járványai (korona vírus, baromfi influenza), a szigorodó állatvédelmi szabályok és az állatvédő szervezetek kampányai miatt kialakult helyzetben az ágazat jövője bizontalan, ezért fontos a hazai szokások ismerete az ágazat reális jövőképének kialakítása érdekében. A munkánk során a libamáj alapú termékek vásárlási és fogyasztási preferenciái vonatkozásában végeztünk kérdőíves felmérést. Kutatási céljaink közé tartozott, annak feltérképezése, hogy a magyar emberek milyen vásárlási és fogyasztási szokásokat képviselnek a libamáj és libamáj alapú termékek vonatkozásában, ezen belül összehasonlító elemzést is végeztünk, továbbá feltártuk a termékek vásárlására és fogyasztására ösztönző tényezőket, paramétereket, valamint értékeltük a libamáj fogyasztásának gyakoriságát. Képet kaptunk arról, hogy a fogyasztók körében milyen mértékben számít gasztronómiai kuriózumnak a termék, illetve a hazai fogyasztásra abszolút jellemző, hogy valamilyen alkalomhoz kötik az emberek a libamáj fogyasztását. A vizsgálatunk kitért arra is, hogy a vizsgálatba vont személyek a magyar – vagy a külföldi libamáj termékek közül melyiket preferálják jobban.

Migratory fishes are important components of the rich wildlife of our waters. Amongst them there are certain species which spend the vast majority of their lives in fresh water (catadromous) and migrate to the sea for spawning, for instance eel species. Others migrate the other way around (anadromous), spending their main growth period and reaching sexual maturity in the sea, then spawning in the freshwaters. Notable representatives of this group are salmonids and sturgeons. The populations of the aforementioned species have decreased significantly in the past decades. The reasons for this can be affected by many factors. Apart from overfishing and the spread of diseases, the dams built on rivers, posing artificial obstacles greatly hinder the achievement of a sufficient natural growth. The outdated dams make approaching the spawning grounds impossible for the fish striving to get there. Having noticed this adverse effect on biodiversity, many of these obsolete dams have already been removed. Where the opportunity arose, fish ladders were constructed, which facilitate the movement of fish. Besides helping the migration, fish ladders provide many species with a habitat.