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Background. Fish introductions have been a common tool to increase efficiency of utilization of water bodies and diversification of aquaculture production. As a result of increased interest in aquaculture and recreational fishing, throughout the past 70 years, the number of non-native fishes in Bulgaria has dramatically increased. This paper reviews the history, current state, and tendencies of the fish introductions in Bulgarian freshwaters. Materials and Methods. The statistical data about introductions and aquaculture production were provided by the National Agency Fisheries and Aquaculture (Ministry of Agriculture and Forestry). A part of the data for restocking activities was provided by Bulgarian Union of Hunters and Fishermen. The taxonomy of freshwater fishes was based on the review of Eschmeyer (2006). Results. At present, twenty-six exotic species have been intentionally or unintentionally introduced in Bulgarian inland waters. They represent 15% of Bulgarian′s freshwater fish fauna and provide more than 60% of aquaculture production. The most abundant are exotic cyprinids (Cyprinidae) and salmonids (Salmonidae), constituting 22% and 18% of all introductions, respectively. The most intensive import of non-indigenous fishes, namely East Asian herbivorous carps (Cyprinidae), into Bulgaria occurred in the middle of the 1960s. Only twelve species have been naturalized. Two of them (Lepomis gibbosus and Perccottus glenii) are considered invasive. Along with these fish introductions, parasites, bacterial and viral pathogens were imported. Conclusion. The results of different fish introductions into Bulgarian freshwaters are controversial. Along with the positive influence on the aquaculture development, some extremely negative consequences, such as introduction of pathogens and spread of invasive species were observed. New introductions of fish species should not be made without scientific analyses evaluating the potential effects of introductions. Research, education, and strict control are the key tools of any effort to prevent the spread of the alien fish species.
Gas chromatography was used to determine lindan and methoxychloride residues in the muscle, brain and liver of selected fish species caught in Popielewo pond in Białystok province. The fish (Carassius carassius L, Cyprinus carpio L, Leucaspius delineatus Heckel) were exposed to an effective concentration of 0,5 ppm Gamametox Powder in water for 30 days. The experiment showed that the highest accumulation of lindan and methoxychlor was in the brain. In the brain of Cyprinus carpio the level was up to 2.41 ppm lindan. The level methoxychlor in livers was similar to the level of this pesticide in the brain, while the level of lindan in livers was considerably the lowest The lowest residues of lindan and methoxychlor accumulation were observed in muscle, where the levels were up to 0.0149 and 0.0351 ppm (Leucaspius delineatus and Cyprinus carpio). Organochlorine pesticide was detected in samples offish from Popielewo pond (control group), but this level was very low. Therefore, it is suggested that the natural environment (Popielewo pond) also contains low concentrations of organochlorine.
Two males of a camallanid nematode belonging to the genus Zeylanema were obtained from the intestine of Channa (Ophiocephalus) punctatus Bloch. The specimens do not agree with the description of known species of the genus Zeylanema, hence a new species Zeylanema chiralensis has been established to describe these nematodes. The new species is distinguished by body size, location of the nerve ring, length of oesophagus, number of longitudinal ridges and size of spicules.
This study is the first investigation on seasonal dynamics of parasites component community of the Aequidens tetramerus from an Amazon River tributary, in Northern Brazil. A total of 239,2407 parasites were recovered from 92 hosts examined from February to October 2011. Such parasites included Ichthyophthirius multifiliis, Tripartiella tetramerii and Trichodina nobilis (Protozoa), Dolops longicauda (Argulidae), Gussevia alioides, Gussevia disparoides (Monogenoidea), Digenea metacercarie, Pseudoproleptus larvae, Anisakidae larvae (Nematoda), Proteocephalidea plerocercoid (Eucestoda) and Gorytocephalus spectabilis (Acanthocephala). Ciliates were the most dominant and abundant taxon, while cestodes were the least prevalent. The parasites showed seasonal variation in their infection dynamics associated with environmental changes during the Amazonian drainage season, except the infection with I. multifiliis. The parasites community in A. tetramerus was also characterized by higher diversity, species richness and uniformity during the drainage season when compared to Amazon flood season. With the exception of T. tetramerii, these parasite species are new records for A. tetramerus.
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