Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 25

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  Ctenopharyngodon idella
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The study was conducted on common carp and grass carp embryos and larvae developed under laboratory conditions, at various temperatures and in the presence of heavy metals (Cu 0.20-0.27 mg dm⁻³ , Pb 2.0-4.0 mg dm⁻³ , Cd 0.2 mg dm⁻³ ). Heart rate was measured at various developmental stages and was observed to increase along with fish development in all experimental groups. This may be explained by the increase in the metabolic rate of developing embryos. Development was faster at higher temperatures, and the heart rate was usually higher. The results of the present study confirm that heart rate is a reliable indicator of the metabolic rate of developing fish embryos.The embryos and larvae which were exposed to heavy metals had higher heart rates in comparison to those of the control group. This indicates that metal-induced stress caused an increase in metabolic rate. A decrease in heart rate during hatching was observed at non-optimum temperatures and was particularly pronounced in metal-exposed embryos; this indicates that the disturbances were related to the high sensitivity of the fish at this stage.
The parasite fauna of autochthonous Cyprinus carpio and introduced Ctenopharyngodon idella, Hypophthalmichthys molitrix and Aristichthys nobilis, cultured together in fish ponds, was analyzed. In common carp four introduced parasites were found, while in introduced fishes 19 autochthonous parasite species occurred. The transfer of parasites between native and introduced fishes requires that the parasites have a rather wide circle of hosts. The autochthonous parasites which occurred in both autochthonous and introduced fishes were generally more frequent in introduced fishes, and vice versa. This fact can indicate a greater susceptibility of new hosts toward non specific parasites, and lack of balance in new host-parasite systems.
This work proposes modifications to the existing system for identifying the steps of embryonic and larval development in fish. The term “compensatory phase of development” is proposed for the phase from hatching to the first intake of food. Both the new designations of these steps and the new name of this phase do not require a declaration of whether the hatched individual is considered to be an embryo or a larva, something that has been, to date, a matter of dispute. Unification will allow for the wider use of the new nomenclature, and make easier the comparison of results. This work examines the influence of the thermal history during the embryonic period (temperatures of 20, 24, 28, and 32°C) on later development, growth, and survival of common carp, Cyprinus carpio L., and grass carp, Ctenopharyngodon idella (Val.) larvae, at a constant temperature of 23°C. It was confirmed that the optimal temperature ranges for the embryonic development of common carp and grass carp are higher than those currently applied widely in practice of 18-22°C and 21-26°C, respectively. Based on the evaluation of the development, growth, and survival of the larvae, it was determined that the optimal temperature for embryonic development is 26-28°C for the common carp and 32°C for the grass carp. It was confirmed that even a short-term increase in temperature from 20°C to 24°C during the compensatory phase has a positive influence on subsequent common carp larvae growth.
Fishery and aquaculture play an enormous role in reducing poverty and alleviating food insecurity at household level. The first fish stocking program in Ethiopia was reported as early as 1925. Indigenous Oreochromis niloticus, Tilapia zilli, Clarias gariepinus and non-native Cyprinus carpio, Carassius carassius, Carassius auratus, Ctenopharyngodon idella and Salmo trutta fish species were used for stocking. Even though most of the fishery enhancement programs are low-cost operations, they often seem to be very efficient actions. Fish harvested in the reservoirs Fincha and Amerti in Oromia region, lakes Haik and Ardibo in Amhara region and Hashengie in Tigray region, enhanced by stocking, contribute up to 15% of the annual fish production of the country. Thus fisheries programs challenging the growing protein-rich food demand should be considered as a necessary and valuable aspect of management strategy in all waters, independently from its major operational goal like hydropower or irrigation.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.