An outdoor tank experiment was carried out for the assessing of the impacts of Sarotherodon galilaeus (Galilee Saint Peter’s Fish;Cichlidae) (SG) and Hypophthalmichthys molitriox (Silver Carp;Cyprinidae) (SC) on Lake...An outdoor tank experiment was carried out for the assessing of the impacts of Sarotherodon galilaeus (Galilee Saint Peter’s Fish;Cichlidae) (SG) and Hypophthalmichthys molitriox (Silver Carp;Cyprinidae) (SC) on Lake Kinneret (Israel) plankton. In order to evaluate the interaction effect, the experiments were of replicated 2 × 2 factorial design: TG × SC. A lot of interaction effects were indicated showing that the effects of the two fishes were not independent and potentially competitors. SG suppressed most crustaceans and rotifers while increasing gross and net primary production and chlorophyll concentration. SC had less intense effects on zooplankton than SG. Although SC suppressed most crustaceans and rotifers, it had less interaction effects than SG. SC had no statistically significant effects on phytoplankton production or chlorophyll concentration. It is suggested that these experiments indicate that although the plankton community impacts of SG and SC do differ, both fishes utilize similar food resources in Lake Kinneret. Fingerlings of SG and SC are planted in Lake Kinneret annually aimed at the improvement of fishermen’s income and prevention of water quality deterioration. SC is known as efficient consumer of Microcystis. It is therefore recommended to limit SC introduction to periods when Microcystis is abundant.展开更多
Among fresh water fishes, silver carp because of fast growth rate and desired meat quality, is a dominant species in polyculture systems in Iran. This fish mainly feed on phytoplankton. In present survey kidney and in...Among fresh water fishes, silver carp because of fast growth rate and desired meat quality, is a dominant species in polyculture systems in Iran. This fish mainly feed on phytoplankton. In present survey kidney and intestine of 120 silver carp (Hypophtalmictys molitrix) from 4 regions in Khuzestan province-Iran have been studied. Tissue samples were provided from kidney and intestine and sectioned by routine method after paraffin embedding and finally stained with hematoxilin and eosin (H & E). The microscopic results were analyzed qualitatively and quantitatively. Microscopical analysis showed that kidney tissue had lesions including: edema, necrosis, uroliths, hemorrhage and degeneration. In different regions, fishes showed different prevalence of lesions. Edema and urolith were the most prevalent lesions (30 and 25 percent respectively). In histometric analysis the diameter of layers of intestine in some of the fish farms were significantly higher than the other regions. This increase was because of increase in muscular layer. The intensity of all lesions was estimated as light according to distribution of lesions. The probable cause of these lesions may be the high stocking density, intoxication, water quality problem such as excessive carbon dioxide. The only lesion in intestine was the excessive proliferation of mucus cells that this lesion may be created due to the improper plankton diet.展开更多
文摘An outdoor tank experiment was carried out for the assessing of the impacts of Sarotherodon galilaeus (Galilee Saint Peter’s Fish;Cichlidae) (SG) and Hypophthalmichthys molitriox (Silver Carp;Cyprinidae) (SC) on Lake Kinneret (Israel) plankton. In order to evaluate the interaction effect, the experiments were of replicated 2 × 2 factorial design: TG × SC. A lot of interaction effects were indicated showing that the effects of the two fishes were not independent and potentially competitors. SG suppressed most crustaceans and rotifers while increasing gross and net primary production and chlorophyll concentration. SC had less intense effects on zooplankton than SG. Although SC suppressed most crustaceans and rotifers, it had less interaction effects than SG. SC had no statistically significant effects on phytoplankton production or chlorophyll concentration. It is suggested that these experiments indicate that although the plankton community impacts of SG and SC do differ, both fishes utilize similar food resources in Lake Kinneret. Fingerlings of SG and SC are planted in Lake Kinneret annually aimed at the improvement of fishermen’s income and prevention of water quality deterioration. SC is known as efficient consumer of Microcystis. It is therefore recommended to limit SC introduction to periods when Microcystis is abundant.
文摘Among fresh water fishes, silver carp because of fast growth rate and desired meat quality, is a dominant species in polyculture systems in Iran. This fish mainly feed on phytoplankton. In present survey kidney and intestine of 120 silver carp (Hypophtalmictys molitrix) from 4 regions in Khuzestan province-Iran have been studied. Tissue samples were provided from kidney and intestine and sectioned by routine method after paraffin embedding and finally stained with hematoxilin and eosin (H & E). The microscopic results were analyzed qualitatively and quantitatively. Microscopical analysis showed that kidney tissue had lesions including: edema, necrosis, uroliths, hemorrhage and degeneration. In different regions, fishes showed different prevalence of lesions. Edema and urolith were the most prevalent lesions (30 and 25 percent respectively). In histometric analysis the diameter of layers of intestine in some of the fish farms were significantly higher than the other regions. This increase was because of increase in muscular layer. The intensity of all lesions was estimated as light according to distribution of lesions. The probable cause of these lesions may be the high stocking density, intoxication, water quality problem such as excessive carbon dioxide. The only lesion in intestine was the excessive proliferation of mucus cells that this lesion may be created due to the improper plankton diet.
