جستجوی مقالات مرتبط با کلیدواژه "plankton" در نشریات گروه "شیلات"

An experiment was conducted to test efficiency of biofloc technique for production of Indian white prawn, Fenneropenaeus indicus in HDPE liner ponds (300 m2) for 90 days.  There were control (water exchange to maintain transparency at 40-50 cm) and treatment (zero water exchange) ponds and both were triplicated. Soya hull and molasses were added to treatment ponds as carbon sources to induce biofloc formation. Post larvae (PL20) were stocked at the rate of 50/m2 and fed with a standard fishmeal based supplementary pellet feed. Physico-chemical parameters of water, microbial and plankton population, immune response, physical quality and shrimp growth were monitored during the period. High growth and survival was observed in treatment ponds compared to control. Heterotrophic bacteria, phytoplankton population and total haemocyte count (THC) were found to be enhanced in treatment ponds. A strong linear relationship (R2=0.8758) was found between growth rate and biofloc content. Shrimp raised through biofloc culture strategy showed better colour and quality compared to control.  Biofloc technology is an ideal culture method for biosecure production of white shrimp in semi arid lands.

Four feeding levels (40%, 60%, 80% and 100% of satiation) were designed as the different treatment groups to assess its effects on water quality and plankton community structure in the yellow catfish rearing enclosure ecosystem. The results showed that the weight gain and specific growth rate decreased significantly as the feeding level decreased. The soluble nutrients (except for NO2-N) concentrations were significantly affected by the feeding level with the prolonging of rear time. A significant increase in phytoplankton biomass before 9 days was observed in all the treatments, and then decreased significantly until 21 days, while the zooplankton biomass was significantly increased during the entire experiment. Both the phytoplankton and zooplankton biomass were significantly affected by the feeding level. Our results suggested that the increment of nitrogen compounds before 9 or 12 days could be explained by the input of compound diets, while the decrement of nitrogen compounds afterward and phosphorous compounds could be explained by the changes of zooplankton biomass. Based on water quality and plankton structure, moderate nutrient restriction (60%-80% of satiation) is a feasible feeding strategy for better growth performance as well as better water quality and balanced plankton structure. On the other hand, input of moderate phosphorus by dietary supplementation and/or fertilization is necessary in yellow catfish culture both for the better plankton structure and the health of fish. In addition, the polyculture of the minority members of zooplankton filter feeders might be a feasible strategy to control the excessive zooplankton.