Mechanical Spillway: A principal water control structure (such as a drop inlet, weir, or monk) installed through the pond embankment.
Its function is to allow excess water to drain safely during heavy rains or normal pond filling, maintaining the design pond water depth while preventing floodwaters from overtopping and washing away the earthen dyke.
Correct Option: Option 2 (Allows excess water to drain).
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7
ICAR JRF Aquaculture 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
Which chemical is used to control obnoxious gas in culture water?
In aquaculture ponds, zeolite is applied to selectively trap and adsorb toxic unionized ammonia and ammonium ions ($\text{NH}_4^+$) and bind hazardous metabolic gases (such as hydrogen sulfide, $\text{H}_2\text{S}$), thereby purifying the pond water column and benthic sediment.
Correct Option: Option 3 (Zeolite).
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8
ICAR JRF Aquaculture 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
Application of Gypsum in a pond corrects the. of pond water
Gypsum (Calcium Sulfate Dihydrate, $\text{CaSO}_4 \cdot 2\text{H}_2\text{O}$): Dissociates to provide soluble calcium ions ($\text{Ca}^{2+}$) without releasing carbonate or bicarbonate anions.
In ponds with excessively high total alkalinity ($\gt 300-400\text{ mg/L}$) and elevated $\text{pH}$, calcium from gypsum precipitates excess carbonate as insoluble calcium carbonate:
Quick Lime (Calcium Oxide, $\text{CaO}$): Applied to aggressively neutralize soil acidity, rapidly raise bottom soil $\text{pH}$ to the productive alkaline range ($6.5 - 7.5$), release fixed phosphates, and disinfect the pond bottom against pathogenic spores and parasites.
Correct Option: Option 3 (Quick lime).
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10
ICAR JRF Aquaculture 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
Which one of the following is the most harmful water quality parameter for fish culture?
Unionized Ammonia ($\text{NH}_3$): An uncharged, lipid-soluble gas that diffuses readily across fish gill membranes into the bloodstream. It disrupts cellular ionic balance, damages gill epithelia, causes blood alkalosis, and destroys brain tissue.
Ionized Ammonium ($\text{NH}_4^+$): Charged and polar; unable to easily traverse lipid membranes, making it significantly less toxic.
Correct Option: Option 2 (Unionized ammonia).
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