Fish Hatchery Management - fisheries & aquaculture

HATCHERYOPERATIONSIllTABLE 15. AMOUNTS oF oxYGEN ADDED TO POND WATERS BY DIFFERENT TECHNIqUES OF EMERGENCY AI.RATTON (SOURCE: BOYD 1979.)TYPE OF EMERGENCY AREATIONPaddlewheel aeratorCrisafulli pump with sprayerCrisafulli pump to discharge oxygenatedwater from adjacentpondOtterbine aerabr (3.7 kilowatts)Crisfulli pump to circulate pondwaterOtterbine aerator (2.2 kilowatts)Rainmaster pump to circulatepond waterRainmaster pump to dischargeoxygenated water from adjacentpondAir-o-later aerator (0.25 kilowatt)OXYGENADDED{LBlACRE)48.931.219.0| 5.2l 1.8I 1.3t0.76.03.9RELATIVEEFFI C I ENCYf)10064393l242322t28(COr:1 or hydroxyl (OH ;, that react with H1 and reduce the latter's concentration.Excessively high pH values can occur in ponds during summer, whenphytoplankton are abundant and photosynthesis is intense. As carbon dioxideis added to ponds, either by diffusion from the atmosphere or fromrespiration, it reacts with water to form a weak carbonic acid. The basicreaction involved is:CO2+HrO r- H2CO3.= H+ +HCO' e 2H+ +COt.As more CO2 is added, the reaction moves farther to the right, generatingfirst bicarbonate and then carbonate ions; H+ is released at each step,increasing the acidity and lowering the pH. Photosynthesizing plantsreverse the reaction. They take CO2 from the water, and the HCO;CO3: ions bind hydrogen; acidity is reduced and pH rises-oftenandto levelsabove ten.Two types of treatment for high pH can be applied. One involves additionof chemicals that form weak acids by reacting with water to releaseH+; they function much like CO, in this regard. Examples are sulfur, ferroussulfate, and aluminum sulfate, materials also used to acidify soils. Theaction of sulfur is enhanced if it is added together witn organic matter,such as manure.A second treatment for high pH is the addition of positively chargedions that bind preferentially with COt;they keep the carbonate from