Fish Hatchery Management - fisheries & aquaculture

HATCHERY RDqUIREMENTS5101520Water temperatures'Cent0xygen mgmpef I ter (PpM)6 / 8 9 l0 llFIGURE l. Rawson's nomagram of oxygen saturation values at different temperaturesand altitudes. Hold ruler or dark-colored thread to join an observed temperatureon the upper scale with the observed dissolved-oxygen value on thelower scale. The values or units desired are read at points where the thread orruler crosses the other scale. The associated table supplies correction values foroxygen saturation at various altitudes. For example, if 6.4 ppm of oxygen isobserved in a sample having an altitude of approximately 500 m (1,640 feet), theamount of oxygen that would be present at sea level under the same circumstancesis found by multiplying 6.4 by the factor 1.06, giving the product6.8; then the percentage saturation is determined by connecting 6.8 on the lowerscale with the observed temperature on top scale and noting point of intersectionon the middle (diagonal) scale.OXYGENOxygen is the second-most abundant gas in water (nitrogen is the first)and by far the most important-fish cannot live without it. Concentrationsof oxygen, like those of other gases, typically are expressed either as partsper million by weight, or as percent of saturation. In the latter case, saturationrefers to the amount of a gas dissolved when the water and a[mosphericphases are in equilibrium. This equilibrium amount (for any gas)