Fish Hatchery Management - fisheries & aquaculture

HATCHERY OPERATIONS7ITasr-E 9. DlssoLvED oxycEN rN PARTS pER MrLLroN FOR FRESH WATER rN EqurlrBRIUM WITH AIR. {SOURCE: LEITRITZ AND LEWIS 197(i.l1'[,M P!,RAI'I-REi'F)F,I,EVATIoN IN FEEI'1,000 2,000 3,000 4,000 5,000 6,000 7,000 tJ,000 9,000 10,000.1045,+04u49505l52535.155(i065707513.0 t2.5t2.t | | .7I 1.1) l 1.5ll.n ll.3ll.(i tl.211.5 ll.lI 1.3 10.9tt.2 lO.ttI 1.0 lO.tiI 0.{) 10.5l0.u l0.'1l 0. (; 10.310.0 9.(t9.4 1).I9.0 8.7u.(; t|.312.1 I 1.6| | .'2 10.1.iI l.l t0.710.9 10.510.8 I 0..110.6 10.310.5 l0.l10.,1 l 0.010.2 9.910. 1 9.ll10.0 9.69.9 9.lr9.3 U.t)tt.tJ u.4tt..1 u.0u.0 7 .7I 1.2 l0.ul0.ir l0.l10.3 9.9to.2 g.ltI 0.0 !,.79.9 9.59.U 9.49.7 9.39.5 9.29.4 9.19.3 9.09.2 U.9u.6 u.3n.l 7 .87.8 7.47.4 7.l10.,19.79.rt9.,t9.39.2LI9.0rJ.98.7u.(iu.58.07.57.26.tl10.09.39.29.19.08.98.7u.(iu.58..1tJ.3u.27.77.2(i.96.59.6 9.39.0 8.7ti.g ti.ritt.ti ti.lr8.7 8.38.6 U.2u.,1 tt.lu.3 ti.0rJ.2 7.9u.l 7 .8u.0 7.77.9 7.67.,1 7.17.0 6.76.7 tt.46.3 6.19.0u.,1u.38.'2r'1.07.97.u7.77.67.57.36.u(i.4tt. I5.llreduced. In this way, maximum rearing unit and water flow requirementswill be delineated and frequent adjusting of water flows or fish transferscan be avoided.Generally, these methods are limited to intensive culture of fish in situationswhere oxygen availability is regulated by the inflowing water. In extensiveculture systems involving large ponds, oxygen availability dependsto a greater extent on oxygen replacement through the surface area of thewater. Water inflow in such situations is not as significant as pond surfacearea and water volume in determining carrying capacity.Estimates of oxygen consumption under intensive cultural conditionshave been determined for channel catfish. Oxygen consumption rates declineas the available oxygen decreases, and there is a straight-line (semilog)relationship between fish size and oxygen consumption; smaller fishrequire more oxygen per unit size than larger fish (Figure 27).The data in Figure 27 can be used to estimate the carrying capacity forchannel catfish if the available oxygen in a rearing unit is determined. Oxygenconsumption will change proportionately as the water temperature increasesor decreases.DENSITY INDEXCarrying capacity has been discussed in relation to water inflow or, morespecifically, oxygen availability. What affect does density, as pounds of fish