Fish Hatchery Management - fisheries & aquaculture

HATCHL,RY REQUIREMENTSTABLE 3. pot-t.urANT LEVELS IN'fHE Et'FL(-rEN-T'FRoM EAR.IHUN cAfFIsHREARINGPONDS DURIN(; TISH SI]INING AND DRATNING OI I'HE PONI)- IA['TER BOYI) I1]71).]PONI)I'ISI IP()l.l.t-ltANIdI)R IN IN(;S!,INI\(Settleable solids (ppm)Settleable oxygen demand (ppm)Chemical oxygen demand (ppm)Soluble orthophosphate (ppb as P)Total phosphorus (ppm as P)Total ammonia (ppm as N)Nitrate (ppm as N)0.0u1.3130.2t(i0.1 I0.!)tt0.I('2tJ.52u.I)l1'25{)0..11)'2..110. 1.1aConcentrations (parts per million or per billion) are on a weight basis except for settleablcsolids. which are on a volume basis.The levels of pollutant in a hatchery effluent can be determined with thefollowing general equation:Average ppm Pollutant:pollutant factorr lbs food fedwater flow (gpm)The following pollutant factors should be used in the equation:Total ammonia 2.67Nitrate 7.25Phosphate Q.417Settleable solids 25.0BOD 2U.3Example: A trout hatchery in which fish are fed 450 pounds of food perday and which has a water flow of 1,500 gallons per minute has a totalammonia concentration of 0.8 parts per million in the hatchery effluent.ppm ammont":?Jli# 0.8Studies in warmwater fish culture have shown that there is no consistentrelationship between the weight of fish harvested in earthen Ponds and theamount of settleable solids discharged in the effluent. In general, anincrease in fish weight results in an increase in settleable solids. Pollutantlevels in the discharge from earthen ponds vary with the volume of waterbeing discharged and the pond design. Some pollutant levels that havebeen reported in the effluent of catfish ponds are presented in Table 3.SEDIMENTATION BASINSThe principle of sedimentation basins is to spread flowing hatchery effluentout in area, thus slowing it down, so that suspended solids will settle out of