Fish Hatchery Management - fisheries & aquaculture

I ISH HA'I'CHLRY NTANAGEME,NTINORGANIC FERTILIZERSInorganic fertilizers are relatively inexpensive sources of nitrogen, phosphorus,and potassium, which stimulate algal growth, and calcium, whichhelps to control water hardness and pH.In nitrogen-free water,0.3 to 1.3 parts per million of nitrogen must be addedto stimulate phytoplankton growth, and to sustain this growth aboutone part per million must be applied at weekly intervals. In a normalhatchery pond this comes to about eight pounds of nitrogen per surfaceacre. Because nitrogen can enter the pond system from the atmosphere,watershed, and decomposing organic matter, it is not always necessary toadd more.For the operation of warmwater hatchery ponds, it is recommended thatnitrogen be included in the fertilizer applications during the late springand summer months for all ponds except those which have been weed-freefor at least three years. If development of phytoplankton is delayed longerthan four weeks, nitrogen should be added.Forms of nitrogen available for pond fertilization are listed on Table 12.Phosphorus is an active chemical and cannot exist alone except undervery specialized conditions. It is generally considered to be the most essentialsingle element in pond fertilization and the first nutrient to become alimiting factor for plant growth. Plankton require from 0.01U to 0.09 partper million as a minimum for growth. Several workers have recommendedapplications of about 1.0 part per million phosphorus pentoxide (P2O5)periodically during the production season.T'\BLI.] 12. \.. l t R()ct.tN Il.tR I I t-tzl.){s lf oR p()N D ENRIcII\I IiNT.pFl O IiC H l.NI I Cr\ t,PF]R(]I]N IAqL E( )r,Ss()t R( t.t \{.\ I URIAIF( )Rt\t I ]l..\NI I'ROCI.]Ns()l-t't I()\Ammonium nretaphosphateAmmonium nitrateAmmonium phosphateAmmonium sull'ateAnhydrous ammoniirAqua-ammoniaCalcium cyanamideDiammonium phosphatcU rcaSodiurn nitrate{NH r).rP()rt7"NHlNO.l33.5(Nu.,),,tct,ll,(NH,)rso,'20NH r.H2C)tt2NHr.H2()10 50CaCN22'2(NHr)2HI'o '2t'lH2HC()NH2,l ()NaNO I l(t+.o.1.05.0u.07.27.0"Also contains 7iJ P2O',.1'Also contains -llt ' I'2O t.rAlso contains,tlJ ,12' l'2Oi.