s ▁ 1 8   ° C . ▁They ▁h unt ▁for ▁living ▁pre y ▁in ▁the ▁upper ▁levels . ▁They ▁prefer ▁mes ot roph ic ▁waters , ▁while ▁the ▁ro ach ▁is ▁sometimes ▁found ▁together ▁with ▁the ▁per ch ▁in ▁waters ▁that ▁are ▁nut ri ent ▁poor . ▁ ▁Rud d ▁appear ▁to ▁prefer ▁non - ac id ic ▁water . ▁ ▁It ▁pre fers ▁shall ow ▁we edy ▁areas ▁in ▁la kes ▁and ▁river ▁back w aters , ▁where ▁m ature ▁females ▁lay ▁up ▁to ▁ 2 0 0 , 0 0 0 ▁eggs ▁on ▁sub mer ged ▁veget ation . ▁Young ▁rud d ▁eat ▁zo op l ank ton , ▁aqu atic ▁insect s , ▁and ▁occasionally ▁other ▁small ▁fish . ▁M ature ▁rud d , ▁which ▁are ▁about ▁ 1 8 ” ▁in ▁length ▁and ▁we igh ▁about ▁ 3 ▁pounds , ▁eat ▁mostly ▁aqu atic ▁veget ation . ▁The ▁rud d ▁can ▁consume ▁up ▁to ▁ 4 0 % ▁of ▁their ▁body ▁weight ▁in ▁veget ation ▁per ▁day , ▁as ▁much ▁as ▁ 8 0 % ▁of ▁which ▁is ▁dis charg ed ▁as ▁waste , ▁re le asing ▁nut ri ents ▁into ▁the ▁water ▁column . ▁They ▁can ▁toler ate ▁a ▁wide ▁range ▁of ▁temper atures ▁and ▁water ▁conditions , ▁including ▁e ut roph ic ▁or ▁poll uted ▁waters . ▁In ▁the ▁labor atory ▁rud d ▁readily ▁hy brid ize ▁with ▁the ▁U . S . ▁golden ▁sh iner ▁( Not em ig on us ▁cry sole uc