Induced polyploidy has been identified for yellow croaker P.crocea at various developmental stages and with various tissues during 2001~2004.Ploidy levels from eyed embryos were determined by chromosome counts.Ploidy analyses of fish juveniles and adults were implemented using flow cytometry.The results indicated that chromosomal number of diploid embryos was 48 as 72 being triploids.For fish juveniles and adults,ploidy levels were detected by comparing DNA relative content of known diploid individuals with those of unknown ploidy levels,of which the individuals with as 1.5 fold DNA content as the control were identified as triploids and the same content as diploids.Ploidy levels of the individuals could be investigated using either muscle or tail fin tissues.