A basic assumption for carrying out the breeding work is to have well-organised broodstock management. Taking into account the number of populations bred and the limited number of ponds available, it is impossible to avoid rearing several juvenile or adult breeds in mixed stocks. Fish of individual breeds are group-marked with regular renewal of the freeze-branded mark and broodstock adults should be marked individually. To minimise inbreeding or losses in genetic variation, at least 120 fish per strain are reared and when the strain is restored, factorial crosses of at least 15 females and 25 males should be applied. All activities are individually registered in the “Evidence 2003” data-recording software and data can be sorted by the origin of the fish population, of the strain or of individual fish; reproductive and performance parameters are recorded individually also. Further breeding operations with tench comprise the selection after over-wintering and rearing of fish before, during and after the reproductive season.