Simulation of statistics for a large-scale mutant screening. A, population of fish/family; B, total population of fish that should be bred; C, crossed pairs/family; D, total crossed pairs = families in the next generation. If you perform mutagenesis to 100 males and raise 100 fish/F1 families, you need the environment in which 10,000 fish can be raised. If you can cross at least 40 pairs/F1 families, you must cross 4,000 paired in F1 generation. Then, you will get 4,000 F2 families. For (Pn > 94%), F2-C is 10 pairs. For crossing 10 pairs at F2-C, you should raise 40 fish/families (F2-A). Therefore, you need an environment in which 160,000 (= 4,000 x 40) fish can be raised and 40,000 (= 4,000 x 10) pairs can be crossed.