(A) Morpholinos or mRNA are injected into embryos to transiently knock down or overexpress a potential disease gene. Phenotypic analysis is performed on these embryos. Alternatively, mRNA encoding ZFN or TALEN is injected into the embryos. Putative founders are raised to adulthood and outcrossed to identify carriers. Founders carrying the allele of interest are then outcrossed to generate an F1 population. Heterozygous F1 carriers are identified by genotyping. (B) TILLING: adult males that have been mutagenized by treatment with ENU are crossed to wild-type females. A DNA library of tailfin clips or frozen sperm is prepared from F1 males. PCR amplification of exons of a specific gene of interest followed by sequencing is performed on the genomic library. Once a mutation is identified, the fish carrying the mutation will be recovered by crossing the corresponding fish from the live library to a wild-type fish or by thawing the cryopreserved sperm and using it for in vitro fertilization (IVF). The resulting progeny are then intercrossed to generate heterozygous and homozygous mutants for the disease gene.