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Single and multiple nucleolus organizer regions in ribosomal genes have been studied in three closely related coregonine salmonid fishes, the vendace, European whitefish, and the peled. All positive Ag-NORs found corresponded to rDNA-ISH- and DMA(sub.3)-positive signals. This result suggests extensive structural polymorphism in locations of rDNA sites.

DNA fingerprinting and stock identification of salmonid fish increasingly uses polymorphism at minisatellite loci. It is expected that such highly polymorphic loci will play a major part in developing genetic maps for salmonid's complex karyotypes. Details of an examination of the genetic structure of the salmonid Ssa1 minisatellite locus are presented.

Salmonid species contain numerous short interspersed repetitive elements (SINEs), known collectively as the HpaI family, in their genomes. Amplification and successive integration of individual SINEs into the genomes have occurred during the evolution of salmonids. We reported previously a strategy for determining the phylogenetic relationships among the Pacific salmonids in which these SINEs were used as temporal landmarks of evolution. Here, we provide evidence for extensive genomic rearrangements that involved retropositions and deletions in a common ancestor of all the Pacific salmon and trout. Our results provide genetic support for the recent phylogenetic reassignment of steelhead and related species from the genus Salmo to the genus Oncorhynchus. Several other informative loci identified by insertions of HpaI SINEs have been isolated, and previously proposed branching orders of the Oncorhynchus species have been confirmed. The authenticity of our phylogenetic tree is supported both by the isolation of more than two informative loci per branching point and by the congruence of all our data, which suggest that the period between successive speciations was sufficiently long for each SINE that had been amplified in the original species to become fixed in all individuals of that species.

Isolation and amplification of 14 tRNA-derived short interspersed repetitive elements (SINEs) from HpaI subfamilies reveal five subfamilies containing specific diagnostic nucleotides. Amplification of the SINEs indicates that multiple dispersed loci account for the amplification and the horizontal transmission of SINEs. The SINEs are homologous to vertebrate 7SL-derived Alu family members and the HpaI SINEs in salmonids are parasitic in nature.

An analysis of genetic variation in the third intron (C) of the growth hormone genes of salmonid fishes, coho salmon, involved application of the polymerase chain reaction. A variable number of copies of 31-nt repeat, not evident for GH-1 of the intimately associated chinook salmon and rainbow trout, is responsible for a polymorphism in the length of intron C.