Viability and development of diploid and triploid salmonid hybrids

Three single-pair matings were made of each possible cross among Atlantic salmon ( Salmo salar), brook trout ( Salvelinus fontinalis), brown trout ( Salmo trutta), chum salmon ( Oncorhynchus keta), coho salmon ( Oncorhynchus kisutch), and rainbow trout ( Oncorhynchus mykiss). Portions of fertilized eggs from each of the 108 matings were heat shocked to induce triploidy. Analysis of development in 9- and 18-day-old embryos showed that hybrids with a high proportion of malformed embryos usually also showed poor survival. Diploids usually survived better than triploids in within-species matings but poorer in hybrids. Crossing a female from a rapidly developing species with a male from a more slowly developing species usually produced progeny with greater viability than the reciprocal cross, and closely related species usually produced more viable hybrid progeny than did more distantly related species. Although no new hybrids that show potential for aquaculture purposes were identified, the experiments confirmed the potential utility of some hybrids and identified crosses which may be useful for gynogenesis.