Comparative anatomy of the dorsal hump in mature Pacific salmon.

Mature male Pacific salmon (Genus Oncorhynchus) demonstrate prominent morphological changes, such as the development of a dorsal hump. The degree of dorsal hump formation depends on the species in Pacific salmon. It is generally accepted that mature males of sockeye (O. nerka) and pink (O. gorbuscha) salmon develop most pronounced dorsal humps. The internal structure of the dorsal hump in pink salmon has been confirmed in detail. In this study, the dorsal hump morphologies were analyzed in four Pacific salmon species inhabiting Japan, masu (O. masou), sockeye, chum (O. keta), and pink salmon. The internal structure of the dorsal humps also depended on the species; sockeye and pink salmon showed conspicuous development of connective tissue and growth of bone tissues in the dorsal tissues. Masu and chum salmon exhibited less-pronounced increases in connective tissues and bone growth. Hyaluronic acid was clearly detected in dorsal hump connective tissue by histochemistry, except for in masu salmon. The lipid content in dorsal hump connective tissue was richer in masu and chum salmon than in sockeye and pink salmon. These results revealed that the patterns of dorsal hump formation differed among species, and especially sockeye and pink salmon develop pronounced dorsal humps through both increases in the amount of connective tissue and the growth of bone tissues. In contrast, masu and chum salmon develop their dorsal humps by the growth of bone tissues, rather than the development of connective tissue.

Hybrids between chum Oncorhynchus keta and pink Oncorhynchus gorbuscha salmon: age, growth and morphology and effects on salmon production.

Mature hybrids between chum salmon Oncorhynchus keta and pink salmon Oncorhynchus gorbuscha, which were identified by an intermediate colour pattern, were caught at the Kurilsky Hatchery, Iturup Island, Russia. Most of them were female and 3 years old (a partial freshwater year and 2 marine years), which is intermediate between the ages of maturity of the parental species. The hybrids exceed both parental species in the rate of growth, are large in size and robust and might successfully compete for mating in the wild or be chosen for artificial reproduction. The ratio of the scale length over width, R, is oblate (R < 1), whereas scales of the parental species are prolate (R > 1). From scale analyses, the c.v. in body size of hybrid females at the second marine year is twice that of O. keta, which suggests developmental instability in the hybrid. A dynamic model predicted that continuing hybridization at a low rate does not produce a substantial hybrid load due to selection against advanced-generation hybrids and backcrosses. A high hybridization rate, however, may be an additional risk for genetic management and should be taken into account in programmes of artificial reproduction of Pacific salmon Oncorhynchus spp., although such hybrids might have commercial use in confined production systems.

Early human use of anadromous salmon in North America at 11,500 y ago.

Salmon represented a critical resource for prehistoric foragers along the North Pacific Rim, and continue to be economically and culturally important; however, the origins of salmon exploitation remain unresolved. Here we report 11,500-y-old salmon associated with a cooking hearth and human burials from the Upward Sun River Site, near the modern extreme edge of salmon habitat in central Alaska. This represents the earliest known human use of salmon in North America. Ancient DNA analyses establish the species as Oncorhynchus keta (chum salmon), and stable isotope analyses indicate anadromy, suggesting that salmon runs were established by at least the terminal Pleistocene. The early use of this resource has important implications for Paleoindian land use, economy, and expansions into northwest North America.

[Effects of salinity on haematological biochemistrical indices and liver tissue in juvenile Oncorhynchus keta].

In order to simulate the catadromous migration environment of the juvenile salmon (Oncorhynchus keta), five experimental groups containing different salinities (0, 5, 10, 15 and 20) were set up. The juvenile salmons with average body mass of (26.57 +/- 6.32) g and average full length of (14.44 +/- 1.05) cm were cultured for 130 days, and then the haematological biochemistrical indices was analyzed and the structure of liver tissue was observed to investigate the changes in physiological indices during the catadromous migration of juvenile salmon. The results showed that serum osmolality and the concentration of Na+, Cl- illustrated the same tendency with water salinity variation. Specifically, the serum Na+, C- and Mg2+ levels in the salinities of 15, 20 were significantly different from those in the salinity 5 and the freshwater and serum K+ in different salinities were all obviously lower than that in the freshwater. Also, the blood glucose level in salinity 10 was significantly higher than that in salinity 5 and 20, whereas total serum protein (TP), albumin (ALB) and globulin (GLB) levels all declined with the increase of salinity and the serum TP and GLB content in the freshwater group was remarkably higher than those in the salinity 15 and 20. There also existed an obvious discrepancy on total bile acids in freshwater group and the other salinity groups. The alanine aminotransferase (ALT) activity and aspartate aminotransferase (AST) activity in fresh water group were far different from those of the high salinity groups. Furthermore, in the low salinities (0 and 5), the liver cells of juvenile chum salmon partly broke down, and liver tissue was serious vacuolization. Collectively, the growth and survival rate had no significant difference in all groups and according to the physiological and biochemical indices, the appropriated salinity for juvenile chum salmon ranged from 10 to 20 during the catadromous migration.

[The epithelial reaction of the gastrointestinal tract in dog salmon fry to exposure to an organophosphorus cholinesterase inhibitor]. / Reaktsiia épiteliia zheludochno-kishechnogo trakta molody kety na vozdeistvie fosfororganicheskogo ingibitora kholinésterazy.

Reaction of the gastrointestinal tract epithelium of Siberian salmon kept in fresh and salt water exposed to the effect of irreversible cholinaestherase inhibitor was studied by means of transmissive and scanning electron microscopy. Excessive secretory processes of cells, tetanus of the digestive tract smooth muscles and elements of the epitheliocyte, swelling and vesiculation of cytoplasm and other osmotic effects were noted. Different changes were discovered after poisoning in fish, kept in fresh and salt water.