scholarly journals Timing of Spawning of Wild Chum Salmon in a Non-enhanced River and their Seaward Migration in Northern Honshu, Japan

2019 ◽  
pp. 49-50
Author(s):  
Masaya Iida ◽  
Yuta Yagi ◽  
Tomoaki Iseki
Keyword(s):  
Chum Salmon ◽  
Seaward Migration ◽  
Timing Of Spawning

Behavioral Ecology of Chum Salmon Fry (Oncorhynchus keta) in a Small Estuary

1974 ◽  
Vol 31 (1) ◽  
pp. 83-92 ◽  
Author(s):  
J. C. Mason
Keyword(s):  
Fresh Water ◽  
Behavioral Ecology ◽  
Chum Salmon ◽  
Oncorhynchus Keta ◽  
Natural Systems ◽  
Active Selection ◽  
Resource Managers ◽  
Salmon Fry ◽  
Seaward Migration ◽  
And Behavior

Chum salmon fry (Oncorhynchus keta) in the estuary of a small coastal stream exploited fresh water, estuarine, and marine food chains and, by so doing, were exposed to marked, daily fluctuations in salinity that demanded active selection of fresh water on ebbing tides day and night. The resulting delay in seaward migration and associated behavioral observations are inadequately reflected in published accounts of the life history and behavior of chum fry in natural systems and laboratory situations, and the downstream displacement theory. The biological basis for delayed seaward migration of chum fry merits the attention of fishery researchers and resource managers alike.

scholarly journals Predation of Chum Salmon Fry During the Course of its Seaward Migration-II

1972 ◽  
Vol 38 (3) ◽  
pp. 223-229 ◽  
Author(s):  
Yoshio HIYAMA ◽  
Yukio NOSE ◽  
Makoto SHIMIZU ◽  
Tadakazu ISHIHARA ◽  
Hisashi ABE ◽  
...  
Keyword(s):  
Chum Salmon ◽  
Salmon Fry ◽  
Seaward Migration

Decreased Seawater Adaptability of Chum Salmon (Oncorhynchus keta) Fry Following Prolonged Rearing in Freshwater

1982 ◽  
Vol 39 (3) ◽  
pp. 509-514 ◽  
Author(s):  
Munehico Iwata ◽  
Sanae Hasegawa ◽  
Tetsuya Hirano
Keyword(s):  
Body Weight ◽  
Chum Salmon ◽  
Sea Water ◽  
Oncorhynchus Keta ◽  
Direct Transfer ◽  
Chum Salmon Oncorhynchus Keta ◽  
Salmon Fry ◽  
Seaward Migration ◽  
Osmoregulatory Ability

Chum salmon (Oncorhynchus keta) fry weighing about 1 g maintained plasma Na+ concentrations at 134–140 mmol/L during seaward migration in the Otsuchi River. The plasma Na+ level increased slightly in the estuary, and reached 150–160 mmol/L in the fry caught in the bay. On direct transfer from freshwater to seawater, the plasma Na+ concentrations of the fry weighing 0.4–2.3 g increased markedly after 1 h and reached a maximum after 3–12 h. The fry of < 1.4 g attained sea water-acclimated plasma Na+ level of 156 mmol/L within 24 h after transfer, whereas fry of 1.8–2.3 g failed to adapt to seawater within 24 h. When seawater adaptability of fry of different lots was examined simultaneously in late April, 83–109 d after hatch, the smaller fry adjusted their plasma Na+ levels more easily than the larger fry: the smallest fry attained seawater level after 12 h without showing any peak. Changes in seawater adaptability of the same lots of fry were also followed until 5 mo after hatching, and the osmoregulatory ability of the fry in seawater decreased gradually with an increase in body weight or in the time spent in freshwater.Key words: chum salmon fry, seaward migration, plasma Na+ concentration, seawater adaptability, Oncorhynchus keta

Notes on the Seaward Migration of Pink and Chum Salmon Fry

1955 ◽  
Vol 12 (3) ◽  
pp. 369-374 ◽  
Author(s):  
Ferris Neave
Keyword(s):  
Vertical Distribution ◽  
Chum Salmon ◽  
Pink Salmon ◽  
Strong Light ◽  
Salmon Fry ◽  
Seaward Migration ◽  
Schooling Behaviour ◽  
And Migration ◽  
A Current ◽  
Downstream Movement

The seaward migration of pink and chum salmon fry takes place at night. Strong light is avoided. In pink salmon negative rheotaxis (swimming with a current) is strongly developed and migration is not primarily effected by random swimming and passive displacement. Downstream movement is mainly at or close to the surface. In slack water vertical distribution is more uniform. In the shortest streams examined, each night's migrants appeared to reach the sea before daybreak. In a longer stream, fry were seen to bury themselves at the onset of daylight. After being held in fresh water for an undetermined period, fry show positive rheotaxis and schooling behaviour and no longer avoid light. Behaviour of fry after reaching the sea also differs from that shown during actual migration. Changes in behaviour may coincide with commencement of feeding.

THE THYROID GLAND IN RELATION TO THE SEAWARD MIGRATION OF PACIFIC SALMON

1950 ◽  
Vol 28d (3) ◽  
pp. 126-136 ◽  
Author(s):  
William S. Hoar ◽  
G. Mary Bell
Keyword(s):  
Fresh Water ◽  
Chum Salmon ◽  
Pacific Salmon ◽  
Pink Salmon ◽  
River Estuary ◽  
Salt Balance ◽  
Thyroid Activity ◽  
Salmon Fry ◽  
Thyroid Glands ◽  
Seaward Migration

Histological examination of the thyroid glands from chum salmon fry taken in the river, estuary, or sea shows the organ to be in a quiescent condition at the time of migration. If, however, this species is retained in fresh water for two or three months the gland becomes extremely hyperplastic. The pink salmon thyroid behaves in essentially the same way as that of the chum, but migrating pink fry taken at great distances from the sea have active glands. The thyroids of yearling coho and sockeye moving into the sea display heightened activity. Thyroid activity is apparently greater in coho migrants taken later in the season from the headwaters of rivers. In part, the heightened thyroid activity seen in these migrating Pacific salmon is probably a spring-time seasonal change. It seems, however, to be more particularly related to the increased metabolic work of osmotic regulation and salt balance in a fish physiologically prepared for life in the sea. In general, this study suggests that the increased thyroid activity seen in young migrating salmonoids is largely due to increased demands for thyroid hormone in the metabolism of a fish no longer completely adjusted physiologically to fresh water.

scholarly journals River temperature drives salmon survivorship: is it determined prior to ocean entry?

2015 ◽  
Vol 2 (1) ◽  
pp. 140312 ◽  
Author(s):  
Kentaro Morita ◽  
Nakashima Ayumi ◽  
Motohiro Kikuchi
Keyword(s):  
Chum Salmon ◽  
Pacific Salmon ◽  
Total Mortality ◽  
Adult Survival ◽  
Oncorhynchus Keta ◽  
River Temperature ◽  
Seaward Migration ◽  
Key Factor ◽  
Short Term Mortality ◽  
Adult Survival Rate

Early life is believed to be a critical stage for determining survivorship in all fish. Many studies have suggested that environmental conditions in the ocean determine the fry-to-adult survival rate of Pacific salmon but few investigations have been conducted on the importance of the brief freshwater period during the seaward migration on overall survivorship. Here, we found that most of the variation in survivorship of hatchery-reared chum salmon ( Oncorhynchus keta ) was explained by river temperature during the fry stage, despite spending most of their life (approx. 99%) at sea. After the annual release of a constant number of fry, the number of fry moving through the river at a downstream location varied greatly. The number of returning adults was positively correlated with the number of fry moving downstream. This result suggests that most salmon mortality occurred prior to ocean entry, and that short-term mortality in the river is a key factor determining major fluctuations in total mortality. Although marine mortality is often invoked in the literature as a key factor determining total mortality of chum salmon, attention should also be paid to freshwater mortality to understand the population dynamics of this species.

Importance of Estuarine Residence for Adaptation of Chum Salmon (Oncorhynchus keta) Fry to Seawater

1984 ◽  
Vol 41 (5) ◽  
pp. 744-749 ◽  
Author(s):  
Munehico Iwata ◽  
Shichiko Komatsu
Keyword(s):  
Surface Layer ◽  
Brackish Water ◽  
Chum Salmon ◽  
Oncorhynchus Keta ◽  
Otsuchi Bay ◽  
Chum Salmon Oncorhynchus Keta ◽  
Salmon Fry ◽  
Seaward Migration ◽  
Subsequent Exposure ◽  
Salmon Hatchery

Within 24 h after release from the Otsuchi Salmon Hatchery in Japan, most chum salmon (Oncorhynchus keta) fry migrated the 1.7 km and were found in the surface layer (10–15‰ salinity) of the estuary. No fish were seen in the underlying seawater. Many fry remained in the brackish water for 2 d before migrating seaward. Plasma Na concentrations increased gradually from 134 to 156 mmol/L during seaward migration from the river to Otsuchi Bay. When fry were acclimated to one-third seawater for 3 and 6 h and then transferred to seawater, the Na concentration of the fry increased maximally to 161–172 mmol/L within 12 h. When they were acclimated to one-third seawater for 12 h, the Na concentrations reached the seawater-acclimated level without showing any peak; subsequent exposure to seawater did not cause any further change in plasma Na. Acclimation to isotonic estuary water for 12 h is thus sufficient for efficient adaptation of chum salmon fry to seawater.

scholarly journals Predation of Chum Salmon Fry During the Course of its Seaward Migration-I

1972 ◽  
Vol 38 (3) ◽  
pp. 211-221 ◽  
Author(s):  
Yoshio HIYAMA ◽  
Yukio NOSE ◽  
Makoto SHIMIZU ◽  
Tadakazu ISHIHARA ◽  
Hisashi ABE ◽  
...  
Keyword(s):  
Chum Salmon ◽  
Salmon Fry ◽  
Seaward Migration
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