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.

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

Changes in Body Chloride, Density, and Water Content of Chum (Oncorhynchus keta) and Coho (O. kisutch) Salmon Fry when Transferred from Fresh Water to Sea Water

1951 ◽  
Vol 8b (3) ◽  
pp. 164-177 ◽  
Author(s):  
Virginia Safford Black
Keyword(s):  
Water Content ◽  
Fresh Water ◽  
Chum Salmon ◽  
Coho Salmon ◽  
Sea Water ◽  
The Body ◽  
Oncorhynchus Keta ◽  
Normal Range ◽  
Experimental Conditions ◽  
Salmon Fry

Changes in body chloride, density and water content of chum and coho salmon fry were measured when these fish were transferred from fresh water to sea water, and the reverse. Both species tolerated 50% sea water (8–9‰ Cl). Chum fry survived direct transfer from fresh water to sea water (15–17‰ Cl), but showed a marked increase in body chloride during the first 12 hours, followed by a return to the normal range between 12 and 24 hours. Coho, however, died within the first 36 hours, after a 60% increase in chloride. Coho fry lost more water than chum fry after introduction to sea water. The density of both species approximated that of the water within an hour of transfer to the new medium. When returned to fresh water after 12 hours in sea water the body chloride, density, and water content of both species regained normal levels within 10 hours. Chum salmon go to sea as fry, whereas cohos remain in fresh water a year or more. Although coho fry seem capable of some adjustment to sea water after a preliminary period in 50% sea water, permanent acclimatization could not be demonstrated under the experimental conditions.

Influence of Temperature, Salinity, and Photoperiod on the Aggregations of Chum Salmon Fry (Oncorhynchus keta)

1966 ◽  
Vol 23 (2) ◽  
pp. 293-304 ◽  
Author(s):  
J. E. Shelbourn
Keyword(s):  
Fresh Water ◽  
Chum Salmon ◽  
Cold Water ◽  
Salt Water ◽  
Oncorhynchus Keta ◽  
Influence Of Temperature ◽  
Hatchery Stock ◽  
Salmon Fry ◽  
Different Temperatures ◽  
History Of

Underyearling chum fry from hatchery stock were held in fresh water and salt water at two different temperatures and under two different photoperiods and acclimated to these conditions for 40 days before testing started. Aggregations were greater in salt water than in fresh water (p <.01). Fish acclimated to cold water schooled more strongly than those acclimated to warm water but this effect was not considered statistically significant. There were no differences in intensity of aggregation due to photoperiod (p >.05). The significance of these findings is discussed in relation to life history of the fry.

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.

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.

The utilization of cold-water zooplankton as prey for chum salmon fry (Oncorhynchus keta) in Yamada Bay, Iwate, Pacific coast of northern Japan

2019 ◽  
Vol 29 ◽  
pp. 100633
Author(s):  
Yuichiro Yamada ◽  
Kei Sasaki ◽  
Kodai Yamane ◽  
Miwa Yatsuya ◽  
Yuichi Shimizu ◽  
...  
Keyword(s):  
Chum Salmon ◽  
Pacific Coast ◽  
Cold Water ◽  
Oncorhynchus Keta ◽  
Salmon Fry ◽  
Northern Japan

Effects of Some Environmental Factors on Survival, Condition, and Timing of Emergence of Chum Salmon Fry (Oncorhynchus keta)

1970 ◽  
Vol 27 (1) ◽  
pp. 196-201 ◽  
Author(s):  
L. M. Dill ◽  
T. G. Northcote
Keyword(s):  
Environmental Factors ◽  
Chum Salmon ◽  
Oncorhynchus Keta ◽  
Burial Depth ◽  
Gravel Size ◽  
Salmon Fry ◽  
Survival Condition

In an experiment in incubation channels at Robertson Creek, B.C., survival of chum salmon from planting of eggs to emergence of fry was higher in large gravel (2–4 inches, 5.1–10.2 cm) than in small gravel (0.4–1.5 inches, 1.0–3.8 cm). Neither condition coefficient nor timing of emergence was affected by gravel size. There were no significant effects of egg burial depth (8 and 12 inches, 20.3 and 30.5 cm) or density (50 and 100 per treatment) on condition coefficient, or timing of emergence.

The Behaviour of Chum, Pink and Coho Salmon in Relation to their Seaward Migration

1951 ◽  
Vol 8b (4) ◽  
pp. 241-263 ◽  
Author(s):  
William S. Hoar
Keyword(s):  
Fresh Water ◽  
Coho Salmon ◽  
Pink Salmon ◽  
Water Levels ◽  
Salmon Fry ◽  
Seaward Migration ◽  
Active Swimming ◽  
Increased Activity ◽  
Downstream Movement ◽  
Marked Tendency

In fresh water, chum and pink salmon fry form schools or mills, are constantly active both day and night, show positive rheotaxis and move into fast water. This activity takes them into the swiftest currents. At night loss of visual and contact stimuli reduces the intensity of the rheotactic response and results in downstream movement. An active swimming downstream occurs only with unusually high temperatures. Coho salmon fry occupy and defend territory, maintain definite positions in relation to particular objects in their environment, show a less marked tendency to move into fast water and are quiet at night. They are thus displaced downstream to a much lesser degree. Coho smolts, in contrast to the fry, demonstrate a lowered threshold for stimulation both day and night, a tendency to aggregate and a lessening in territory behaviour. During the day smolts group in deeper water or under cover. At night they rise to the surface and manifest increased activity which, in swift water, will result in displacement seaward. Pronounced changes in temperature modify these reactions. Sudden elevation of water levels hastens the downstream displacement.

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