The loss of hyperosmoregulatory ability in migrating juvenile American shad, Alosa sapidissima
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Abstract
Investigations on juvenile American shad (Alosa sapidissima) revealed several physiological changes associated with downstream migration. Plasma chloride decreased 20% in wild juvenile shad during the autumn migration. Migrants had lower condition factor and hematocrit than non-migrant shad captured by beach seining. Gill Na + ,K + -ATPase activity of migrant shad was higher than non-migrant; a 2.5-fold increase was observed in 1993, while a 57% increase was observed in 1994. Similar changes were observed in laboratory studies of shad maintained in fresh water under simulated natural temperature and photoperiod. Plasma chloride dropped 68% and gill Na + ,K + -ATPase activity increased 3-fold over a 3-month period. Decreased plasma chloride was associated with increased mortality. Increases in gill Na + ,K + -ATPase activity decreases in plasma chloride and osmolality, and incidence of mortality were delayed and moderated, but not eliminated, in shad maintained at constant temperature (24°C). Shad did not survive in fresh water past December regardless of temperature regime. In seawater, all shad survived and showed no perturbation of plasma chloride at 24°C or simulated natural temperature (above 4°C). The decline in hyperosmoregulatory ability, as influenced by declining temperatures, may serve as a proximate cue for autumnal migration.
Publication type | Article |
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Publication Subtype | Journal Article |
Title | The loss of hyperosmoregulatory ability in migrating juvenile American shad, Alosa sapidissima |
Series title | Canadian Journal of Fisheries and Aquatic Sciences |
DOI | 10.1139/f97-144 |
Volume | 54 |
Issue | 10 |
Year Published | 1997 |
Language | English |
Publisher | NRC Research Press |
Contributing office(s) | Leetown Science Center |
Description | 11 p. |
First page | 2377 |
Last page | 2387 |
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