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The loss of hyperosmoregulatory ability in migrating juvenile American shad, Alosa sapidissima

Canadian Journal of Fisheries and Aquatic Sciences

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ORCID iD and
https://doi.org/10.1139/f97-144

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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.

Additional publication details

Publication type:
Article
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