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The energetics of swimming and upstream migration in adult American shad ({\it Alosa sapidissima\/}) in the Connecticut River

Abstract

This study was designed to assess the energetic cost of upstream migration in American shad (Alosa sapidissima) and to examine physiological changes during migration that relate to swimming performance or energetic efficiency. Overall total stored energy expenditure ranged from 35-60% during upstream migration. Migrating American shad preferentially use energy stores (lipid and protein) in some tissues, such as the skin and its sub-dermal fat layer (depleted by 63%), while sparing other tissue stores such as red muscle protein. American shad generally increased the activity of aerobic and energy mobilization enzymes as much as 60%, while decreasing the activity of anaerobic enzymes as much as 80% during upstream migration. There was a generalized reversal of these enzyme changes seen during migration at the most upriver site sampled. It is suggested that American shad may be able to metabolically prepare for migration prior to its onset and cessation. The data demonstrate that fish migrating in the middle of the migratory period possessed higher (5-42%) total stored energy content than fish migrating early or late in the season, primarily due to elevated lipid in the white muscle and the sub-dermal fat layer. American shad demonstrate a spleen-controlled increase in available blood hemoglobin (22%) and hematocrit likely resulting in increased oxygen carrying capacity during upstream migration. Active and standard metabolic rates of American shad, determined by respirometry, were intermediate between salmonids and fast-swimming perciforms. Active metabolic rate was logarithmically related to swimming speed (r$\sp2$ = 0.26; slope = 0.2) and tailbeat frequency (r$\sp2$ = 0.36; slope = 0.002). Directly determined standard metabolic rate was 71-198 $\rm mgO\sb2kg\sp{-1}h\sp{-1}.$ The energetically optimal swimming speed was 1.45 $\pm$ 0.51 body lengths per second. Using the data from the swimming respirometer, an empirical model of the Cabot Station fish ladder in Turners Falls, MA was constructed which suggests that the impact of the fish ladder on migration is highly dependent on passage time. This study demonstrates that American shad are equipped with a variety of mechanisms for increasing energetic efficiency during upstream migration and highlights the importance of short-term physiological adaption to migration and the ultimate success of an iteroparous, anadromous fish. ^

Subject Area

Biology, Ecology|Biology, Animal Physiology|Biology, Zoology

Recommended Citation

Leonard, Jill Beth Kippax, "The energetics of swimming and upstream migration in adult American shad ({\it Alosa sapidissima\/}) in the Connecticut River" (1997). Doctoral Dissertations Available from Proquest. AAI9737553.
http://scholarworks.umass.edu/dissertations/AAI9737553

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