Swimming behavior and energetics of sharks
Citable URI
https://hdl.handle.net/1912/5367Location
Northwestern AtlanticDOI
10.1575/1912/5367Keyword
Sharks; Blue sharkAbstract
In a field study of blue shark swimming behavior, acoustic telemetry
was used to record depth, swimming speed and tailbeat frequency from
free-ranging blue sharks (Prionace glauca) in northwestern Atlantic
slope waters. Records obtained from five sharks show a consistent
pattern of vertical migration between the surface and depths as great
as 450 meters, with the deepest dives occurring during the daytime and
shallower dives at night. Mean swimming speed was 44.5 ± 1.6 (X±S.E.)
cm.s-1 (0.179 ± 0.014 lengths.s-1) for three sharks, with short
bursts up to 180 cm.s-1. Mean tailbeat frequency was 0.335 ± 0.021
beats.s-1. Measurement of swimming speed and rate of vertical
movement during dives permits calculation of angles of ascent and
descent. For 84 dives deeper than 50 m, the descent angle averaged
8.0 ± 0.7 degrees from the horizontal while the ascent angle was 6.4 ±
0.5 degrees. Tailbeat records indicate that blue sharks actively swam
downward during most of the descent, with brief periods of gliding
which appear to be associated with the most rapid descent rates. The
observed diving behavior does not match that predicted by theory to be
energetically optimal for migration, and may instead represent a
strategy for encountering and capturing prey.
Heart rate, metabolic rate and activity were simultaneously recorded
in the laboratory from lemon sharks (Negaprion brevirostris) during
rest and spontaneous exercise, and from leopard sharks (Triakis
semifasciata) during steady swimming at controlled speeds to evaluate
the usefulness of heart rate as a measure of field metabolic rate.
Heart rate was monitored by acoustic telemetry using a frequency
modulated ECG transmitter, and metabolic rate was measured as oxygen
consumption rate. For seven lemon sharks at 25°C, mean resting
values for heart rate and oxygen consumption rate were 52.0 + 0.4
(S.E.) beats.min-1 and 162.0 ± 2.0 (S.E.) mg02.kg-1hr-1,
respectively. Both parameters increased significantly (p<.001)
during swimming, to means of 55.9 ± 0.2 beats.min-1 and 233.6 + 2.3
mg Oz.kg-1hr-1,
at a mean swimming speed of 0.400 ± 0.003 body heart rate and oxygen consumption rate were 36.6 + 1.8 beats.min-1
and 105.3 ± 35.6 mg Oz.kg-1.hr-1.
While swimming-at the maximum
sustained speed (0.84 ± 0.03 lengths.s-1) for 30-60 minutes, these
rates were 46.9 + 0.9 beats.min- and 229.3 + 13.2 mg
Oz.kg-1.hr-1.
The observed elevations in heart rate from rest
to exercise account for 20% of the increase in oxygen uptake in the
lemon shark and 32% in the leopard shark, leaving the remainder to be
brought about by increases in stroke volume and/or arteriovenous
oxygen difference. Significant linear regressions of oxygen
consumption rate on heart rate were obtained for both lemon sharks and
leopard sharks; separate regressions were obtained for individual
lemon sharks . Heart rate was approximately as closely correlated to
oxygen consumption rate as was swimming speed.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution December 1988
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Suggested Citation
Thesis: Scharold, Jill V., "Swimming behavior and energetics of sharks", 1988-12, DOI:10.1575/1912/5367, https://hdl.handle.net/1912/5367Related items
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