Subject: abstract - video sonar and dolphin swimming speed (fwd)

Michael Williamson (
Thu, 1 May 1997 09:53:01 -0400 (EDT)

J. Michael Williamson
   Principal Investigator-WhaleNet <>
   Associate Professor-Science
   Wheelock College, 200 The Riverway, Boston, MA 02215
voice: 617.734.5200, ext. 256
fax:    617.734.8666, or 617.566.7369

---------- Forwarded message ----------
Date: Wed, 30 Apr 1997 08:16:00 -0400
From: Dagmar Fertl <>
Reply-To: Marine Mammals Research and Conservation Discussion
Subject: abstract - video sonar and dolphin swimming speed

     On behalf of a request made by the Marmam editors, I am posting
     abstracts for the lastest issue of Marine Mammal Science.  This is
     being cross-posted as well to the ECS mailbase.  I have included the
     mailing address of the author to whom inquiries should be directed,
     please do not send the mail to me.

     Ridoux, V., C. Guinet, C. Liret, P. Creton, R. Steenstrup, and G.
     Beauplet.  1997.  A video sonar as a new tool to study marine mammals
     in the wild:  measurements of dolphin swimming speed.  Marine Mammal
     Science 13(2): 196-206.

     Laboratorie d'Etude des Mammiferes Marins, Oceanopolis, B.P. 411,
     29275 Brest Cedex, France.

     The use of a multibeam sonar for fine-scale studies of the foraging
     activity of bottlenose dolphins (_Tursiops truncatus_) was tested in a
     coastal environment where a group of 14 individuals is known to be
     resident.  The sonar was set on a rubber boat and the signals were
     received continuously as the dolphins were foraging in a pass swept by
     strong tidal currents.  These signals were recorded in Hi 8 video
     standard.  The system produced real-time undistorted images of the
     dolphins and of their movements within the limits of the sonar beam
     (15 degree vertical width, 90 degree horizontal width, range set at 50
     m).  The average swimming speed relative to the bottom was 1.8 m x sec
     ^-1 but swimming speed relative to the water was 2.2 m x sec ^-1 when
     allowance was made for the average 1.2 m x sec ^-1.  Maximum swimming
     speed relative to the water was as high as 4.8 m x sec ^-1.  It is
     estimated from studies of swimming energetics that continuously
     foraging in a current vein flowing at 1.2 m x sec ^-1 would represent
     only small additional costs compared to foraging out of these
     currents.  However, previous observations of the same pod have shown
     that these dolphins keep foraging in this site when current speed
     reaches 2.7 m x sec ^-1; under such circumstances, the cost of
     foraging in this site was calculated to increase by 96%.  This
     suggests that foraging efficiency should be dramatically enhanced
     during rising tide since the dolphins consistently forage in these
     currents year round.