Design and calibration of an acoustic telemetry system subject to upwelling events

  • L Singh
  • NJ Downey
  • MJ Roberts
  • DM Webber
  • MJ Smale
  • MA van den Berg
  • RT Harding
  • DC Engelbrecht
  • BM Blows

Abstract

The experiments described were designed to calibrate a hexagonal array of VEMCO VR2 receivers and transmitters (model V9P-6L-S256) in isothermal and stratified water columns off the south coast of South Africa. The array, configured with 500 m between receivers, was  designed to study the influence of water temperature and turbidity on the spawning behaviour of chokka squid Loligo reynaudii. Range tests comprised fixing a single VR2 receiver 2 m from the seabed and placing  a V9P transmitter at distances of 0 m, 75 m, 150 m, 225 m, 300 m, 375  m, 450 m and 500 m from the receiver for periods of 10 minutes at each position under isothermal conditions and in the presence of a  thermocline. The data indicated a range of 300 m for the former and 75 m for the latter conditions. The field performance of the V9P transmitter in a non-stratified water column compared well with the theoretical range of 352 m calculated using software to calculate  range. System saturation was investigated by repeating the range test using four, eight and 14 transmitters simultaneously. Field data indicated a significant decrease in signal detections due to signal collisions when more than eight transmitters were active simultaneously. It was demonstrated that the hexagonal configuration  of VR2s is optimal during isothermal conditions but inadequate during stratified conditions when acoustic dead zones of 350 m between VR2  receivers can occur.

Keywords: acoustic telemetry; isothermal; system saturation; thermocline; transmitter range

African Journal of Marine Science 2009, 31(1): 355–364

Author Biographies

L Singh
Marine and Coastal Management, Department of Environmental Affairs, Private Bag X2, Rogge Bay 8012, South Africa
NJ Downey
Bayworld Centre for Research and Education, Private Bag X2, Rogge Bay 8012, South Africa
MJ Roberts
Marine and Coastal Management, Department of Environmental Affairs, Private Bag X2, Rogge Bay 8012, South Africa; Bayworld Centre for Research and Education, Private Bag X2, Rogge Bay 8012, South Africa
DM Webber
VEMCO Ltd, 77 Chain Lake Drive, Halifax, Nova Scotia, Canada, B3S 1E1
MJ Smale
Bayworld Centre for Research and Education, Private Bag X2, Rogge Bay 8012, South Africa; Port Elizabeth Museum at Bayworld, PO Box 13147, Humewood 6013, South Africa
MA van den Berg
Marine and Coastal Management, Department of Environmental Affairs, Private Bag X2, Rogge Bay 8012, South Africa
RT Harding
Marine and Coastal Management, Department of Environmental Affairs, Private Bag X2, Rogge Bay 8012, South Africa
DC Engelbrecht
Damen Shipyards CT (Ltd), PO Box 6075, Rogge Bay 8012, South Africa
BM Blows
Bayworld Centre for Research and Education, Private Bag X2, Rogge Bay 8012, South Africa
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X