Topography and biological noise influence acoustic telemetry on coral reefs

F. Cagua, M. Berumen, E. Tyler
Coral Reefs, 32, pp. 1123-1134, (2013)

Topography and biological noise influence acoustic telemetry on coral reefs


Passive monitoring ,  Acoustic transmitters,   Detection efficiency,  Saudi Arabia


​Acoustic telemetry is an increasingly commontool for studying the movement patterns, behavior and site fidelity of marine organisms,  but  to  accurately  interpret acoustic  data,  the  variability,  periodicity  and  range  of detectability  between  acoustic  tags  and  receivers  must  be understood.  The  relative  and  interactive  effects  of  topog-raphy  with  biological  and  environmental  noise  have  not been quantified on coral reefs. We conduct two long-term range tests (1- and 4-month duration) on two different reef types in the central Red Sea to determine the relative effect of  distance,  depth,  topography,  time  of  day,  wind,  lunar phase,  sea  surface  temperature  and  thermocline  on  detec-tion  probability.  Detectability,  as  expected,  declines  with increasing distance between tags and receivers, and we find average detection ranges of 530 and 120 m, using V16 and V13 tags, respectively, but the topography of the reef can significantly  modify  this  relationship,  reducing  the  range by* 70 %,  even  when  tags  and  receivers  are  in  line-of- sight. Analyses that assume a relationship between distance and detections must therefore be used with care. Nighttime detection range was consistently reduced in both locations, and  detections  varied  by  lunar  phase  in  the  4-month  test, suggesting a strong influence of biological noise (reducing detection probability up to 30 %), notably more influential than  other  environmental  noises,  including  wind-drivennoise,  which  is  normally  considered  important  in  open-water   environments.   Analysis   of   detections   should   becorrected in consideration of the diel patterns we find, and range  tests  or  sentinel  tags  should  be  used  for  more  than1 month to quantify potential changes due to lunar phase. Some  studies  assume  that  the  most  usual  factor  limitingdetection  range  is  weather-related  noise;  this  cannot  be extrapolated to coral reefs.


DOI:  10.1007/s00338-013-1069-2


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