Are vertical migrations driven by circadian behaviour? Decoupling of activity and depth use in a large riverine elasmobranch, the freshwater sawfish (Pristis pristis)

Adrian C. Gleiss, David L. Morgan, Jeff M. Whitty, James J. Keleher, Sabrina Fossette, Graeme C. Hays

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Circadian rhythms occur widely amongst living organisms, often in response to diel changes in environmental conditions. In aquatic animals, circadian activity is often synchronised with diel changes in the depths individuals occupy and may be related to predator–prey interactions, where the circadian rhythm is determined by ambient light levels, or have a thermoregulatory purpose, where the circadian rhythm is governed by temperature. Here, these two hypotheses are examined using animal-attached accelerometers in juvenile freshwater sawfish occupying a riverine environment displaying seasonal changes in thermal stratification. Across seasons, diel patterns of depth use (shallow at night and deep in the day) tended to occur only in the late dry seasons when the water was stratified, whereas individuals were primarily shallow in the early dry season which featured no thermal stratification. Activity was elevated during crepuscular and nocturnal periods compared to daytime, regardless of the thermal environment. Our observation of resting at cooler depths is consistent with behavioural thermoregulation to reduce energy expenditure, whereas activity appears linked to ambient light levels and predator–prey interactions. This suggests that circadian rhythms in activity and vertical migrations are decoupled in this species and respond to independent environmental drivers.

Original languageEnglish (US)
Pages (from-to)181-191
Number of pages11
JournalHydrobiologia
Volume787
Issue number1
DOIs
StatePublished - Feb 1 2017
Externally publishedYes

Keywords

  • Accelerometer
  • Behavioural thermoregulation
  • Crepuscular
  • Diel vertical migration
  • Fish
  • Isolume
  • Sawfish

Fingerprint Dive into the research topics of 'Are vertical migrations driven by circadian behaviour? Decoupling of activity and depth use in a large riverine elasmobranch, the freshwater sawfish (Pristis pristis)'. Together they form a unique fingerprint.

Cite this