Environmental Influences on Long-term Movement Patterns of a Euryhaline Elasmobranch ( Carcharhinus leucas ) Within a Su
- PDF / 2,380,309 Bytes
- 18 Pages / 595.276 x 790.866 pts Page_size
- 12 Downloads / 183 Views
Environmental Influences on Long-term Movement Patterns of a Euryhaline Elasmobranch (Carcharhinus leucas) Within a Subtropical Estuary R. D. Pillans 1
&
G. C. Fry 1 & A. D. L. Steven 1 & T. Patterson 2
Received: 2 December 2019 / Revised: 27 April 2020 / Accepted: 30 April 2020 # Coastal and Estuarine Research Federation 2020
Abstract It is well established that juvenile bull sharks (Carcharhinus leucas) use rivers and estuaries as nursery areas; however, there is a large degree of variation in habitat preference (with respect to salinity and distance upstream) between studies at national and international scales. To investigate habitat preference and the influence of water quality on movement of bull sharks, we monitored 36 juveniles using an array of acoustic receivers in the Logan and Albert Rivers, Australia, for 30 months. Acoustic data were used to estimate mean daily distance upstream, and generalized additive models were used to determine the influence of flow, salinity, temperature, dissolved oxygen, turbidity, and chlorophyll a on movement. A model that included flow, salinity, dissolved oxygen, and chlorophyll a explained 89% of the variance. Movement was tightly correlated to both flow and salinity with sharks moving downstream in response to increasing flow/declining salinity and upstream during low flow/ increasing salinity. During periods of negligible flow and stable salinity, animals moved upstream and downstream in response to decreasing and increasing dissolved oxygen, respectively. Dissolved oxygen and temperature were strongly negatively correlated and interchangeable within the model. Despite fluctuations in environmental salinity (0–32 psu) and a strong declining gradient in salinity with increasing distance upstream, bull sharks remained within a narrow band of salinity (6–10 psu) throughout the tracking period. The results of this study indicate that habitat choice by juvenile bull sharks is a complex tradeoff between physiology, food availability, and predator avoidance, resulting in large differences between adjacent systems and more broadly across their range. Keywords Bull shark . Movement . Acoustic telemetry . Habitat preference . Estuary . Floods . Salinity
Introduction Euryhaline elasmobranch species are physiologically adapted to live in both marine (~ 35 psu) and freshwater (0 psu) environments and are capable of living in and moving freely between salinity gradients (Hazon et al. 2003; Pillans and Franklin 2004; Pillans 2006; Pillans et al. 2006; Werry et al. Communicated by Mark S. Peterson Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12237-020-00755-8) contains supplementary material, which is available to authorized users. * R. D. Pillans [email protected] 1
CSIRO Oceans and Atmosphere, 306 Carmody Road, St Lucia, Queensland 4072, Australia
2
CSIRO Oceans and Atmosphere, Castray Esplanade, Hobart, Tasmania 7000, Australia
2011). As a group, over one-third of the world’s obligate freshwater and euryhaline elasmo
Data Loading...
