Fine-scale movement and habitat use of whitespotted eagle rays Aetobatus narinari in the Indian River Lagoon, Florida, USA

BC DeGroot,L Brewster,MJ Ajemian,G Roskar

doi:10.3354/esr01047

Abstract

Despite being crucial to the conservation of batoids (skates and rays), assessments of fine-scale movements and habitat use of these taxa are lacking in the scientific literature. Here we used active acoustic telemetry to characterize habitat use and movement behavior of the state-protected whitespotted eagle ray Aetobatus narinari in the Indian River Lagoon, Florida, USA. Seven mature individuals (6 males and 1 female) were individually tracked for a total of 119.6 h. Brownian bridge movement models of ray distribution showed the importance of habitats with high anthropogenic activity (i.e. boat traffic) such as inlets and channels, as well as clam aquaculture lease sites close to shore. This was supported by the significantly lower rates of movement in these habitats relative to other regions (offshore, open lagoon). Rate of movement significantly increased with temperature, suggesting that rays are more active during warmer periods. No tidal patterns in ray habitat use or distribution were evident. On average, rays used the deeper portions of the lagoon during the day and shallower portions during the night. While more extensive tracking is required to elucidate long-term movement patterns, this study is the first to characterize fine-scale habitat use by the whitespotted eagle ray in Florida while also identifying areas of potential interactions between this species and multiple anthropogenic threats.

Highlights

Estuaries and lagoons support a wide diversity of fishes and invertebrates due to high primary and secondary productivity (Beck et al 2001)
While general data on the occurrence and habitat use of whitespotted eagle rays in the Indian River Lagoon (IRL) were provided by Gilmore (1977, 1995) and Snelson & Williams (1981), the present study is the first to delineate fine-scale habitat use in Florida waters and assess how abiotic factors influence Rate of movement (ROM) for the species
As with other studies examining the role of abiotic factors in the movement ous acoustic tracking study of Hawaiian stingrays of sharks and rays (Matern et al 2000, Sims et al Hypanus lata showed increased ROM for the first 2 h 2006, Cartamil et al 2010), we found that ROM was of the track, assumed to be due to handling and tag- significantly affected by temperature

Summary

Introduction

Estuaries and lagoons support a wide diversity of fishes and invertebrates due to high primary and secondary productivity (Beck et al 2001) These complex systems are dynamic, varying considerably in abiotic factors (e.g. temperature, salinity, tidal range, sedimentation) that influence the diversity and behavior of animals in the system (Kennish 2002). The fine- and large-scale movements of many shark and ray species are attributed to abiotic factors (temperature, salinity, pH, tidal cycle), with the animals seeking out and/or remaining within the preferred environmental conditions (Schlaff et al 2014). Modeling has been used to understand how a species will respond to increased anthropogenic activities (Ivanova et al 2020), which can help to create or improve conservation plans These approaches require empirical data on habitat preferences in order to project a species’ distribution and response

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