Bull shark ( Carcharhinus leucas ) exclusion properties of the sharksafe barrier and behavioral validation using the ARIS technology

Abstract

a b s t r a c tMagnetic deterrents have recently been employed to assess their ability to reduce elasmobranch mortality in beach nets. With previous studies exhibiting promise, the present study examined the ability of a magnetic barrier technology, known as the Sharksafe Barrier, to exclude bull sharks (Carcharhinus leucas) from bait, and how behavioral interactions may change with variations in environmental and biological factors. Generalized linear mixed model analyses based on 114, 30-min trials illustrate that all interacting C. leucas were successfully excluded from baited procedural control and magnetic regions (i.e. zero entrances through either region). Avoidance and pass around frequencies significantly differed from the control region and were based on situational context. To enhance behavioral analysis techniques, an Adaptive Resolution Imaging Sonar (ARIS) was employed which revealed that C. leucas distance from and swim speed associated with the magnetic barrier region were significantly greater than those associated with the procedural control region. This study demonstrates the Sharksafe barrier's effectiveness in excluding C. leucas from baited regions, regardless of variations in biological and/or environmental parameters. While other bather protection systems (e.g. beach nets and drumlines) continue to be used, this study exhibits promise that the Sharksafe barrier can be an eco-friendly alternative to beach nets.

Testing the exclusion capabilities and durability of the Sharksafe Barrier to determine its viability as an eco‐friendly alternative to current shark culling methodologies

“…Over 18 days, a minimum of 23 different C. leucas interacted with the Sharksafe Barrier and no sharks entered through the barrier elements to feed on the bait. Thus, the exclusion capabilities observed in the present study and those in O'Connell, Hyun et al () illustrate that the system is not C. carcharias ‐ specific and, additional research on species that pose a potential threat to beachgoers (e.g. tiger sharks – Galeocerdo cuvier ) is required to determine if this technology can be a viable alternative to general shark culling methods.…”

“…This small gap in magnetism may be sufficiently large enough to facilitate small elasmobranch entry. In contrast to these findings and suggestive that this system is not C. carcharias ‐specific, O'Connell, Hyun et al () conducted a similar Sharksafe Barrier exclusion study on the bull shark ( Carcharhinus leucas ), another potentially dangerous species. Over 18 days, a minimum of 23 different C. leucas interacted with the Sharksafe Barrier and no sharks entered through the barrier elements to feed on the bait.…”

“…~30–50 cm) between adjacent pipes overlapped creating a continuous magnetic field region on the horizontal scale. Unlike previous experiments where multiple replicates of each section were deployed (O'Connell, Andreotti et al, ) and a completely randomized experimental design was implemented (Hulbert, ) or the placement of the experimental barrier units was changed during experimentation (O'Connell, Hyun, Rillahan & He, ), researchers were limited by permit regulations and therefore, utilized the same experimental setup throughout the experimental period.…”

Spawning behaviour of Allis shad Alosa alosa: new insights based on imaging sonar data

“…A dual-frequency-identification-sonar (DIDSON -Soundmetrics Corp.; www.soundmetrics.com) served for data acquisition. It is independent of light and insensitive to turbidity by delivering video-like sequences (Belcher et al, 2001) with monitoring ranges up to 30 m. Imaging sonar technology has been used successfully in a variety of studies to analyse fish behaviour (Tiffan et al, 2010;Rakowitz et al, 2012;Jůza et al, 2013;Price et al, 2013;Becker & Suthers, 2014;O'Connell et al, 2014). In the present study the imaging sonar was tested for its suitability to monitor A. alosa spawning by means of detection and quantification of mating events.…”

Hydroacoustic and Pressure Turbulence Analysis for the Assessment of Fish Presence and Behavior Upstream of a Vertical Trash Rack at a Run-of-River Hydropower Plant

“…DIDSON (Dual-Frequency Identification [33]) and ARIS (Adaptive Resolution Identification [34]) sonars, which produce video-identical image sequences, represent the state of the art technology in the field of visualization sonars and are often referred to as "acoustic cameras" [35]. The technology is most commonly used in dark and turbid waters where optical systems cannot capture meaningful data.…”