Significant reduction in shark (cucut) depredation rates when using an electrical deterrent device at Cocos (Keeling) Islands, Australia

Jonathan D. Mitchell; Victoria Camilieri-Asch; Dylan Skilton; William G. MacBeth; David Smith; Daryl Peter McPhee; Gary Jackson; Osman Macrae; Adam Amith

doi:10.1071/MF25165

Significant reduction in shark (cucut) depredation rates when using an electrical deterrent device at Cocos (Keeling) Islands, Australia

Jonathan D. Mitchell^*
, Victoria Camilieri-Asch
, Dylan Skilton
, William G. MacBeth
, David Smith
, Daryl Peter McPhee
, Gary Jackson
, Osman Macrae
, Adam Amith

^*Corresponding author for this work

Faculty of Society & Design

Research output: Contribution to journal › Article › Research › peer-review

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Abstract

Context:
Shark depredation is a human–wildlife conflict occurring in many fisheries around the world. At Cocos (Keeling) Islands in the Indian Ocean, high shark (known as cucut in the local Cocos–Malay language) depredation rates are causing costly loss of target catch and fishing gear for artisanal fishers, increased mortality for target species and negative attitudes towards sharks.

Aims:
This study tested the effectiveness of an electrical shark deterrent device (RPELX) for reducing shark depredation during line fishing for demersal fish species.

Methods:
A randomised experimental design was used to test the RPELX against a control treatment, during 11 days of deepwater fishing for demersal fish.

Key results:
Across 51 fishing sessions, 262 fish were caught. Results of a generalised linear model indicated that treatment and skipper had a significant effect on the number of fish depredated, with the RPELX reducing the probability of a depredation event occurring by 63%. The RPELX device also reduced shark bycatch and loss of fishing gear.

Conclusions:
Overall, the RPELX device can provide substantial environmental and socio-economic benefits to the marine ecosystem and community at Cocos (Keeling) Islands.

Implications:
Further testing of the RPELX in other demersal line fisheries, where depredation is occurring around the world, is strongly recommended.

Original language	English
Article number	MF25165
Pages (from-to)	1-13
Number of pages	13
Journal	Marine and Freshwater Research
Volume	77
Issue number	4
DOIs	https://doi.org/10.1071/MF25165
Publication status	Published - Mar 2026

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 3 Good Health and Well-being
SDG 14 Life Below Water

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Significant reduction in shark (cucut) depredation rates when using an electrical deterrent device at Cocos (Keeling) Islands, AustraliaFinal published version, 1.2 MBLicence: CC BY-NC-ND

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@article{2ff0d9b486b544cd8029f0a2b7d12070,

title = "Significant reduction in shark (cucut) depredation rates when using an electrical deterrent device at Cocos (Keeling) Islands, Australia",

abstract = "Context: Shark depredation is a human–wildlife conflict occurring in many fisheries around the world. At Cocos (Keeling) Islands in the Indian Ocean, high shark (known as cucut in the local Cocos–Malay language) depredation rates are causing costly loss of target catch and fishing gear for artisanal fishers, increased mortality for target species and negative attitudes towards sharks. Aims: This study tested the effectiveness of an electrical shark deterrent device (RPELX) for reducing shark depredation during line fishing for demersal fish species. Methods: A randomised experimental design was used to test the RPELX against a control treatment, during 11 days of deepwater fishing for demersal fish. Key results: Across 51 fishing sessions, 262 fish were caught. Results of a generalised linear model indicated that treatment and skipper had a significant effect on the number of fish depredated, with the RPELX reducing the probability of a depredation event occurring by 63\%. The RPELX device also reduced shark bycatch and loss of fishing gear. Conclusions: Overall, the RPELX device can provide substantial environmental and socio-economic benefits to the marine ecosystem and community at Cocos (Keeling) Islands. Implications: Further testing of the RPELX in other demersal line fisheries, where depredation is occurring around the world, is strongly recommended.",

author = "Mitchell, \{Jonathan D.\} and Victoria Camilieri-Asch and Dylan Skilton and MacBeth, \{William G.\} and David Smith and McPhee, \{Daryl Peter\} and Gary Jackson and Osman Macrae and Adam Amith",

year = "2026",

month = mar,

doi = "10.1071/MF25165",

language = "English",

volume = "77",

pages = "1--13",

journal = "Marine and Freshwater Research",

issn = "1323-1650",

publisher = "CSIRO",

number = "4",

}

Significant reduction in shark (cucut) depredation rates when using an electrical deterrent device at Cocos (Keeling) Islands, Australia. / Mitchell, Jonathan D.; Camilieri-Asch, Victoria; Skilton, Dylan et al.
In: Marine and Freshwater Research, Vol. 77, No. 4, MF25165, 03.2026, p. 1-13.

Research output: Contribution to journal › Article › Research › peer-review

TY - JOUR

T1 - Significant reduction in shark (cucut) depredation rates when using an electrical deterrent device at Cocos (Keeling) Islands, Australia

AU - Mitchell, Jonathan D.

AU - Camilieri-Asch, Victoria

AU - Skilton, Dylan

AU - MacBeth, William G.

AU - Smith, David

AU - McPhee, Daryl Peter

AU - Jackson, Gary

AU - Macrae, Osman

AU - Amith, Adam

PY - 2026/3

Y1 - 2026/3

N2 - Context: Shark depredation is a human–wildlife conflict occurring in many fisheries around the world. At Cocos (Keeling) Islands in the Indian Ocean, high shark (known as cucut in the local Cocos–Malay language) depredation rates are causing costly loss of target catch and fishing gear for artisanal fishers, increased mortality for target species and negative attitudes towards sharks. Aims: This study tested the effectiveness of an electrical shark deterrent device (RPELX) for reducing shark depredation during line fishing for demersal fish species. Methods: A randomised experimental design was used to test the RPELX against a control treatment, during 11 days of deepwater fishing for demersal fish. Key results: Across 51 fishing sessions, 262 fish were caught. Results of a generalised linear model indicated that treatment and skipper had a significant effect on the number of fish depredated, with the RPELX reducing the probability of a depredation event occurring by 63%. The RPELX device also reduced shark bycatch and loss of fishing gear. Conclusions: Overall, the RPELX device can provide substantial environmental and socio-economic benefits to the marine ecosystem and community at Cocos (Keeling) Islands. Implications: Further testing of the RPELX in other demersal line fisheries, where depredation is occurring around the world, is strongly recommended.

AB - Context: Shark depredation is a human–wildlife conflict occurring in many fisheries around the world. At Cocos (Keeling) Islands in the Indian Ocean, high shark (known as cucut in the local Cocos–Malay language) depredation rates are causing costly loss of target catch and fishing gear for artisanal fishers, increased mortality for target species and negative attitudes towards sharks. Aims: This study tested the effectiveness of an electrical shark deterrent device (RPELX) for reducing shark depredation during line fishing for demersal fish species. Methods: A randomised experimental design was used to test the RPELX against a control treatment, during 11 days of deepwater fishing for demersal fish. Key results: Across 51 fishing sessions, 262 fish were caught. Results of a generalised linear model indicated that treatment and skipper had a significant effect on the number of fish depredated, with the RPELX reducing the probability of a depredation event occurring by 63%. The RPELX device also reduced shark bycatch and loss of fishing gear. Conclusions: Overall, the RPELX device can provide substantial environmental and socio-economic benefits to the marine ecosystem and community at Cocos (Keeling) Islands. Implications: Further testing of the RPELX in other demersal line fisheries, where depredation is occurring around the world, is strongly recommended.

U2 - 10.1071/MF25165

DO - 10.1071/MF25165

M3 - Article

SN - 1323-1650

VL - 77

SP - 1

EP - 13

JO - Marine and Freshwater Research

JF - Marine and Freshwater Research

IS - 4

M1 - MF25165

ER -

Significant reduction in shark (cucut) depredation rates when using an electrical deterrent device at Cocos (Keeling) Islands, Australia

Abstract

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