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Marine Ecology Progress Series

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MEPS 720:117-131 (2023)  -  DOI:

Persistent transboundary movements of threatened sharks highlight the importance of cooperative management for effective conservation

Ryan Daly1,2,*, Stephanie K. Venables3, Toby D. Rogers4,5, John D. Filmalter2, Tessa N. Hempson6,7,8, Taryn S. Murray2, Nigel E. Hussey9, Isabel Silva10, Marcos A. M. Pereira11, Bruce Q. Mann1, Bilardo A. S. Nharreluga3, Paul D. Cowley2

1Oceanographic Research Institute, PO Box 10712, Marine Parade, Durban 4056, South Africa
2South African Institute for Aquatic Biodiversity (SAIAB), Private Bag 1015, Makhanda 6140, South Africa
3Marine Megafauna Foundation, Centro de Investigação Científica Megafauna Marinha, Tofo Beach, Mozambique
4Institute for Communities and Wildlife in Africa (iCWild), University of Cape Town, Cape Town 7701, South Africa
5Shark Spotters, Cape Town 7945, South Africa
6ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia
7Oceans Without Borders, 164 Katherine Street, Sandown, Johannesburg 2010, South Africa
8Mission Blue, PO Box 6882, Napa, California 94581, USA
9University of Windsor, Department of Integrative Biology, Windsor, Ontario N9B 3P4, Canada
10Universidade do Lúrio, Bairro Eduardo Mondlane, 3200 Pemba, Mozambique
11Fundação Likhulu, 4115 Maputo, Mozambique
*Corresponding author:

ABSTRACT: Migratory sharks play a key ecological role through movements within and among marine ecosystems, yet many populations are declining. Addressing the decline is especially challenging for wide-ranging species, as they may undertake movements between countries with disparate conservation priorities. To investigate the transboundary migrations of threatened sharks between neighbouring South Africa and Mozambique, we tracked 4 commonly occurring carcharhinid species (bull, blacktip, tiger and grey reef sharks). A total of 102 individuals were fitted with long-life acoustic transmitters and monitored for 4 yr (2018-2022) on an acoustic receiver network of 350 receivers. During this period, 63% of tagged bull sharks (n = 19), 87% of blacktips (n = 13), 94% of tiger (n = 16) and 25% of grey reef sharks (n = 3) undertook transboundary movements. The frequency of mean transboundary movements per year ranged between 1.3 ± 1.5 (SD) for grey reef sharks and 81 ± 35.6 for tiger sharks. Blacktip, bull and tiger sharks all undertook long-distance transboundary migrations ranging from 980 to 2256 km. These data confirm high connectivity between neighbouring countries by threatened sharks undertaking persistent transboundary movements. This study emphasizes the need for collaborative transboundary cooperation between the 2 countries and the alignment of regional management plans and interventions to address declining shark populations in this region of the Western Indian Ocean.

KEY WORDS: Carcharhinidae · South Africa · Mozambique · Acoustic telemetry · Connectivity

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Cite this article as: Daly R, Venables SK, Rogers TD, Filmalter JD and others (2023) Persistent transboundary movements of threatened sharks highlight the importance of cooperative management for effective conservation. Mar Ecol Prog Ser 720:117-131.

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