When large marine predators feed on fisheries catches: Global patterns of the depredation conflict and directions for coexistence

Abstract

The sustainable mitigation of human-wildlife conflicts has become a major societal and environmental challenge globally. Among these conflicts, large marine predators feeding on fisheries catches, a behaviour termed "depredation," has emerged concomitantly with the expansion of the world's fisheries. Depredation poses threats to both the socioeconomic viability of fisheries and species conservation, stressing the need for mitigation. This review synthesizes the extent and socio-ecological impacts of depredation by sharks and marine mammals across the world, and the

The Challenges of Managing Depredation and Bycatch of Toothed Whales in Pelagic Longline Fisheries: Two U.S. Case Studies

“…Switching from energetically costly, natural foraging on free-swimming prey to consumption of high-energy, restrained prey may provide energetic benefits to depredators and it has been shown that the reproductive output of depredating whales has increased in at least two populations (Tixier et al, 2015a;Esteban et al, 2016). However, this behavior also increases the risk of hooking or entanglement in fishing gear (e.g., Garrison, 2007;Forney et al, 2011) or lethal retaliation or harassment by fishermen (Guinet et al, 2015), both of which have led to negative population consequences for depredating populations (Poncelet et al, 2010;Guinet et al, 2015;Tixier et al, 2020b).…”

“…Interactions between cetaceans and pelagic longlines have been documented as a concern for fishermen since shortly after the establishment of industrial longline operations in the 1950s (e.g., Sivasubramaniam, 1964). An increase in published reports on depredation in the past two decades suggest that depredation is an increasing problem (Tixier et al, 2020b), and there has been strong interest in characterizing patterns of interactions between cetaceans and longlines to generate mitigation strategies (Werner et al, 2015;Tixier et al, 2020b). Numerous workshops involving fishermen, scientific experts, and fishery managers have assessed available mitigation strategies and considered approaches for research, testing, and implementation.…”

When opportunistic predators interact with swordfish harpoon fishing activities: shark depredation over catches in the Strait of Messina (central Mediterranean Sea)

“…This opportunistic behaviour often results in an interaction between sharks and fishing activities, when these predators are attracted by captured fish or baits (Gilman et al 2007(Gilman et al , 2008MacNeil et al 2009;Papastamatiou et al 2010;Raby et al 2014;Kumar et al 2016;Mitchell et al 2018Mitchell et al , 2019Ryan et al 2019;Tixier et al 2021). Indeed, sharks have been observed approaching the fishing catch at sea, using different behaviours: nudging, mouthing, visually selecting their prey or using olfactory sense (O'Shea et al 2015;Mitchell et al 2019).…”

“…Indeed, sharks have been observed approaching the fishing catch at sea, using different behaviours: nudging, mouthing, visually selecting their prey or using olfactory sense (O'Shea et al 2015;Mitchell et al 2019). Shark depredation affects commercial and recreational fisheries worldwide and this interaction has been recorded for several fishing gears, mainly longlines and hook-and-lines (Gilman et al 2007(Gilman et al , 2008MacNeil et al 2009;Raby et al 2014;Kumar et al 2016;Mitchell et al 2018Mitchell et al , 2019Ryan et al 2019;Tixier et al 2021). Recently, Tixier et al (2021) analysed the global patterns of the depredation conflicts between several large marine predators and fisheries across the world, underlining the importance of shark interactions with longlines.…”

“…On one hand, this interaction causes economical losses to fisheries (such as fishing gear and catches' damages, catches' reduction, financial losses, time, etc.) as well as increase the risks of injury for the opportunistic sharks, which may be hooked, caught or receive a fisherman' reaction (e.g., lethal responses from fishers) (Stevens et al 2000;Lewison et al 2004;Gilman et al 2007;Bradai et al 2018;Tixier et al 2021). This is a major concern when vulnerable or threatened sharks are involved.…”