Reducing the environmental impact of shark-control programs: a case study from KwaZulu-Natal, South Africa

Abstract

Abstract. Large-scale shark-control programs at popular beaches in New South Wales and Queensland, Australia, and KwaZulu-Natal (KZN), South Africa, provide protection against shark attack. Although these programs have enhanced bathing safety, reducing the environmental impacts of decades of fishing for large sharks and the associated by-catch remains a challenge. Over the past three decades, there have been several interventions to reduce such impact in the KZN program. The first was the release of all live sharks, including those species known to be responsible for fatal shark attacks. Measures to reduce catches of sharks associated with the winter influx of shoals of sardines, Sardinops sagax, have been increasingly successful. In addition, extensive removal of nets has resulted in a major reduction in effort. Collectively, these initiatives reduced mortalities of sharks by 64%. Baited lines, termed drumlines, were introduced at 18 beaches, where they replaced some of the nets. The former had a far lower by-catch of rays, turtles and cetaceans and significantly lower catches of certain shark species. Replacement of some nets with drumlines is planned for the remaining beaches. Only two attacks, both non-fatal, have occurred at protected beaches in KZN over the past three decades, indicating that the program has maintained its public safety mandate while it has succeeded in reducing its impact on the environment.

The importance of research and public opinion to conservation management of sharks and rays: a synthesis

“…However, these public safety programs also come at an environmental cost of elevated mortality, not just of sharks, but also other species (turtles, dolphins, dugongs, rays and fishes). This collateral environmental damage has resulted in the removal of some programs (Wetherbee et al 1994) and others have made changes to minimise these environmental effects while maintaining public safety (Cliff and Dudley 2011). In addition to their perceived public-safety benefits, shark-control programs have also been an invaluable source of information on shark and ray life histories (e.g.…”

Transforming shark hazard policy: Learning from ocean-users and shark encounter in Western Australia

“…According to the program's board the nets (totalling 23.4km) and drumlines 'function by reducing shark numbers in the vicinity of protected beaches, thereby lowering the probability of encounters between sharks and people at those beaches' (KwaZulu-Natal Sharks Board, 2011; see also Cliff and Dudley, 2011). In other words, human risk is reduced by killing large numbers of sharks, most of which pose no threat to human life.…”

“…The impacts of kill-based control programs on shark populations and marine ecology are substantial, including negative implications for populations of threatened shark species, potential effects of removal of large predators from near-shore areas, and mortality of diverse by-catch of non-target shark species, rays, turtles and cetaceans (Cliff and Dudley, 2011;McPhee, 2012). O'Connell et al (2014,38) have noted that 'anthropogenic sources of shark mortality have had a major negative influence on local and migratory shark populations'.…”

The Importance of Academic Research in the Field of Shark-Human Interactions: A Three-Pronged Approach to a Better Understanding of Shark Encounters

“…This raises the question why prevention of incidents, based on this emerging picture, is still in its infancy despite this knowledge, and the only solutions for beach protection seem to remain shark nets and drum lines, which are harmful to the sharks and other marine life [60,61]. One problem is that there is a severe lack of awareness of which areas should be avoided for any water sport activity.…”