ABSTRACT
As scientists have been documenting the decline of many shark populations (Manire and Gruber, 1990; Stevens et al, 2000; Baum et al, 2003; Ferretti et al, 2010; Clarke et al, 2013), it is now widely acknowledged that there is an urgent need to manage and regulate shark fisheries more effectively (FAO, 1999; Musick et al, 2000; Ward-Paige et al, 2012). Shark fisheries likely pre-date recorded history, but it is only over the last 50 years that shark catches have increased sharply and are now estimated conservatively at 1.4 million tonnes or 100 million individuals per year (Worm et al, 2013). Yet, due to sharks’ life history of slow growth, late maturity and limited reproduction, most species are intrinsically vulnerable to exploitation (Smith et al, 1998; Musick et al, 2000; Dulvy et al, 2008). Compounding this problem is the lack of spatial refuges due to the global expansion and industrialization of fishing (Watson et al, 2012). Today, the average annual exploitation rate of sharks is estimated to range from 6.4 per cent to 7.9 per cent of total biomass fished per year, which significantly exceeds the rebound rate of many species, averaging 4.9 per cent per year (Worm et al, 2013). Hence, it is unsurprising that shark populations have declined to a fraction of their former abundance, and that many continue to decline under current exploitation rates.
