ABSTRACT
Shark populations have experienced a dramatic global decline over the past few decades (Baum et al, 2003; Ferretti et al, 2008; Baum and Myers, 2004). The almost universal global collapse of shark populations is driven by two main factors. The first is the rise in demand for shark products (Lack et al, 2006; Rose, 1996), which has led to a sharp increase in fishing effort and landings over the last 30 years. The second is the intrinsic vulnerability of sharks to fishing pressure, due to their conservative life history strategies (Field et al, 2009). In general, sharks are K-selected, i.e. they are long-lived, slow-growing and take a long time to reach sexual maturity (Last and Stevens, 2009; also see Chapter 2). They invest considerable amounts of energy in the production of a few offspring that then have a high survival rate. These characteristics make them susceptible to even modest levels of fishing mortality. Unlike in many bony fishes (teleosts), recruitment is tightly linked to stock size, meaning that any level of mortality in adult stocks will have immediate consequences in terms of recruitment in the following years (Smith et al, 1998). Recruitment overfishing, the level of harvesting at which the reproductive potential of a population is affected, starts early in the history of most shark fisheries. The rebound potential for shark populations is therefore lower than most other harvested marine resources. However, while this provides the rationale for sharks’ intrinsically high risk of extinction, by the same reasoning lies therein a nugget of hope for successful management.
