Ongoing Collapse of Coral-Reef Shark Populations

Abstract

Marine ecosystems are suffering severe depletion of apex predators worldwide; shark declines are principally due to conservative life-histories and fisheries overexploitation. On coral reefs, sharks are strongly interacting apex predators and play a key role in maintaining healthy reef ecosystems. Despite increasing fishing pressure, reef shark catches are rarely subject to specific limits, with management approaches typically depending upon no-take marine reserves to maintain populations. Here, we reveal that this approach is failing by documenting an ongoing collapse in two of the most abundant reef shark species on the Great Barrier Reef (Australia). We find an order of magnitude fewer sharks on fished reefs compared to no-entry management zones that encompass only 1% of reefs. No-take zones, which are more difficult to enforce than no-entry zones, offer almost no protection for shark populations. Population viability models of whitetip and gray reef sharks project ongoing steep declines in abundance of 7% and 17% per annum, respectively. These findings indicate that current management of no-take areas is inadequate for protecting reef sharks, even in one of the world's most-well-managed reef ecosystems. Further steps are urgently required for protecting this critical functional group from ecological extinction.

Reef-use and residency patterns of a baited population of silky sharks, Carcharhinus falciformis, in the Red Sea

“…There is a lack of validated age and growth information, limiting the ability of fisheries managers to make informed decisions (Beerkircher and Shivji 2003;Watson et al 2009). In addition, there is insufficient knowledge of their movement patterns that may confound management efforts, exemplified in the ongoing collapse of reef shark populations on the Great Barrier Reef, Australia (Robbins et al 2006), where grey reef sharks, Carcharhinus amblyrhynchos, have been reported to display limited reef fidelity (Heupel et al 2010).…”

From hunters to nature observers: a record of 53 years of diver attitudes towards sharks and rays and marine protected areas

“…Many species of sharks and rays are under increasing pressure around the world including the GBR (Robbins et al 2006;Heupel et al 2009). Sharks and rays perform important ecological roles in marine ecosystems (Stevens et al 2000;Kitchell et al 2002;Heithaus et al 2008) and growing concerns have prompted GBR managers to list shark conservation and management as a priority issue (GBRMPA 2009a).…”

Retained fishing gear and associated injuries in the east Australian grey nurse sharks (Carcharias taurus): implications for population recovery

“…The viability of certain shark populations is of global concern (Robbins et al 2006;Dulvy et al 2008;Ferretti et al 2008). Many shark species that are targeted commercially, caught and harvested as bycatch, or captured incidentally and released by recreational or commercial fishers are at risk of over-exploitation and possible extinction (Baum et al 2005;Campana et al 2006;Myers et al 2007).…”