Can shark research lead to better marine protected areas? A recent study of the D’Arros and St Joseph Special Reserve in the Seychelles suggests this could be the case. And the solution lies in changing a single word in the definition of a marine protected area’s boundaries. A solution that’s as good for the people of the Seychelles as it is for the sharks.
In the Seychelles, marine protected areas tend to focus on the protection of a single species or part of the coast. As a result, in this island nation they rarely extend further than 400 metres (450 yards) offshore. Even the largest marine protected area in the Seychelles, Aldabra, stretches a mere kilometre (1,100 yards) from the high tide mark of the beach. ‘Given the strong historical focus on the conservation of turtles and reefs, and given the potential value of sharks, we thought we’d look at how existing models in the Seychelles work for things like sharks,’ explains James Lea, lead author of the study. The D’Arros and St Joseph Special Reserve would have followed the same model as Aldabra, declaring the boundary of the reserve one kilometre from the high tide mark. However, James suspected that this would leave gaps in the protection of top predators like sharks. He argues that the lagoon habitat found in St Joseph Atoll is rare in the Seychelles and is crucial for numerous species, from creatures at the bottom of the ocean to soaring seabirds. ‘A lagoon habitat that is completely cut off from the surrounding ocean at low tide is incredibly rare in the Seychelles. There are very few atolls like St Joseph, and none close by. If they provide the only nursery habitats for species like the lemon shark and the turtles and rays and various reef fishes either regionally or in the Seychelles as a whole, they might be more valuable than they appear.’
The study used data from tagged sharks and turtles to understand how the habitat use of six species relates to the traditional one-kilometre boundary from the high tide mark. ‘One of the most important things about the D’Arros and St Joseph Special Reserve is that it has a very large and wide reef flat that is completely covered at high tide,’ says James. ‘In some places, the reef flat at St Joseph can be more than a kilometre wide, so actually, along some of these sections there might as well be no marine protected area.’ But shifting the boundary from one kilometre from the high tide mark to one kilometre from the low tide mark makes a considerable difference.
The single word change to the definition increases the size of the marine protected area by 50% and augments the protection of shark habitat by 30%. James concedes that although it’s neither a perfect nor a final solution, such a minor change that leads to significant improvements in the level of protection provided looks like a win.
Two species of shark benefit the most from the change: the blacktip reef shark Carcharhinus melanopterus and the lemon shark Negaprion acutidens, which use the lagoon and flats most intensively. Shifting the boundary definition to the low tide mark protects all reef and atoll habitats, as well as any species that spend all their time in those habitats. Telemetry data tell us that juvenile lemon sharks in particular don’t leave the atoll. The change to increase the size of the marine protected area affords them protection at a vulnerable life stage. ‘Suddenly you’re protecting these sharks until they’re just about mature,’ James says. Other studies on sharks have suggested that protecting individuals as they approach sexual maturity is the most important way to achieve population stability. James concurs, saying ‘Protecting maturing individuals can be the most efficient way to protect a species.’ For threatened lemon sharks, this is crucial.
Whereas some species receive complete protection, the protection for others is only partial. The tagging data on large grey reef sharks show them essentially patrolling the outer reefs that are not protected by the current special reserve. However, smaller grey reef sharks are protected – and that is a positive. Nonetheless, protecting sharks on the outer reefs, and more pelagic sharks in the Seychelles, will take more work. This could perhaps be the focus of future study for James.
Although his work concentrates on sharks, James is hesitant to put too much importance on sharks alone. ‘One of the main goals of conservation, I think, should be to maintain the functionality of an ecosystem rather than just ensuring that one species doesn’t get exploited,’ he says. ‘Degradation of habitat and the exploitation of other species can cause the ecosystem to fall apart anyway and then what’s the point?’ His study highlights the importance of understanding the use of habitat by a number of species, from manta rays Manta alfredi to hawksbill turtles Eretmochelys imbricata, if marine protected areas are to be effective.
So can shark research improve the management of these areas? Potentially, answers James. When presented with the results of the study, the Seychelles’ Ministry of Environment, Energy and Climate Change listened. The study contributed to the government applying the low tide boundary to the special reserve, effectively ensuring protection to the entire lagoon system and coastal reefs. That’s thanks to sharks.
Sharks, rays, turtles and many other marine species benefit from this, but James stresses that people also benefit. In the years he has spent studying sharks in the Seychelles, he’s seen how they are part of the culture of the islands. ‘There is a strong cultural identity with shark fishing in the Seychelles,’ he explains. Historically, these waters teemed with sharks and people made the most of their abundance. Although shark population numbers have undoubtedly declined, James takes the stance that fishing for sharks and protecting sharks are not mutually exclusive. ‘There is often this misconception that we just want to stop fishermen, to stop people living off the sea,’ he points out. ‘Actually what we want to do is ensure that their grandchildren will still be able to live off the sea.’
That’s why it’s so important to protect the waters around D’Arros Island and St Joseph Atoll. If these waters are as crucial to the regional recruitment of various marine species as James suspects, there is a broader benefit to the special reserve. Protection may also support the long-term sustainability of a culturally important practice. The D’Arros and St Joseph Special Reserve is good for sharks and it’s good for the people of the Seychelles.
A biological field station based on D’Arros Island in the Amirantes Group, Seychelles, the SOSF D’Arros Research Centre (SOSF–DRC) conducts research on the pristine D’Arros Island and St Joseph Atoll and the waters around them. In recognition of the islands’ outstanding natural values, the research centre was established in 2004 and tasked with becoming a regional centre of excellence for marine and tropical island conservation. Initially, collaborations were established with local and international institutions and baseline ecological surveys were conducted in the various habitats. Over the ensuing years an increasing number of research projects and monitoring programmes were implemented in response to questions raised by the baseline surveys and by visiting scientists. More recently, the centre expanded its activities to include ecosystem restoration and environmental education.
Today the SOSF–DRC boasts the longest-running nesting turtle monitoring programme in the Amirantes and the most detailed and technically advanced coral reef monitoring programme in the Seychelles, making use of techniques such as stereo-video photogrammetry, photoquadrats, remote underwater video systems (BRUVs) and visual census. The research centre also maintains the largest acoustic receiver array in the Seychelles, which monitors the local movements of sharks, manta rays, stingrays, turtles and fish. Since its inception in 2004, the centre has initiated no fewer than 36 research projects in collaboration with more than 26 conservation institutions. The projects have resulted in 10 peer-reviewed scientific papers, one PhD and one MSc dissertation, five conference presentations and 27 scientific reports.