It’s not often that a chance to wrangle a wrasse comes up. Nor is it a common perception that fishes – outside the realms of animated film – are endowed with charisma. Yet when the team at the SOSF-D’Arros Research Centre did find themselves tagging humphead wrasse, they came to the conclusion that this was very much more than merely an extremely large fish.
The facial expression of the humphead wrasse can fairly be described as one of concern. First there is its furrowed brow, made by the fish’s namesake forehead hump; then its mouth, downturned and slightly agape. But look more closely at those chameleon-like eyes and you’ll find an essence of curiosity and astuteness that pushes this reef fish’s charisma arguably past that of Nemo.
Listed by the IUCN as an Endangered and conservation-dependent species, the humphead wrasse has reason to be concerned. The species is naturally uncommon and faces a significant and increasing threat from the food trade in live reef fish, where it is one of the species with the highest market value. At the SOSF-D’Arros Research Centre in the Seychelles we were also concerned. And curious.
During annual coral reef and fish surveys, we had observed humphead wrasse but had very little understanding of the species’ population size and structure. Was it common or were we just seeing the same five individuals? A 2014 study near Farquhar Atoll, in the southernmost island group of the Seychelles, found a remarkable abundance of humphead wrasse. The numbers suggested that Seychelles waters may host the highest known densities of the species in the world. Were these healthy populations limited to the country’s most remote reaches or would we find a similar number around our little island as well? And if we did, which marine habitats provide refuge for them? Making the most of the acoustic receiver network around D’Arros Island and St Joseph Atoll, we set out to answer these questions by embarking on a study to acoustically tag humphead wrasse.
A meaningful study would need a decent sample size to answer our questions accurately, so we set the tagging target at 20 wrasse. Even then I worried that this was too ambitious a goal; the humphead wrasse we’d seen were shy and we still didn’t know how many there were. The team at the SOSF-DRC has worked on tagging sharks, rays and other fish for years, but humphead wrasse would be a different kettle. Expert help was the only way forward.
We first reached out to researcher and friend Andrew Gray from the National Oceanic and Atmospheric Administration (NOAA), who had been involved in a study of humphead wrasse at Palmyra Atoll in the Pacific. He was encouraging, but warned us about the challenges. ‘First off, don’t try to catch any until you are fully prepared,’ he wrote. ‘They are smart and wary and you only have one chance per wrasse. If you try and fail, you’re never going to get that wrasse again – it will just swim off when it sees you.’
One chance per wrasse. For a viable study, we needed to tag a minimum of 10 wrasse. If there really were only five of them, the project was doomed. If we discovered large numbers but bungled attempts to catch more than six, we’d fail.
With little room for mistakes, we knew we needed more help. The study would have to be led by the best. We’d have to find the person with the most experience of tagging humphead wrasse in the world, preferably in an environment similar to that of D’Arros Island and St Joseph Atoll. Someone with a passion for these fish, the kind of person who would go so far as to shave his hair into an outline of a humphead wrasse. That could only be Dr Kevin Weng, lead researcher for a landmark study of the species at Palmyra Atoll. Lucky for the D’Arros Research Centre, he accepted the position of project leader and fine-tuned the research proposal into an SOSF-funded project. When asked to assemble his team, he called on Andrew Gray as chief wrasse wrangler.
Our expert Kevin and wrangler Andrew joined us in the Seychelles in October 2017. With the help of SOSF-DRC research assistant Luke Gordon, we’d done our best to prepare for these wary fishes. But challenges arose from the start: schedule changes crunched our window for field work from one month to just under three weeks and Andrew’s luggage had been lost somewhere along his four connecting flights. The pressure was on: 20 tags in 20 days. Actually, less than 20 days – before deploying any tags we had to complete surveys to establish the population and develop a reliable catch method.
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.