Little fish carrying big hopes

Antonia Cooper and Rick Stuart-Smith explain finding the elusive red handfish

AMEMBER of the public who had been diving in Frederick Henry Bay reported that they’d seen what we suspected might be a red handfish. For the last 15 years or so there’s only been one known population of red handfish in the world, on a small patch of reef in the same region as the reported sighting, so we were keen to follow the report up.

Sightings of any handfish are rare so we always look into them, and this time we were also given a good set of GPS coordinates. But finding handfish isn’t easy, even with good directions. Red handfish are smaller than a human hand and they shelter under algae and seaweed where their colours blend in against the vegetation.

We planned to go diving in the reported location for around 3½ hours. At about the two-hour mark we hadn’t found anything and were all looking at each other thinking it’s not looking promising.

I signalled to my dive buddy and said we should start to head back in slowly. While they went to tell the other divers that we were going to leave I was half-heartedly flicking algae aside. And suddenly there it was, a red handfish. It was a very exciting moment as it was by pure chance that I saw its tail under a piece of red algae.

Once we’d found that first one we signalled to the other divers that we had a sighting, which then meant we could focus our search area to that same proximity. Sure enough, in a small area about 50 metres by 20 metres — about the size of a couple of tennis courts — we discovered another seven fish.

Until this discovery we thought there might have only been the one remaining population, which could number 20 to 40 individuals. We’re not really sure of the exact number because sightings are so rare and there hasn’t been much research into their population size.

Finding a new population, further than handfish walking distance from the existing one, is fantastic. It means there’s potentially a much bigger gene pool, and maybe also other populations out there that we’re yet to find. We need to look after the habitat and make sure that people are aware of how rare and endangered they are, so we can work to ensure they don’t become extinct. Antonia Cooper is a technical officer with the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS) and a Reef Life Survey diver. THE

red handfish has got to be close to the rarest fish in the world, especially when we thought there was just one population. Finding a second population is a huge relief. It effectively doubles how many we think there are left on the planet. It also gives us hope that there may be other populations out there. There probably are others but because they’re restricted to very small patches of reef it’s very hard to find them.

Unlike most fish, handfish don’t disperse across the ocean via a larval stage, so their range is very limited. They’re born from an egg, and look like a small version of an adult, with fins that resemble hands, and they walk to disperse. As a result, the only way for populations to mix is to walk. Increasing fragmentation of populations has probably been a major problem for them, and could easily have contributed to their increasing rarity over the last few decades.

We’ve already learned a lot from finding this second population. The habitat differs to where we usually know to look for them, so we can take some heart from knowing they don’t seem to be as critically dependent on that particular habitat. Perhaps the fact that both populations are so small is an indication that they’re very much sociable animals. Because the sites are so small, and the original one has remained in the exact same place for decades, locationbased management may be a good option to help protect them.

In between the two days surveying for red handfish, we also surveyed the locations

where Ziebell’s handfish have been seen in the past, around the Tasman Peninsula. Unfortunately the Ziebell’s handfish hasn’t been seen for more than a decade, and there’s a feeling it is quite possibly extinct, or at least close to. The only thing that would have been more exciting than finding more red handfish the other day would have been to find the Ziebell’s.

One of the reasons my colleague Professor Graham Edgar and I founded the citizen science program Reef Life Survey in 2007 was because as a small number of scientists we couldn’t possibly hope to survey the whole ocean and collect data on countless marine species. By enlisting 200 volunteer recreational divers through RLS we’ve been able to carry out surveys at more than 3200 sites in 51 countries. As a result we can provide high quality, unbiased and publicly available data that is used to better inform management and policy decisions and build public knowledge on the status of reefs.

The best chance of us finding more handfish populations in Tasmania, and indeed any rare species around the world, is for more divers to report sightings that they make, just as the diver did who helped us to find this new population of one of the world’s rarest fish.

While they went to tell the other divers that we were going to leave I was halfheartedly flicking algae aside. And suddenly there it was, a red handfish.