WM: From an environmental perspective, are the artificial reefs bringing in more species? Is our bay becoming richer?
They will not bring more species into the bay, but they have increased biodiversity in a small area, although as far as making the bay richer it’s hard to tell just yet. As far as habitat goes, it’s not going to compete with a natural reef that’s been there for a long time - it’ll take time to find out. But other research has shown that even shipwrecks that have been there for over a hundred years have assemblages that are completely different to a nearby natural reef, but it still does support a diverse array of species. [Artificial reefs] worked for snapper and other fish, and recreational fishers do catch fish there.
WM: Do you find that recreational fishers are happy to work with fisheries and scientists?
Yes, they have been quite helpful. Anglers have provided ‘angler diaries’ which list various things, including the species they’ve caught and how many. The concept and implementation of artificial reefs are popular amongst recreational fishers and part of the research looks at the public perception of artificial reefs and how they use them. We asked whether they knew about the reefs, whether people fished off the reefs, and what their success rate was. We found the general public, including recreational fishers, were happy with the implementation of reefs.
WM: Were there any initial concerns regarding the implementation of artificial reefs?
The EPA (Environmental Protection Agency) and the former DSE (Department of Sustainability and Environment) were concerned about introduced species in that the reefs may be a stepping stone for them to move into other areas of the bay and that the reefs may become a ‘hub’ for colonisation. There was also a concern that the reefs may draw fish off natural reefs, making them easier to catch.
WM: You mentioned that snapper use the reefs. How exactly do they use both the artificial and natural reefs?
The ones tagged on natural reefs didn’t really move off the natural reefs, but those on artificial reefs tended to move amongst all types of habitats. This meant that the artificial reefs being a vacuum, drawing in fish where fishers at the top can easily catch them, isn’t the case. The catch rates above the artificial reefs were similar to natural reefs after the reefs went in. They’re catching a similar number of species, but it seems that it’s mainly smaller, sub-adult juveniles.
WM: What is the production value of the artificial reefs as far as new recruitments year after year are concerned? Or is it yet to be established because of the time required to assess this?
It’s not just a matter of time, but more size. Fish spawning and production is such a large scale thing that three reefs are not going to have a discernible impact. There may be some species you could do it with: the more philopatric species (animals that tend to reside or return to specific areas), like the southern hulafish, which are residents of a given reef and recruit in particular areas of the bay.
WM: As far as artificial reefs being a hub or spawning point for introduced/invasive species, has this occurred?
No, not really. The starfish asterias has turned up at some of the artificial reefs. However, they are known to move around in large numbers depending where the food is. There was one time we saw quite a few of them, but there’d been a whole lot of drift algae and bivalves that had built up [on the artificial reef which they were feeding on. The next time we went, [the starfish] were all gone and so it didn’t seem like they were settling and staying on the reef.
WM: What’s involved in a typical day of assessing the reefs?
Some days we dive and count the fish, look at the invertebrates and assess the reef structure. You also dive on soft sediment and natural reef areas to compare with the artificial reefs. The other work also includes baited video recordings where you can see the snapper move in and out and you place these on the soft sediment and both reef types to compare.