Biologist Jeffrey Low responds to blog post: Study says man-made reefs don't impact negatively on natural ones
I worked on artificial reefs for my Masters thesis way back when, so, I was intrigued by the newspaper reporting a "final solution" to one of the long standing arguments about artificial reef-natural reef interactions. After reading the article though, there was no evidence to conclude either way. I did see some similarities between the report and my studies, but also some differences.
The fish community of the artificial reefs (ARs) in Singapore were certainly different from the natural one, but in contrast to the study posted, I saw mostly adults, of fish species that were not usually seen on the reef. These included the Yellow spot Rabbitfish (Siganus guttatus), snappers (Lutjanus argentimaculatus and L. carponotatus), and several species of batfish (Platax spp).
I speculated that these differences were caused by:
1. the distance the artificial reef was from the natural reef (there have been studies done on trying to determine optimal distances of artificial reefs from each other and to the natural reefs),
2. the different structure and shape of the artificial reef compared to the natural reef (there were more "spaces" in the ARs for fish to hide then on our natural reefs)
3. the depth at which the artificial reef was placed (the ARs were placed on the seabed in 15m of water, about 30m away from the natural reef).
Other studies on fish communities talk about habitat- or supply-limited systems (meaning that there was no habitat for juvenile fish to make a home, or not enough juvenile fish to fill up the "homes"), but usually in terms of juveniles. I speculate that in Singapore, at least, fish adults are constrained primarily by the lack of habitat, so any artificial reef laid down will probably show results that approximate to drawing fish away from the reef.
I tend to be very cautious about "artificial habitats" as a panacea to our environmental problems, because it has often been used as a crutch to overlook the real damage to a natural ecosystem. It is a useful tool that can assist in ecosystem recovery, but the how and why of it needs to be carefully considered, and its implementation not seen as an end unto itself.