Artificial Reefs, Conservation and the Environmental Rationale behind sinking a vessel

In summary:

• Functions as a new habitat for a multitude of fish and invertebrate species.
• Creates effective marine habitats on a soft-bottomed featureless environment (Appendix 5).
• Alters the connectivity patterns between natural reefs in a positive way.
• Provide corridors so smaller fish can safely move from one reef to another.
• Conserves pre-existing habitats as well as form new habitats of complex ecological systems.

In detail:

Many studies have demonstrated higher fish densities, biomass, and diversity on artificial reefs than natural habitats (Diamant et al. 1986, Bohnsack 1991, Bohnsack et al. 1994, Wilhelmsson et al. 1998, Clark & Edwards 1999, Rilov & Benayahu 2000, Arena et al. 2007, Burt et al. 2009).

In contrast to Rilov and Benayahu (2000) and Arena et al. (2007) observed greater species richness on concrete pillars and shipwrecks, respectively. Fishing on dive reefs can rapidly reduce target fish populations and drastically decrease the value of a dive for tourism (Brock 1994). Artificial reefs are good for fishing and divers but bad for fish (Arena 2013).

In line with this, Arena et al. (2007) suggested that the high vertical relief of four vessel reefs studied might have accounted for increased settlement of juvenile fishes leading to greater fish abundance and species richness recorded. Of interest, Granneman and Steele (2014) found total fish tissue production tended to be greater on artificial reefs than natural reefs, with a positive correlation occurring between tissue production and the abundance of large boulders that were more numerous on artificial reefs.

Some authors note however, that given sufficient time and similar structural features, differences in benthic community structure can become almost indistinguishable.

Three authors and colleagues studied seven shipwrecks of differing ages (20 to 100 years old) and observed increasing age of the artificial reef influenced its degree of similarity to its adjacent natural reef (Aseltine-Neilson et al. 1999, Perkol-Finkel et al. 2006, Thanner et al. 2006). This was most evident with stony coral cover. Moreover, Perkol-Finkel et al. (2006) noted a similar benthic community structure on a 119-year old shipwreck to that of a neighbouring natural reef.

Of great interest is a study by Suthers and colleagues (Folpp 2020) that showed that 3 species of Sparidae fish seen on artificial reefs were not attracted from the nearby rocky reefs and were produced by the addition of artificial reefs at estuary locations in Lake Macquarie, Botany Bay and St George Basin NSW. The study showed that overall total fish abundance increased up to 20 times in each reef across a two year period.” Folpp, H., Schilling, H.T. Clark, G.F., Lowry, M.B., Maslen, B., Gregson, M., Suthers, I., Artificial reefs increase fish abundance in habitat-limited estuariues. Journal of Applied Ecology