Complexity is key: fish diversity and tropical inshore seascapes
Reef fish seek shelter - be it coral or rocks

One of our papers received a good reception from the Journal of Fish Biology:

Published in the section of the journal entitled  ‘Between the covers’

Tropical inshore seascapes are truly captivating environments, and they conjure up images of pristine blue waters punctuated with the vibrant colours of reef fish. These properties often make tropical inshore seascapes the dream study system for many fish biologists. In addition to the inspiring aesthetics, tropical inshore seascapes support a rich and diverse range of fascinating ecology. Ecology that supports a wealth of ecosystem services such as costal defence, fisheries, recreation, tourism and all importantly, carbon sequestration (Barbier, 2017).

Despite their value, tropical inshore seascapes such as reefs (De’ath et al., 2012) and macroalgae beds (Kumagai et al., 2018) are being degraded by a variety of anthropogenic pressures, with one of the most pressing being climate change. With this habitat degradation comes loss of fish diversity, for example, global reef fish richness could decline by a half if corals are lost (Strona et al., 2021). Therefore, to understand and prevent further loss of fish species, and to ensure ecosystem stability, it has never been more important to understand what drives fish assemblage in tropical inshore seascapes.

In this issue, Hall & Kingsford (2021) push the boundaries of our understanding of fish community assemblage in tropical inshore seascapes, using baited remote underwater video stations (BRUVS) around continental islands of the central Great Barrier Reef. They assessed habitat type: coral reef, rocky reef, macroalgae beds and sand/rubble beds, as well as habitat complexity. Hall & Kingsford (2021) uncover the importance of habitat complexity in supporting the greatest number of fish species. Complex habitats like those found in coral and rocky reefs. Perhaps the most surprising finding, however, is that coral and rocky reefs had 60% of species in common, with habitat complexity on rocky reefs coming from boulders of various sizes, as well as cracks and crevices, instead of the coral overhangs.

These results provide some small reassurance that the continued loss of coral reefs will not completely decimate fish assemblages, so long as there are other complex habitats to replace them. Although, of course, there is the potential to lose 40% of those fish species that are unique to coral habitats, and whose decline we have already seen due to coral habitat degradation (Bozec et al., 2005; Pratchett et al., 2006). As highlighted by Hall & Kingsford (2021), however, rocky reef habitats are resilient to bleaching, storms and costal pollutants and could therefore provide refugia for many fish species. Rocky reefs could become key to conservation planners, especially as it is unknown how coral reef restoration impacts fish assemblages in the short and long term (Seraphim et al., 2020). It also provides indirect support for other methods of increasing fish diversity through increasing habitat complexity, such as the creation of artificial reefs (Burns et al., 2020; Wen et al., 2010).

William Bernard Perry

Assistant Editor


Barbier, E. B. (2017). Marine ecosystem services. Current Biology, 27, R507–R510.

Bozec, Y.-M., Dolédec, S., & Kulbicki, M. (2005). An analysis of fish-habitat associations on disturbed coral reefs: chaetodontid fishes in New Caledonia. Journal of Fish Biology, 66, 966–982.

Burns, E. S., Clevenstine, A. J., Logan, R. K., & Lowe, C. G. (2020). Evidence of artificial habitat use by a recovering marine predator in southern California. Journal of Fish Biology, 97, 1857–1860.

De’ath, G., Fabricius, K. E., Sweatman, H., & Puotinen, M. (2012). The 27-year decline of coral cover on the Great Barrier Reef and its causes. PNAS, 109, 17995–17999.

Hall, A. E., & Kingsford, M. J. (2021). Habitat type and complexity drive fish assemblages in a tropical seascape. Journal of Fish Biology.

Kumagai, N. H., Molinos, J. G., Yamano, H., Takao, S., Fujii, M., & Yamanaka, Y. (2018). Ocean currents and herbivory drive macroalgae-to-coral community shift under climate warming. Proceedings of the National Academy of Sciences, 115, 8990–8995.

Pratchett, M. S., Wilson, S. K., & Baird, A. H. (2006). Declines in the abundance of Chaetodon butterflyfishes following extensive coral depletion. Journal of Fish Biology, 69, 1269–1280.

Seraphim, M. J., Sloman, K. A., Alexander, M. E., Janetski, N., Jompa, J., Ambo-Rappe, R., … Harborne, A. R. (2020). Interactions between coral restoration and fish assemblages: implications for reef management. Journal of Fish Biology, 97, 633–655.

Strona, G., Lafferty, K. D., Fattorini, S., Beck, P. S. A., Guilhaumon, F., Arrigoni, R., … Parravicini, V. (2021). Global tropical reef fish richness could decline by around half if corals are lost. Proceedings of the Royal Society B, 288.

Wen, C. K.-C., Pratchett, M. S., Shao, K.-T., Kan, K.-P., & Chan, B. K. K. (2010). Effects of habitat modification on coastal fish assemblages. Journal of Fish Biology, 77, 1674–1687.


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