Increasing habitat complexity on seawalls: investigating large- and small-scale effects on fish assemblages

  • Published source details Morris R.L., Chapman M.G., Firth L.B. & Coleman R.A. (2017) Increasing habitat complexity on seawalls: investigating large- and small-scale effects on fish assemblages. Ecology & Evolution, 7, 9567-9579.


This study is summarised as evidence for the following.

Action Category

Create 'rock pools' on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures
  1. Create 'rock pools' on intertidal artificial structures

    A replicated, paired sites, controlled and site comparison study in 2014–2015 on three intertidal seawalls in Sydney Harbour estuary, Australia (Morris et al. 2017) found that creating rock pools on one seawall did not increase the fish species richness on and around the wall, but had mixed effects on fish abundances depending on the species group and site. Over the first 12 months, pelagic fish species richness was similar around the seawall with rock pools (1–3 species/survey) and those without (1–2/survey) and there were no clear differences in maximum abundances (0–26 vs 0–13 individuals/survey), which varied by species group and site (see paper for results). For the seawall with pools, pelagic fish species richness in and around pools (1–2 species/survey) was similar to seawall surfaces without (2–4/survey), and maximum abundances varied by species group (with pools: 0–39 individuals/survey; without: 0–30/survey). After 15–21 months, benthic fish species richness in and around pools was similar to seawall surfaces without (both 9 species in total). Total abundance was higher for pools than surfaces for one species (12 vs 1 individuals), but similar for 10 others (0–15 vs 0–22). One species recorded in and around pools was absent from surfaces without. Rock pools were created by attaching concrete pots to a vertical sandstone seawall in February 2014. Five half-flowerpot shaped pools (top diameter: 315 mm; volume: 7l; depth not reported) were attached at midshore in each of two sites along the seawall. Pools were compared with seawall surfaces without pools (dimensions not reported) adjacent to each site and on two other seawalls without pools. Fishes were counted in, on and around pools and seawall surfaces from time-lapsed photographs and videos during 7–10 high tides over 21 months.

    (Summarised by: Ally Evans)

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