Effects of enhancing pontoons on abundance of fish: initial experiments in estuaries

Published source details Hair C.A. & Bell J.D. (1992) Effects of enhancing pontoons on abundance of fish: initial experiments in estuaries. Bulletin of Marine Science, 51, 30-36.
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This study is summarised as evidence for the following.

	Action	Category
	Create long flexible habitats (>50 mm) on subtidal artificial structures Action Link

Create long flexible habitats (>50 mm) on subtidal artificial structures

One replicated, randomized, controlled study in 1989 on 36 subtidal pontoons in Port Hacking estuary, Australia (Hair & Bell 1992) found that creating long flexible habitats (artificial seagrass units, ASUs) on pontoons did not increase the fish species richness or abundance under pontoons in one trial, but did in a second trial in which pontoons had been cleared of fishes initially. In the first trial, after six weeks, fish species richness and abundance (excluding blennies Parablennius sp.) was similar under pontoons with ASUs (3–4 species/pontoon, 5–7 individuals/pontoon) and those without (1–2 species/pontoon, 2–4 individuals/pontoon). In the second trial, six weeks after clearing fishes from beneath pontoons, species richness and abundance was higher under pontoons with ASUs (4–5 species/pontoon, 6–11 individuals/pontoon) than without (0–1 species and individuals/pontoon). Blenny abundance was similar under pontoons with and without ASUs (0–17 vs 0–22 individuals/pontoon) in both trials. Three species recorded under pontoons with ASUs were absent from those without. Long flexible habitats (ASUs) were created by suspending steel mesh sheets (7 m²) with buoyant plastic fragments (length: 280 mm; density: 800/m²) under pontoons. One ASU was attached at 0.3 m depth under each of six randomly-selected pontoons in each of three sites within an estuary in September 1989. Fishes under pontoons with ASUs and under six without were netted (1 mm mesh size) and counted after six weeks. The trial was repeated in October after clearing fishes from under pontoons. Five ASUs were dislodged and no longer provided habitat.

(Summarised by: Ally Evans)