Striking a balance between retaining populations of protected seahorses and maintaining swimming nets

Published source details Harasti D., Glasby T.M. & Martin-Smith K.M. (2010) Striking a balance between retaining populations of protected seahorses and maintaining swimming nets. Aquatic Conservation: Marine and Freshwater Ecosystems, 20, 159-166.
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This study is summarised as evidence for the following.

	Action	Category
	Cease or alter maintenance activities on subtidal artificial structures Action Link

Cease or alter maintenance activities on subtidal artificial structures

A replicated, randomized, controlled study in 2007–2008 on a subtidal swimming-enclosure net in Sydney Harbour estuary, Australia (Harasti et al. 2010) found that enclosure-net panels cleaned only along the top section supported a higher abundance of seahorses Hippocampus abdominalis and Hippocampus whitei than panels cleaned only along the bottom or from top-to-bottom. Over four months, enclosure-net panels cleaned only along the top supported more seahorses (20% of original abundance) than panels cleaned along the bottom (5%) or from top-to-bottom (3%). Maintenance activities were altered on a polypropylene swimming-enclosure net (length: 150 m; height: 3–4 m from sea surface to seabed; mesh size: 100 mm) in November 2007. Net panels (4-m sections) were either cleaned along the top only (surface to 1 m depth), the bottom only (seabed to 1 m above), or from top-to-bottom (surface to seabed). There were four panels of each treatment, randomly arranged along the net. Seahorses were removed during cleaning then replaced in the same position, while all other organisms were scraped from the net. Some panels were left uncleaned but this treatment was not considered a feasible conservation action since the weight of the net could cause it to break or sink. Eleven seahorses on each panel were tagged and monitored over four months.

(Summarised by: Ally Evans)