Fish and sea urchin grazing opens settlement space equally but urchins reduce survival of coral recruits

Published source details O'Leary J.K., Potts D., Schoenrock K.M. & McClahanan T.R. (2013) Fish and sea urchin grazing opens settlement space equally but urchins reduce survival of coral recruits. Marine Ecology Progress Series, 493, 165-177.
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This study is summarised as evidence for the following.

	Action	Category
	Designate a Marine Protected Area and prohibit all types of fishing Action Link

Designate a Marine Protected Area and prohibit all types of fishing

A replicated, site comparison study in 2007–2008 in six coral reef sites off the coast of Kenya (O'Leary et al. 2013) found that in protected areas that prohibited all types of fishing, the number of coral recruits was similar compared to the number of recruits in fished areas. Overall, average density of coral recruits (live and covered) was not significantly different between protected areas (32 recruits/m²) and fished areas (149 recruits/m²). Authors also reported that caging settlement tiles to exclude grazers after six months had different effects on the number of live recruits in protected areas with fish grazers (caged lower with 70 recruits/m², uncaged: 140 recruits/m²) and fished areas with urchin grazers (caged higher with 750 recruits/m², uncaged: 450 recruits/m²). Three well-enforced protected areas were selected where all fishing was prohibited for >15 years, along with three nearby fished reefs. Settlement tiles were deployed in cement blocks at all six sites (4 tiles/block, 16 blocks/site). Two tiles on each block were caged to exclude grazers and two were left uncaged for six months, after which time half of the treatments were switched for a further six months. All coral recruits were counted, including those that were alive and those covered by other organisms.

(Summarised by: William Morgan)