Enhanced numbers of two temperate reef fishes in a small, partial-take marine protected area related to spearfisher exclusion

Reviews of global studies suggest that even small no-take marine protected areas (MPAs) can have localized benefits on harvested organisms of varying mobility. The generality of this conclusion, however, has been questioned due to poor experimental designs of some studies included in reviews, and the relatively small proportion of studies which focused on very small MPAs (⩽1 km2). Here we use a correlative approach to test for possible effects of a 0.1 km2 partial-take MPA (closed to spearfishing for 12.5 years) on the abundance and size of key harvested fishes using an asymmetrical spatial comparison of the MPA vs. three unprotected control areas. Positive impacts were detected, despite our prediction that a small MPA would not provide protection to highly mobile taxa. Densities of legal-sized (⩾200 mm SL) Cheilodactylus fuscus (red morwong; relatively sedentary) were 2.8 times greater within the MPA than at the controls and densities of legal-sized Acanthopagrus australis (yellow-fin bream; relatively mobile) were 2.3 times greater on shallow (⩽3.5 m) but not deeper (4-12 m) areas of reef within the MPA. While benefits of protection were evident, the cost-benefit of implementing similar MPAs should be carefully considered as the partial protection status and small size of the MPA limit both the adequacy of the MPA for protecting a larger range of species, and the magnitude and thus detectability of effects.