ABSTRACT. 'No-take' marine reserves provide a valuable tool for managing marine resources as well as for providing relatively undisturbed habitat with which to assess modifications to ecosystems. We studied 2 marine reserves in northeastern New Zealand, the Leigh Marine Reserve (established 1975) and Tawharanui Marine Park (established 1982) in order to assess whether changes in protected predator populations had resulted in other indirect changes to grazers and consequently to algal abundance. Estimates of abundance of the most common demersal predatory fish Pagrus auratus indicated that adults of this species (i.e. large enough to prey upon urchins) were at least 5.75 and 8.70 times more abundant inside reserves than in adjacent unprotected areas. Overall, P auratus were also much larger inside reserves with mean total lengths of 316 mm compared with 186 mm in fished areas. The spiny lobster Jasus edwardsii displayed similar trends, and was approximately 1.6 to 3.7 times more abundant inside the reserves than outside. Lobsters within the reserves had a mean carapace length of 109.9 mm, compared with 93.5 mm outside the reserves. In one of the reserves, densities of the sea urchin Evechinus chloroticus had declined from 4.9 to 1.4 m-2 since 1978 in areas formerly dominated by it. Consequently, kelp forests were more extensive in 1998 than they were at the time of reserve creation. Urchin-dominated barrens occupied only 14 % of available reef substratum in reserves as opposed to 40"4 in unprotected areas. These changes in community structure, which have persisted since at least 1994, demonstrate not only higher trophic complexity than anticipated in Australasian ecosystems but also increased primary and secondary productivity in marine reserves as a consequence of protection. Trends inside reserves indicate large-scale reduction of benthic primary production as an indirect result of fishing activity in unprotected areas.

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Size and abundance data were compiled and collated for blue cod Parapercis colias and rock lobster Jasus edwardsii from New Zealand marine reserve (MR) studies for a meta-analysis to test the null hypotheses that reserve status does not affect the size or abundance of either species. Calculation of meta-analysis effect sizes revealed that significant differences in effect size existed among studies, meaning that the biological response to MR status of both species in terms of their changes in size and/or abundance differed significantly among the MRs. Analysis revealed that blue cod were bigger inside compared with outside MRs in 9 of 10 studies and were more abundant inside MRs in 8 of 11 studies, and that rock lobster were bigger inside the MRs in 12 of 13 studies and more abundant inside the MRs in 11 of 14 studies. These findings indicate that MR protection can result in more and bigger individuals soon after the establishment of the MR (mean of 6.5 yr for blue cod, 8.5 yr for rock lobster) despite small sample sizes of studies (≤10 for blue cod, ≤14 for rock lobster). Focused comparison tests did not reveal any relationship between rock lobster or blue cod size or abundance and either age or area of MRs. Our results demonstrate that no-take MRs are valuable conservation tools for species such as blue cod and rock lobster (and probably also for other exploited species with similar life history characteristics and habitat requirements) and that statistically detectable conservation benefits are apparent after only a few years of protection.

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