A safety network against regional population collapse: mature subpopulations in refuges distributed across the landscape

Abstract

Theory suggests that marine reserve networks can maintain wide geographical distributions of exploited fish and invertebrates. Since 2005, ten regions in southwest New Zealand have been designated no‐take marine reserves nested within eleven commercial fishing exclusion zones. We observed increases in abundance of rock lobster (Jasus edwardsii) and blue cod (Parapercis colias) from 2002–2010 within some marine reserves, but not in the other management zones. Mature size distributions of rock lobsters were only observed within protected areas. Model based inference ranked environmental descriptors versus area under protection in explaining abundance and changes in abundance observed within marine reserves and indicated that J. edwardsii became most abundant in larger marine reserves, but only under specific environmental conditions. P. colias became most abundant in large marine reserves, particularly those with larger buffers against commercial fishing. Analysis of population changes for both species across Fiordland since implementation of the reserve network (2006–2010) indicated that marine reserves resulted in either increases in, or maintenance of abundance in the face of regional declines. We highlight the potential effectiveness of networks of marine reserves in maintaining subpopulations with high abundance and mature size structure across large geographical areas, particularly if key criteria are incorporated.