Maintenance of old-growth size structure and fecundity of the red rock lobster Jasus edwardsii among marine protected areas in Fiordland, New Zealand

Persistence of long-lived coastal species depends on the maintenance of mature age distributions of reproductive individuals at the landscape scale. We investigated patterns in abundance and size structure of the red rock lobster Jasus edwardsii across a network of marine protected areas in Fiordland, New Zealand. Abundance of J. eclwardsd across 53 sites in 2006-2007 was highest in marine reserves established in 1993 and comparatively low in reserves and commercial exclusion zones established in 2005 and in commercially fished regions. Within the Doubtful-Bradshaw Sound complex, we observed a high abundance of lobsters at Te Awaatu Channel marine reserve (est. 1993), intermediate abundances in the commercial exclusion zone and within Kutu Parera marine reserve (est. 2005), but no lobsters in Taipari Roa marine reserve (est. 2005), where habitat quality was degraded. We used an accurate and precise videogrammetric technique to non-invasively measure size structure of lobsters within each reserve and compared this new method with established techniques. Sex ratios were determined and an estimate of fecundity per unit area was calculated for each reserve. Results indicate that within the Doubtful Bradshaw Sound complex the reproductive contribution of lobsters per unit area from the marine reserve at Te Awaatu Channel was significantly greater than that at Taipari Roa, while that from the commercial exclusion zone and Kutu Parera were intermediate. These data highlight the importance of marine reserves encompassing high quality habitats for maintaining optimal reproductive potential of red rock lobster populations by harbouring high abundances and mature size distributions at the landscape scale.