Prey base shifts in red rock lobster Jasus edwardsii in response to habitat conversion in Fiordland marine reserves: implications for effective spatial management

Abstract

Persistence of subpopulations dispersed among spatial management units, such as marine reserves, relies heavily upon the quality of local habitat, as well as size and connectivity of habitat patches. We examined the relative abundance of the red rock lobster Jasus edwardsii and its primary bivalve food resources within 3 marine reserves in the Doubtful–Bradshaw Sound complex in Fiordland, New Zealand. We used stable isotope analysis (δ13C, δ15N and δ34S) to resolve differences in the carbon sources to food webs supporting J. edwardsii inhabiting these regions. Furthermore, we examined patterns in the relative concentration and δ13C signature of specific fatty acid biomarkers as an independent test of the carbon sources to each population. We found distinctive patterns in the relative abundance of red rock lobsters, with significantly more animals in the marine reserves at Te Awaatu Channel and Kutu Parera than in the surrounding open fishing areas and within the reserve at Taipari Roa. Taipari Roa Reserve is distinctive in that bivalve abundance is extremely low due to freshwater input from the Manapouri hydroelectric power plant. Analysis of δ13C, δ15N and δ34S of red rock lobster muscle tissue as well as δ13C of 16:1ω7 and 18:1ω7 indicated that, in those areas where heterotrophic bivalves are rare, red rock lobsters rely more on recycled carbon made available by chemoautotrophs. These findings suggest that efficacy of the new marine reserves is influenced by habitat quality in terms of the availability and abundance of food resources for red rock lobsters. We highlight the importance of considering habitat quality for effective implementation of marine reserves.