Chateau, O., and Wantiez, L. 2009. Movement patterns of four coral reef fish species in a fragmented habitat in New Caledonia: implications for the design of marine protected area networks. – ICES Journal of Marine Science, 66: 50–55. Acoustic telemetry was used to examine the patterns of fish movements between a marine reserve and two unprotected reefs separated by large areas of lagoon soft bottoms (900–2000 m) in the South Lagoon Marine Park of New Caledonia. Four commercial fish species (Epinephelus maculatus, Plectropomus leopardus, Chlorurus microrhinos, and Scarus ghobban) were studied for 17 months (45 fish). Nine fish (20%) were detected on reefs other than the reef onto which they were released. Four patterns of inter-reef movement were identified during the survey, including home range relocations, movements larger than the scale of the study, many inter-reef movements within the study area, and punctual excursions outside the daily home range. The information gathered in this study demonstrates the ability of the fish to carry out medium-scale movements in a fragmented habitat. Consequently, the effectiveness of the reserve to protect the entire population is probably limited for these species. Because all the identified patterns implied at least one movement across the reserve boundaries, our results support the hypothesis that the Larégnère Marine Reserve, part of the South Lagoon Marine Park, could benefit the adjacent fished area through spillover.
Context
Migratory species are known to pose a challenge for conservation because it is essential to understand their complex life history in order to implement efficient conservation actions.
Aims
In New Caledonia, large seagrass habitats in the Grand Lagon Sud (GLS) are home to resident green turtles (Chelonia mydas) of unknown origins. To assess the stock composition in the GLS, 164 foraging turtles were sampled for genetic analysis of ~770 base pairs of the mitochondrial DNA (mtDNA) control region.
Methods
Foraging turtles ranging in size from 48.0 to 108.4 cm curved carapace length were captured at five different sites within the GLS between September 2012 and December 2013. To provide baseline data for mixed stock analysis, published data from rookeries were used in addition to 105 samples collected at rookeries in the d’Entrecasteaux Islands and Chesterfield Islands in New Caledonia and at Malekula Island in Vanuatu. Exact tests of population differentiation and pairwise FST estimates were used to test for differences in mtDNA haplotype frequencies.
Key results
These analyses indicated that rookeries in the d’Entrecasteaux Islands and Vanuatu form unique management units and that the Chesterfield Islands rookeries are linked to the Coral Sea management unit. Mixed stock analysis indicated the highest proportion (mean = 0.63) of foraging turtles originate from the d’Entrecasteaux stock.
Conclusions
The larger contribution is estimated to be from a large rookery from New Caledonia, but smaller contributions are suggested from other rookeries in the South Pacific.
Implications
Marine conservation policies in New Caledonia need to consider the links between the foraging and nesting populations of C. mydas in New Caledonia and other rookeries and foraging grounds in the Coral Sea.
This study examines the short-term site fidelity, the home range size and the activity patterns of one specimen of the emblematic and threatened humphead wrasse, Chelinus undulatus. Four omnidirectional hydrophones were deployed for 7 months in the mooring area of Laré gnè re marine reserve (New Caledonia). The hydrophone network covered 50 ha. The monitored fish was caught in the study site and surgically implanted with an ultrasonic transmitter. The fish displayed a regular diurnal rhythm during 25 days before leaving the area. Different patterns of spatial use were identified. The temporal succession of these patterns indicates that the minimum distance covered by the fish every day ranged between 20 and 200 m. Its home range was at least 5 ha. A decrease of the detection was observed before the departure of the fish. This decrease coincided with the beginning of the reproduction period in New Caledonia and supports the hypothesis of a fish departure for the reproductive event. Despite the survey of only one specimen, the home range and movement calculated using acoustic telemetry are different in scale than the reported scuba-based visual estimations. Such information is essential for the development of management policies and conservation measures of large reef fish species highly vulnerable to disturbance and fishing pressure.
The interest in reef manta rays (Mobula alfredi) from the scientific community is growing in reaction to the major decline of populations around the world. Studies have highlighted the need to further investigate the spatial ecology of this species to inform conservation and management initiatives. Here we briefly report the results from nine SPLASH10-F-321A pop-off satellite archival tags (PSAT-tags) deployed in New Caledonia that recorded the world's deepest known dives for reef manta rays. All tagged individuals performed dives exceeding 300 m in depth, with a maximum depth recorded of 672 ± 4 m. Diel comparisons revealed that most of the deepest dives occurred during night-time. We hypothesize this deep-diving behaviour is employed to access important food resources at these depths during the night and may also indicate that zooplankton abundance in the surface waters surrounding New Caledonian coral reefs is insufficient to sustain these megafauna. These results add new information on the habitat use of this species in a region where manta behaviour has not previously been studied, and increase the known depth range of M. alfredi by more than 200 m.
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