Role of different seagrass habitats in the southwest lagoon of New Caledonia as nurseries for fish juveniles: a spatial approach
Cornubert, O. (2010). Role of different seagrass habitats in the southwest lagoon of New Caledonia as nurseries for fish juveniles: a spatial approach. MSc Thesis. Erasmus Mundus Master of Science in Marine Biodiversity and Conservation (EMBC)/University of Pierre and Marie Curie, Paris VI: Paris. 36 pp.
A wide range of interacting environmental patterns and processes operating at multiple scales determine marine species distribution and abundance. The goal of this study was to understand in which proportions eight different seagrass beds localized in the southwest lagoon of New Caledonia act as nursery grounds for juvenile fish and the main environmental factors explaining species diversity and abundance variations. Visual censuses of juvenile fish population were conducted at these eight seagrass beds from October 2008 to March 2010 while biotope descriptions were performed at three different spatial scales, 0.1 to 1 m, 1 to 10 m, and 100 to 1000 m, using different techniques, between 2009 and 2010. Generalized Linear Models predicting juvenile fish species richness and abundance were developed using the spatial habitat variables measured at the different scales. This study revealed that: (1) habitat variables at 0.1 to 1-m scale explained 95% of variability in juvenile species richness, (2) a small improvement (99%) was gained when a combination of habitat variables at different spatial scales was used. Habitat variables at all scales thus appear important for juvenile fish abundance and species diversity, with the seagrass structure explaining more of the assemblage variation. Juvenile fish species diversity was strongly influenced by canopy height (represented by the maximum length and width of leaves of Cymodocea serrulata and of Halophila ovalis respectively) and by local hydrodynamism. Juvenile fish abundance was influenced by the density canopy and by the perimeter-area fractal index. The present study demonstrated that juvenile fish assemblages seem dependent on the local habitat characteristics and that Generalized Linear Models are efficient to identify the environmental factors which affect juvenile fish species diversity and abundance.
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