Abstract
Movement and exchange of individuals among habitats is critical for the dynamics and success of reef fish populations. Size segregation among habitats could be taken as evidence for habitat connectivity, and this would be a first step to formulate hypotheses about ontogenetic inter-habitat migrations. The primary goal of our research was to find evidence of inter-habitat differences in size distributions and density of reef fish species that can be classified a priori as habitat-shifters in an extensive (-600km2) Caribbean shelf area in NW Cuba. We sampled the fish assemblage of selected species using visual census (stationary and transect methods) in 20 stations (sites) located in mangrove roots, patch reefs, inner zone of the crest and fore reef (12-16m depth). In each site, we performed ten censuses for every habitat type in June and September 2009. A total of 11 507 individuals of 34 species were counted in a total of 400 censuses. We found significant differences in densities and size compositions among reef and mangrove habitats, supporting the species-specific use of coastal habitats. Adults were found in all habitats. Reef habitats, mainly patch reefs, seem to be most important for juvenile fish of most species. Mangroves were especially important for two species of snappers (Lutjanus apodus and L. griseus), providing habitat for juveniles. These species also displayed well defined gradients in length composition across the shelf.
Highlights
The nursery function of back-reef habitats has been inferred by studying spatial and temporal patterns in the size distribution of juveniles and adults across such habitats (Mumby et al, 2004; Verweij, Nagelkerken, Wartenbergh, Pen & van der Velde, 2006; Dorenbosch, Verbeck, Nagelkerken & van der Velde, 2007)
Study area: We included the spatial coverage assumed to be the normal range of reef fish species (e.g. Nemeth, Blondeau, Hezlieb & Kadison, 2007; Pina-Amargós et al, 2008), we studied an extensive area of the Caribbean shelf in Northwestern Cuba (Fig. 1)
H. aurolineatum was present in large numbers at a few sites of the patch reefs (PR) habitat resulting in a high aggregation (61.5±29.5)
Summary
The nursery function of back-reef habitats has been inferred by studying spatial and temporal patterns in the size distribution of juveniles and adults across such habitats (Mumby et al, 2004; Verweij, Nagelkerken, Wartenbergh, Pen & van der Velde, 2006; Dorenbosch, Verbeck, Nagelkerken & van der Velde, 2007). Fish assemblages of the NW Cuban shelf have been recently investigated and spatial variations of assemblage composition have been discussed at a region-wide scale (González-Sansón et al, 2009a; González-Sansón, Aguilar, Hernández, Cabrera & Curry, 2009b), and at smaller scales (Aguilar, González-Sansón, Munkittrick & MacLatchy, 2004; Aguilar, González-Sansón, Faloh & Curry, 2008; González-Sansón, Aguilar, Hernández & Cabrera, 2009c; González-Sansón & Aguilar, 2010) The goals of these studies were to identify natural and anthropogenic factors that may influence fish assemblage structure. All of these and other studies across the Caribbean (Nagelkerken & van der Velde, 2002; Beets et al, 2003; Aguilar-Perera & Appeldoorn, 2007) suggest a degree of habitat connectivity, but none was designed to test the hypothesis of ontogenetic, habitat migrations, which probably occur across larger spatial scales of >100km. The specific predictions were: (1) fish density and size composition for selected species among habitats have significant differences; and (2) a gradient in length composition across the island shelf from mangrove to fore reef is found
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