The relationship between coral-reef fish (larvae, juveniles, and adults) and mangroves : a case study in Honduras

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Algal cover in mangroves affects distribution and predation rates by carnivorous fishes

Distribution and survival of fish are influenced by benthic habitat and complexity. While many studies have investigated the effects of algal cover on fishes in reef habitats, comparatively less is known regarding this relationship in mangrove habitats. Possible links between substrate macro-algal cover and fish distribution were studied in a Caribbean mangrove lagoon via visual surveys and algal removal experiments. In addition, the effects of algae on relative predation were tested by calculating survival of tethered brachyuran prey, whose predators are known to include larger lutjanid (snapper) juveniles. Comparisons of algae and fish distributions show that percent cover of algae and juvenile lutjanid, Lutjanus griseus (gray snapper) abundances were significantly negatively correlated. Results from the algae removal experiment showed that algae had a negative effect on abundance of carnivorous fishes in two (out of three) locations in the lagoon. In addition, tethered prey had significantly higher proportional survival in plots with algae-present relative to plots with algae-absent. We present here experimental evidence that increased algal growth in mangroves may reduce predator encounter rates by prey. These observations are important, as the presence of carnivorous fishes is a key factor for the maintenance of high diversity in mangrove and on neighboring coral reefs. Furthermore, findings from this study imply that algal cover must be considered when protecting mangrove habitat. © 2012 Elsevier B.V

Distribution of fish in seagrass, mangroves and coral reefs: life-stage dependent habitat use in Honduras.

Many coral reef fish exhibit habitat partitioning throughout their lifetimes. Such patterns are evident in the Caribbean where research has been predominantly conducted in the Eastern region. This work addressed the paucity of data regarding Honduran reef fish distribution in three habitat types (seagrass, mangroves, and coral reefs), by surveying fish on the islands of Utila and Cayos Cochinos off the coast of Honduras (part of the Mesoamerican barrier reef). During July 2nd - Aug 27th 2007 and June 22nd - Aug 17th, 2008, visual surveys (SCUBA and snorkel) were performed in belt transects in different areas: eleven coral reef, six seagrass beds, and six mangroves sites. Juvenile densities and total habitat surface area were used to calculate nursery value of seagrass and mangroves. A total of 113 fish species from 32 families were found during underwater surveys. Multi-dimensional analyses revealed distinct clusters of fish communities in each habitat type by separating fish associated with seagrass beds, mangroves, and coral reefs. Coral reefs showed the highest mean fish species richness and were dominated by adult fish, while juvenile fish characterized seagrass beds and mangrove sites. Habitat use differed widely at the fish species level. Scarus iseri (Striped Parrotfish), the most abundant fish in this study, were found in all three habitat types, while Lutjanus apodus (Schoolmaster Snapper) juveniles were located primarily in mangroves before migrating to coral reefs. Many species used seagrass beds and mangroves as nurseries; however, the nursery value could not be generalized at the family level. Furthermore, for some fish species, nursery value varied between islands and sites. Our results suggest that connectivity of seagrass, mangrove, and coral reef sites at a species and site levels, should be taken into consideration when implementing policy and conservation practices