Mangrove Habitat Use by Juvenile Reef Fish: Meta-Analysis Reveals that Tidal Regime Matters More than Biogeographic Region

Abstract

Identification of critical life-stage habitats is key to successful conservation efforts. Juveniles of some species show great flexibility in habitat use while other species rely heavily on a restricted number of juvenile habitats for protection and food. Considering the rapid degradation of coastal marine habitats worldwide, it is important to evaluate which species are more susceptible to loss of juvenile nursery habitats and how this differs across large biogeographic regions. Here we used a meta-analysis approach to investigate habitat use by juvenile reef fish species in tropical coastal ecosystems across the globe. Densities of juvenile fish species were compared among mangrove, seagrass and coral reef habitats. In the Caribbean, the majority of species showed significantly higher juvenile densities in mangroves as compared to seagrass beds and coral reefs, while for the Indo-Pacific region seagrass beds harbored the highest overall densities. Further analysis indicated that differences in tidal amplitude, irrespective of biogeographic region, appeared to be the major driver for this phenomenon. In addition, juvenile reef fish use of mangroves increased with increasing water salinity. In the Caribbean, species of specific families (e.g. Lutjanidae, Haemulidae) showed a higher reliance on mangroves or seagrass beds as juvenile habitats than other species, whereas in the Indo-Pacific family-specific trends of juvenile habitat utilization were less apparent. The findings of this study highlight the importance of incorporating region-specific tidal inundation regimes into marine spatial conservation planning and ecosystem based management. Furthermore, the significant role of water salinity and tidal access as drivers of mangrove fish habitat use implies that changes in seawater level and rainfall due to climate change may have important effects on how juvenile reef fish use nearshore seascapes in the future.

Highly localized replenishment of coral reef fish populations near nursery habitats

“…Only 3 habitats were present at our sites (reef, mangrove, seagrass), and we collected fish size-frequency data in each of these habitats. These data, as well as those from many other studies on Caribbean islands, consistently show that juveniles of nursery-dependent species are rarely found on coral reefs (see also meta-analysis by Igulu et al 2014). Furthermore, we se lected our sites in such a way that the gradient of reef sites was located close to only a single nursery area, to reduce possible influxes from other nursery patches that were not included.…”

Spatial distribution of juvenile fish species in nursery grounds of a tropical coastal area of the south-western Atlantic

“…Such variability may result from specialization in habitat exploitation by species and by habitat dynamics (Igulu et al 2014, Ebner et al 2016). The ability to use different environments within single ecosystems may depend on species trophic level, morphological characteristics, and functional attributes (Matthews et al 2010, Mouillot et al 2013, de Andrade et al 2015.…”

Habitat Configuration Alters Herbivory across the Tropical Seascape

“…Previous studies on tropical seagrasses find the mangrove-seagrass continuum to provide a corridor for diel and tidal feeding migrations of juvenile fish in shallow sheltered habitats (Nagelkerken et al, 2001;Unsworth et al, 2009). Many fish typically spend time in mangroves during the day and move into nearby seagrass meadows at night to feed upon leaves (Igulu et al, 2015).…”