Quantifying fisheries ecosystem services of mangroves and tropical artificial urban shorelines

Study Number

98

Author

Rayna Benzeev, Neil Hutchinson, Daniel A. Friess

Abstract

Rapid development has fragmented Singapore’s coastal habitats and converted them into
artificial shorelines, with implications for the ecosystem services they provide. This study investigated the impact of urban development on two ecosystem services related to fisheries (direct provisioning and indirect nursery functions) by comparing adjacent mangrove and artificial rocky shore sites at two locations. In terms of fisheries provisioning ecosystem services, fish video data indicated that fish assemblage structure was significantly different between the two habitat types, with Ellochelon vaigiensis, Ambassis kopsii, Ambassis interrupta, and Zenarchopterus buffonis contributing most significantly. Trap data indicated that there were significantly more fish on the artificial rocky shore than mangrove at one of our locations in Pasir Ris. There were also significant differences in the size distribution of fish between habitat types at both locations, with high proportions of smaller fish in the mangroves. Even with higher juvenile presence, the role of urban mangroves in providing nursery ecosystem services is less clear, since we cannot determine whether this habitat type is essential for any individual fish species. This study indicates that mangroves provide a level of fisheries ecosystem services as part of a heavily developed and fragmented landscape in conjunction with other substrate types.

Main Results and Conclusions

• There were significant differences in the fish populations between mangroves and artificial rocky shorelines.
  • “The species that made the most significant contributions to differences in assemblage structure between the two habitat types, were Ellochelon vaigiensis
  • Quoy & Gaimard, 1825 (20.77%), Ambassis kopsii Bleeker, 1858 (17.9%), Ambassis interrupta Bleeker, 1853 (14.21%), and Zenarchopterus buffonis Valenciennes, 1847 (11.65%).” (230)
  • “At each location, the mean abundances were higher in mangroves than rocky shores for all five species evaluated.” (230)
• There were differences in fish populations between mangroves and artificial rocky shore in different locations.
  • “…there were significantly more fish on the artificial rocky shores than mangroves at Pasir Ris, while there was no significant difference in numbers between the habitats at Pulau Ubin. The mean abundances were higher in rocky shores for A. kopsii at Pasir Ris, but higher in mangroves at Pulau Ubin. E. vaigiensis was only recorded on rocky shores at Pasir Ris. Abundances of A. interrupta, Stigmatogobius sadanundio Hamilton, 1822, and Butis butis Hamilton, 1822, were higher in mangroves.” (231)
• Although the dynamics are not completely clear, it is evident that mangroves and artificial rocky shores work together to foster fish populations and that mangroves must be protected if fisheries are to be protected.
  • “…we identified significant differences between fish assemblages at adjacent mangrove and artificial rocky shore sites. This indicates that the two habitat types may provide different, yet complementary, direct provisioning services to local fish populations.” (231)
  • “We found significant differences between mangrove and artificial rocky shore sites within the fish assemblages and in terms of the ecosystem services provided by each habitat type. The mangrove sites provided key fishery habitat for certain mangrove-dependent species. Although fish abundances were higher at one of the artificial rocky shore sites, we found that fish species of smaller size classes were located within mangroves compared to artificial rocky shore sites, indicating a potential indirect nursery service for juvenile fish.” (235)
  •  “…it is crucial to enforce local conservation strategies to protect mangroves as critical habitats for mangrove-dependent species and species that may rely on these populations, to protect global fisheries resources. Singapore, with its rapid development and mangrove fragmentation, is an important tropical case study that allows us to understand how increasingly urbanized coastal areas may influence fish population dynamics.” (235)