Hwey-Lian Hsieh, Po-Fen Lin*, Chang-Po Chen Institute of Zoology, Academia Sinica, Taipei, Taiwan

1. Conservation strategies in coastal wetland: compromise based on habitat conflicts between mangroves and the fiddler crab, Uca formosensis in Taiwan Hwey-Lian Hsieh, Po-Fen Lin*, Chang-Po Chen Institute of Zoology, Academia Sinica, Taipei, Taiwan Research Center for Biodiversity, Academia Sinica, Taipei, Taiwan

2. Outline • Taiwanese fiddler crab, Uca formosensis. • Why mangrove is important to Taiwan coastal zone? • The habitat characteristics of mangroves and Uca formosensis. • How mangroves could change the habitat of Uca formosensis? • Conservation Strategies

3. Introduction The fiddler crab Uca formosensis is endemic to Taiwan Other Uca species Uca formosensis

4. The habitats of Uca formosensis : Non-vegetated, high tidal zones in firm mud intertidal flats

5. Life history stage Zoea and Megalop stage Spread/distribution Juvenile Feeding/ growth Adult Burrowing/ breeding Aspect of organism Competition between fauna Benthic environment Benthic environment Water column Micro- habitat Temperature, humidity, sediment salinity, oxygen content, water content, quantity and quality of food, toxic materials, etc. support influence Aspect of habitat influence Water Vegetation Sediment Macro- habitat estuary tide flow tidal level mangrove benthic microalgae particle size topography elevation influence Coastal environments erosion/siltation emerging/sinking

6. 121°E 120°E 122°E 25°N 24°N 23°N 23°N Distributional records of Uca formosensis (from 1918 to 1997) • Black stars represent areas with active population of U. formosensis • Open stars represent areas where the population of U. formosensis has extinguished. (Shih,1999)

7. Threats to fiddler crabs: Land reclamation, dike and road construction

8. Another threat to fiddler crabs: Improper planting of mangroves on the Uca formosensis habitats

9. Goals of this study: • To examine the habitat characteristics of both U. formosensis and mangroves • To provide a scientific basis for conserving the diversity of intertidal habitats and populations of U. formosensis • To propose conservation strategies for the protection of intertidal habitats in coastal wetlands of Taiwan

10. Material and Methods

11. Taipei City Kuantu (KT) Hsinchu City Jenchang Lake (JCL) Tachuang Creek North Shore (TCN) Tachuang mangrove (TCS) Tatu (TT) Haishanku-1 (HSI) Changhua County Haishanku-2 (HSII) Haishanku Mangrove (HS) Haishanku-3 (HSIII)

12. Depth of the oxidation layer Sedimentary substrates of microhabitats • Grain size (Silt/Clay content) • Total organic carbon and nitrogen content • Water content • pH • Salinity of interstitial water • Depth of the oxidation layer • Benthic macroinvertebrates

13. JCL JCL TCN TCN HSI HSI HSII HSII HSIII HSIII TT TT HS HS TCS TCS KT KT Results and Discussion ○ The habitat of Uca formosensis (△mean±S.E.) ● The habitat of mangroves(▲mean±S.E.)

14. JCL JCL TCN TCN HSI HSI HSII HSII HSIII HSIII TT TT HS HS TCS TCS KT KT ○ The habitat of Uca formosensis (△mean±S.E.) ● The habitat of mangroves(▲mean±S.E.)

15. JCL JCL TCN TCN HSI HSI HSII HSII HSIII HSIII TT TT HS HS TCS TCS KT KT ○ The habitat of Uca formosensis (mean±S.E.) (including polychaetes, insects and crabs ) ● The habitat of mangroves (mean±S.E.) (including polychaetes, insects, crabs and oilgocheates)

16. Potential negative impacts on U. formosensis caused by mangrove intrusion A. Alternation of sediment characteristics Siltation increases Depth of oxidation layer decreases pH decreases

17. B. Direct effects by mangrove trees • Shading effects (Hsieh,1999; Hsieh et al.,2002; Wainright et al., 2000) Productivity of benthic microalgae declines • Aboveground structures Stems and branches block crabs’ view and movement Leaves shaken by wind may scare crabs • Underground structures Roots become obstacles to crabs’ burrowing

18. C. Benthos changes (Shih,1999; Hsieh et al.,2002) Helice formosensis, H. wuana, U. arcuata prefer mangrove habitats Helice formosensis U. arcuata

19. Conservation Strategies • Accelerate studies on the habitat characteristics of each stage of the life history of U. formosensis • Apply ecological engineering practices to restore habitats of U. formosensis • Monitor the impacts of mangroves on estuarine ecosystems and manage mangroves accordingly

20. Conserve coastal wetlands which 1) retain those still sound function, 2) improve those that have been disturbed, and 3) restore those that have been destroyed. We try to connect these three types of habitats to form a “Coastal Wetlands Conservation Greenway along Taiwan’s Western Coastal Zone” (Hsieh et al., in press) • Promote the wise use of coastal wetlands

21. Mangrove trees Buffer zones Uca formosensis reserve For examples: remove mangroves from Uca formosensis reserve and buffer zones Mangroves should be eliminated from U. formosensis reserve areas.

22. Carry out public education on biodiversity and habitat diversity. When U. formosensis encounters mangroves

23. Summary • The invasion of mangroves into U. formosensis habitats has a negative impact on the fiddler crab’s population. • Mangroves on estuarine ecosystems and coastal zones should be managed properly in Taiwan. • Future coastal management should emphasize on maintaining biodiversity and habitat diversity.

24. Acknowledgements Funding agencies Institute of Zoology Academic Sinica Research Center for Biodiversity Academia Sinica Hsinchu City Government Assistants and Graduate students Yuan-Hsien Chen, Hsin-Yi Yeh, Hsiao-Hui Yang, Tai-An Chen, Song-Lin Wu, Wu-Hsiung Ou, Shu-Ting Lin, Feng-Lin Wang, Chang-Hao Hoa, Ming-Che Yang, Meng-Jeng Guo.

25. Thanks!