1. Influence of landscape and reach-scale variables on aquatic community structure in tropical island streams
Catherine L. Hein, Andrew S. Pike, J. Felipe Blanco, Todd A. Crowl, Fred N. Scatena, Melinda Laituri, and Alan P. Covich

4. 6 Native Fishes
Eels
Mullet
Eleotrids
Gobies

5. 10 Native Shrimps and 1 River Crab
Palaemonid
Shrimp
Atyid Shrimp

6. Tropical Island Streams
Diadromy
Larvae
Eggs/Adults
Post-larvae
Adults

8. Modeling Complex Interactions of Overlapping River and Road Networks in a Changing Landscape
Overarching hypothesis: An integrated, individual based modeling framework will better predict interactive effects of humans on river landscapes than will individual physical, chemical, biological and social models

9. Sample Sites Espiritu Santo Mameyes 4 pools/riffles at
each of 24 sites

10. Integrated framework Social models Physical models Biological models

11. What natural and anthropogenic variables at landscape and/or reach-scales determine fish and decapod community structure in two Puerto Rican watersheds?
Distribution of each species
(6 fishes and 8 decapods)
Community assemblage

12. Field Sampling Trapping Snorkeling Electrofishing Sampled 90 pools
and associated
riffles

13. Landscape Variables Largest downstream vertical drop (m) Elevation
% land cover within a 250 m radius of each site (urban, agriculture, or forest)
Number of downstream road crossings
Road type

14. Geomorphology Pool Variables Grain size Length Width
Variation in width
Maximum depth
Variation in depth
Grain size
Bedrock
Megaboulder
Boulder
Cobble
Gravel
Sand
Fines

15. Individual Species Distributions – Waterfalls
Vertical Drop
> 3.5 m No
Yes
Atya lanipes
Absent
Present
Anguilla rostrata
Gobiomorus dormitor
Absent
Present
Agonostomus monticola

16. Individual Species Distributions – Elevation
Macrobrachium carcinus
Elevation
> 100 m
Absent
Present No
Yes
< 439 m
Macrobrachium crenulatum
Elevation
< 439 m No
Yes
Absent
Present

17. Individual Species Distributions – Pool Length
Xiphocaris elongata
Awaous tajasica
Pool length
< 23 m
Pool length
> 28 m No
Yes No
Yes
Absent
Present
Absent
Present

18. Individual Species Distributions – Grain Size
Eleotris pisonis
Sicydium plumieri
% Fine
sediment
< 0.004
Median grain
size <64 mm No
Yes No
Yes
Absent
Present
Absent
Present

19. Community Assemblage

20. Community Assemblage Headwaters Ocean
Large circles indicate greater decapod species richness

22. Conclusions
Natural landscape-level barriers are largely responsible for patterns in community structure
Fishes are below waterfalls and most decapods are above

23. Conclusions
Roads, dams, and urban and agricultural land covers do not significantly affect species distributions in these watersheds
Why not?

24. Culverts
Bridge piles
Narrow squared culvert
Large bridge

26. Why do anthropogenic factors not have an effect on diadromous fauna in the Espίritu Santo and Mameyes watersheds?
Metrics besides presence/absence were not tested (e.g. abundance)
Diadromous fauna are resilient

28. Why do anthropogenic factors not have an effect on diadromous fauna?
Metrics besides presence/absence were not tested (e.g. abundance)
Diadromous fauna are resilient
Chronic changes to the landscape have not yet occurred

29. High Head Dams & Exotic Species

30. Acknowledgements Dave Kikkert Ruth Kikkert Maria Ocasio Torres
Enrique Marrero
Coralys Ortiz
Andy Crowl
Paul Nicholson
Kaua Friola
Wyatt Cross
Chelse Prather
Funded by NSF