This document discusses the threats to global freshwater fish biodiversity and how the biogeography of freshwater fishes has changed due to human activities. It notes that over a third of freshwater fish species are threatened with extinction due to habitat loss, pollution, overexploitation, invasive species, and climate change. Historically, river basins formed isolated areas for fish populations but humans have increased connectivity through activities like shipping, bait bucket releases, and transport of fish for sport fishing and aquaculture. This has challenged conservation efforts by changing the historical biogeography of native fishes through invasions. Ecologists now need to reconcile native fish distributions with expanding invasive species to effectively conserve freshwater fish diversity.

1. Species invasions, environmental change and
the future biogeography of freshwater fishes
Julian D. Olden
University of Washington, Seattle, Washington, USA

2. Water – The lifeline of the biosphere
Freshwater ecosystems touch nearly all aspects of human society:
– acting as centers of organization within the landscape
– providing countless cultural and ecological services
– supporting a rich diversity of biological life
Freshwater fishes represent almost
one-quarter of the global vertebrate diversity

3. The Freshwater Fish Crisis
• Freshwater ecosystems are
almost always embedded in a Freshwater biodiversity in peril
matrix of human use,
dependence, and modification Freshwater
Have fish
fishes in crisis
• Conflicts between human had their
chips?
demands and ecosystem needs
for water currently are growing
• 37% of evaluated freshwater fish
species are considered Sink or swim:
threatened with global One third of Europe’s
Vanishing
freshwater fish face extinction
extinction (IUCN 2009) freshwater
fishes

4. Threats to Freshwater Fishes
Habitat loss Invasive species Pollution
Over-exploitation Disease Climate change

5. Biogeography of Freshwater Fishes
• Fishes are uniquely constrained because their ability to respond
to environmental change is limited to movement defined by the
connectivity of water

6. Biogeographic barriers in fresh waters
Global Fauna
Oceans,
mountains
Continental Fauna
Catchment
divides
Basin Fauna
Waterfalls,
cascades
Local
Species
Pool
Wallace (1876)

7. Glaciations shaped faunal exchange
Glacial Refugia
Beringian (13%)
Banff-Jasper (1%)
Cascadia (4%)
Missourian (20%)
Mississippian (85%)
Atlantic (7%)
Crossman and McAllister (1986)

8. Catchment divides shaped fish faunas
• River basins in North America
that escaped glaciation tend to
have more unique fish faunas
• Catchment divides have been a
formidable barrier to fish
movement

9. Biogeographic barriers in fresh waters
Global Fauna
Oceans,
mountains
Continental Fauna
Catchment
divides
Basin Fauna
• The hierarchy of movement
Waterfalls,
cascades barriers have resulted in river
Local
basins forming what can be
Species considered biogeographical islands
Pool

10. The changing biogeography of fishes
• There is a long history of introduction of non-indigenous fishes
in freshwater ecosystems, the rate of which has accelerated
greatly over time as methods of transportation have improved
and trade barriers have relaxed
• Historical motivation dates back to the Roman Empire and the
extensive fish culturing of the common carp (Cyprinus carpio)
• Today, fish introductions number in the thousands, occurring
via a multitude of intentional and inadvertent vectors, and
whose establishment is promoted by human activities

11. Circumventing natural barriers
to fish movement
Global Fauna • Inter-continental transport of
Oceans, species for sport fishing,
mountains aquaculture, ornamental trade,
and live seafood
Continental Fauna
• Ballast water transport
Catchment
divides
Basin Fauna
Waterfalls,
cascades
Local
Species
Pool

12. Ballast Water Ornamental Trade
Global shipping traffic
Halpern et al. 2008
June 5, 2005 - Woman charged with
smuggling fish in skirt
Customs officials hear ‘flipping’ noises,
find 51 tropical species

13. Intentional Introductions of
Freshwater Fishes
J. D. Olden (unpublished)

14. Global distribution of rainbow trout,
Oncorhynchus mykiss

15. Circumventing natural barriers
to fish movement
Global Fauna
Oceans,
mountains
Continental Fauna
Catchment
• Inter- and intra-basin transport
divides of species for sport fishing,
aquaculture
Basin Fauna • Bait bucket and aquarium
releases
Waterfalls,
cascades • Shipping canals
Local • Overland transport via boats
Species
Pool

16. Intentional transport of sport fishes
Photos Courtesy of the Catskill Archive

17. Fish invasions: Challenges and
opportunities for ecological research
• Through a variety of mechanisms, humans have increased the
connectivity of freshwater systems that were historically
isolated by biogeographic barriers to movement
• As the number of introduced species continue to grow, the
need to logically consider how this process influences the
present-day biogeography of freshwater fish faunas becomes
more and more critical
• Invasive species also provide an unique opportunity to test
various ecological, evolutionary, and biogeographical concepts
and theories in freshwater ecology

18. Fish conservation biogeography in a
rapidly changing world
• Ecologists are now challenged to
reconcile the historical biogeography
of long-evolved native fishes with the
emerging and rapidly expanding
spread of invasive species
• Advances will be achieved with a
globalization of ecological thought
• Janus-approach to fish conservation
biogeography Roman God, Janus

19. Acknowledgements
• Emili García-Berthou
• Mark Kennard
• Fabien Leprieur
• Pablo Tedesco
• Kirk Winemiller
Contact information:
Julian Olden
School of Aquatic and Fishery Sciences
University of Washington
olden@u.washington.edu
http://www.fish.washington.edu/people/olden/