Trouble in Paradise (the Fishy Kind) as Introduced Tilapia Dine on Native Fish Fry
- Fish known for sustainability is invasive species on
islands
NEW
YORK (January 12, 2010)—The poster
child for sustainable fish farming—the tilapia—is actually a problematic
invasive species for the native fish of the islands of Fiji, according to a new
study by the Wildlife Conservation Society and other groups.
Scientists
suspect that tilapia introduced to the waterways of the Fiji Islands may be
gobbling up the larvae and juvenile fish of several native species of goby,
fish that live in both fresh and salt water and begin their lives in island
streams.
The
recently published paper appears in Aquatic Conservation: Marine and
Freshwater Ecosystems. The authors
include: Stacy Jupiter and Ingrid Qauqau of the Wildlife Conservation Society;
Aaron P. Jenkins of Wetlands International-Oceania; and James Atherton of
Conservation International.
“Many
of the unique freshwater fishes of the Fiji Islands are being threatened by
introduced tilapia and other forms of development in key water catchment
basins,” said Dr. Jupiter, a co-author of the study and one of the
investigators examining the effects of human activities on the native fauna.
“Conserving the native fishes of the islands will require a multi-faceted
collaboration that protects not only the waterways of the islands, but the
ecosystems that contain them.”
The most
surprising finding of the study centers on the tilapia, a member of the cichlid
family of fishes from Africa that has become one of the most important kinds of
fish for aquaculture, due in large part to its rapid rate of growth and palatability.
Aside from its value as a source of protein, the tilapia is sometimes
problematic to native fish species in tropical locations.
To
gauge the impacts of tilapia and other human activities on native fish species
in the Fiji Archipelago, researchers surveyed the fish species and other
denizens of 20 river basins on the major islands of Vitu Levu, Vanua Levu, and
Taveuni. In addition to catching and identifying fishes with gill and seine
nets, the scientists also rated other environmental factors such as: the
potential of erosion due to loss of forest cover and riparian vegetation; road density
near rivers and streams; the distances and complexity of nearby mangroves and
reefs; and the presence or absence of invasive species (tilapia mainly).
The
team found that streams with tilapia contained 11 fewer species of native
fishes than those without; species most sensitive to introduced tilapia
included the throat-spine gudgeon, the olive flathead-gudgeon, and other
gobies. In general, sites where tilapia were
absent had more species of native fish.
Since tilapia are
known to consume the larvae and juvenile fish, the researchers assume that the
introduced species may be consuming the native ones as they make their way
upstream and down. Absence of forest cover adjacent
to streams was also correlated to fewer fish species.
Based
on the spatial information compiled in the study, the researchers found that
remote and undeveloped regions—with waterways containing a full complement of
native species and no tilapia—on the three islands should be considered
priority locations for management. The main management activities, the authors
recommend, should include conserving forests around waterways and keeping the
tilapia out.
“Protecting
marine and aquatic biodiversity takes more than managing isolated rivers or
coral reefs,” said Dr. Caleb McClennen, Director of the Wildlife Conservation
Society’s Marine Program. “A holistic conservation approach is needed, one that
incorporates freshwater systems, the surrounding forest cover, coastal estuaries and seaward coral
reefs. As aquaculture continues to develop worldwide, best practices must
include precautionary measures to keep farmed species out of the surrounding
natural environment.”
Contact:
John Delaney: 1-718-220-3275, jdelaney@wcs.org
Stephen Sautner: 1-718-220-3682, ssautner@wcs.org
The
Wildlife Conservation Society saves
wildlife and wild places worldwide. We do so through science, global
conservation, education and the management of the world's largest system of
urban wildlife parks, led by the flagship Bronx Zoo. Together these
activities change attitudes towards nature and help people imagine wildlife and
humans living in harmony. WCS is committed to this mission because it is
essential to the integrity of life on Earth.
Special Note to the Media: If
you would like to guide your readers or viewers to a web link where they can
make donations in support of helping save wildlife and wild places, please
direct them to: www.wcs.org/donation