Subject: RE: NANFA-L-- Fw: NAS Species Alert - Piaractus brachypomus
From: Hoover, Jan J ERDC-EL-MS (Jan.J.Hoover-in-erdc.usace.army.mil)
Date: Thu Nov 04 2004 - 12:22:06 CST
>>>Most tropical breeding populations have been highly localized and not
significantly damaging.<<<
This might be true for native fishes with wide geographic distributions, but
not for endemic fishes. For any species, extirpation or extinction is
significant damage. Of the 40 taxa of North American fishes to go extinct
during the 20th century, approximately three-fourths had small geographic
distributions (< 3 states), and approximately two thirds were impacted by
exotic species (Miller, et al., 1989: Extinctions of North American fishes
during the past century. Fisheries 14(6): 22-38).
Also, its worth noting that peninsular Florida, south Texas, and western
streams and springs, where exotics are creating problems, together comprise
a significant chunk of North American geography.
>>> Even in places like south Florida it is beginning to be clear that the
exotic releases have not had the catastrophic effects that were expected to
take place.<<<
Catastrophe is relative. Sailfin catfishes are causing measurable erosion
problems in several south Florida communities and are dominating catches of
fish from Lake Okeechobee. If you are a homeowner in Boca Raton watching
your backyard slide into a lake, or a commercial fisherman paying to dipose
of unsellable fish, you may consider that a catastrophe.
>>>Florida official have backed off the disaster status for most of the
releases and the numbers you quote are misleading.<<<
Florida Game and Freshwater Fish Commission officials stocked peacock bass
in Florida waters during the 1980s.
>>>The San Antonio R. in Texas is loaded with fish from the aquarium trade,
including loracoriids, firemouth cichlids, and on and on and on.<<<
My co-workers and I have surveyed fishes in the San Antonio River and found
that approximately 85 % of the fish biomass consisted of introduced species:
sailfin catfishes (3 spp), 41%; tilapia (3 spp) 19%, Rio Grande cichlid, 9%;
common carp, 6%; Mexican tetra, 4%; redbreast sunfish, 3%; mollies (2 spp),
2%.
>>>This is very bad and I don't want to down grade the effect in this river
but again this river is a special case and not representative of rivers
every where.<<<
The San Antonio River may not be typical (since it is sub-tropical and
spring-fed) but it is representative of urban streams and the fate of native
fishes assaulted by habitat alterations and exotic fish introductions.
- Jan Hoover
Vicksburg, MS
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: Fri Dec 31 2004 - 12:42:46 CST