[acn-l] NANFA-- Fw: [Clemmys] Fwd: Herpdigest Vol 2#7 (fwd)

peter.unmack at asu.edu
Tue, 10 Aug 1999 19:25:39 -0700 (MST)

Of interest

> >Update 8)Mosquitofish Threaten Amphibians
> >
> >Sometimes you have to prove the obvious to get something
> >done. The mosquitofish is being distributed around the world
> >to control mosquitoes--without regard for its effects on
> >other aquatic species. New research shows that mosquitofish
> >devour tadpoles just as readily as mosquito larvae and so can
> >decimate native amphibians.
> >
> >"Handing out exotic mosquitofish as a control of mosquitoes
> >is an outdated government policy that needs to be changed,"
> >says Lee Kats of Pepperdine University in Malibu, California,
> >who presents this research with Jeff Goodsell in the August
> >issue of Conservation Biology. This is the first study to
> >demonstrate unequivocally that mosquitofish show no
> >preference for mosquito larvae.
> >
> >Distributed by the Los Angeles County Mosquito Abatement and
> >Vector Control Center, mosquitofish have become established
> >in many streams in the Santa Monica Mountains within the last
> >15 years. Because these streams have no native fish, the
> >amphibians that live there lack defenses against fish
> >predation. Amphibians native to these streams include the
> >California newt, the Pacific treefrog and the California
> >treefrog, which is a candidate for protected status.
> >
> >Previous studies have shown that mosquitofish eat amphibians
> >such as California newt larvae in Santa Monica Mountain
> >streams. But these studies have been criticized because the
> >mosquitofish were not offered alternate prey, leaving them no
> >choice but to eat newt larvae.
> >
> >Kats and Goodsell addressed this criticism by offering
> >mosquitofish both Pacific treefrog tadpoles and mosquitoes.
> >The researchers put bottomless two-by-two-foot tubs in
> >fishless Santa Monica Mountain streams and added two
> >mosquitofish, 20 tadpoles and 40 (low-density) or 80 (high
> >density) mosquito larvae. These predator and prey densities
> >approximated those naturally found in local streams.
> >
> >After six hours, the mosquitofish in the "low-density" tubs
> >had eaten all the mosquito larvae and more than 85% of
> >tadpoles. Similarly, the mosquitofish in the "high-density"
> >tubs had eaten more than half of both prey types.
> >
> >The fact that mosquitofish eat tadpoles even when there are
> >plenty of mosquito larvae shows that the fish have no
> >preference for mosquito larvae. "If mosquitofish are to be an
> >effective means of biological control for mosquitoes, they
> >should consume primarily mosquito larvae rather than other
> >native organisms," say Kats and Goodsell.
> >
> >The researchers urge local governments to reconsider their
> >policies of using mosquitofish to control mosquitoes.
> >"Mosquitoes are not a major problem in Southern California--
> >this is a desert with little freshwater--and there are other
> >controls including a pathogen that kills larvae," says Kats.
> >
> >For more information, contact Lee Kats (310-456-4310,
> >lkats at pepperdine.edu).
> ------------------------------------------------------------------------

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