Thanks, all very good. Interested in hearing others too.
Nick Zarlinga
Aquarium Biologist
Cleveland Metroparks Zoo
216.661.6500 ext 4485
><)> -----Original Message-----
><)> From: owner-nanfa-in-aquaria.net
><)> On Behalf
><)> Of ichthos-in-comcast.net
><)> Sent: Thursday, May 27, 2004 10:45 AM
><)> To: nanfa-in-aquaria.net
><)> Subject: Re: NANFA-- exotic species impact
><)>
><)>
><)> > A surprisingly simple question came up this
><)> morning. Have there been any
><)> > native species that have become endangered or
><)> threatened by the release of
><)> > an introduced species, whether through the
><)> aquarium trade or otherwise?
><)>
><)> Among North American fishes, the answer is yes,
><)> especially in the West and in spring environments.
><)> In fact, some ichthyologists believe that it's the
><)> spread of exotic fishes, rather than loss of
><)> habitat, that's accelerating if not driving many
><)> Southwest fishes towards extinction.
><)>
><)> In small, isolated habitats, where native fishes
><)> may not have evolved adaptations to withstand
><)> competition, the impact of an exotic can be swift
><)> and catastrophic. The Grass Valley speckled dace
><)> (Rhinichthys osculus reliquus) is a case in point.
><)> This dace, which had a distinctively speckled
><)> lower lip and a generally unspeckled body,
><)> occurred in one spring-fed creek in a grassy
><)> meadow in eastern Lander County, Nevada. It was
><)> collected once, in 1938, and never seen again.
><)> Brook and rainbow trout, which had been stocked in
><)> the creek, ate the dace into extinction.
><)>
><)> The Banff longnose dace (Rhinichthys cataractae
><)> smithi) was declared extinct in 1987. This
><)> diminutive version of the eastern longnose dace
><)> was restricted to a small marsh fed by two hot
><)> springs in Banff National Park in Banff, Alberta.
><)> With water temperatures between 17-24C (63-75F),
><)> the area was popular with bathers, who enjoyed the
><)> public spas near the springs. Unfortunately, these
><)> spas sometimes dumped sewage into the dace's
><)> habitat. Human waste, however, was just one threat
><)> facing the dace. The Banff springs were also an
><)> ideal place for aquarists to release unwanted
><)> tropical fishes. Guppies and sailfin mollies, as
><)> well as introduced mosquitofish, reproduce
><)> year-round in the marsh, whereas the dace only
><)> spawned once a year. Eventually, the exotic fishes
><)> took over, out-competing the dace for food, and
><)> preying on the dace's eggs. The last remaining
><)> Banff longnose dace hybridized with the eastern
><)> longnose dace from the nearby Bow River. Since the
><)> Banff subspecies' unique gene
><)> tic structure is now irreversibly mixed with
><)> another subspecies (termed introgressive
><)> hybridization), it is considered extinct.
><)>
><)> In 1989, the High Rock Spring tui chub (Siphateles
><)> bicolor spp.) slipped out of existence six years
><)> after the spring's owner was granted an
><)> aquaculture permit by the California Department of
><)> Fish and Game to farm Mozambique tilapia
><)> (Oreochromis mossambicus), an exotic cichlid. The
><)> voracious tilapia escaped from its holding
><)> facility and destroyed the chub, as well as
><)> various undescribed invertebrates that were also
><)> unique to this miniature ecosystem. In this case,
><)> however, the landowner wasn't totally-in-fault.
><)> The agency that granted the permit did not
><)> recognize the unique taxonomic status of the High
><)> Rock Spring tui chub, nor did it consider the
><)> potential consequences of the tilapia's inevitable escape.
><)>
><)> In most cases, though, exotic fishes is not the
><)> sole cause of imperilment, but a major
><)> contributing factor. Dams, dewatering, habitat
><)> destruction, etc., may be pushing species to the
><)> edge, but exotics are finishing them off.
><)>
><)> Chris Scharpf
><)> Baltimore
><)> ---------------------------
><)> /"Unless stated otherwise, comments made on this
><)> list do not necessarily
><)> / reflect the beliefs or goals of the North
><)> American Native Fishes
><)> / Association"
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><)> American Native Fishes Association
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><)> / For more information about NANFA, visit our web
><)> page, http://www.nanfa.org
/-----------------------------------------------------------------------------
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/ For more information about NANFA, visit our web page, http://www.nanfa.org