| Virgin
Spinedace |
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Virgin
Spinedace (Lepidomeda mollispinis mollispinis)
By Tim G. Hurst, Native Fish Biologist |
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Scientific
Name:
Lepidomeda mollispinis mollispinis. From the Greek lepi meaning scale and
dom meaning house. Mollispinis is from the Latin root molli meaning soft,
and spinis meaning spine. The name is derived from the characteristic feature
of the fusion of the two hardened spiny rays on the dorsal and pectoral
fins. |
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Description:
The Virgin spinedace is a member of an endemic group of western minnows
that share the modified dorsal fin trait. This small stream fish ranges
between 2 and 4 inches in total length. Its sides are silvery with
speckles and a touch of brassy coloration. Sexual dimorphism is only
apparent during the breeding season. Males are typically streamlined,
while females are more robust. |
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Habitat:
Virgin spinedace live in cooler, clear tributaries and in moderately swift
areas with scattered pools. Extensive research on the species found
that they will migrate more than half a mile and often frequent pools
with some form of protection, such as overhangs, boulders, or debris. |
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Distribution:
Historic distribution is not well documented. Virgin spinedace are believed
to have occupied (historically) most of the perennial streams and rivers
within the Virgin River Basin. Today, they are found in portions of
the Santa Clara and Virgin rivers and several of their tributaries
in Utah, Nevada, and Arizona. In Arizona, Virgin spinedace are restricted
to limited portions of Beaver Dam Wash and the Virgin River. |
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Biology:
Virgin spinedace, like many other southwestern fish, mainly eat aquatic
insect larvae, but also eat algae when other foods are scarce. They
feed on the bottom, in the midwater column, and on the surface. Virgin
spinedace usually do, however, maintain an equilibrium in the midwater
column and will dart to the surface to capture prey.
Virgin spinedace typically live three years and reach sexual maturity in
about one year. During breeding, the vent of the female becomes swollen
and both sexes develop reddish-orange coloration at the bases of the paired
fins. Spawning generally occurs from April to June; approximately 90 percent
of the spawning population consists of one-year-old fish. Females move
to a group of congregating males near the lower ends of pools to spawn
at or near the bottom. |
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Status:
Virgin spinedace occur in approximately 60 to 63 percent of their historic
range. In addition, about 24 percent of their current habitat has been
adversely modified. Declines are attributed to effects of water diversion,
impoundment, channelization, degradation of water quality, and introduced
species, both fishes and crayfish.
The Virgin spinedace is included on the Department's draft list of Wildlife
of Special Concern in Arizona (AGFD in prep.). It was proposed by the U.S.
Fish and Wildlife Service in May 1994 for listing as a threatened species,
but the proposal was withdrawn in lieu of implementation of a multi-agency
Virgin Spinedace Conservation Agreement and Strategy that will ensure the
conservation needs of the fish are met. The Agreement's goal is to reestablish
and maintain water flows, enhance and maintain spinedace habitats, maintain
genetic viability, and monitor populations. |
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Management
Needs:
Several objectives aimed at eliminating or reducing threats must be addressed
to ensure continued existence of the species. Habitats must be protected
and managed through establishment of instream flows that maintain the pattern
of historic flows. Non-native fishes and crayfish should be removed or
reduced from selected reaches of streams. In addition, populations must
be reestablished into historical habitat and maintained at adequate numbers
to ensure genetic viability. The Virgin spinedace is only one of several
Arizona native fishes that seem to be on a course toward extinction. Progressive
management of the spinedace in particular, and native fishes in general,
is therefore, extremely critical. |
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