[Federal Register Volume 59, Number 138 (Wednesday, July 20, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-17576]
[[Page Unknown]]
[Federal Register: July 20, 1994]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
RIN 1018-AB88
Endangered and Threatened Wildlife and Plants; Final Rule To List
the Rio Grande Silvery Minnow as an Endangered Species
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Final rule.
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SUMMARY: The U.S. Fish and Wildlife Service (Service) determines the
Rio Grande silvery minnow (Hybognathus amarus) to be an endangered
species under the Endangered Species Act of 1973 (Act), as amended.
This fish occurs only in the middle Rio Grande from Cochiti Dam
downstream to the headwaters of Elephant Butte Reservoir, New Mexico.
Threats to the species include dewatering, channelization and
regulation of river flow to provide water for irrigation; diminished
water quality caused by municipal, industrial, and agricultural
discharges; and competition or predation by introduced non-native fish
species. Currently, the species occupies about five percent of its
known historic range. This action will implement Federal protection
provided by the Act for the Rio Grande silvery minnow. The Service
further determines that finalization of proposed critical habitat will
not occur at this time, as critical habitat is not now determinable
because the required economic analysis has not been completed. Pursuant
to section 4(b)(6)(C)(ii) of the Act, a final determination on critical
habitat may be delayed up to 1 year beyond the normal deadline.
EFFECTIVE DATE: August 19, 1994.
ADDRESSES: The complete file for this rule is available for inspection,
by appointment, during normal business hours at the U.S. Fish and
Wildlife Service, New Mexico Ecological Services State Office, 3530 Pan
American Highway NE., Suite D, Albuquerque, New Mexico 87107.
FOR FURTHER INFORMATION CONTACT: Jennifer Fowler-Propst, State
Supervisor, at the above address (505/883-7877).
SUPPLEMENTARY INFORMATION:
Background
The Rio Grande silvery minnow is one of seven species in the genus
Hybognathus found in the United States (Pflieger 1980). The species was
first described by Girard (1856) from specimens taken from the Rio
Grande near Fort Brown, Cameron County, Texas. It is a stout silvery
minnow with moderately small eyes and a small, slightly oblique mouth
(Pflieger 1975). Adults may reach 90 mm (3.5 in) in total length
(Sublette et al. 1990). Its dorsal fin is distinctly pointed with the
front located slightly closer to the tip of the snout than to the base
of the tail (Pflieger 1975). Life color is silver with emerald
reflections. Its belly is silvery white, fins are plain, and barbels
are absent (Pflieger 1975, Sublette et al. 1990).
This species was historically one of the most abundant and
widespread fishes in the Rio Grande basin, occurring from Espanola, New
Mexico, to the Gulf of Mexico (Bestgen and Platania 1991). It was also
found in the Pecos River, a major tributary of the Rio Grande, from
Santa Rosa, New Mexico, downstream to its confluence with the Rio
Grande in south Texas (Pflieger 1980). Collection data indicate the
species presently occupies about five percent of its historic range
(Platania 1993). It has been completely extirpated from the Pecos River
and from the Rio Grande downstream of Elephant Butte Reservoir.
Currently, it is found only in a 275 km (170 mi) reach of the middle
Rio Grande, New Mexico, from Cochiti Dam, Sandoval County, to the
headwaters of Elephant Butte Reservoir, Socorro County (Bestgen and
Platania 1991). Throughout much of its historic range, decline of H.
amarus may be attributed to modification of stream discharge patterns
and channel desiccation by impoundments, water diversion for
agriculture, and stream channelization (Bestgen and Platania 1991, Cook
et al. 1992).
The Rio Grande silvery minnow no longer exists in the Pecos River
where it was replaced by a congener, the introduced plains minnow (H.
placitus) (Hatch et al. 1985, Bestgen et al. 1989, Cook et al. 1992).
It is believed that the plains minnow was introduced into the Pecos
drainage during 1968, probably the result of the release of ``bait
minnows'' that were collected from the Arkansas River drainage. The
replacement that ensued was complete in less than one decade (Cowley
1979). The plains minnow may be more tolerant of modified habitats and
therefore able to replace H. amarus in the modified reaches of the
Pecos River where it was introduced. It is also believed the two
species hybridized (Cook et al. 1992). Habitat alteration and resulting
flow modification could have also contributed to extirpation of the Rio
Grande silvery minnow in the Pecos River.
Decline of the species in the Rio Grande probably began in 1916
when the gates at Elephant Butte Dam were closed. Elephant Butte was
the first of five major mainstream dams constructed within the Rio
Grande silvery minnow's habitat (Shupe and Williams 1988). These dams
allowed the flow of the river to be manipulated and diverted for the
benefit of agriculture. Often this manipulation resulted in the
desiccation of some river reaches and elimination of all fish.
Concurrent with construction of the mainstream dams was an increase in
the abundance of non-native and exotic fish species, as these species
were stocked into the reservoirs created by the dams (Sublette et al.
1990). Once established, these species often completely replaced the
native fish fauna (Propst et al. 1987). Development of agriculture and
the growth of cities within the historic range of H. amarus resulted in
a decrease in the quality of water in the river that may have adversely
affected the range and distribution of the species.
Most land bordering the river where the species currently exists is
owned by the Middle Rio Grande Conservancy District, which is a quasi-
public agency of the State of New Mexico. Other landowners include six
Native American Pueblos, the U.S. Bureau of Reclamation, the Service,
the U.S. Bureau of Land Management, New Mexico State Parks, New Mexico
Department of Game and Fish, New Mexico State Lands Department, and the
U.S. Army Corps of Engineers (Corps).
Water flow in the middle Rio Grande is controlled by the Rio Grande
Compact Commission. Established in 1929 for the purpose of permanently
and equitably apportioning the flows of the Rio Grande, the Commission
is composed of a Federal chairperson appointed by the President of the
United States and three voting members--a representative designated by
the Texas Governor and the State Engineers of New Mexico and Colorado.
The Commission meets annually to review compliance with the compact
over the preceding year, to hear reports from Federal water management
agencies, and to consider water management decisions that have
interstate implications. Federal agencies that also determine timing
and amount of flow in the river include the International Boundary and
Water Commission, the Bureau of Reclamation, and the Corps.
Previous Service Actions
The Rio Grande silvery minnow was listed on the Service's Animal
Notice of Review (56 FR 58804; November 21, 1991) as a category 1
species. A category 1 species is one for which the Service has on file
substantial information on biological vulnerability and threat(s) to
support a proposal to list it as an endangered or threatened species. A
proposed rule to list the Rio Grande silvery minnow as endangered with
critical habitat was published in the Federal Register on March 1, 1993
(58 FR 11821).
Summary of Comments and Recommendations
In the March 1, 1993, proposed rule and associated notifications,
all interested parties were requested to submit factual reports or
information that might contribute to the development of a final rule.
The comment period originally scheduled to close on April 30, 1993, was
extended until August 25, 1993, (58 FR 19220; April 13, 1993) to
conduct public hearings and allow submission of additional comments.
Appropriate Tribal governments, State agencies, county governments,
Federal agencies, scientific organizations, and other interested
parties were contacted and requested to comment. Newspaper notices
inviting public comment were published in New Mexico in the Albuquerque
Journal on May 2, 1993; Las Cruces Sun News on April 30, 1993; Socorro
Defensor Chieftain on April 28, 1993; Santa Fe New Mexican on April 20,
1993; and in Texas in the El Paso Times on March 20, 1993.
Because of anticipated widespread public interest, the Service held
two public hearings that were announced in an April 13, 1993, Federal
Register notice. Interested parties were contacted and notified of the
hearings. Thirty-seven people attended the hearing in Albuquerque, New
Mexico, and 58 attended the hearing in Socorro, New Mexico. Oral or
written comments were received from 25 parties at the hearings; none
directly supported the proposed listing. Transcripts of these hearings
are available for inspection (see ADDRESSES). Briefing sessions were
also held for tribal leaders on May 18, 1993, in Albuquerque, New
Mexico; and for a number of northern pueblos at Santo Domingo Pueblo,
New Mexico, on September 9, 1993.
A total of 40 written comments were received at the Service's
Ecological Services State Office in Albuquerque, New Mexico: 13
supported the proposed listing; 14 opposed the proposed listing; and 13
commented on information in the proposed rule but expressed neither
support nor opposition.
Oral or written comments were received from 7 Federal and 5 state
agencies, 14 local officials, and 36 private organizations, companies,
and individuals. Written comments and oral statements presented at the
public hearings and received during the comment periods are covered in
the following summary. Comments of a similar nature or point are
grouped into a number of general issues. These issues, and the
Service's response to each, are discussed below.
Issue 1: The Service has come to the conclusion that only instream
flow will assure the species' existence. Will the Service propose a
program for the purchase of water rights in order to provide water for
the species?
Response: The Service has not reached this conclusion. Possible
instream flow requirements of the species are among several factors
that need to be considered in the recovery planning process. If, during
the recovery planning process, the Service determines that the purchase
of water rights will enhance recovery of the species, the Service would
explore with other State and Federal entities the possible purchase of
water rights from willing sellers.
Issue 2: The United States, under the terms of the Convention of
1906, has the obligation to deliver 60,000 acre-feet of water annually
to the Republic of Mexico. The U.S. International Boundary and Water
Commission (IBWC) is responsible for ensuring that the U.S. government
meets those obligations. The IBWC is concerned that the listing may
interfere with their ability to meet these treaty requirements.
Response: The Service recognizes the treaty obligation of the
United States to provide to the Republic of Mexico 60,000 acre-feet of
water annually from the Rio Grande. Measures taken to protect and
recover the Rio Grande silvery minnow will take into consideration this
treaty obligation and IBWC's ability to meet treaty requirements.
Issue 3: Completion of the dams above Elephant Butte Dam has had
the effect of extending stream flow. Flood control and conservation
storage operations do not, cannot, and have not been used to create or
extend reaches of no flow in the riverbed.
Response: The Service agrees with the statement. Availability of
flow is likely not the only factor affecting decline of the silvery
minnow. These operations change the natural flow regime of the river
and thus may affect survival of the Rio Grande silvery minnow. The
final rule recognizes these other factors in the ``Summary of Factors
Affecting the Species.''
Issue 4: Reservoirs do not, as implied, store all spring runoff and
summer inflows. Water is normally released during summer, not winter
months. Diversion dams and canals have limited capacities to divert
flows. They cannot ``completely divert all flows . . . into irrigation
ditches'' under flood conditions.
Response: The Service agrees with the statement that reservoirs do
not store all spring runoff and summer inflow. While most water is
released during the spring and summer, a fall and winter release does
occur in the Middle Rio Grande Valley when conditions permit (Beal and
Gold 1988, Borland and Gold 1989). Under flood conditions, the
irrigation diversions do not have the capacity to divert all flows.
Under non-flood flows they do have the capacity to divert all flows.
United States Geological Survey (USGS) records substantiate the
occurrence of no-flow periods downstream of the various irrigation
diversion dams.
Issue 5: The proposed regulation is unsupported by any hydrological
study as to the statements that irrigation uses have depleted the water
flow. Not a single source of information is cited for comments
regarding hydrology of the river. Depletions of water in the system may
be the result of the construction of wildlife watering impoundments by
the Forest Service and Bureau of Land Management.
Response: It can be readily documented by examining USGS flow gage
records that river flows decrease when the irrigation season starts. In
addition, the Service reviewed Bullard and Wells (1992), which provides
information on the hydrology of the middle Rio Grande. This reduction
in flow is most noticeable in mid-summer after the spring to early
summer peak flow has passed. Wildlife impoundments are often very small
(less than one acre in size) and are considered to be insignificant in
the amount of water they deplete from the drainage.
Issue 6: Economic considerations should be given more weight when
communities may be affected.
Response: Section 4(a)(1) of the Act identifies five factors that
are considered in making a determination of whether a species should be
listed as threatened or endangered. Section 4(b)(1)(A) of the Act
requires that listing determinations be based solely on the best
available scientific and commercial data, and prohibits the Service
from considering economic factors (50 CFR 424.11(b)). However, because
economics are considered in the designation of critical habitat, the
Service will conduct an economic analysis in the process of evaluating
proposed critical habitat for the Rio Grande silvery minnow.
Issue 7: The Service needs to ensure public input before listing
the Rio Grande silvery minnow. The Service is required to notify
counties and other affected parties to solicit their input prior to
listing a species under the Act. The Service failed to meet this
obligation.
Response: On February 19, 1991, about 80 pre-proposal letters of
inquiry were mailed to various governmental agencies, knowledgeable
individuals, and the New Mexico Congressional delegation. On March 20,
1992, the Service held a meeting in Albuquerque, New Mexico, with
various interested governmental and private entities to explore
existing or potential flexibility in water delivery schedules that
might avoid dewatering of the Rio Grande within the range of the Rio
Grande silvery minnow. The Service also published notices of the
proposal in 5 local newspapers and mailed copies of the proposed rule
to 148 different government agencies, private organizations, and
interested individuals, including all counties having lands that border
the area being proposed for critical habitat designation. Two public
hearings were also held. The Service has fully met or surpassed the
requirements of the Endangered Species Act for public notification.
Issue 8: The Service held public hearings only to fulfill a legal
obligation and will not pay attention to any public comment. The
Service should have held public hearings in El Paso and Las Cruces.
Response: The Service disagrees. All comments are carefully
evaluated before the Service makes a determination on whether to
proceed with a final rule. Numerous notifications of the proposed rule
and extension of the comment period were distributed, and Service
biologists traveled to several areas, including El Paso and Las Cruces,
to present briefings on the proposed rule and accept comments.
Issue 9: The Service should establish a coordinating committee
composed of interests below Elephant Butte Reservoir whose task would
be to develop a full-scale report on the existing data available on the
Rio Grande silvery minnow and how the river could be managed for the
benefit of all, including the Rio Grande silvery minnow.
Response: After the species is listed the Service will consider,
through the recovery planning process, establishing a coordinating
committee to develop a report on the Rio Grande silvery minnow and how
the river could be managed for the benefit of all, including the Rio
Grande silvery minnow.
Issue 10: During periods of dewatering of the river, the ditches
provide habitat for the species. The Service should consider exploring
with the Middle Rio Grande Conservancy District, the counties, and
other agencies the multiple use of riverside drains for the species and
the preservation of bosque habitat.
Response: The Service agrees that during periods of drought, which
result in the dewatering of the mainstream Rio Grande, the various
irrigation ditches and drains may provide a temporary place of refuge
for the Rio Grande silvery minnow. However, these areas do not contain
suitable habitat for long-term use by the species. Few Rio Grande
silvery minnows are found in the ditches and drains. Those that are
found are believed to represent Rio Grande silvery minnows that became
entrapped due to the diversion of irrigation water from the mainstream.
The Service intends to investigate, with all interests, the potential
use of the riverside drains for recovery of the species.
Issue 11: Few data exist on the abundance of the species on Pueblo
lands or whether it can survive in the mud and sand when the river bed
is dry.
Response: The Service used all available biological information in
making the determination to list the Rio Grande silvery minnow as an
endangered species. Recent census data from Pueblo lands are reported
by Bestgen and Platania (1991), Platania and Bestgen (1988), Platania
and Clemmer (1984), and the U.S. Bureau of Reclamation (1992). As
additional information becomes available, including information from
Pueblo waters, the Service will use that information in the recovery
planning process. The Service hopes that, through initiation of
recovery efforts for the species, and in cooperation with the Pueblos,
additional information can be obtained on the status of the species on
Pueblo lands. The Service has no scientific data indicating that the
species survives in the mud and sand during periods when the river is
dry.
Issue 12: Competition between H. amarus and its congener H.
placitus could have also contributed to extirpation of the species from
the Pecos River. Studies should be conducted to determine if predation
or competition by non-native fishes impacts the species. The studies
should not just determine if it is a problem, they should also
determine where and to what extent it is a problem.
Response: The Service has no data to substantiate any reasons for
extirpation of the Rio Grande silvery minnow from the Pecos River and
replacement by its congener H. placitus. Competition may have been a
factor in its extirpation; however, it is more likely that
hybridization between the two species was the primary factor. Studies
designed to determine if predation or competition by non-native fishes
impacts the survival of the Rio Grande silvery minnow will be conducted
as part of recovery efforts for the species.
Issue 13: Recent biological studies have been conducted during a
period of high flow; therefore, the results of those studies do not
accurately reflect the distribution of the species under normal
conditions.
Response: It is true that, other than 1989, recent data have been
collected during a period of higher than normal flow. However, even
these data show that the species is not as abundant as it was during
other periods of above-normal flow. This leads to a conclusion that
factors other than flow may be impacting the species and its habitat.
Issue 14: It seems a fair conclusion that the Cochiti downstream
reach is no longer favorable habitat because of lowered water
temperatures and degradation of favored H. amarus substrate. This
further limits the area in which the species has to survive.
Response: Although the reach immediately downstream of Cochiti Dam
may not be favorable habitat for the Rio Grande silvery minnow, it is
not known how far downstream these conditions persist. As part of
recovery efforts for the species, studies will be conducted on this
question, and attempts may be made to correct the unfavorable
conditions.
Issue 15: Since little is known of feeding habits or reproduction,
the claim that channel modification would adversely affect the Rio
Grande silvery minnow is not supported by the best scientific evidence.
Changes in food supply, not water supply, may be a factor affecting the
species in the Rio Grande. Also, the effects of non-native plants upon
the habitat need to be investigated.
Response: Recent data have shown that spawning activity occurs
during peak spring and early-summer flows. The fertilized eggs drift
with the current for about 24 hours and then hatch. The larval fish
continue to drift downstream until they are swept into calm backwater
and edge areas where food is abundant and they can continue to grow.
Because of this spawning behavior, any modifications to the channel
that result in changes that sweep the eggs and larval fish into less
favorable habitats would adversely affect the species. There are no
data presently available to support the contention that a reason for
decline of the species was a decrease in the species' food supply or
the invasion of non-native plants. As part of recovery efforts, the
impacts of all habitat modifications will be investigated to determine
if and how they impact the species.
Issue 16: Very little information was presented at the public
hearing or in the Federal Register to show a cause-and-effect
relationship between water quality and decline of the species.
Response: Limited information exists on the relationship between
water quality and the decline of the species. A better understanding of
this relationship will be developed as a result of recovery efforts.
Issue 17: The proposed listing of the Rio Grande silvery minnow is
just a part of a much larger problem--the modification of the
floodplain. Are activities at Bosque del Apache National Wildlife
Refuge (NWR) affecting the species?
Response: The Service agrees. Listing the species will invoke
protective provisions of the Act, such as those contained in section 7.
The Service has no information that indicates activities at Bosque del
Apache NWR impact the species. The Service will work with Federal
agencies, including Bosque del Apache NWR, to ensure that their actions
do not jeopardize the species through adverse effects on the
floodplain. In addition, the Service is involved in several cooperative
efforts with Federal, State, and private entities to protect the Rio
Grande Bosque and associated floodplain.
Issue 18: The facts presented in the status report do not support
the conclusion that ``anticipated additional modifications'' would
limit prospects of survival for the species in the middle Rio Grande.
Response: The facts presented in the status report do support the
conclusion that ``anticipated additional modifications'' would limit
prospects of survival for the species in the middle Rio Grande.
According to the authors of the status report, ``Conservation measures
are necessary as continued habitat and flow modifications,
introductions of non-native species, and lack of refugia threaten
survival of H. amarus.'' The present status of the species is such that
any activity that could negatively impact the species may limit
prospects for its survival.
Issue 19: Only two facts support listing; that the species is
presently found in only 5 percent of its historic range, and that other
fish native to the middle Rio Grande (Rio Grande bluntnose shiner,
phantom shiner, Rio Grande shiner, and speckled chub) have been
extirpated from the river. The Service does not have adequate data to
support the conclusion that the Rio Grande silvery minnow is endangered
and should be listed under the Act.
Response: The Service agrees that the above two facts support
listing. However, other facts that support listing include the species'
decrease in abundance within the area it presently occupies, and its
extirpation from the Pecos River after the introduction of the plains
minnow into that system. The Service concludes, as detailed in the
``Summary of Factors'' section, that there is sufficient evidence to
support listing the species as endangered under the Act. The Service
reviewed the best scientific and commercial data available to make this
determination.
Issue 20: The Rio Grande silvery minnow is not a distinct species.
It is just a local population of the Mississippi silvery minnow. The
Service should consider conducting studies for two years on the
species' taxonomy.
Response: The Service has taxonomic information that verifies the
Rio Grande silvery minnow as a distinct species. The Rio Grande silvery
minnow is recognized by the American Fisheries Society, which is
considered the scientific authority for the names of fishes, as a full
species (American Fisheries Society 1991). Cook et al. (1992), using
starch gel electrophoretic methods, found that phenetic and
phylogenetic analyses corroborated the hypothesis that H. amarus is
distinct at the species level from H. nuchalis and H. placitus, with
which it was previously grouped.
Issue 21: The Service has not conducted in-depth studies to
determine the number of silvery minnows that exist in the Middle Rio
Grande Valley and associated drainage ditches. The species may be doing
well without protection of the Federal government.
Response: Since 1987, studies have been conducted to document the
population of Rio Grande silvery minnows in both the Middle Rio Grande
Valley and its associated irrigation and drainage ditches from Velarde
to Elephant Butte Reservoir, New Mexico. These studies have shown that
very few Rio Grande silvery minnows survive in the drainage ditches.
The listing is based, in part, upon the extirpation of the species from
about 95 percent of its historic range. The species was once thought to
be one of the most numerous fish in the Rio Grande. In 50 fish
collections made between Bernalillo and Elephant Butte Reservoir
between 1987 and 1988, the Rio Grande silvery minnow was the second
most abundant species, comprising 18 percent of the total fish
collected. From 1989 to 1992, 56 collections were made in the same area
and only 3 Rio Grande silvery minnows were collected. During that
period, the Rio Grande silvery minnow went from being the second most
abundant native fish species to the least abundant native species
(Platania 1993). The Service believes that without the protection
afforded through Federal listing, the species is likely to become
extinct. Two native Rio Grande fish species have already become
extinct.
Issue 22: The fish exist in stretches of the river that have been
subject to drying for at least 50 years, but have disappeared from
areas where there has been instream flow for the past 50 years.
Response: The Service agrees that the species has persisted in
reaches of the river that have experienced seasonal drying during the
past 50 years and has been extirpated from reaches where there has been
continual flow during the last 50 years. In the past, during periods of
extremely low flow, the species survived in areas where irrigation
water returned to the river, in seepage and leakage pools located
downstream of irrigation diversion dams, and, prior to construction of
Cochiti Dam, in the canyon reach of the Rio Grande upstream of Cochiti.
Prior to the construction of irrigation and flood control dams in the
southwest, it was not unusual for portions of major rivers to become
dry during periods of drought. During these drought periods, native
fishes would retreat to canyon reaches where permanent water existed.
After the drought ended, they would re-inhabit the reaches of river
that had formerly been dry. There was a constant expansion and
contraction of fish populations. Construction of mainstream dams
prevented this movement and may have contributed to the extitirpation
of downstream populations of native fishes.
The reasons for the extirpation of the species from continual flow
reaches of the river are not known but probably relate to factors other
than flow. Changes in species composition, flow regimes, and water
quality could all have been causative factors in the decline of the Rio
Grande silvery minnow from these areas. Even in those areas where the
species presently persists, its abundance has been substantially
reduced (Platania 1993).
Issue 23: Listing is not necessary because of existing protection
that is afforded the species by the requirements of the Coordination
Act, National Environmental Policy Act, and other habitat protection
regulations, such as section 404 of the Clean Water Act. Any activity
that could affect the habitat of the species would have to undergo
these reviews, including the Middle Rio Grande Conservancy District's
work on its structures. Such work could not be done with impunity.
Protection is also provided to the species because of its listing as
endangered by the State of New Mexico.
Response: To date, the species has declined even with these
regulations in place. These regulations do not ensure that habitat for
the Rio Grande silvery minnow will be protected. Listing of the species
by the State of New Mexico only regulates collecting of the species. It
does not provide protection for its habitat or for its recovery. The
Service believes the protective mechanisms of the Act are necessary to
prevent the species' extinction.
Summary of Factors Affecting the Species
After a thorough review and consideration of all information
available, the Service has determined that the Rio Grande silvery
minnow should be classified as an endangered species. Procedures found
at section 4(a)(1) of the Act (16 U.S.C. 1531 et seq.), and regulations
(50 CFR Part 424) promulgated to implement the listing provisions of
the Act were followed. A species may be determined to be an endangered
or threatened species due to one or more of the five factors described
in section 4(a)(1). These factors and their application to the Rio
Grande silvery minnow (Hybognathus amarus) are as follows:
A. The Present or Threatened Destruction, Modification, or Curtailment
of Its Habitat or Range
The only existing population of H. amarus continues to be
threatened by annual dewatering of a large percentage of its habitat.
This dewatering is primarily the result of diversion of river flow for
agriculture within the Middle Rio Grande Valley of New Mexico. During a
year when an average or above-average amount of water is available, the
impacts of the diversions are not severe. During a below-average water
year, the river channel may be dry from Isleta Diversion Dam downstream
about 179 km (111 mi) to the headwaters of Elephant Butte Reservoir for
two months or more. When two below-average flow years occur
consecutively, a short-lived species such as H. amarus can be severely
affected, if not completely eliminated from the dry reaches of river.
During the 94 years for which flow records have been maintained for the
middle Rio Grande, it has not been unusual for the 245 km (153 mi)
reach of the Rio Grande from the Angostura Diversion Dam downstream to
Elephant Butte Reservoir to experience periods of no flow. Even before
construction of mainstream dams, the middle Rio Grande frequently
experienced periods of no flow. During such periods, it is suspected H.
amarus survived in areas where irrigation return flows re-entered the
river, in the pools formed by water leaking through the gates of the
diversion dams, in the irrigation ditches and drains, and in the
reaches of stream above the diversions from which their offspring could
repopulate downstream reaches when conditions permitted. It is not
known why these same factors do not provide sufficient habitat to
support H. amarus under current conditions. Other factors, such as an
increase in non-native and exotic fish species, or an increase in
contamination may be exacerbating the stress placed upon the species
during low-flow periods.
Mainstream dams permit the artificial regulation of flow, prevent
flooding, trap nutrients, alter sediment transport, prolong flows, and
create reservoirs that favor non-native fish species. These changes may
affect the Rio Grande silvery minnow by reducing its food supply,
altering its preferred habitat, preventing dispersal, and providing a
continual supply of non-native fishes that may compete with or prey
upon the species. Altering flow regimes may also improve conditions for
other native fish species that occupy the same habitat as the Rio
Grande silvery minnow and may thereby cause their populations to expand
at the expense of the Rio Grande silvery minnow.
Since completion of Elephant Butte Dam in 1916, four additional
mainstream dams have been constructed on the middle Rio Grande, and two
dams have been constructed on one of its major tributaries, the Rio
Chama (Shupe and Williams 1988). Construction and operation of these
dams, which are either irrigation diversion dams such as Angostura,
Isleta, and San Acacia; or flood control and water storage dams such as
Elephant Butte, Cochiti, Abiquiu, and El Vado, have modified the
natural flow of the river. The dams make it possible during a low-flow
year to completely divert all of the flow from the river channel into
irrigation ditches. The species does not persist in the irrigation
ditches or the low-flow conveyance channel. Platania (1993) collected
fish samples from 11 locations along the low-flow conveyance channel
between 1987-1989 and failed to locate any Rio Grande silvery minnows.
The dams also store spring runoff and summer inflow, which would
normally cause flooding, and release this water back into the river
channel over a prolonged period of time. This release is often made
during the winter months when low flows would normally occur.
Artificially-controlled flows depart significantly from natural
conditions. Reduced flows may limit the amount of preferred habitat
available to the species and may limit dispersal of the species.
Although the mechanisms of how the decline of the species occurred are
not fully understood, manipulation of flow may be one of the primary
reasons H. amarus has been extirpated from portions of its historic
range.
Channelization of the middle Rio Grande has resulted primarily from
the placement of Kellner jetty fields, or jacks, along the river. They
are designed to protect the levees by retarding flood flows, trapping
sediment, and promoting the establishment of vegetation. Since 1951,
the Bureau of Reclamation and Corps have installed in excess of 100,000
individual jetties occupying more than 2,000 ha (5,000 ac) (Bullard and
Wells 1992).
From Elephant Butte Dam downstream about 325 km (200 mi) to its
confluence with the Rio Conchos, the Rio Grande is fully controlled by
reservoir releases and irrigation return flows. Meanders, oxbows and
other components of historic aquatic habitat have been eliminated in
order to pass water as efficiently as possible for agricultural
irrigation and downstream deliveries. These changes affected the Rio
Grande silvery minnow by altering its habitat to the extent that its
survival was not possible. The sandy substrate, which it prefers, has
been replaced by gravel and cobble, and no backwater areas exist where
the young can develop. Winter flows released from Caballo Dam often
equal .06 cubic meters per second (2 cubic feet per second), which is
not enough flow to maintain habitat for fishes.
In 1958, in an effort to meet Rio Grande Compact water delivery
requirements, the Bureau of Reclamation initiated operation of a 97 km
(60 mi) long conveyance channel from San Acacia to Elephant Butte
Reservoir. The purpose of the conveyance channel is to divert all flow
less than 63 cubic meters per second (2000 cubic feet per second) in
order to prevent loss of the Rio Grande flow to seepage and evaporation
from the aggraded riverbed. Prior to 1985, the conveyance channel had
been operated to its full capacity for about 28 years. Since 1985, it
has not been operated at full capacity. If, however, the channel were
to be operated at full capacity, the natural stream bed downstream of
San Acacia would be dry more frequently and for longer periods of time.
Both the Corps and the Bureau of Reclamation are drafting plans to
rehabilitate and protect the conveyance channel in order to bring it
into full operation. Should the conveyance channel be placed in full
operation, the portion of the Rio Grande silvery minnow's habitat
downstream of San Acacia dam would be desiccated when river flows at
the dam became less than 63 cubic meters per second (2000 cubic feet
per second), resulting in death or displacement of individuals.
Water diversions also occur above the Middle Rio Grande Valley in
both Colorado and New Mexico. These diversions, which provide
irrigation for about 248,000 ha (620,000 ac) in Colorado and about
24,400 ha (61,000 ac) in New Mexico, have a significant effect on flows
(Cruz et al. 1993). In addition to these upstream diversions, about
94,000 acre-feet of water are diverted annually from the San Juan River
basin and transported via a tunnel into the Rio Grande basin. This
diversion may benefit the species since it is used to supplement flows
during periods of low flow.
Growth of agriculture and cities along the Rio Grande during the
last century may have adversely affected the quality of the river's
water. During low-flow periods, a large percentage of the river's flow
consists of municipal and agricultural discharge and less water is
available to dilute pollutants. This degradation of water quality may
affect H. amarus survival. Poor water quality in the Rio Grande near
Albuquerque, especially during low flows, may be a problem, as low
numbers of H. amarus and an overall reduced fish community are found
there (Bestgen and Platania 1991).
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
It is not presently known if the species is being overutilized for
commercial, recreational, scientific, or educational purposes. New
Mexico Department of Game and Fish controls scientific taking of the
species through a permit process. Licensed commercial bait dealers may
sell bait minnows only within the drainage where they have been
collected. They are also restricted from selling any State-listed fish
species. However, it has been demonstrated on the Pecos River, New
Mexico, that often the dealers and retailers cannot identify listed
fish species. Utilization of the species for recreational purposes
could occur should an individual unknowingly collect the species while
gathering bait minnows for personal use.
C. Disease or Predation
When fish are forced into confined habitats due to low flow, they
are more susceptible to both disease and predation. Predation takes
place when non-native species, including northern pike (Esox lucius),
walleye (Stizostedion vitreum), white crappie (Pomoxis annularis),
white bass (Morone chrysops), black and brown bullheads (Ameiurus
melas, A. nebulosus), smallmouth bass (Micropterus dolomieui), and
largemouth bass (Micropterus salmoides) are confined, during low flow
or no flow, in limited habitat with H. amarus and other native species.
These species have been introduced primarily by State and Federal fish
and wildlife management agencies in efforts to develop sport fisheries
in reservoirs created by the mainstream dams. The species have not
remained confined to the reservoirs and have become established in the
river both upstream from the impoundments and downstream of the dams
where it is suspected they may compete with H. amarus for space and
food in addition to preying upon them. Native predatory fish species,
including the Rio Grande chub (Gila pandora) and bluegill (Lepomis
macrochirus), may also prey upon subadult H. amarus under these
circumstances. Avian and mammalian predation probably increases when H.
amarus become confined in small clear-water pools.
Confining fish to pools causes stress that can often result in
outbreaks of parasitic disease. Most notable is parasitism by the
protozoan Ichthyophthirius multifilis, which can be promoted by stress.
External parasites, such as the copepod Lernaea, are more common among
fish in confined conditions. No studies have been conducted on the
impact of disease and parasites upon H. amarus; therefore, the
significance of these threats for existing populations of the species
is not known. However, stress-induced outbreaks may be exacerbated when
high levels of pollutants or other stresses are present.
D. The Inadequacy of Existing Regulatory Mechanisms
The State of New Mexico lists H. amarus as an endangered species,
Group 2 (New Mexico Department of Game and Fish 1993), which includes
those species ``. . . whose prospects of survival or recruitment within
the State are likely to be in jeopardy within the foreseeable future.''
This listing provides the protection of the New Mexico Wildlife
Conservation Act (Section 17-2-37 through 17-2-46 NMSA 1978) and
prohibits taking of such species except under the issuance of a
scientific collecting permit. The protection afforded to the species by
the State does not provide protection to the habitat upon which the
species depends.
New Mexico water law does not include provisions for acquisition of
instream water rights for protection of fish and wildlife and their
habitats. This has been a major factor affecting the survival of
species dependent upon the presence of instream flow. Agencies
responsible for administering water rights have been unable to
administer the rights in a manner that protects, maintains, and
recovers the Rio Grande silvery minnow. Under the existing water rights
administration, two native fish species in the Rio Grande have become
extinct, and two others have been extirpated.
State Game and Fish regulations in New Mexico allow the use of live
minnows, including those brought into the State from other drainages,
for sport fishing. This practice has encouraged the spread of these
species, one of which, the plains minnow, has completely replaced and/
or hybridized with H. amarus in the Pecos River.
E. Other Natural or Manmade Factors Affecting Its Continued Existence
In 1979, Cowley discovered the introduction of plains minnow (H.
placitus) into the Pecos River drainage, New Mexico, from collections
made as early as 1968, and also recognized the disappearance of native
H. amarus. The last known collections of H. amarus from the Pecos River
took place in 1968 near Roswell, New Mexico. These same collections
verified the first specimens of H. placitus from the river. It is
suspected, because of the widespread use of H. placitus as a commercial
bait species, that its introduction into the Pecos River was the result
of release of bait fish by anglers.
The Service has carefully assessed the best scientific and
commercial information available regarding the past, present, and
future threats faced by this species in determining to make this rule
final. Based on this evaluation, the preferred action is to list the
Rio Grande silvery minnow (Hybognathus amarus) as endangered throughout
its historic range. A decision to take no action would constitute
failure to properly classify this species pursuant to the Endangered
Species Act and would exclude it from protection of the Act. The
Service believes threatened status is not the proper classification for
the species because of the extremely limited habitat the species
presently occupies and the threats it faces. Endangered status is
appropriate because of the significantly reduced range and declining
abundance of the species, and because of the remaining threats to this
fish and its habitat. Without Federal protection, the Rio Grande
silvery minnow can be expected to become extinct in the foreseeable
future.
Critical Habitat
Section 4(a)(3) of the Act requires, to the maximum extent prudent
and determinable, that the Secretary designate critical habitat at the
time a species is determined to be endangered or threatened. Section
4(b)(6)(C) states that a concurrent critical habitat designation is not
required, and that the final decision on designation may be postponed
for 1 year from the date of publication of the final rule to list the
species. Section 4(b)(6)(C)(ii) allows the Service to delay critical
habitat designation if it is not then determinable. The Service's
regulations (50 CFR 424.12(a)(2)) state that critical habitat is not
determinable if information sufficient to perform required analyses of
the impacts of the designation is lacking or if the biological needs of
the species are not sufficiently well known to permit identification of
an area as critical habitat. Section 4(b)(2) of the Act requires the
Service to consider economic and other impacts of designating a
particular area as critical habitat. The Service is in the process of
evaluating the information obtained during the comment period on the
economic impacts of designating critical habitat, and has started the
process of having an economic analysis prepared on the proposed
critical habitat designation. The complexities and extent of the
activities that must be assessed preclude completion of the economic
analysis within the 1-year deadline for listing the species. The
completed draft economic analysis will be made available for public
review and comment. The final decision on designation of critical
habitat for the Rio Grande silvery minnow must be made by March 1,
1995, pursuant to section 4(b)(6)(C)(ii) of the Act.
Available Conservation Measures
Conservation measures provided to species listed as endangered or
threatened under the Endangered Species Act include recognition,
recovery actions, requirements for Federal protection, and prohibitions
against certain practices. Recognition through listing encourages and
results in conservation actions by Federal, State, and private
agencies, groups, and individuals. The Endangered Species Act provides
for possible land acquisition and cooperation with the States and
authorizes recovery plans for all listed species. The protection
required of Federal agencies and the prohibitions against taking and
harm are discussed, in part, below.
Section 7(a) of the Act, as amended, requires Federal agencies to
evaluate their actions with respect to any species that is proposed or
listed as endangered or threatened and with respect to its critical
habitat if any is proposed or designated. Regulations implementing this
interagency cooperation provision of the Act are codified at 50 CFR
part 402. Section 7(a)(2) requires Federal agencies to ensure that
activities they authorize, fund, or carry out are not likely to
jeopardize the continued existence of a listed species or to destroy or
adversely modify its critical habitat. If a Federal action may affect a
listed species or its critical habitat, the responsible Federal agency
must enter into formal consultation with the Service.
Federal actions that are expected to occur that may affect the
survival of H. amarus include the operation and maintenance of dams and
other structures that regulate the flow of water in the Rio Grande.
Federal agencies that serve as water managers and decision-makers who
determine timing and amount of flow in the river include the
International Boundary and Water Commission, which ensures delivery of
water to Mexico under international treaties; the Bureau of
Reclamation, which has played an important role in water development in
the middle Rio Grande and has been actively involved in the major water
supply networks of the basin; and the Corps, which is responsible for
controlling any dredging or filling within navigable waterways and
associated wetlands under section 404 of the Clean Water Act. The Corps
also has constructed and operates Abiquiu, Cochiti, Galisteo, and Jemez
dams to control flood waters and sediment in the Rio Grande. The
Environmental Protection Agency oversees water quality issues that may
affect the river. In addition, actions on the northern pueblos that are
funded, authorized, or carried out by the Bureau of Indian Affairs may
affect the Rio Grande silvery minnow.
The Act and implementing regulations found at 50 CFR 17.21 set
forth a series of general prohibitions and exceptions that apply to all
endangered wildlife. These prohibitions, in part, make it illegal for
any person subject to the jurisdiction of the United States to take
(includes harass, harm, pursue, hunt, shoot, wound, kill, trap, or
collect, or to attempt any of these), import or export, ship in
interstate commerce in the course of a commercial activity, or sell or
offer for sale in interstate or foreign commerce any listed wildlife
species. It also is illegal to possess, sell, deliver, carry,
transport, or ship any such wildlife that has been taken illegally.
Certain exceptions apply to agents of the Service and State
conservation agencies.
Permits may be issued to carry out otherwise prohibited activities
involving endangered wildlife species under certain circumstances.
Regulations governing permits are at 50 CFR 17.22 and 17.23. Such
permits are available for scientific purposes, to enhance the
propagation or survival of the species, and/or for incidental take in
connection with otherwise lawful activities. In some instances, permits
may be issued for a specified time to relieve undue economic hardship
that would be suffered if such relief were not available. This species
is not in trade, and such permit requests are not expected.
National Environmental Policy Act
The Fish and Wildlife Service has determined that an Environmental
Assessment, as defined under the authority of the National
Environmental Policy Act of 1969, need not be prepared in connection
with regulations adopted pursuant to Section 4(a) of the Endangered
Species Act of 1973, as amended. A notice outlining the Service's
reasons for this determination was published in the Federal Register on
October 25, 1983 (48 FR 49244).
References Cited
A complete list of all references cited herein, as well as
others, is available upon request from the State Supervisor, New
Mexico Ecological Services State Office (see ADDRESSES section).
Author: The primary author of this final rule is Gerald L.
Burton (see ADDRESSES section).
List of Subjects in 50 CFR Part 17
Endangered and threatened species, Exports, Imports, Reporting and
recordkeeping requirements, and Transportation.
Regulation Promulgation
PART 17--[AMENDED]
Accordingly, part 17, subchapter B of chapter I, title 50 of the
Code of Federal Regulations, is amended as set forth below:
1. The authority citation for part 17 continues to read as follows:
Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C.
4201-4245; Public Law 99-625, 100 Stat. 3500; unless otherwise
noted.
2. Amend Sec. 17.11(h) by adding the following, in alphabetical
order under ``FISHES'', to the List of Endangered and Threatened
Wildlife:
Sec. 17.11 Endangered and threatened wildlife.
* * * * *
(h) * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
Common name Vertebrate population
Species -------------------------- Historic range where endangered or Status When listed Critical Special
Scientific name threatened habitat rules
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * * * *
Fishes
* * * * * * *
Minnow, Rio Grande Hybognathus amarus...... U.S.A. (NM, TX), Mexico. Entire.................. E 541 NA NA
silvery.
* * * * * * *
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Dated: June 30, 1994.
Mollie H. Beattie
Director, Fish and Wildlife Service.
[FR Doc. 94-17576 Filed 7-19-94; 8:45 am]
BILLING CODE 4310-55-P
