State of California
The Resources Agency
DEPARTMENT OF FISH AND GAME
LIFE HISTORY, STATUS, AND MANAGEMENT OF THE MODOC SUCKER,
CATOSTOMUS MICROPS (RUTTER) IN CALIFORNIA,
WITH A RECOMMENDATION FOR ENDANGERED CLASSIFICATION
by
Terry J. Mills
Inland Fisheries, Sacramento
Inland Fisheries Endangered Species Program
Special Publication 80-6
November 1980
LDA
Endangered Species Program Special Publications are
nonrefereed reports generally of two types: they
may contain -information of sufficient importance to
be preserved for future reference but which may not
be currently appropriate for journal publications;
or they may be reports which contain information of
current significance that warrants early dissemination
to biologists, managers, and administrators but which
may later be submitted for formal scientific publication. These reports can be cited in publications, but
their manuscript status should be recognized.
Subject matter reflects the broad array of research
and management conducted in California on nongame
species of reptiles, amphibians, and nonmarine
fishes and invertebrates, with primary emphasis on
endangered, threatened, and rare taxa.
Inquiries concerning any particular report should be
directed to the Inland Fisheries Branch, 1416 Ninth
Street, Sacramento, California 95814.
LIFE HISTORY, STATUS, AND MANAGEMENT OF THE MODOC SUCKER,
CATOSTOMUS MICROPS (RUTTER) IN CALIFORNIA,
1/
WITH A RECOMMENDATION FOR ENDANGERED CLASSIFICATION—
by
2/
Terry J. Mills
ABSTRACT
The Modoc sucker, Catostomus miorops, designated as
rare by the California Fish and Game Commission, is in
jeopardy of extinction through loss of habitat to
agricultural activities and hybridization with the
Sacramento sucker, C. occidentalin. Only an estimated
1,300 fish, found in Hulbert, Johnson, and Washington
creeks, Modoc County, remain. This species should be
classified as endangered, and fish from the three
remaining populations should be transplanted to
additional waters, Including streams where hybridized
populations can be removed, so that the survival and
genetic integrity or the Modoc sucker will be ensured.
'
Inland Fisheries Endangered Species Program Special
Publication 80-6. This report was prepared as part
of an Endangered Species Act grant-in-aid project,
"California E-F-4, Endangered, Threatened, and Rare
Fish".
/
Fishery Biologist, Endangered Species Program, Inland
Fisheries Branch, 1701 Nimbus Road, Rancho Cordova,
Califorula 95670.
Current address: Wild and Scenic Rivers Program,
Planning Branch, 1416 Ninth Street, Sacramento,
California 95814.
-3INTRODUCTION
The Modoc sucker, recognized as a distinct species In 1907 (Rutter 1908),
is one of four species of Catostomidae found only within California.
Since its discovery, it has become imperiled by habitat degradation in
the form of stream channelization, water diversion, and overgrazing of
riparian vegetation, with concurrent trampling of streambanks by livestock.
Secondary to these has been the resultant erosion and stream incision of
overgrazed meadows, and loss of isolating barriers. A tertiary, but
major effect resulting from the loss of barriers is hybridization with
Sacramento suckers. Adding to the effects from agriculture is the past
introduction of exotic fishes such as brown trout (SALMO TRUTTA), which
prey on Modoc suckers (Moyle and Marciochi 1975).
Miller (1961) and Martin (1966) expressed concern about the continued
survival of the only known population of this species in Rush Creek,
Modoc County. In 1973, Moyle (1974) investigated the status and distribution of the Modoc sucker and reported the discovery of populations from
four additional streams. He maintained that the species deserved classification as a rare and fully protected species.
Based on these studies, the California Fish and Came Commission listed the
Modoc sucker as a rare species under authority of the California Endangered
Species Act of 1970. Cited as cause for classification was a general
decline of populations within the native range due to hybridization and
habitat. loss (Leach, Nicola, and Brode 1976).
Recently, hybridization between Modoc and Sacramento suckers was examined
and found to be extensive. The opportunity for hybridization is related
to habitat degradation and combined, these two factors pose a serious
threat to the continued survival of the species.
Current data indicate that the status of the Modoc sucker is more uncertain
than previously thought. This report constitutes a review of its status
through a literature summary of its taxonomy, distribution, and life
history. Also included is information on hybridization of the species.
Habitat descriptions and a discussion of habitat modifications are
included since habitat protection and restoration are of major importance
to the survival of this species.
Overall, this report provides a current source of data on the Modoc sucker
which can assist resource management agencies in planning and expediting
recovery efforts. It also provides documentation that the Modoc sucker
is, indeed, endangered.
NOMENCLATURE
Catostomuil MICROPS
Rutter (1908)
Unlike many of the native California fishes, the scientific nomenclature
of the Modoc sucker has never been subject to change or question. CATOSTOMUS
refers to mouth location and means inferior (position) mouth (Moyle 1976a).
-4Micrope means small eye. Modoc appears to be a shortening of Moatakni
makZaks, the name of a local Indian tribe which means the "People of the
Moatak" or "People of Tule Lake" (Pease 1965).
DESCRIPTION
Rutter's species description of the Modoc sucker was based on three paratypes collected from Rush Creek, Modoc County, California, on September 1,
1898 (Rutter 1908). Compared to the Sacramento sucker, the Modoc sucker
is much smaller, less robust in appearance, and has fewer dorsal rays
and finer scales. It is very similar to the Tahoe sucker, C. tahocrw7:7.
Meristic counts and morphometric data of the three paratypes (Table 1)
are taken directly from Rutter's (1908) report.
Martin (1972) collected 10 topotypes of the Modoc sucker and provided
additional data on meristic variation. His account of variation is
expressed as the count followed by the number of specimens with that
count in parentheses. Paired fin ray counts are of the left and right
fins, respectively.
"Dorsal fin rays 10(7), 11(3); anal fin rays 7(10); pectoral
fin rays 15-15 (3), 16-16(5), 17-17(2); pelvic fin rays 9-9(7),
10-10 (3); caudal fin rays 18(7), 19(3). Scales in lateral
line 80(1), 81(3), 82(2), 84(1), 85(1), 87(1), 89(1); scales
above lateral line 15(1), 16(6), 17(1); scales below lateral
line 9(1), 10(6), 11(2), 12(1); scales around caudal peduncle
20(1), 22(2), 23(2), 25(3), 26(2); predorsal scales 45(1),
46(2), 49(1), 50(3), 51(2), 53(1). Gill rakers 18(1), 19(1),
22(3), 23(2), 24(1), 25(1), 26(1)."
Martin (1972) also provided a description of Modoc sucker life colors.
"The back varies from greenish-brown through bluish to deep
grey and olive; the sides are lighter with light yellowish
below; caudal, pelvic, and pectoral fins are light yellowish
orange. There are three characteristic dark spots along
the sides in the region of the lateral line. The belly region
is cream-colored to white."
It is not apparent why Rutter chose "microps" (small eye) for the specific
name since the relative eye diameter of the Modoc sucker is essentially
the same as that of its congeners.
The characters that readily distinguish Modoc suckers from other catostomids
are the number of dorsal rays (n = 1(1 , commonly; n = 11, occasionally; and
n = 12, rarely), the number of scales in the lateral line series (n = 79
to 89), and small body size [< 160 mm (< 6.30 in.)].
GEOLOGIC AND ZOOGEOGRAPHIC HISTORY
The Pit River, located in northeastern California, is tributary to the
Sacramento River. Its fish fauna not only reflects its connection to the
-5-
TABLE 1.
/
and Merlstle Measurements of Three Calc:;1,1m1:7
microrl (Rutter 1908).
Morphometric
Standard length (mm)
134
103
89
Length head
.22
.23
.23
Depth
.205
.22
.22
Diameter orbit
.035
.04
.04
Interorbital space
.09
.09
.09
Length snout
.105
.10
.10
Depth caudal peduncle
.085
.09
.09
Length caudal peduncte
.17
.16
.16
Insertion dorsal
.40
.51
.51
Insertion ventral
.56
.57
.58
Insertion anal
.78
.79
.78
Length dorsal
.15
.15
.15
Height dorsal
.16
.16
.165
Dorsal rays
11
10
11
7
7
7
Scales in lateral line
82
81
81
Scales above lateral line
15
16
16
Scales below lateral line
11
11
11
Scales before dorsal
40
40
41
Anal rays
1/
- Expressed as proportion of body length.
-6Sacramento system hut also contains fishes derived from the Klamath River
drainage to the northwest (Moyle 1976a). This diverse complement of fishes
is a result of past geologic events. Evidently the upper Pit River was
0 I 110 K I ;thin 1 Ii River dra I 11:1g0 dur I ng 1 110 I at 0 1' 1 1()00110
1 ()Imo I - 1 y 001111001 0(1
and llowed lu a m)rihweslerly direction. However, early In the Pleistocene,
an extensive lava flow completely blocked the upper Pit River's course to
the Klamath Basin and created a deep lake (Lake Alturas) (Pease 1965). This
I ake later became par( of the Sacramento River Basin by overflow and drainage
through tile Ad In Mountains which provided the connection to the lower Pit.
River in Big Valley located to the south (Pease 1965).
Apparently, the Modoc sucker was already present when the Sacramento sucker,
a relatively recent addition, gained access to the upper Pit River. Even
though tishes of two drainages came to inhabit the Pit River, Moyle (1976a)
noted that the Modoc sucker has no close affinities to the fishes of the
Klamath or of the Sacramento drainages. The phylogeny of the Modoc sucker
has not been adequately investigated.
DISTRIBUTION AND ABUNDANCE
Except for the type locality, Rush Creek, little was known of Modoc sucker
distribution. Fisk (1972) reported the Modoc sucker from upper Ash Creek,
Lassen County and from Dorris Reservoir, near Alturas, Modoc County. The
pie:wore of Hu. Modoc sucker In Dorris Reservoir has never been confirmed
and It Is nnlikely Ihey were ever present (here. Moyle (19/4) l ound !hem
I nhabiting fonr additional streams: Hulbert, Johnson, Turner, and
Washington creeks, Modoc County (Figure 1). He estimated the populalion
of Modoc suckers in Rush and Johnson creeks at less than 5,000 fish
(Moyle 19;4). His estimate, in my opinion, was generous and likely included
hybrid suckers.
In a recent survey, Ford (1977) found Modoc suckers in two more streams;
Dutch Flat Creek, Modoc County and Willow Creek, Lassen County. Ford
placed the entire population of all eight creeks during the drought of
1977 at about 2,600 fish (Table 2), but noted that only Hulbert, Johnson,
and Washington creeks contained only pure Modoc suckers. The estimated
population size of pure Modoc suckers for these three creeks was only
1,250 fish.
Additional distribution surveys to locate populations of Modoc suckers
have been completed (Cooper, Koch, and Lider 1979). In all, fifteen
additional streams tributary to the Pit River have been surveyed with
none found to contain Modoc suckers (Appendix 1).
HABITAT
In general, the terrain or Modoc County is dominated by a sir ies ol lava
Flows with much or the land characterized as a high volcanic plateau.
Unlike other plateaus, the Modoc plateau is not "flat-topped" but is
rather a wide highland area resulting from large-scale volcanic activity
(Oakeshott 1971). The plateau is bounded on the west by the Cascade Range
and on the eat by Warner Range.
NODOC
LASSEN
sites
FIGURE 1. Pit River and tributaries in the vicinity of Adin, Modoc County, California.
-8TABLE 2-
Slreams Containing Either Modor or Modoc nnd Hybrld Sucker
and Their Estimated Populations (Ford 1977).
Stream
Length (km)
Estimated population
Dutch Flat Creek
0.1
40
Ash Creek
6.0
200
Rush Creek
7.2
1,000
Jounson Creek
2.0
700
Turner Creek
3.2
100
Hulbert Creek
1.2
500
Wnshingion Creek
0.8
50
Willow Creek
0.05
15
TOTAL
2,605
_9._
The average elevation of the Modoc plateau is 1,372 m (4,501 ft) (Oakeshott
1971), with Modoc suckers generally inhabiting streams between elevations
of 1,286 to 1,567 m (4,210 to 5,141 ft) (Moyle and Marciochi 1975).
:to r all 1 01,111 I v I0
1.1 01 .0leam. 4 1111101 011r M(1411)1 • 'sill' 1(4
River (Figure I). Vegetation in the area of these creeks includes valley
and meadow grasslands found on some southwestern facing slopes with most
of the remaining open areas covered with sagebrush (Arlcmisla tridcHlalo)
and western juniper (duniperus ocoidentalis). The forested areas are
mostly ponderosa pine (Pinus ponderosa), Jeffrey pine (Pinus jeffreyi)
California black oak ((?ueroun kaloggii), California incense cedar
(Libooedrus do(urrons), and white fir (Abios eonoolor).
The eight streams containing Modoc or hybrid suckers typically have
moderate stream gradients with moderate to lower flows through meadow
areas. Streamside vegetation and shade canopy is provided by junipers,
aspens. , conifers, cottonwoods, willows, and chokecherries.
Rush, Turner, and Ash creeks flow continuously throughout the year, but
Dutch Flat, Hulbert, Johnson, Washington, and upper Willow creeks flow
intermittently during the summer and fall with some sections dry except
for isolated pools. Physical descriptions of the eight streams, extracted
from stream surveys conducted by personnel of Modoc National Forest,
arc contained in Append ices 2 through 10.
HABITAT MODIFICATIONS
Modification of pristine habitat by agricultural activities has been cited
as the foremost cause leading to the rare status of the Modoc sucker
(Fisk 1972; Leach, Nicola, and Brode 1976). Livestock have been the
primary source of habitat damage through overgrazing and streambank
trampling, while channelization and agricultural water diversion are
noted as secondary causes contributing to this loss.
Livestock
Pease (1965) found that many upland range meadows In Modoc County had
been degraded by 1940. He reported that wet meadow surfaces had been
destroyed through trampling and compaction by livestock until some areas
had become little more than mud flats. Trampled, compacted meadows have
little ability to absorb water or to reduce runoff. As a result, the
increased stream flows of many Modoc County creeks eroded meadow floors
which in turn lowered water tables and eliminated most wet meadow areas.
Today, these former meadow areas have deteriorated into dry grasslands
covered with sagebrush through which deeply incised streams flow (Figure
2). A few extant meadow areas have survived and provide prime Modoc
sucker habitat. Pease (1965) reported that upland meadows comprised
only 2% of the total land area of Modoc County.
Irrigation Practices
Further loss of fish and habitat resulted from early irrigation practices.
Earthen or plank dams placed across streams caused overflow and flooding
FIGURE 2. Stream incision of lower Turner Creek, Modoc County.
-11of adjacent meadow lands (Pease 1965). Streams were likely dry for a
distance below these dams which would result in loss of fish. Ford
(1977) reported 26 diversions, ranging from 5 to 109 Ns (0.18 to 1.9
cis), from Ash, Rush, Johnson, Turner, and Hulbert creeks (Table 3).
The most damaging diversion presently occurs on Johnson Creek approximately
150 m (492 ft) upstream from Highway 299. At that location, Johnson
Creek is totally diverted to irrigate a pasture on private land (Higgins
Flat). While water is returned at the lower end of the pasture, the
dewatered area, about 20% of available habitat on Johnson Creek, is lost
(Ford 1977).
Channelization
Channelization (Figure 3) has not been as widespread as diversions in
the streams inhabited by Modoc suckers. However, two creeks, Rush and
Johnson, have been subjected to channelization (Table 4). Through
technical advice provided by the Soil Conservation Service, landowners
have used channelization to control streambank erosion and to confine
high winter flows (Moyle 1976b). In addition to eliminating habitat,
channelization reduces stream productivity. Moyle (1976b) found the
total fish biomass in the channelized sections of Rush Creek to be less
ihan one-third of the unchannetized areas.
LIFE HISTORY AND ECOLOGY
Habitat Preference
Modoc suckers are most abundant in areas of low summer flow, including
intermittent streams; in areas with large shallow pools and mud substrates; in creek areas with partial overhead shade provided by trees,
shrubs, and boulders; and in areas having clear water (Moyle and
Marciochi 1975). They were absent from swift-flowing stream sections
with high gradients as well as channelized sections. Channelization
eliminates Modoc sucker habitat by creating long, shallow riffles with
no shade or cover. Martin (1972) reported that juvenile Modoc suckers
[< 50 mm SL (< 1.97 in. SL)] were found near the bottom In the shallow
areas of large pools. Adults were found In deeper water near or resting
on the bottom.
Food Habits and Feeding Adaptations
Moyle and Marciochi (1975) examined stomach contents of 14 Modoc suckers
and found 47% (by volume) detritus, 19% diatoms, 18% chironomid larvae,
10% filamentous algae, 4% crustaceans, and 2% insect larvae. The suckers
apparently feed either along the slow-flowing stream edges or in pool
bottoms where detritus settles and chironomid larvae live. The diet of
the Modoc sucker is essentially the same as for other members of the
genus Catostanw (Carlander 1969).
Martin (1972) found the jaws of the Modoc sucker to be strongly adapted
as substrate scrapers, more so than for the Sacramento sucker. He also
noted that the musculature of the Modoc sucker oromandibular region was
heavier than that of the Sacramento sucker.
-12TABLE 3.
Water Diversion Data for Ash, Rush, Johnson, Turner, and
Hulbert Creeks, Modoc County (Ford 1977).
Stream
Number of
diversions
Total allotment
Area irrigated
Ash Creek
7
272 Sils (9.6 cfs)
296.2 ha (731.6 acres)
Rush Creek
11
148 k/s (52.5 cfs)
125.4 ha (309.7 acres)
Johnson Creek
5
28.3 k/s (1.0 cfs)
20.2 ha (50 acres)
Turner Creek
2
20.4 t/s (0.72 cfs)
20.2 ha (50 acres)
Hulbert Creek
1
24.4 t/s (0.86 cfs)
24.3 ha (60 acres)
FIGURE 3. Stream channelization, Rush Creek, Modoc County.
-14TABLE 4. Channelized Stream Sections of Johnson and Rush Creeks
(Ford 1977).
Stream
Location
Year
Length channelized
Johnson Creek
T. 40 N., R. 8 E.,
Sec. 23
1964
975 in (3,200 ft)
Rush Creek
T. 40 N., R. 8 E.,
Sec. 24, 25, 26
1966
335 in (1,100 ft)
Rush Creek
T. 40 N., R. 8 E.,
Sec. 35
1966
25 in (80 ft)
Rush Creek
T. 40 N., R. 8 E.,
Sec. 26
1967
225 in (735 ft)
Rush Creek
T. 40 N., R. 8 E.,
Sec. 35
1968
65 in (210 ft)
-15Fish Associations
Fishes commonly found in association with the Modoc sucker include;
speckled dace, Rhinichthys oscutus; rainbow trout, Seam gairdneri;
California roach, Hesperoleucus symmetricus; Pit sculpin, Cottus
pitonsis; Sacramento sucker; and brown trout. Other fishes found
occasionally with ihe Modoc sucker are the Pit-Klamath brook lamprey,
Lampetra lethophaga; Sacramento squawfish, Ptychocheilus grandis;
hardhead, Mylopharadon conocephalus; brown bullhead, Ictalurus nebulosus;
and green sunfish, Lepomis cyanellus (Moyle and Marciochi 1975).
Age and Growth
Modoc suckers rarely exceed 160 mm SL (6.30 in. SL). Moyle and Marciochi
(1975) reported that growth of the Modoc sucker is comparable to other
California catostomids. The oldest fish they examined was 5 years old
and 280 mm (11.0 in.) in length (SL). Moyle and Marciochi (1975) found
the age-length relationship to be length cm = 3.99 age (years) + 2.90
[length (in.) = 1.57 age (years) + 1.14]. The small size of adult
Modoc suckers is thought to be a result of species preference for
small, cool stream habitats (Moyle and Marciochi 1975).
Reproduction
Moyle and Marciochi (1975) collected ripe male and female Modoc suckers
from mid-April to late May. Boccone and Mills (1979) determined that
the spawning season began in mid-April and ended in early June with the
actual spawning period in different streams lasting only 3 to 4 weeks.
Like other catostomids, Modoc suckers exhibit upstream migrations during
the spawning season and use intermittent tributaries for spawning.
Spawning takes place in the lower end of pools over fine to medium
gravels from midmorning to late afternoon at water temperatures of
13.3 to 16.1°C (55.9 to 61.0°F) (Boccone and Mills 1979). The pools
contained abundant vegetation comprised of emergent grasses, sedges,
rushes, and filamentous algae. Stream flow in the pools ranged from
42.7 to 56.8 24s (1.5 to 2.0 cfs) (Boccone and Mills 1979).
Spawning typically occurred in 15 cm (6 in.) of water. After choosing
a suitable site, a female and usually three males, one on either side
and one slightly behind, completed the spawning act. Spawning occurred
during a 6- to 8-second interval during which eggs and milt were simultaneously released (Boccone and Mills 1979).
Sexual Dimorphism
Boccone and Mills (1979) observed several secondary sexual characteristics
of Modoc suckers. They found that nuptial males were generally smaller
than nuptial females FR = 95 mm SL and R = 111 mm SL, respectively (R =
3.74 in. SL and 5 = 4.37 in. SL, respectively)]. All male Modoc suckers
exhibited spawning coloration comprised of a bright red-orange lateral
band on the side of the body from the opercular flap extending posterior
to the pelvic fins. One female was observed with a reddish-orange band
-16but it was much duller than the stripe found on males. Males develop
body tubercles from the snout to the area between the caudal and dorsal
fins, on the pectoral, pelvic, and anal fins, and a few tubercles on the
caudal fin. The dorsal fin rarely has tubercles. Females may also
develop a few tubercles but never to the extent that males do. One
female [104 mm (4.09 in.)] was found to have tubercles on the 2nd, 3rd,
and 4th elements of the anal fin, and on the 3rd, 4th, and 5th elements
of the left pelvic fin. No other females exhibited tubercles (Boccone
and Mills 1979).
Hybridization
Numerous authors (Leach et al. 1974; Moyle and Marciochi 1975; Ford 1977;
Boccone and Mills 1979; and Cooper et al. 1979) have stated that the Modoc
sucker is threatened by hybridization with the Sacramento sucker. it is
assumed that prior to the habitat modifications that have taken place
Modoc suckers existed only as isolated populations within each of the
current habitats. Meadow areas and instream barriers present then may
have excluded Sacramento suckers. The action of meadow incision by
streams may have eroded these barriers thus allowing Sacramento suckers
to invade the streams with the resultant hybridization. Moyle and
Marciochi (1975) give support to this assumption speculating that the
Sacramento sucker recently gained access to Rush Creek by means of manmade modifications in the lower stream section. Pasture land in this
section is actually a reclaimed marsh that possibly served as a barrier,
but a series of ditches were constructed during the reclamation effort
which could have provided Sacramento suckers a direct passage into Rush
Creek.
In examining meristic characters of populations thought to be Modoc
suckers from Dutch Flat, lower Johnson, Turner, lower Hulbert, lower
Washington, and Willow creeks, Ford (1977) reported wide variations.
He found some suckers exhibiting meristic characters common to both
Modoc and Sacramento suckers and some specimens with characters between
the two. He interpreted the overlap and intermediacy of characters to
be indicative of hybridization. Cooper et al. (1979) reported Willow
Creek suckers were hybrids based on meristic characters that were intermediate between those of Modoc and Sacramento suckers.
Hubbs (1955) attributes hybridization between sympatric fish species to
several causes: (1) proximity of spawning areas, enabling the sex products
of related species to mix, (2) absence of a mate of the same species, a
result of one species being greatly outnumbered by another species, and
(3) overlapping spawning seasons. Hybridization between Modoc and
Sacramento suckers may be attributed to these causes, but the actual
process leading to hybridization has not been adequately investigated.
Since little datawere available on characters useful in identifying
hybrid suckers, I examined preserved specimens of Modoc, Sacramento, and
suspected hybrid suckers to determine the key distinguishing characters.
A total of 65 specimens was available: 26 Modoc suckers, 25 Sacramento
suckers, and 14 hybrids (Table 5). I recorded four meristic characters
for each specimen: lateral line scalcs, scales above and scales below
-17TABLE 5.
Specimens Examined to Determine Meristic Characters of Modoc x
Sacramento Hybrids Sucker. All Specimens were Collected in Modoc
County, California Unless Specified Otherwise. A Total of 65
Specimens were Examined.
Catof;tomus micropi
csusti. SSC 168-2 (5 specimens), Rush Creek, collected 9 April 1967;
SSC 162-1(2), Rush Creek, 26 December 1966; SSC 149-2(1), Rush Creek,
8 October 1966. DFG2/. DFG 0628(1), Turner Creek, 12 October 1977;
DFC 0473(1), Rush Creek, 9 May 1973; DFC 0554(1), Washington Creek,
1 August 1977; DFG 0472(1), Ash Creek, 23 June 1974. ucial/. (2),
Rush Creek, 14 April 1973; (5), upper Hulbert Creek, 25 July 1973;
(1), Hulbert Creek, 18 July 1973; (1), Ash Creek, 23 June 1973; (5),
Johnson Creek, (no date). (n = 26).
Catostomus occidentalis
DFC. DFG 0582(4), Turner Creek, 2 November 1977; DFG 0623(5), Turner
Creek, 12 October 1977. DFG 0612(6), Blacks Canyon Creek, 21 September
1978. DFG 0557(4), lower Hulbert Creek, 2 November 1977. UCD. (2),
Rush Creek, 14 April 1973; (2) Rush Creek, 9 May 1974; (2), Ash Creek,
22 May 1973. (n = 25).
micropiT x occidentalim hybrids
SSC 162-1(1), Rush Creek, 26 December 1966; DFG. DFG 0627(4),
Willow Creek, Lassen County, 16 July 1973; DFG 0557(2), lower Hulbert
Creek, 2 November 1977; DFG 0582(2), Turner Creek, 2 November 1977;
DFG 0625(1), Willow Creek, Lassen County, 27 October 1977; DFG 0626(3),
Dutch Flat Creek, 21 October 1977. UCD. (1), Rush Creek, 14 April
1973. (n = 14).
CSUS.
1/
- California State University, Sacramento, Museum of Natural History.
3I
Ca1ifornia Department of Fish and Game, Ichthyological Museum.
3/
University of California, Davis, Collection of Peter B. Moyle.
-18the lateral line, the number of dorsal rays; and two morphometric ratios,
head length/standard length and eye diameter/standard length.
Modoc and Sacramento suckers exhibited no overlap between the six characters
and are most readily distinguished by scales in lateral line and number of
dorsal rays (Table 6). The character means of the hybrid group were between
the mean values for the Modoc and Sacramento groups in all characters except
standardized eye diameter. The hybrid value for that character exceeded
the values for both the Sacramento and Modoc suckers (Table 6). Hybrid
suckers can be identified using two characters - lateral line scales and
number of dorsal rays. The ranges of the key meristic characters for
76.5), and
the hybrid sucker are: scales in lateral line: 68-90 (51
dorsal rays: 10-12 (Fc = 10.9).
ESSENTIAL HABITAT
Habitat that is essential to the continued existence of the Modoc sucker
is broadly defined as all eight creeks known to contain Modoc sucker or
its hybrid: Ash, Dutch Flat, Hulbert, Johnson, Rush, Turner, Washington,
and Willow creeks, and their tributaries.
These essential habitats provide, or through restoration can be expected
to provide, the following habitat requirements: (1) pool areas for
normal growth and movement, (2) spawning areas, (3) nursery areas,
(4) feeding areas, (5) stream cover, (6) adequate flows, and (7) suitable
water temperatures.
Of the 20.5 km (12.6 miles) of stream inhabited by both Modoc suckers
and hybrid suckers, 72% is on privately-held land and 28% is on Forest
Service land. However, 95% of the pure Modoc suckers are found in
streams within Modoc National Forest.
CURRENT MANAGEMENT
The immediate management objective for the Modoc sucker is to preserve
the species by preventing further habitat degradation and protecting
the genetic integrity of the pure populations. Personnel of Modoc
National Forest are already making inroads in habitat protection and
plan to fence key riparian habitat areas of Washington and Johnson
creeks. Other preservation efforts by Forest Service personnel include
barrier and barrier site evaluations for each of the eight streams with
emphasis on Hulbert, Johnson, and Washington creeks. At this time, only
the Washington Creek population is protected by an effective barrier from
the threat of hybridization with the Sacramento sucker, but potential
barrier sites on Hulbert and Johnson creeks have been identified.
Securing the isolation of these three creeks is of particular importance
as they contain the only known pure populations of Modoc suckers.
The reproductive dynamics
under further study since
leading to hybridization.
useful information on the
of Modoc and Sacramento suckers is currently
little is known about the actual processes
Results of this study are expected to yield
status of populations presently regarded as
-19TABLE 6.
Variable
Group Means (and Standard Deviations) of Meristic Characters
for Modoc and Sacramento Suckers and Their Hybrids.
Group
Modoc
(n = 26)
Hybrid
(n = 14)
Sacramento
(n = 25)
Scales in lateral
line
80.9 (4.7)
76.5 (5.9)
70.9 (4.1)
Scales above lateral
line
14.8 (1.2)
14.1 (.9)
13.3 (1.1)
Scales below lateral
line
10.0 (.9)
Number of dorsal rays
10.1 (.4)
9.8 (1.1)
10.9 (.6)
8.8 (.7)
11.9 (.5)
Standardized head
length
.250 (.018)
.248 (.013)
.249 (.015)
Standardized eye
diameter
.043 (.007)
.048 (.004)
.044 (.008)
20all hybrid fish. These populations may in fact be a mixture of pure
Modoc suckers and hybrid suckers.
Ford (1977) identified five streams as potential transplant sites for
the Modoc sucker (Appendix 11). These streams, however, need further
evaluation of their value as transplant sites. Range extension is
important at this time because the current range of the Modoc sucker
is restricted and population numbers are low, Establishing additional
populations will provide an expanded range, allow an increase in population abundance, and provide a source of parental fish for reintroduction
into rejuvenated habitats.
STATUS
Moyle's (1974) report on the status of the Modoc sucker showed that it
qualified as a rare species since the population was small and could
be further reduced (endangered) if habitat degradation continued. The
recent population estimate is less than 1,300 fish restricted to three
streams. This reduction in population from the previous estimate of
5,000 fish is a reflection of the effect of the 1977 drought and does
not include populations containing hybrid fish. There are several
factors which impose further jeopardy upon the Modoc sucker: (1) habitat
alteration resulting from continued water diversions and grazing, (2)
competition and predation from native and exotic fishes, and (3) hybridization with the Sacramento sucker. These existing threats qualify the
Modoc sucker for listing as an endangered species through the California
Endangered Species Act.
FUTURE MANAGEMENT
Perpetuation of the Modoc sucker can best be accomplished by the cooperative
efforts of the U. S. Forest Service and the Department of Fish and Game in
identifying and correcting the factors jeopardizing this species. An
interim recovery plan, identifying problems and solutions for managing
the Modoc sucker, is currently being prepared. Three major objectives
have been identified which must be met to ensure the survival of this
species. Habitat protection and restoration, as well as barrier construction, are needed to provide stable, isolated habitats. Streams containing
hybrid Modoc suckers and Sacramento suckers need to be chemically
rejuvenated then restocked with pure fish. Additionally, several transplant sites need to be located immediately to both expand the present
range and population abundance and to provide a source of fish to repopulate rejuvenated streams. Transplants should only be made into
areas having sufficient pool habitat, cover, and flow, and which are not
accessible to Sacramento suckers.
Habitat protection and restoration is one of the most important objectives
but riparian vegetation can only become reestablished in the absence of
livestock. Certain meadow areas need to be fenced to allow the reestablishment of streamside vegetation and to provide streambank protection.
Headcutting and stream incision of meadows is still occurring within
essential habitat areas and needs to be stopped.
-21Upper :Johnson Creek remains a very important habitat area for the Modoc
sucker. Although vflorts by the Forest !;ervlce to acquire this privatelyheld land have been unsuccessful, they should continue.
RECOMMENDATIONS
Based on existing data, the following actions are recommended to assist
in and provide for the protection and management of the Modoc sucker.
1.
Change the status of the Modoc sucker from the "rare" category to the
"endangered" category under authority of the California Endangered
Species Act of 1970.
2.
Develop a management plan for the Modoc sucker using the Forest Service
interdisciplinary team approach and incorporate team recommendations
and alternatives into the forest-wide land management plan.
3.
Complete the barrier evaluation for the eight essential habitats, and
improve incomplete barriers.
4.
EvaluaLe all potential transplant sites and introduce Modoc suckers
into soveral suitable locations.
5.
Continue efforts to acquire essential habitat areas held in private
ownership, especially upper Johnson Creek.
REFERENCES
Boccone, V, and T. J. Mills. 1979. Spawning behavior and spawning
substrtte preference of the Modoc sucker, Catostomus microps
(Rutte ). Calif. Dep. Fish Game Inland Fish. End. Sp. Prog. Spec.
Publ. '9-2, 33 p.
Carlander, K. D. 1969. Handbook of freshwater fishery biology, Vol. 1
Iowa State Univ. Press, Ames, Iowa, 281 p.
Cooper, J., D. Koch, and E. Lider. 1979. A fishery investigation of
the Modoc sucker (Catoatomun micropn) and the rough sculpin (Cottug
aop('rvimun) In the Pit River drainage between Turner Creek and
Juniper Creek, Lassen and Modoc counties, California. Univ. Nev.
Desert Res. Inst., Reno. U.S.D.I. Contract Study No. 8-07-20-V0030,
79 p.
Fisk, L. 1972. Status of certain depleted inland fishes. Calif. Dep.
Fish Game, Inland Fish. Admin. Rep. 72-1, 13 p.
Ford, T. 1977. Status summary report on the Modoc sucker (Catotomun
microps Rutter). Modoc Nat. For., Alturas, California, 44 p.
(typewritten)
Hubbs, C. L. 1955.
Zool. 4:20.
Hybridization between fish species in nature.
Syst.
-22Leach, H. R., S. J. Nicola, and J. M. Brode. 1976. At the Crossroads,
1976. Calif. Dep. Fish Came, Sacramento, 101 p.
Martin, M. 1967. The distribution and morphology of the North American
catostomid fishes of the Pit River system, California. M. A. thesis,
Sacramento State College, Sacramento, Calif., 60 p.
. 1972. Morphology and variation of the Modoc sucker, Catostomw
mberops Rutter, with notes on feeding adaptations. Calif. Fish Came
58(4):277-284.
Miller, R. R. 1961. Man and the changing fish fauna of the American
soL_t%west . Pap. Mich. Acad. Sci. Arts Letters 46:365-404.
Moyle, P. B.
(Pisces:
1974. Status of the Modoc sucker, (atontomun micropv
Catostomidae). Cal. Nev. Wildl. 1974:35-38.
. 1976a.
Berkeley, 405 p.
Inland fishes of California. Univ. Calif. Press,
. 1976b. Some effects of channelization on the fishes and
invertebrates of Rush Creek, Modoc County, Calif. Calif. Fish
Game 62(3):179-186.
Moyle, P. B., and A. Marciochi. 1975. Biology of the Modoc sucker,
Catostomus microps (Pisces: Catostomidae) in northeastern California.
Copeia 1975(3):556-560.
Oakeshott, G. B. 1971. California's changing landscapes.
Co., New York, N.Y., 388 p.
McCraw-Hill
Pease, R. W. 1965. Modoc County, a geographic time continuum on the
California volcanic tableland. Univ. Calif. Publ. Geog. 17, 304 p.
Rutter, C. 1908. The fishes of the Sacramento-San Joaquin basin, with
a study of their distribution and variation. Bull. U. S. Bur. Fish.
27(637):103-152.
-25-APPENDIX 1. Additional Streams Surveyed and Found not to Contain Modoc
Suckers.
Stream
County
Surveyed
Widow Valley Creek (6 stations)
Modoc
1/
DRI.
Taylor Creek (2 stations)
Modoc/Lassen
DRI
Halls Canyon Creek (3 stations)
Modoc
DRI
Rose Canyon Creek (3 stations)
Modoc
DRI
Unnamed tributary to Pit River (1 station)
(.75 mile west of Allen Camp, Sec. 30)
Modoc
DRI
West Allen Camp Creek (3 stations)
Modoc
DRI.
East Allen Camp Creek (1 station)
Modoc
DRI
Stone Coal Creek (3 stations)
Modoc
DRI
Unnamed tributary to Stone Coal Creek
(.5 mile upstream of confluence of
Stone Coal Creek and Pit River)
(1 station)
Modoc
DRI
Unnamed tributary to Upper Stone
Cod_ Creek (Sec. 6) (I station)
Modoc
DRI
Big Canyon Creek (1 station)
Modoc
DRI
Blacks Canyon Creek (1 station)
Modoc
CF&G—
Pit River (12 stations)
Modoc/Lassen
DRI
Ash Creek below Adin (1 station)
Lassen
DRI
Cedar Creek (2 stations)
Lassen
CF&G
2/
DRI = Desert Research Institute, University of Nevada, Reno.
2/
CF&G = California Department of Fish and Game, Endangered Native Fishes Project,
Sacramento, California.
-26APPENDIX 2. Habitat Characteristics of Dutch Flat Creek, Modoc County.
Stream section
Stream character
lower half
upper half
Width (ave.)
2 feet
2 feet
Pool abundance
common
isolated pools
Pool shelter
common
scarce
undercut banks
willows
rocks
rocks
algae
debris
formed by
Bottom type
bedrock-boulder
rocks-rubble
gravel-sand
silt-mud
Shade canopy
% pool % riffle
10
5
55
45
25
25
10
25
% pool % riffle
0
. 5
40
20
50
35
20
30
medium
light
willows
conifer
oak
conifer
eroded banks
willow
Watershed soil stability
unstable
moderately
unstable
Stream channel stability
moderately
unstable
moderately
unstable to
unstable
provided by
-27APPENDIX 3.
Habitat Characteristics of Hulbert Creek, Modoc County
Stream section
middle third
Stream character
lower third
Width (ave.)
5 feet
3 feet
2 feet
Pool abundance
few
common
few
Pool shelter
good
good
medium
debris
rocks
rubble
undercut banks
rocks
rubble
small, deep pools
rocks
rubble
formed by
Bottom type
bedrock-boulder
rock-rubble
gravel-sand
silt-mud
Shade canopy
% pool
10
45
20
25
% riffle
15
55
20
10
% pool
7
23
20
50
% riffle
9
30
21
40
upper third
% pool
5
20
40
35
% riffle
0
25
40
35
medium
light
medium
aspens
conifer
stream banks
grass
aspens
conifer
Watershed soil stability
stable
stable
stable
Stream channel stability
unstable
unstable
unstable
provided by
-28APPENDIX 4.
Habitat Characteristics of Johnson Creek, MOdoc County.
Stream section
middle third
Stream character
lower third
Width (ave.)
6 feet
3 feet
2.5 feet
Pool abundance
few
few
few
Pool shelter
medium
abundant
medium
undercut banks
aquatic
vegetation
undercut banks
aquatic
vegetation
algae
rocks
formed by
Bottom type
bedrock-boulder
rock-rubble
gravel-sand
silt-mud
% pool
2
28
40
30
% riffle
5
35
30
30
% pool
2
23
55
20
% riffle
5
40
35
20
upper third
% pool
2
20
30
48
% riffle
5
35
40
20
light
medium
light
willow
conifer
willow
conifer
conifer
Watershed soil stability
moderately
unstable
unstable
moderately
unstable
Stream channel stability
unstable
unstable
unstable
Shade canopy
provided by
-29APPENDIX 5.
Habitat Characteristics of Turner Creek, Modoc County.
Stream section
middle third
Stream character
lower third
Width (ave.)
12 feet
10 feet
4 feet
Pool abundance
abundant
abundant
common to
abundant
Pool shelter
abundant
abundant
abundant
aquatic
vegetation
rocks
aquatic
vegetation
rocks
undercut banks
algae
undercut banks
rubble
formed by
Bottom type
bedrock-boulder
rock-rubble
gravel-sand
silt-mud
Shade canopy
% pool
5
35
25
35
% riffle
10
30
30
30
% pool
12
28
25
35
% riffle
13
27
20
40
upper third
% pool
15
45
30
10
% riffle
10
55
25
10
light
light
medium
conifer
willow
conifer
willow
conifer
willow
WaterOled soil stability
stable
stable
stable
Stream channel stability
unstable
unstable
moderately
unstable
provided by
-30APPENDIX 6. Habitat Characteristics of Lower Rush Creek, Modoc
County, from Mouth to Highway 299 Bridge.
Stream section
middle third
Stream character
lower third
Width (ave.)
5 feet
10 feet
10 feet
Pool abundance
common
common
few
Pool shelter
stream banks
stream banks
stream banks
rocks
stream banks
provided by
Bottom type
bedrock-boulder
rock-rubble
gravel-sand
silt-mud
% pool
0
15
15
70
% riffli!
0
25
35
40
% pool
1
15
15
69
% riffle
1
70
24
5
upper third
rocks
% pools
15
15
35
35
% riffle
15
70
15
0
light
medium
light
willows
cottonwoods
willows
brush
willows
Watershed soil stability
stable
stable
stable
Stream channel stability
unstable
moderately
unstable
moderately
stable
(channelized)
Shade canopy
provided by
'11
APPENDIX 7. Habitat Characteristics of Middle and Upper Rush Creek, Modoc
County, from Highway 299 Bridge to Headwaters.
Stream section
Stream character
lower half
upper half
Width (ave.)
10 feet
8 feet
Pool abundance
common (50%)
common (40%)
Pool shelter
abundant
abundant
undercut banks
rocks
debris
undercut banks
rocks
log
formed by
Bottom type
bedrock-boulder
rock-rubble
gravel-sand
silt-mud
Shade canopy
% pool % riffle
2
6
35
59
20
38
25
15
% pool % riffle
1
6
50
20
35
49
9
30
medium
medium
conifer
willow
conifer
willow
Watershed soil stability
moderately
stable
moderately
stable
Stream channel stability
moderately
stable
moderately
stable
provided by
-32APPENDIX 8. Habitat Characteristics of Washington Creek, Modoc County.
^
Stream section
Stream character
lower half
upper half
Wi.dth (ave.)
12 feet
12 feet
Pool abundance
few
few
Pool shelter
medium
medium
rocks
undercut banks
rocks
undercut banks
% pools % riffle
2
7
50
69
14
13
30
15
% pools % riffle
2
7
79
60
9
13
20
10
formed by
B)ttom type
bedrock-boulder
rocks-rubble
gravel-sand
silt-mud
light
light
chokecherry
willows
chokecherry
willows
W Ltershed soil stability
moderately
stable
moderately
stable
S:ream channel stability
moderately
stable
moderately
stable
Shade canopy
provided by
-33APPENDIX 9. Habitat Characteristics of Willow Creek, Lassen County.
Stream section
Stream character
lower half
Width (ave.)
5 feet
4 feet
Pool abundance
common
common
Pool shelter
medium
medium
undercut banks
rubble
undercut banks
rubble
upper half
•
formed by
Bottom type
bedrock-boulder
rock-rubble
gravel-sand
silt-mud
% pool % riffle
2
0
23
35
53
55
22
10
% pool % riffle
2
0
20
30
45
50
33
20
light
medium
pine
willow
aspen
pine
willow
aspen
Water soil stability
stable
moderately
stable
Stream channel stability
moderately
unstable
unstable
Shade canopy
provided by
-34APPENDIX 10. Habitat Characteristics of Ash Creek, Modoc County
Stream Character
Stream Section
above Rail Canyon
Width (ave.)
18 ft.
Pool abundance
Abundant
Pool shelter
formed by
Fair
Diversion dams
Streanbanks
Bottom type
bedrock-bounder
rock-rubble
gravel-sand
silt-mud
% Pool % Riffle
0
0
5
40
15
50
80
10
Shade canopy
provided by
Light
willows
tules
cattails
Watershed soil stability
Stable
Stream channel stability
Stable
-35-
APPENDIX 11. Potential Transplant Sites for Modoc Suckers.
Stream
County
Location
Butte Creek
Modoc
T.38N., R.9E., Sec. 23 and 24
T.38N., R.10E., Sec. 19 and 20
Halls Canyon Creek
Modoc
T.40N., R.8E., Sec. 18
North Adin Pass Creek
Modoc
T.41N., R.9E., Sec. 29
Coffee Mill Gulch
Modoc
T.42N., R.8E., Sec. 26
Howards Gulch Creek
Modoc
T.42N., R.9E., Sec. 18