State of California the Resources Agency DEPARTMENT of FISH and GAME

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

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—

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. -3-

INTRODUCTION

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). -4-

Micrope 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. Morphometric / and Merlstle Measurements of Three Calc:;1,1m1:7 microrl (Rutter 1908).

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

Anal rays 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

1/ - Expressed as proportion of body length. -6-

Sacramento 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 - 1 ()Imo I 1 y 001111001 0(1 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 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. -8-

TABLE 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).

1.1 01 .0leam. 4 1111101 011r M(1411)1 • 'sill' 1(4 :to r all 1 01 ,111 I v I0 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. -11- of 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 sub- strates; 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. -12-

TABLE 3. Water Diversion Data for Ash, Rush, Johnson, Turner, and Hulbert Creeks, Modoc County (Ford 1977).

Number of Stream 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. -14-

TABLE 4. Channelized Stream Sections of Johnson and Rush Creeks (Ford 1977).

Stream Location Year Length channelized

Johnson Creek T. 40 N., R. 8 E., 1964 975 in (3,200 ft) Sec. 23

Rush Creek T. 40 N., R. 8 E., 1966 335 in (1,100 ft) Sec. 24, 25, 26

Rush Creek T. 40 N., R. 8 E., 1966 25 in (80 ft) Sec. 35

Rush Creek T. 40 N., R. 8 E., 1967 225 in (735 ft) Sec. 26

Rush Creek T. 40 N., R. 8 E., 1968 65 in (210 ft) Sec. 35 -15-

Fish 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 simulta- neously 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 -16- but 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 man- made 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 inter- mediate 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 -17-

TABLE 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

CSUS. 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).

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. -18- the 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 the hybrid sucker are: scales in lateral line: 68-90 (51 76.5), and 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 of Modoc and Sacramento suckers is currently under further study since little is known about the actual processes leading to hybridization. Results of this study are expected to yield useful information on the status of populations presently regarded as -19-

TABLE 6. Group Means (and Standard Deviations) of Meristic Characters for Modoc and Sacramento Suckers and Their Hybrids.

Modoc Group Hybrid Sacramento Variable (n = 26) (n = 14) (n = 25)

Scales in lateral 80.9 (4.7) 76.5 (5.9) 70.9 (4.1) line

Scales above lateral 14.8 (1.2) 14.1 (.9) 13.3 (1.1) line

Scales below lateral 10.0 (.9) 9.8 (1.1) 8.8 (.7) line

Number of dorsal rays 10.1 (.4) 10.9 (.6) 11.9 (.5)

Standardized head .250 (.018) .248 (.013) .249 (.015) length

Standardized eye .043 (.007) .048 (.004) .044 (.008) diameter 20- all 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 construc- tion, 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 re- populate 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 reestablish- ment 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. -21-

Upper :Johnson Creek remains a very important habitat area for the Modoc sucker. Although vflorts by the Forest !;ervlce to acquire this privately- held 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. Hybridization between fish species in nature. Syst. Zool. 4:20. -22-

Leach, 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. 1974. Status of the Modoc sucker, (atontomun micropv (Pisces: Catostomidae). Cal. Nev. Wildl. 1974:35-38.

. 1976a. Inland fishes of California. Univ. Calif. Press, Berkeley, 405 p.

. 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. McCraw-Hill Co., New York, N.Y., 388 p.

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

1/ Widow Valley Creek (6 stations) Modoc 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) Modoc DRI (.75 mile west of Allen Camp, Sec. 30)

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 Modoc DRI (.5 mile upstream of confluence of Stone Coal Creek and Pit River) (1 station)

Unnamed tributary to Upper Stone Modoc DRI Cod_ Creek (Sec. 6) (I station)

Big Canyon Creek (1 station) Modoc DRI 2/ 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

DRI = Desert Research Institute, University of Nevada, Reno. 2/ CF&G = California Department of Fish and Game, Endangered Native Fishes Project, Sacramento, California. -26-

APPENDIX 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

formed by undercut banks rocks willows algae rocks debris

Bottom type % pool % riffle % pool % riffle bedrock-boulder 10 5 0 . 5 rocks-rubble 55 45 20 40 gravel-sand 25 25 50 35 silt-mud 10 25 30 20

Shade canopy medium light

provided by willows conifer conifer eroded banks oak willow

Watershed soil stability unstable moderately unstable

Stream channel stability moderately moderately unstable unstable to unstable -27-

APPENDIX 3. Habitat Characteristics of Hulbert Creek, Modoc County

Stream section Stream character lower third middle third upper third

Width (ave.) 5 feet 3 feet 2 feet

Pool abundance few common few

Pool shelter good good medium

formed by debris undercut banks small, deep pools rocks rocks rocks rubble rubble rubble

Bottom type % pool % riffle % pool % riffle % pool % riffle bedrock-boulder 10 15 7 9 5 0 rock-rubble 45 55 23 30 20 25 gravel-sand 20 20 20 21 40 40 silt-mud 25 10 50 40 35 35

Shade canopy medium light medium

provided by aspens stream banks aspens conifer grass conifer

Watershed soil stability stable stable stable

Stream channel stability unstable unstable unstable -28-

APPENDIX 4. Habitat Characteristics of Johnson Creek, MOdoc County.

Stream section Stream character lower third middle third upper third

Width (ave.) 6 feet 3 feet 2.5 feet

Pool abundance few few few

Pool shelter medium abundant medium

formed by undercut banks undercut banks algae aquatic aquatic rocks vegetation vegetation

Bottom type % pool % riffle % pool % riffle % pool % riffle bedrock-boulder 2 5 2 5 2 5 rock-rubble 28 35 23 40 20 35 gravel-sand 40 30 55 35 30 40 silt-mud 30 30 20 20 48 20

Shade canopy light medium light

provided by willow willow conifer conifer conifer

Watershed soil stability moderately unstable moderately unstable unstable

Stream channel stability unstable unstable unstable -29-

APPENDIX 5. Habitat Characteristics of Turner Creek, Modoc County.

Stream section Stream character lower third middle third upper third

Width (ave.) 12 feet 10 feet 4 feet

Pool abundance abundant abundant common to abundant

Pool shelter abundant abundant abundant

formed by aquatic aquatic algae vegetation vegetation undercut banks rocks rocks rubble undercut banks

Bottom type % pool % riffle % pool % riffle % pool % riffle bedrock-boulder 5 10 12 13 15 10 rock-rubble 35 30 28 27 45 55 gravel-sand 25 30 25 20 30 25 silt-mud 35 30 35 40 10 10

Shade canopy light light medium

provided by conifer conifer conifer willow willow willow

WaterOled soil stability stable stable stable

Stream channel stability unstable unstable moderately unstable -30-

APPENDIX 6. Habitat Characteristics of Lower Rush Creek, Modoc County, from Mouth to Highway 299 Bridge.

Stream section Stream character lower third middle third upper third

Width (ave.) 5 feet 10 feet 10 feet

Pool abundance common common few

Pool shelter stream banks stream banks

provided by stream banks stream banks rocks rocks

Bottom type % pool % riffli! % pool % riffle % pools % riffle bedrock-boulder 0 0 1 1 15 15 rock-rubble 15 25 15 70 15 70 gravel-sand 15 35 15 24 35 15 silt-mud 70 40 69 5 35 0

Shade canopy light medium light

provided by willows cottonwoods willows willows brush

Watershed soil stability stable stable stable

Stream channel stability unstable moderately moderately unstable stable (channelized) '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

formed by undercut banks undercut banks rocks rocks debris log

Bottom type % pool % riffle % pool % riffle bedrock-boulder 2 6 1 6 rock-rubble 35 59 20 50 gravel-sand 38 20 49 35 silt-mud 25 15 30 9

Shade canopy medium medium

provided by conifer conifer willow willow

Watershed soil stability moderately moderately stable stable

Stream channel stability moderately moderately stable stable -32-

APPENDIX 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

formed by rocks rocks undercut banks undercut banks

B)ttom type % pools % riffle % pools % riffle bedrock-boulder 7 2 7 2 rocks-rubble 50 69 60 79 gravel-sand 13 14 13 9 silt-mud 30 15 20 10

Shade canopy light light

provided by chokecherry chokecherry willows willows

W Ltershed soil stability moderately moderately stable stable

S:ream channel stability moderately moderately stable stable -33-

APPENDIX 9. Habitat Characteristics of Willow Creek, Lassen County.

Stream section Stream character lower half upper half

Width (ave.) 5 feet 4 feet • Pool abundance common common

Pool shelter medium medium

formed by undercut banks undercut banks rubble rubble

Bottom type % pool % riffle % pool % riffle bedrock-boulder 2 0 2 0 rock-rubble 23 35 20 30 gravel-sand 53 55 45 50 silt-mud 22 10 33 20

Shade canopy light medium

provided by pine pine willow willow aspen aspen

Water soil stability stable moderately stable

Stream channel stability moderately unstable unstable -34- APPENDIX 10. Habitat Characteristics of Ash Creek, Modoc County

Stream Character Stream Section above Rail Canyon

Width (ave.) 18 ft.

Pool abundance Abundant

Pool shelter Fair formed by Diversion dams Streanbanks

Bottom type % Pool % Riffle bedrock-bounder 0 0 rock-rubble 5 40 gravel-sand 15 50 silt-mud 80 10

Shade canopy Light provided by 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