Acknowledgments

River carpsucker,9glp!9999 carplo (Raflnesqre), fno'm Elephant hrtte Lake

Acknowledgments

I wish to thank former and present graduate reseanch assistants D. J. Ozmina, C.D. Rael, R.R. Patterson, D.E. Jennings, C. Sanchez, Jt., T.M. Mood5/, B.L. Jensen, R. Padilla, W. R. Uhland, and G. L. Wisdom for careful obsenration, recording of data, and other assistance during these investigatlons. Special thaaks are due to commercial fisherman B.C. fuarkman for cooperation and assieta^nce throughout the study. T.halks are also extended to NMSU shrdent Douglas B. Jester' Jr. , for assistance in programming a^nd use of the IBM System/S6O computer br several investigations.

Personnel of the Rio Grande Prcject, U. S. Ilureau of Reclamation, have been extremely cooperative in providing facilities and physical-operational data.

Financial support of Projects CF 6-11-R and D-J F-22-F" by the New Mexico Department of Game and Fish made the shrdy possible. This support is sincerely appreciated. CF 6-11-R funds were derived fnom PL 88-309 and administered by the National Marine Fisheries Senrice, NOAA. D-J F-22-R funds were derived from the Federal Aid to Fish Restoration program administered by the Btreau of Sbort Fisheries and Wildlife, U. S. Fish and Wildlife Service.

December 1972 Lae Cmces, New Mexico Absfrocf

Results frpm eight years of investigations of river carpsucker in Elephant Butte Lake are combined with all available literattre into this monographic relnrt, which includes ecological life history, population ecolory, commercial potential, md management methods and technlques.

Published reports of the range of the species are modified, extending the western boundary into Wyoming, Colorado, New Mexico, West Texas, and Chihuahua, Mexico. Classification and turonomy are reviewed and a new dichotomous key to species of Carpiodes is presented.

Among the reported populations of river carpsucker, the Elephant Butte Lake population ranhed third in both growth rate and total length. Mean monthly growth was also determined. Grcwth ceases during winter, reaches the highest rate durrng spring, declines or ceases durrng spawning season in early summer, and increases to a higb rate in late zummer and early auhlmn.

In Elephant Butte Lake, carpzucker of both sexes mahre in Age Group III, with a few individuals reaching mahrrity in Age Gnoup II. Lee?s Phenomenon is generally evident and has strong effects on males in Age Gnoups tI and VII and on females in Age Grcups II and VI. In several other waters, mafurit5l occurs in older age groups, and Leets Phenomenon does not occur.

Male carpsucker zunrive at higher rates than females through Age Group III; survival rates are similar for both sexes in Age Group [V; and females survive at higher rates than males in Age Groups V through X. Mean life span of all carpsucker is 3.46 years in Elephant Butte Lake. Life spans of males, females, and all carpsucker which reach Age Group I are also shown. Survival into succeeding age groups decreases er

Length-weigbt relationship was used to determine grand mean weights at formation of each annulus. Semal dimorphism occurs in terms of weight but rpt in length. Females are heavier than males in the same age group from maturity in Age Group Itr through Age Group X.

Carpsucker required four years to reach a weight of 800 grams in a composite sample from Oklahoma, five years in Elephant Butte Lake and two waters in Oklahoma, and six to nine yeafs in six other waters. The largest carpsucker from Elephant Butte Lake was 584 mm long and weighed Lr702 grams. It ranked second in length and fourth in weight among reported specimens.

Coefficients of condition varied erratically with length; followed seasonal trends associated with reproductive development; and followed a trend of decline in young fish, stability in intermediate age groups, and increase in older age groups. Condi- tion values for carpzucker in Elephant Butte LaI

Limnological factors which affect abundance and distribution of carpsucker are summarized, including distribution of food organisms a.nd their associations with depth and types of bottom materials.

Population data reported in the literahrre indicate that carpsucker are a major component of the fish fauna in most waters inhabited by the species. A Schnabel estimate in the Des Moines River, Iowa, and a direct count in the Rio Grande, New Mexico, revealed approximately 500 kg/\a of carpsucker in both streams.

Parameters of the carpsucker population in Elephant Butte Lake were analyzed in terms of percentages of number and weight of all fishes caught, catches per net- unit, and total density estimates made monthly and annually with the Schnabel esti- mator. Interactions between carpsucker and other populations were determined by comparing carpzucker data with various combinations of similar data from other populations. Interactions between carpsucker, smallmouth buffalo, and carp (to a lesser extent) were quite strong. Carpsucker increased from 17,400 fish in 196b-66 to 103,419 fish inL97]-72 with a weight increase of 67,193 kg, in response to reduction of.222,865 smallmouth buffato weighing 245,654 kg during 1964-65 through 1'g?l-72. Necessity of managing commercial species as a group on the basis of such interactions is discussed.

Investigations of movement of marked fish revealed that density of the carpsucker population shifts between thirds of the lake during different seasons but that a bona fide migration does not occur.

Ttre carpsucker appears to have a substantial commercial potential and should command prices comparable to related established commercial forms. Harrrest experiments were carried out to evaluate traps, trawls, and gill nets. Best results were obtained with gill nets composed of four and five-inch (L0.2 and 12.7-cm) stretch meshes, dyed a medium shade of brown, and set in seasonal concentrations of carpsucker. Priorities for seasonal fishing in thirds of the lake to achieve maximum efficiency and extremely high rates of harvest were determined, Effects of changes in water level and population size on catch rates were also analyzed'. Changes in surface area of the lake had a greater effect than changes in population density in Elephant Butte Lake during 1965-66 through l97L-72. Projection of potential harvest shows that an initial mean catch rate of 5.6 carpzucker weighing 4.Gkg per net-unit (25 by 10 feet of net set for 24 hours) couldbe achievedbyutilizing the summer season and area priorities determined for four and five-inch- (10.2 and L2.7 -cm-) mesh, brown nets.

Literature cited constitutes a bibliography composed of 120 references. 3 Confenfs

Reproductlon ...... 55 Introduction ...... D Spawnirngseasm . . . . 55 Systematics...o. 5 Habitatandbehavior . . . . 55 Classification ...... 6 Sexratios. . . . 58 Ta:ronomY...... 6 Sernralmahrrity . . . . 58 Distribution...... 7 Fecundity .... 59 RAnge. . o . . . . . o . 7 Feedingandfood . . . . . 62 Status..o..... I Ecology..o...... 63 Methods...... aaraaa 10 Limnology...... 65 Elephant Butte Lake . aoaa 10 Physicalfactors . . . . 65 Lifehistory...... o . . t2 Chemicalfactors.... 67 Samples...o... L2 Biologicalfactors . . 7L Timedistribution. . o . . . t2 Coliformbacteria . . . . 7l Groups...... L2 PlanKon....7L Reiectionof data . . . . . t3 Benthos. . . . . 73 Size ranges aoaaoa 13 Populations...... 74 Mean dates t4 Various drainales . 74 Ageandgrowth...... t4 South Canadian drainage 74 Length and conversion . . . 15 Pecosdrainage . . . . . 75 Validity...... 16 Rio Grande drainage . . 76 Body-scale relationship . . . 18 Elephant Butte Lake . . 78 Age-growth...... 20 Relative densitY and biomas s 79 Semaldimorphism. . . . 26 Catch per net-unit . . . 80 Monthlygrowth...... 26 Population estimates . . . 89 LeersPhenomenon. o... 30 Population interactions . . 91 Growth curves . . 31 Summary of population Comparison....r..o 31 parameters. . . 91 Survival and mortality . . . . . 34 Length-frequency . . 92 Length-weight relationship . . . 4L Movement . . 93 Lengthandweight . . . . o 42 Diseaseandparasites. . . . . 99 LeCrenMethod. . . . . 42 Management...... 99 Computedweights . . . o 42 Economic value ...... 100 Ageandweight...... 42 Harnestmethods . . . . 101 Comparison.o...... 49 Meshsizes . . . . 101 Condition....o..... 49 Colorof gillnets...... 101 HileMethod... o.. . 49 Seasonal concentrations . . o 103 Conditionandlength . o . . 50 Brown commercial nets . . . 104 Conditionandage . . . . . 50 Effects of population and lake Monthlycondition . . . . 53 sizes on harsrest . . . 10? RioGrandesample. . . . . 53 Potentialharvest ...... 109 Comparison...... 53 Literahrrecited. . . 113

ERRATA

Jester, D. B. L972. Life history, ecology, and management of the river earpsucker, Carpio-des carpi-o (Rafinesque), with reference to Elephant Butte Lake. Ag. Exp. Sta. Resch. Rept. 243, New Mexico State Univ. , Las Cruces. 120 pp. Page Line Correction required

11 26 from approxirnatffi 30...

16 4 sometimes inhibity' growth. L7 6 [email protected]' 18 31 and 0. g/e Gip:re 7).. . L2 27 Caption, Table 11. frorn tabl" 2(, e'. I t-t 31 18 each age groulYsote-. .. \!)\ 55 3 Behmer , L964at; Lake

61 6 either size.er-

6L 7 aAe Or 4...

76 38 according to an extant ecologlcal glossary, "indigenous"

nay be preferrable to "endemic". pounds of 78 15 1,200f ish per mile. . . II 85 6 Line./, both. . . II 89 4 (Line ..{ tigur" 29). .. e 100 I indicat**g: ttrat cd$sucker

100 25 po,rna/F6Tl-( rue . . - a S!:Is /under.

104 Heading, TabLe 62 move superscript I from "clear N.t"{' to - d. Augustrabove,'J-' and superscript 2 ftom "Clear Netd--" \, to March' above. Please excuse these mi-stakes i-n consideration of their having been placed in the manuscript for a purpose. We try to publish something for everyone, and some folks are always looking for mistakes. Since this document is quite long and elaborate, we have taken the liberty of pointing out 16 errors for their enjoyment. L;fu Hi*6roy, JEornrgu, *^dl M*.*germ.ernf of 6he ]Rir*o Cr*pu*olk*o, C*o[oitdluu carpio (R.*ffi^uuq*u), wi6h Ruf*oence 6o E[ue[uam.6 ]Buffe L*ku

Douglas B. Jester, Associate Professor of Fishery Science

Life history, ecologyr and management of river carpsucker, Carpiodes calpio @afinesque), were investigated during eight years of shrdies of the fishery resources of Blephant Butte Lake, New Mexico.

The sport fishery phase of these investigations,l along with numerous other investigations on reservoir fisheries in the Southwest and elsewhere, indicate thatriver carpsucker and other. ftroughtr fishes frequently function as limiting factors on game fish populations and contribute little to the sport fishery or to human food supplies. The commercial fishery phase was carried out as a means of learning enough about the river carpsucker and other I'rough'r fishes to allow intelligent research-based management of these species. This report is intended to serve as a basis for comprehension of the management problem and achievement of the management objec- tirzes of concurrent 'fenhancement of sport fishing and utilization of unharvested rrough fish? resources" (Jester, I97Lal.

Previous investigations of river carpsucker have been limited in scope and scat- tered in geographic locale. Our investigations of the species in Elephant Butte Lake include all aspects studied elsewhere along with several new aspects, and are used here as a focal point to bring together all existing knowledge about river carpsucker into a single publication. I apologize to any author whose work is not cited here; any omission is due to oversight rather than intent or disdain.

Syslem o lics

Systematics of the river carpsucker appear to be well-established and have not been revised in many years, except for changes in several categories of the hierarchy of classification where the hierarchy was revised rather than the place of the fish

1A contrlbutlonofProJectsD-JF-22-R, Gamefleh reprodrctlon and rcughfishpmblens tnElephantButteLake (1964-68); and Commercial Fishertes 6-11-R, Investigations of commerclal frshery potential ofnoughflah speciee (1968-72\ granted to the Agricultural Experiment Station by the New Mexico Department of Game and Fleh. $rithin it. Therefore, systematics are discussed here only in terms of currently- tecognized categories of classification and ta:ronomic description necessary to distingUish the river carpsucker frcm other carpsuckers and the closely-related buffalofishes.

C lo ssif ico lion

The river carpsucker is classified as follows: Phylum Chordata (after Romer, 1955) $rbphylum Vertebrata $rperclass Pisces Class Osteichthyes $rbclass Actinopterygii Srperorder Teleostei Order CSpriniformes (after AFS, 19?0) . Family Catogtomidae Subfamily Ictiobinae Genus Carpiodes Carpiodes carpio (Rafinesque)

Many authors, apparently following Hubbs a^ud Lagler (1949), refer to northem river carpsucker, 9g$!g carpio camio @afinesque). Others refer only to species, Carpiodes carpio @afrnesque). No references to other srbspecies have been found by the writer.

Toxonomy Hubbs and Lagler (1949) distinguish Subfamily lctiobinae (carpsuckers and buffalofishes) from all other suckers by an elongate dorsal fin with more than 22 developed rays as compared to a short dorsal fin with fewer than 20 developed rays.

Gems Carpiodes is separated fnom buffalofishes by a well developed anterior fontanelle, thin phar5mgeal arch, a^rrd sub-triangular subopercle. Buffalofishes are compared, with anterior fontanelle poorly developed or absent, robust pharyngeal arch, and zub-semicircular subopercle.

Moore (Blair et aL., 195?) and Eddy (195?) agree essentially with Hubbs and Lagler (1949) on characteristics which separate four species of Carpiodes. One of these, C. forbesi, has been placed in s5nronomy with C. cyprinus by Bailey and Allum (1962), so that only three species are recognized at the present time (AFS, 1970).

Koster (1957) characterized Carpiodes carpio, the only Carpiodes known in New Mexico, as follows: 1r1 anteE@ oE6-rs-at rin longFTh-Iffisterior rays but less than one-half the length of dorsal base, (2) dorsal tays 23-27, (3) lateral line scales 33-3? (usually 35), and (4) a small knob at tip of mandible. Ihe writer examined several hundred river carpsucker from Elephant Butte Lake and found none which deviated from recognized generic or species characteristics. A key to the three recognized species of Carpiodes is as follows:

Key to Species of CarPiodes

1. A small knob at tip of mandible. Dorsal rays?7 or fewer . . 2 Noknobattipof ma:rdible. Dorsalrays2S-30...... C. cJrprinus (LeSueur) Quillback

2. Anterior rays of dorsal fin greatly elongated, often equal to or greater than length of dorsal base, Lateral line scales 35 or fewer ...... C. velifer @afinesqre) ffigftF"-urpsucker

Anterior rays of dorsal fin not greatly elongated, seldom longer than L/2 length of dorsal base. Lateral line scales usually 35 (33-3?) . . . . C. carpio (Rafinesque) River carpsucker

The American Fisheries Societ5r, Committee on Common and Scientific Names of q. Fishes, has recognized RIVER CARPST)CKER as the accepted common name of carpio since the committee took its first action following formation in 1938 (AFS: L945, 1948, 1-960' and 1970).

Distrib ution

Ro nge

Carpiodes carpio is widely distributed in the United States. Hubbs and Lagler (1g4ii;Emr$fand Moore (Blair e! al., 1957) vary slightly in reporting limits of the range. The composite range reported by these writers includes the area from the Great plains in Montana to the Ohio River in Pennsylvania; south to the Tennessee Mexico. Moore (Blair 1917)' River system in Tennessee and into northeastern 9! 4.: _ alone, reported the species from northeastern Mexico, which places it in the Rio Grande drainage.

A common omission in these reports consists of failure to report river carpsucker in the Rio Grande drainage in north-central Mexico (Chihuahua), New Mexico drainages east of the Continental Divide (Koster, 195?), some eastern plains waters of Colorado (Beckman, Lg52r, and most Wyoming drainages east of the Continental Divide (Baxter and Simon, L970). Kosterrs description, along with observations made by the author in the South Canadian and upper Rio Grande drainages (Jester, 1962a' b, and 1g63a), Beckmants report of the species in waters of eastern Colorado, and Baxter and Simonts report of distribution of river carpsucker in Wyoming, should suffice to modify the western boundary so that the range of C. carpio (figure 1) may be described as "east of the Continental Divide from the Great Plains in Montana southward into northern Mexico; eastward to the Tennessee River system in Tennessee and to the Ohio River in Pennsylvania. One record from the Maumee River, Ohio. " Fig. 1. Known renge of the river carpzucker, 9.@&1@ carpio @afinesque), in the United States and northern Mexico.

The Maumee River record is listed by Hubbs and Lagler (1949). Local distribution of the river carpzucker in New Mexico is shown in figure 2.

Slotus

River carpsucker are considered to be rhoughtr fish by consensus of fishery workers. They have commercial value vihen taken at market-acceptable sizes and are sold under a different name zuch as tfcoldwater buffalott (8. C. Sparkman, commercial fisherman, Elephant Butte, New Mexico, personal communication). fire species appears to be of great importance in fisheries management, but little is knoum of its life history and eeolory. Therefore, little, if any, research-based management has been applied. lbis writer shares the consensus that Carpiodes camio is a ttnought'fish in Elephant Brtte Lake and other warm watersJfGffiexico, in that it provides little to commercial hanrest and nothing to sport fishing. Popula- tions reach large proportions of both density and biomass in warm-water streams and resenroirs. Obsenrations made by the author (Jester, l962al and others have revealed strong association of river carpsucker with lake bottom. Limited studies of food habits indicate that feeding occurs at a low tnophic level. Carpsucker ingest large qtrantities of bottom materials and seem to assimilate a:nytling containing nutritional value (Brezner, 1956, quoting Forbes and Richardson; Buck and Cross, 1951; Buchholz, L957a; Jester, L962a; and Netsch and Witt, 1962). Thus, competition with other species for food is usually indirect but quite efficient. Fig.2.Distributionoftherivercarpsucker,@carpio(Rafinesque)'in New Mexico.

Cha'ges in density and biomass of smallmouth buffalo, river carpsucker, and discussed carp as a result of selective harvest of buffalo from Elephant Butte Lake are in detail in this report. These changes indicate that considerable competition occurs among the three species and that smallmouth buffalo tend to be dominant over river by carpsucker and carp. Replacement of a large portion of the biomass of buffalo carpsucker shows that management of rough or commercial fishes must be considered in terms of interrelated populations and that the river carpsucker is an important 1970; factor in such management (Jester et al. , 1969; Sanchez, 19?0; Moody et aL' , and Jester, L97l.al. il efhods

Fish populations have been sampled durrng at least three weeks of almost every month since June, L964, with e:

Ercperimental gill nets yielded most of the data for river carpzucker. The standard net is 38 m (125 feet) long by 3 m (10 feet) deep and contains five ?.6 x B m (25 x 10-foot) panels of 5, 7.5, 10, L2.5, and 15 cm (2, 3, 4, 5, and 6-inch) stretch, No. 139, nylon meshes. $rpplemental sets were made with 15 x 3 m (50 x l0-foot) and 30 x 3 m (100 x lO-foot) nets composed of 2.5 cm, 1?.5 cm, and 20 cm (L, 7, and 8-inch) stretch meshes. Random sampling was accomplished by drawing numbers which conform to quarter-sections in a grid superimposed on a reservoir map. Depth of each set was also determined by drawing except in areas where shallow water and terrain features dictated site and depth. Sampling with gill nets was carried out in 24-hour increments of time, varying from 24to 72 hours per week, with 48 hours as the mode and approximate mearr. Nets were relocated at the end of each 24 hours.

Standard methods were used br analysis of many data. In other instances, methods were modified or new ones were devised. Ihese are named or described in context with the appropriate rezults.

Scales were read to the nearest mm from wet mounts at 50x on a Van Oosten- Deason-tobes (1934) projector.

Elephont Butte loke

Elephant Butte Lake is a mainstream reservoir on the Rio Grande, five miles (8 km) northeast of Tnrth or Consequences, Sierra County, in south-central New Mexico (figure 2). It is operated by the U. S. Ihreau of Reclamation.

First.impounded in 1915: the lake is the oldest resenroir in New Mexico aad one of tbe oldest in the United States. It is the second largest impoundment in the state, having a potential storage eapacity of 2, 150,000 acre-f.eet (2,654.3 million mB) with a zurface area of approximately 40r 000 acres (16,32? ha). Original capacrty of the resenroir has been reduced approximately 5001 000 acre-feet (617.3 milliop mg) by silt, Water storage is typically less than ?00,000 acre-feet (864.2 million *31 and is characterized by extreme fluctuations resulting from seasonal inflow and drawdown for irrigation puryoses. Volume of stored water varied between 30,500 and 600,000 acre-feet (37.7 and ?40. ? million m3; during the course of this study.

The lake was impounded primarily for storage of water for irrigation in the lower Rio Grande Valley of southern New Mexico, extreme west Texas, and north- central Chihuahua, Mexico. Additional assets include power generation, sport fishing, and other water-oriented recreation. Maximum storage occurred only once, in 1942.

10 Elevation of Elephant Butte Lake is approximately 4,500 feet (1' 646 m) MSL. In general, the surrounding country consists of low rolling hills interspersed by numerous canyons. Mean annual rainfall is about eight inches (20 cm) (U. S. Dept. of Commerce, 1g?0). Vegetation is typical of that described by Merriam as indicative of the I-ower Sonoran Life Zone (Bailey, 1913). Extensive stands of saltcedar, @!1s pentandra pall., and a few Rio Grande cottonwoods, Populus wislizeni (S. Watts. ) Sarg. ' are present along the shore. Flucfuating water levels prevent permanent establishment of rooted littoral flora. Occasionally, temporary stability allows establishment of large, ephemeral stands of cattail, gphaL latifolia, on the silt delta at the mouth of the Rio Grande.

Elephant Butte Lake is morphometrically oligotrophic (after Odum, 1959). According to Hutchinson and Liiffler (1956), it is essentially dimictic. These class- ifications apply generally but are somewhat modified as density-current phenomena prevent formation of a true thermocline (Jester, 19?1a;b). Temperature gradients L"".r" durgrg all seasons of the year, although there is uniformity from surface to bottom during fall and spring overturns, indicating complete overturn. Moody et al. (1g?0) state that the fall overturn begins in late September to early October and summer gradients form in April and May. Annual mean surface temperature is approximately 15.6oC (60oF) (Jensen a-nd Jester, 1970; Jester and Jensen, L9721.

Bottom types vary greatly throughout the lake with the upstream third of the basin consisting of fine silt deposited during periods of inflow. Silt has also been carried by density cuments and deposited along the length of the river channel to the dam. $rb- strata in the downstream portions of the lake, excluding the main channel, consist of boulder-strewn rocky slopes, sheer rock walls, rocky benches, and sand and gravel shoals. Extensive stands of terrestrial vegetation are frequently inundated by rising water. Maximum depths during this study ranged from approximatley 30 feet (9 m) in the upstream one-third of the lake to 85 feet (26 m) near the dam.

Water chemistry is relatively stable. Dissolved ot(ygen ranges from approximately 5.5 to 8.5 mg/l, methyl orange alkalinity from 100 to 150 mg/l' total (Verslnate) hardness from 1?5 to ZZS mg/|, ffid sulfates vary from approximately iSO to 250 mg/l (Jester, 19?1 a;b). Phosphates range up to 1.5 rng/1, nitrate nitrogen upto 0.9 mg/l (JohnsonandKidd, 19?0), andpHranges from7.5to 9.2, usuallynear 8.3.

plankton and benthos are usually sparse. Low production of bottom organisms is attributed to depth, nahrre of bottom material, and frequent deposition of silt. Chironomidae (bloodworms), Oligochaeta (aquatic earthworms), and Chaoborinae (midges, Culicidae), are the most numerous organisms, in that order. A crawfish, Orconectes causeyi Jester, is periodically abundant. Analysis of plankton samples collected during 19?0 a mean standing crop of 4.62 ml of net plankton/m3 of ""rr"rled water. Zooplankton comprised 96 percent of the number of plankton organisms collected.

Sparsity of plankton in Elephant Butte Lake has been a subject of great interest for many years, but no reliable conclusion has been reached about actual factors

11 involved. Physical and chemical aspects of this problem are currently under investigation by Johnson and Kidd (Iniversity of New Mexico), and Jester and Jensen (1972) have h5pothesized that stunted, hungry gizzard shad are sufficiently ntrmerous to utilize pla^ukton at zuch a rapid rate that dense standing crops do not accumulate.

The fish fauna of Elephant Butte Lake consists of 27 species which are discussed under biological factors of the habitat. Fnom April, 1970, through March, L97L, river carpsucker comprised 6.2 percent ofthe number and 21.2 percent ofthe weight of fish collected in experimental gill nets (Padilla et gl. , 1971). These data show that the river carpsucker population, especially the biomass, constihrtes a major portion of the fish fauna and that these fishes are arr important factor in the trophic ecolory of the fish community.

t ife History

A study of age and growth phenomena--including investigations of age-gnowth, monthly growth, length-weight, condition, and survival of river carpsucker--was made on 2,081 fish taken from Elephant Butte Lake and the Rio Grande upstream fromthe lake, between August 1, 1964, and December 31, L967. Reproduction, food, and feeding data were taken from samples collected for population and ecological investigations. Similar studies, but none including all of these prima:ry or adjunct investigations, have been made on river carpsucker from other waters and other states.

Literahrre concerning the river carpsucker is relatively sparse. That which was found is discussed in this report in context with appropriate rezults frnom Elephant Butte Lake for purposes of comparison and accumulation of knowledge.

Somp les

Time D istribution

The sample of river carpsucker used for age and growth analysis in this shrdy consisted of 2,081 fish fnom Elephant Butte Lake and fnom the Rio Grande approximately five miles (8 km) upstream fnom the lake. Monthly and annual distributions of numbers of fish caught are shovm in table 1.

G rou ps

Carpzucker from Elephant Butte Lake are treated as three annual samples and as a composite sample. The 1964 collection of 21 fish is added to the 1965 sample for all computations. This sample consists of 207 fish. The 1966 sample consists of.277 fish aad the 1967 sample consists of 1,479 fish. These are combined to form a composite sample of 1,963 river carpsucker.

L2 Tabte 1. Dtstributtonof2,0Sl rlver carTsucker among months of catch from Elephant Butte Lake and the Rlo Grande' August, 1964, through December, 1967.

Month of lfumber of Fteh Cauqht from Eleohant Butte Lake- Montlly Catcb 1964 1965 1966 Totalg

January 34 :15 tlz 181 Febmary 7 4 80 91 Ma.rch 3 26 28 Aprtl 2 133 135 May t02 L02 June 4 L7g L77 July g0 126 156 August 3 27 205 256 September 6 l8 145 169 October 2 t4 72 ztr 299 November 64 g2 93 1?9 December 10 68 69 74 zll Totd Iake L,479 1,963 Rlo Grande (October' 196?) 118 Graod total 2,081

A sample consisting of 118 river carpsucker was taken from the Rio Grande on October 16, 196?. Literature indicated that spawning and early life history might occur in tributary streams and few young fish were taken in 1965 and 1966 samples frcm the lake. The river sample was intended to complete representation of all age groups in the implied river-lake population. Young fish were relatively numerous in the 196? sample from the lake. Growth patterns of young fish revealed that populations of river carpsucker in Elephant Butte Lake and the Rio Grande are relatively discrete. Therefore, fish from the river are treated separately in all computations except determination of empirical factors used to convert total length to fork and standard length.

Re jection of Doto

Data fnom individual fishes were rejected only as necessary. This resulted in small differences in numbers of fishes used in various investigations of each sample. Regenerated scales were numerous but only 21 (one percent) of the scale samples were entirely rejected because all scales were replacements. Other reiections resulted from missing data zuch as date of catch, length, or weight.

Size Ronges

Total lengths of river carpsucker in the composite sample from Elephant Butte Lake ranged from 115 mm to 584 mm (4. 5 - 23 inches). Weight ranged from t6 grams to L,702 grams (0.6 - 60 ounces).

Carpsucker in the sample from the Rio Grande 1'anged from 105 mm to 360 mm (4.1- 14.2 inches) total length and 15 grams to 557 grams (0.6 - 19.7 ounces) inweight.

13 Meon Dotes

Scale samples were taken from river carpsucker during almost every week in 1967. Mean date of catch was July 8, 1967, the 189th day of the year, which represents 51.8 percent of the calendar year. Growth-years of river carpsucker in the Iake were found to coincide closely with calendar years. Therefore, approximately 52 percent of the growth year had passed on the mean date of the catch. It was assumed that approximately the same proportion of anrmal growth had been achieved. Ttris was confirmed when mean monthly growth was determined (figure 8). Mean dates of collection of other samples were as follows: 1965 sample, mean date September 18, 261st day, 71.5 percent of calendar year; 1966 sarnple, mean date September 6, 249th day, 68.2 percent of calendar year; composite sample, mear date July 25, 206th day, 54.6 percent of calendar year; or composite sample, mealr date March 7, 1967, 948th day, 76.0 percent of sampling period; and Rio Grande sample, date October 16, 289th day, ?9.2 percent of calendar year.

Age ond Growth

Investigatlons of age and gfoutlh of river carysucker have been reported in 13 publications, theses, and state fisheries reports. Scale analysis was used exclusively in all investigations except one. Tbe combined reports included 51994 fish from six states. Twelve waters were dealt with specifically, including seven reserrroirs and five streams, with rezults frcm 3,636 fish. Forty percent (2,358) of these fish were reported in a composite group fmm the State of Oklahoma (Houser and Bross, 1963). River carpsucker fnom Oklahoma were collected during a period of 13 years as follows: 11 910 from reserrroirs, 18 from natural lakes, 11 frcm ponds, and 41g from streams. Eschmeyer g gl. $9441 collected 77 river carpsucker from Chicamauga Reserrroir, Tennessee. All were in Age Gnoup I.

Davis (1955), Brenzer (1956), Bucbholz (I957a and b), Bass and Riggs (1959), Jester (1962a), AI-Rawi (1965), and Rael (1966) tested validity of the scale method for determining age and growth of river carpsucker against criteria listed by Lagler (1956). Correlations between age and lengttr appeared to suggest validity of the method. However, all of these investigators fqrnd considerable overlapping among length lang€s of age groups. Younger age groups, uihich should give a better indication, were poorly represented in all collections except those from the Des Moines River, Iowa, taken by Al-Rawi (1965). In that collection, fish in Age Groups I and II showed close correlation between age and length.

Rrrkett (1957) apparently assumed validity of the scale method for his age-growth studies of fishes, including river carpsucker, from Salt River, Missouri.

Calculated growth histories are in reasonable agreement except for those reported by Huntington and llill (1956) for Elephant Bnrtte Reservoir, ffid Little (1964a) for

14 pecos River, New Mexico. Huntington and Hill used data from 19 fish and Little reported on 39 fish.

Rael (1966) tested scale and opercular bone methods statistically. Each method was found to be precise within itself, and computed lengths and increments were not significantly different except for Age Group I. On this basis, he presented tables of lengths determined by both methods and used the opercular method for all additional computations because of personal preference. The Lee (corrected direct-proportion) Method was found to be adequate in all instances.

The writers cited above concluded that the scale method and their computations were valid on the basis of agreement among calculated growth histories and persistence' abundance, and scarcity of certain year classes. Al-Rawi (1965) presented a critical evaluation of the scale method which demonstrated this validity and stated that this had not previously been done. However, several of the other cited writers had calculated body-scale relationships as linear regressions and had used the three listed criteria with similar results.

Le nglh Conve rsion

All length data used in this paper are based upon total lengths of fish. Many age- growth studies are based upon standard length and a few studies have been based upon fork length. Therefore, factors for conversion of data between the three methods of measurement are reported to allow comparison of findings. Length conversion factors are also important, p9I E, in taxonomic shrdies. Conversion factors are reported here for 1L8 river carpsucker from the Rio Grande (table 21, 517 from Elephant Butte Lake (tabte 3), and for a composite sample of 635 fish from both waters (table 4).

length (factor S) of 118 Table 2. Factore br convertrng total lergth to fork lengtl (&ctor F) and total length to standsd rlver carpeucker from the Rlo Grsnd€. Factor Factor Intenrallnmn N k k F Le s 0.792 100-199 38 138.4 126.8 0.916 109. ? o.797 200-299 ?0 239.6 219.2 0.915 191.0 0.798 300 + 10 318.4 291.9 0.914 254.O

S) 517 rtver Table 3. Factore br convertlng total length to fork lengtl (factor F) aDd totsl length to stsrdatd lengttr (factor of carysucker from Elephant hltt€ Ld

15 Table 4. Factore for convertlng total length to fork length (&ctor F) aDd total length to staDdard leDglh (factor S) of 635 rtver catBsucker fnom Rlo Grande and Elepbaat Brtte lake. AU Ssh tr iDterval 100-199 fmm the Rto Grande andaU flgh tn lnterval 500 + frcm Elephad htte t.o&e.

Factor Factor Iderval ln mm Lt rr F I€ s

1(X)-199 38 138.4 126.8 0.916 109. ? 0.792 200-299 L02 254.1 252.3 0.914 20t.4 0.792 8(X)-399 s22 859. ? 920.9 0.909 282.7 0.786 400-499 L72 441.0 397.1 0.901 348.1 0.789 500 + I 500.0 448.0 0.896 390.1 0. ?80

Grand meane 351. ? 318.9 0.90? 277.2 0.788

Vo lid ity

Carlander (1956) evaluated methods used in shrdying age and growth and found that recapture of tagged fishes had been the most-used method. Black (1957), Ricker (1958), and Woodbury (1956) found that measurement of tagged-and-recaptured fish was not an acceptable method because tags on fish sometimes inhibite growth. Hile (1941) analyzed use of length-frequency for age determination. He found inaccuracies in older age groups caused by varying growth rates of individuals which eliminated peaks of abundance of length groups. Most investigators agree that interpretation of growth rings on scales, vertebrae, otoliths, opercular bones, spines, and fin rays is the best source of information on age and growth of wild fish (Carlander, 9p. cit. ).

For many years, age and growth computations were made on individual fishes and mean lengths were computed from individual lengths. Van Oosten (1953) compared age-growth determinations made from means derived from individual fishes with determinations made fnom mean lengths and mean scale measurements of age groups. He found comparable results with the two methods and a major advantage in the latter method in that it reguires considerably fewer computations. Most investigators agree on use of this option"

Scales of river carpsucker are cycloid with a shape that is rather typical for catostomids. They are squarish to slightly recta^ngular with slightly nounded margins. The focus is medial in the horizontal plane and offset posteriorly in the vertical plane. It is located approximately one-third of scale length from the posterior margin of the scale. Primary radii usually uumber three to five, and secondary radii vary frrcm three to five in most fish and up to perhaps ten in a few older fish. This results in a scalloped anterior matgin. Scallops are uzually shallow to moderate. Boundaries between fields are rather sharply delineated and obvious. The anterior margin is more curved than other margins and is sharply defined dorso-laterally and ventro- laterally by rtshouldersff ufuich occur at the junchrre of the fields. Scales which are taken to be typical are horizontally symmetrical and occur near the lateral line. Common variations exist in the forms of one Itshouldertt being smaller, more posterior in location, or small and defined only by a slightly-recurved notch. Scales with one small trshoulderr usually occur away from the lateral line with the small shoulder away from the lateral plane. Shapes of typical scales and commonvaria- tions are shown in figure 3.

16 A B c Fig. 3. Common shapes of scales of river carpzucker from Elephant Butte Lake. A - above lateral line. B - near lateral line. C - below lateral line. Anterior field to left.

Circuli are numerous and appear to vary in width and spacing with a narrow, close form during cool seasons and wider during summer.

Annuli, at least in scales of river carpsucker from Elephant Butte Lake, are rather sharply defined and may be traced through all fields of the scale. Most of them consist of discontinuities in anterior and posterior fields, and of discontinuities with crossovers in lateral fields. Measurement of annuli is easily accomplishdd in anterior and lateral fields but would be difficult in the posterior field because discontinuities are usually broad, erratic, and sometimes converging in that atea. Scales from several older fish contained annuli which consisted primarily of crowded circuli containing intermittent discontinuities. These probably were formed during mild winters when water temperaftrres could have remained as high as 7 or 8oC (44.5-46.50F).

Lengths of scale radii may be determined in either anterior or lateral fields but must be measured consistently in either field when data are grouped, as they were in this study. Antero-median lengths were used to conform to traditional practice.

Validity of annuli as year marks was tested against criteria listed by Lagler (19b6): (1) annuli are formed yearly at the same time, (2) close correlation between computed lengths at time of annulus formation and empirical mean lengths at capture in younger age groups, and (3) proportional growth ofbody and scale lengths or other discoverable relationshiP.

Annulus formation was found to occur in a period of November through February. Lengths of scale radii between last annuli and margins were quite large during auhrmn. Scale margins became rather irregular in November or December and suggested that annuli might be forming. This appearance persisted through most of January and sometimes into Febmary. In late January to late Febmary, most scales displayed a definite annulus near the margin and small amounts of new growth were evident. This was found in scale samples taken during winters of 1964-65, 1965-66' 1966-67, and was

L7 being repeated when scale collection was completed on December 31, 1967. firerefore, it is concluded that annuli formed at approximately the same time each year. Time of annulus formation is discussed in greater detail in a section on monthly growth.

Body-Sco le Re lof ionsh ip

Proportionality of increments of body and scale lengfh is shown as body scale regressions (figures 4-?). The sample from the Rio Grande and each annual sample frpm Elephant Butte Lake were treated separately, so that separate age-growth studies could be validated and so that the focal intercept, which is used as a conection factor in the Lee (1920) Method, would be more precise for each sample. Fish were grouped into 25 mm (l-inch) intenals of length ranging from L00-L24 mm (4-5 inches) to 500- 524 mm (19. ?-20.6 inches). Mean length of magnified anterior scale radius was plotted against mean body length of each group. lbese plots demonstrated that relationships were linear for all samples and were subject to the linear regression formula X = a + bY. L and S were substihrted for X and Y, respectively. Thus, the following formula was used: L=a+bS when L = mean total length of group S = mean anterior scale radius of group a = empirical constant (L-intercept) b = empirical constant (slope of the line) Empirical constants ttsrr and frbtt were determined as follows:

, when N = number of data groups,

and a=i-bE Each plot was adjusted by computing mean total length (L), and regression lines were constr:ucted by connecting the adjusted plots.

Coefficients of correlation were 0.954 (figure 41, 0.990 (figure 5), 0.989 (figure 6), and 0.988 (figure ?) (r formula after Mendenhall, 1963).

Liner relationship with close correlatlon demonstrates pr.oportional increase in body lengths and scale lengths. The L-intercept, empirical fratt, serves as a correction factor for computing length at annulus formation in the Lee Method (corrected direct- pnoportion).

18 Scole Rodius rn mm h 50) Scole Rodius rn mm (x 50)

L=o*bS L=o+bS = 2350 + 078 S = 73.91 + lO5 S

200 r00 Body Length in mm Body Length in mm Fig. 4. Relationship of body length to Fig. 5. Relationship of body length to scale length of 205 river carp- scale length of.275 river carpsucker from Elephant Butte sucker from Elephant Butte Lake, 1965. Lake, 1966.

Scole Rodius in mm (x 50) Scole Rodius in mm (x 50)

L=olbS L=o*bS = 2870 + = 22.86 + 1.22 S

100 Body Length in mm Eody lenglh in mm Fig. 6. Relationship of body length to Fig. ?. Relationship of body length to scale length of 118 river carp- scale length of 1' 874 river sucker from Rio Grande, carpsucker from ElePhant October 16' 1967. Butte Lake, L967.

19 Age-Growth

The basic formula used to express direct proportion br computation of mean length at time of annrlus formation is: r*=* o rt st when Ln = total length of fish at formation of any annulus It = total length of fish at capture Sa = length of scale radius fnomcenterof focus to annulus corresponding with L1 ft = total length of scale radius at caphrre This formula is restated as: r'=T-,sn (rt) then corrected to - a) Ln=--3-+a,%(t't where tfa't is the L-intercept derived from the body-scale regression (figures 4-7). Some authors have interpreted frarr as length of fish when scales are formed. This interpretation is questionable in view of tfarf values rqnging from 22.9 $igare 7) to 73.9 (figure 5) in this study and frequent occurrence of negative values in other studies. It is difficult to follow a hypothesis that a negative value of rtail represents length of scales when a fish is formed. However, such difficulties are overcome by interpretation of Itart as a comection factor necessary to establish direct pr:oportion between body length and scale length. Extent of imbrication may be involved.

In application of the Lee formula, fo is represented consecutively as 51, fu, ... Slgr cofresponding to lengths of radii from center of focus to Annulus I, Annulus II, . . . Annulus X. Corresponding lengths are designated as L1, LZ, .. . LLg.

Mean lengths at formation of each annulus and mean annual increments of growth were computed for each age group of river carpsucker represented in the sample from the Rio Grande, the three annual samples, and the composite sample from Elephant Butte Lake.

Rezults of analysis of data from 202 fish taken in 1965 are shown in table 5. Table 6 shows results from 275 fish taken in 1966. Discussion of sex ratios, relative and maximum longevity of the sexes, se:mal dimorphism, and strength of certainyear classes in these small samples would be misleading although lengths and increments of growth are reasonably similar to most of those found in the large 1967 and composite samples.

Only 80 (L6.7 percent) of. 477 river carpsucker taken in 1965 and 1966 were younger tha-n Age Group III. Scarcity of young fish in samples may indicate scarcity of young fish in the lake, or may reflect inadequate sampling of young age groups. Observations at Conchas Lake, New Mexico (Jester, l962al, Canton Reservoir,

20 Table 5. Age-growth of 202 rlver carpeircker fnom Elephant Butte Lake, August, 1964, through December, 1965. Lengthe tn mlllimeters aad welghta h grams.

Year Class Soc N

L96l+ do ?2 L49.3 d? 10 153.9

1953 d6 r3t+.9 2s6.7 c4 t29.7 29t+.3 d8 2l+ L33.5 290.3 7962 d30 128.1 2l+7,2 3l+3.2 918 t28.9 ?/{,8.9 35L.O d? 70 t3I.7 251+.1+ 3l+8.9

t967 d ]'l+ L2L.2 234.9 333.3 377.9 915 LL3.r 230.2 322.0 372.7 d? 5L r?o.L r,L.L 3L8,6 371.2 1960 d10 119.1 226.3 3L5.9 363.2 40O.5 910 L32.3 250.0 323.3 364.2 t+O3.4 4? 32 722.8 227.t 320.7 362.9 395.0 1959 do ?2 91.0 L92.3 27?.7 3L7.t+ 359.r l+o2.8 4? 11 108.1 2Ot+.5 291.9 353.8 3st,9 399.2 7958 Jt 119.0 2J4:O.L 295.2 3Z+.5 36t+.9 390.6 t+t5.3 ?o d9 2 112.0 226.6 288.0 333,8 381.3 3e6.3 408.1 195? d0 2t6.2 356.9 435.0 h55.9 4sl.r 5L3.2 5l+l+.1+ 553.2 4? 1 216.2 356.9 t+35.O t+55.9 497.1 513.2 5t&.4 563.2 7956 4 0 J? 1955 d0 91 69.9 L26.3 235.8 270.2 303.4 333.9 35r.8 38t.7 LOe.2 436.7 d9 1 69.9 L26.3 235.8 270.2 30).t+ 333.9 35L.e 34.7 [email protected] t36.1

Nrmbers: 65 6L 55 25 11 11 o 00 o 5t+ 52 48 30 14 42 z 11 d9 n2 !92 158 98 t+7 154 2 11

Grand mean: l,engths: t25.6 z+3.t 334.8 369.9 397,3 3n.6 4L6.3 0 !%,8 2M.4 331.9 365.3 395.9 t+L3.2 338.1 t+72.5 408.2 l+35.1 d8 I27.1+ 2l+1+.7 329.7 365.9 392.e 400.7 428.1 I+72.5 408.2 t36.L lncrqnents t25.6 117.5 97.7 35.1 zt.4 - 6.7 25.7 I L?4.8 tr9.6 st.5 33.1+ 30.6 t7.3 3l+.9 M.l+ - 6t+.j 2i.t+ ,JO r27.4 1L7.3 85.0 36.2 26.9 7.9 2?.4 M.t+ - 6t+.3 23.4 Weights t 38.5 205.0 t+6o.t+ 592.3 709.6 6lg.l 798.6 I 38.O 291 .8 l+5o.t+ 537.9 6gg.z 7$.6 961.8 r.099.8 759.8 898.1 2Q 40.0 208.5 ti+2.9 5?6.3 5e9.5 725.t 857.0 1099.e 759.e 898.1

fncrqnerrts 3e.6 166.4 255.4 t3t.g tr7.3 .- 29.9 118.9 o 38.0 L59.8 2t+2.5 st.5 L61.3 64.4 178.2 138.0 -340.0 138.3 ,JA ,l0.0 168.5 23t+.4 133.t+ L13.2 35.6 r31.9 2J+2.8 -340.0 L38.3

2L Table 6. Age-grtrvth of 275 river carpsucker frrom Elephant hrtte Lake, 1966. Leryths tn mllltmetere and welghts ln grams.

Iear Claes Sex N

t955 d0 90 d? 15 rn.2

1964 d9 152.2 271.3 ?3 Ltil.3 2til.8 d? 30 150.8 268.9 1963 4Lt L5t.5 2l+8.1+ 339.0 ?7 t66.3 lfl .o 3t+4.8 d? 4 151.0 25t.2 3\1.9 1962 d28 ll+9.7 248.2 336.8 376.5 ?23 141.8 236.5 327.6 3?6.3 d9 52 LI+6.2 W.9 334.9 3?7.e

t95t 428 Lt+9.7 251.3 326.2 369.2 &!02.3 ?26 Ln.L W.6 330.2 373.t ,p4.o d3 69 148.8 2t14.O 326.6 370.8 l+O2.1+

L9& d5 t53.4 27L.O 33t.8 35?.3 39t+.O Lte.7 920 L36.3 245.t 328.8 3?O.t 398.L l+o5.t d9 3L 146.6 23?.9 323.9 366.0 394.t I+18.6

19'9 43 tn.5 237.e 328.5 358.8 389.4 l+13.9 1rJ3.8 ?7 w.o 2t9.o 29/0.6 3l+1.9 379.e 411.4 L+35.7 d8 17 r4t.9 22L.7 295.L 3t+o.6 376.O N6.5 rA9.8

1958 d3 148.0 2t3.7 ?95.3 354.6 393.! 408.3 U3O.4 4n.7 ?6 L33.4 2t9.O 308.7 349.3 3&.5 t+o3.7 430.8 t+5t+.3 d9 L2 L35.9 2tO.? 29t.O 339.5 37t.3 396.2 I&L.I l+46.? t9n do 94 136.8 218.0 4?.e 322.t 3:*.2 3cL.t 406.4 tC9.9 t&8.4 4? 6 145.8 2t5.9 269.7 3L3.O 39.3 3&.0 t+Lo.2 /|,5.3 |fi.6

t956 d2 tt5.7 L53.7 225.2 259.1+ 290.8 324,1+ 356.4 394.1+ t&3.L t&9.2 90 4? 3 117.0 tfl.2 2L6.6 254.5 297.3 3U.5 3tC.7 377.O 409.0 I+35.5 Ilhr&ers: d 89e8 80694113e5 zz o 969693&633?1710 40 d9 275 29 229 20o L38 69 38 2t 93

Grand meen: Lengths d 150.1 2l+9.L 328.1+ 367.7 393.5 400.6 4L3.L rag.t rc3.r M9.2 I w.7 2t&.L 323.7 366.6 394.0 w3.t+ w.o ttA.5 /l./q.B.l+ d8 Ll+?.\ 21t2.2 323.2 367.2 3q.6 I+O3.5 t+33.t+ w.? t35.5 '+18.O Increnents d 150.1 gg.o 79.3 39.3 25.8 7.L 72.5 L5.O - 5.O 25.t I !l+6.7 93.1+ 93.6 tc.9 n.4 9.1+ 23.6 L7.5 3.9 d9 Llil .t 95.L 81.0 1t4.0 22.1+ 14.0 L4.4 15.4 7.3 - 5.2 lfeights d 36.4 t?5.t 4L6.4 5gl .o 73t,L 773.O 850.6 9fr.5 9t5.3 rto3.9 33.9 Lr|.L 1C7.7 5e6.5 73t,.t 790.0 9re.9 1068.5 1O98.0 4? 3l+.2 161.4 396.2 589.5 708.9 79L.2 8&..5 9C1.6 1Or,O.3 [email protected] Increments 36.4 L39.7 2l+O.3 170.6 11tl|.1 41.9 77.6 99.9 - 34.2 tgl.6 o 33.9 t23.2 270.5 158.8 LW.6 55.9 L52.9 t25.5 29.5 d8 34.2 L37.2 234.8 L93.3 tr9.4 Q,.3 91.3 105.1 52.7 - 37.7

22 Oklahoma (Buck and Cross, 1951), Tenkiller Reservoir, Oklahoma (Jenkins et al., lgb2), and in an earlier investigation at Elephant Butte Lake (Rael' L966), suggested that most spawning and early life history of river carpsucker might occur in tributary streams, on the basis of (1) poor representation of young fish in lake samples, (2) observed upstream spawning runs, and (3) presence of large numbers of small fish in tributaries throughout the year. When this is considered, it is possible that small numbers of fish in Age Groupq 0, I, and II in samples may be representative of the population in the lake. Therefore, it appeared that young fish in the Rio Grande and older fish in Elephant Butte Lake might constitute a continuum. This would conform to the conclusion reached by Jenkins et {. gP. cit. ) that most river carpsucker pnobably spawn in tributary streams and that young fish tend to remain in streams until they are two years old, then migrate into the lake.

Because of this possibility, a sample of 118 river carpsucker was taken firom the river upstream from the lake in 196?. Thirty-five of these were in Age Group 0' 5? were in Age Group I, 25 were in Age Group II, and one was in Age Group trI' Mean lengths at time of annulus formation, grand mean lengths, and annual increments of length are shown in table 7.

r-engtnslnmllllmetereandwelghteln Table?. Age-growthof BgrlvercarpsuckerfrcmtheRloGrande,october16, 196?. gram8. : : :: -- = claessexNTnnt 126.8 1966 d 22 ? 26 128.1 d9 57 123.5 105.1 220.0 1965 d 11 9 t2 105. ? 246.2 d9 26 105.3 292.L 327.O d I 92.5 222.2 o 0 i9 I 92.5 222.2 327.0

L2 1 Numbera: 4 34 o 38 t2 0 d9 88 26 1 Grand mean: 118.8 220.2 32?.0 Lengths d 9 11?.6 246.2 d9 11?. ? 231. ? 32?.0 101.4 106.8 Incremente 4 118. E 9 11?.6 L27.6 d9 Lt?.7 114.0 95.3 136.6 438.9 Wetghte d 20.7 I 20.o 184.1 d9 20.t 166.2 438.9 115.9 302.3 IncremeDtg d 20.7 20.0 164.1 d?

23 Comparison of lengths and increments of 83 fish in Age Groups I-[I in the river sample with data fnom L,394 fish in the 1967 ssmple from the lake (table 8) reveals that river and lake fish in each age group grew at different rates. Further comparison of fish in the river sample with data fnom 1,871 fish in the composite lake sample (table 9) reveals different rrrcan lengths at annulus formation and similar grand mearr lengths for Age Groups I and III. Grand mean lengths of Age Groups I-Itr in the com-

Table 8. Age-grcrvth of 1,394 rlver carpercker from Elephant Brtte Lalre' 196?. Iangtha tn nllltmetera and welghte la grama.

Ieer Class Sex l{

tw 4 3l+ Ll+5.8 9 t+3 L30.6 d? 94 L3L.t+ 196j d2oL 115.0 a).6 ? !97 105.0 zlL.3 d9 4n LO9.3 zlr.) t96t+ 4?7 t?o.2 250.0 333.9 e67 114.1 z)2., 36.5 4? L55 116.8 u'o,6 32e.6 196) d6? LLz.5 zt|.e 330.2 376.4 918 L2L.7 w.o 3rt+.9 4L2.O d9 t% 11?.0 8e.6 34r.8 3%.4 L96z d 106 115.0 229.2 t25.e 36r.5 9n.2 c 102 tt6.3 z116.o tt+6.4 )91.5 4*.2 d9 W 115.8 z)7.o )36.0 37e.4 l+lL.5 t96t 4n rL?.6 255.1 95e.O 363.2 394.2 4t7.2 9yJ [email protected] zzt.6 326.1 36e.6 403.2 l+3O.3 d9 rT) LL3.2 24.5 32r.t 366.0 3n.o l+Z+.2 1960 dzl 1 l.3 n3.5 2t7.8 33t.L 37L.L 401.5 1429.1+ e l+6 LLI+.2 /)L.3 t?oJ 360.3 39t.t+ L?o.6 M5.\ d? 74 111.6 221.t 3Ot+.3 3t+9.1 3c).7 4t3.5 439.3 t959 4z) 109.6 N).2 8.L ye.o 37r.t 409.9 t+8.6 45o.8 925 104.? ?05.2 zfl.e 345.t+ 37e.8 t+LI.1 t38.3 450.0 49 4A 1O7.0 204.2 2y).3 34r.9 377.1 410.9 438.0 460.t+ L958 d8 %.9 L*.4 %7,o 312.5 3t$.t t?7.7 403.5 42t.6 \53.1 911 10o.7 Ly).e 214,7 321.9 35r.5 39L.U \t6.5 U+2.8 460.8 49 L9 99.1 L94.9 ztL.5 3t7,9 312.4 38r.7 411.1 t+34.4 Lr't.6 19r7 d2 66., L27,8 2t8.6 M.8 3z).5 346.2 36t.8 39t.O ho6.9 457.4 93 &.2 L3r.6 23t.6 3s3.3 32J+.o 363.L 39t.7 r+t7.6 tl+r., |n.o d9 7e.r 132.4 z)o., M.3 38.9 316.2 3&.3 4o5.8 t+4.7 466.7 ' lftnbers: d 62+ 590 38 3t2 2J+j t39 60 33 10 2 ? 9 645 &2 W5 338 28O t78 85 39 14 49 1,391+ 1r30O 81O 65/.+ 58 3t9 116 72 Z+ 5

Grard nean: Lengths 4 Lr6., 25t.6 3Zl.t+ 3&.3 t89.r [email protected] t+z).5 448.5 U+3.9 457.\ ? LLO.2 2r3.t 330.9 3?8.0 404.8 t+2t,6 $7.7 45t.9 457.' |tD.o d9 tt3.6 247.9 32r.6 )69.6 )n.4 t+t6.4 133.2 t49.e 45L.8 t 66.7 Incraentg d 1t6., r}r.t ?r.e 32.9 a.8 n.6 9.8 25.O - 4.6 13.5 I 110.2 u+2.9 77.8 til.L 6.8 16.8 16.1 u+.2 j.6 Lj., 4? rr3.6 134.3 7?.7 44.o 27.8 19.O 16.8 t6.6 2.O 14.9 Telghta 4 17.5 19t.3 t+2L.6 566.3 7L7.7 et+I.3 y)t.1 1,111.9 LrOT?.t 1r181.3 I L4.? 190.7 t+35.6 616.5 810.? 916.9 L,O3L.4 r,t3O.3 I,L82.L t'Jop.9 49 L6.2 178.9 414.5 6t2.5 ?65.9 684.4 999.L 1,121.8 L,r37.3 L3r6.9 Incraente d r7.5 L69.8 z)4.3 tr.4.7 L5L.t+ !z).6 9o.4 180.2 - 34.8 rO4.2 o L4.7 L76.o 44.9 2rO.8 L54.3 106.2 LL2.' 98.9 jL.8 t27.8 d9 L6.2 1:62.7 235.6 198.0 t53.t+ 118.5 tLL.? t22.? $.5 rt9.6

24 posite sample are based on 1, 20T to 1,8?1 fish in Age Groups I-X compared with 1' of iO, uod gB fish in Age Groups I-III fnom the Rio Grande. Therefore, similarity grand mean lengths of Age Groups I and III are probably coincidental rather than comparabte with those in the river sample.

Lake, August, 1964' thrtugh Table 9. Age-growth of a composlte aample of 1,8?1 rlver caryeucker fnm Elepha.nt Hrtte December, 196?. Lengths in mllllmetere and welghts ln grams'

Sec< N trr 43b L45.e ?\5 t3L.4 d? rn L35.8 d 216 117.1 293.2 9 2ol 106.1 nt.4 49 ,t& tr2.7 215.6 d 118 tzr.t A9.r 336.7 ?92 121.0 Z)9.r 332.7 d9 2rj L2J+.8 245.6 335.7 4 LO9 rz).2 7)8.3 332.3 376,6 997 t25.O 49.L 3t+3.O 397.O d9 239 L25.3 89.o 33r.L 3e4,6 4u& L22.O 233.3 325.2 366,t 398.4 I 138 L24.2 2+5.7 341.7 386.r 42o.4 J9 3ro Lz).g 236.9 332.3 37r.1 \a7.e d84 LzoJ 256.L 356.4 363.4 394.2 4t7.3 9 115 Lt5.3 23O.O 325.7 968.0 423.5 423.' d9 2r, 118.0 2?9.L 32?.2 36r.t+ 397.7 122,\ 43L 111.9 2O8.O 2s).3 333.6 372.7 t+o2.h 429.1+ 229.7 116.2 357.9 3e9.9 4t9.t+ u&.1 913 rL7.9 t$6.9 4? 93 117.2 221.3 302.3 9t+7.3 382.2 411.6 426 114.0 N+.4 289.t 339.9 376.0 [email protected] l+28.8 t+59.6 932 tr3.6 212.2 3Ot+.L 3l+9.6 382.' 4L3.t+ 440.2 462.2 4? 6t tL\.5 208.0 295.2 3t+3,3 377.8 [email protected] t+37.o 4r9.t+. L96.t+ %7.o 3L2.5 3t+8.r 377.7 4c3.5 l+27.6 \53.r t8 96.9 t$9.4 l+57.5 I 15 110.3 [email protected] 275.5 322.0 3r5.2 388.7 4r3.8 d9 2' uo.3 L99.9 27L.1 )t6.7 311.9 38\.9 41O.9 t.J,4.6 457.t+ 160.L 392.7 415.0 t+53.3 d4 91. 1 140.8 22L.9 Zt3.I 3vt.2 335.3 t+$.e 82.1 t33.3 232.7 295.0 3L8.9 35r.e 3er.7 406.6 /4,6.2 94 t9l+.I h2o.4 t+52.9 d9 9 w.2 li+O.O 226.' 275.L 3o9.t+ 339.8 364.6 12 4 lfunbers: d 77\ 7l+O ,24 406 297 r53 69 3e 357 2Lg 1O4 5L L9 4 79' 750 5t+6 4r4 t d9 1,871 tt751 1,2u7 9r2 7L3 4o3 188 9' 34

Grand mean: l+53.5 250.6 362.t 390.0 408.8 t+r8.3 l+l+r.8 440.4 Lergths 4 r2r.L 328.3 t+63.8 o 250.8 375.0 to2.6 418.4 n6.2 t+5r.3 4r3.o fl5.6 )29.8 l+52.9 49 120.0 2L6.7 )25.7 368.7 39r.6 4t3.6 430.0 tl+6.7 l+l+7.6 129.5 33.8 27.9 18.8 9.' 27.5 - 5.1+ Lj.t Increnents 6 L2t.r 77.7 10.8 o 27.6 1t.8 17.8 L5.L L.7 tt5.6 t35.2 79.o 4r.2 ,.3 d? 120.0 t26.7 79.O t+3.o 6.9 18.0 L6.4 L6.7 0.9 852.4 Ltyl2.5 Weights d 24.6 tn.t t+26.2 564.L 69't.5 798.L L,O2L.6 9C1.6 t97.) t+3t.8 64.5 764.0 852.9 960.9 r:o59.2 1,0r/o.6 1,L45.2 2L.5 L|O28.6 It03lr., 1'069'9 49 23.9 L88.2 4t6.6 59t+.O 726.6 825.2 922.3 169.2 84.? Increments d 21+.6 t74.5 22'.t.r l37.9 L33.t+ 100.6 ,4.3 - 34.o 2t.5 L75.8 234.5 r9t.7 !t+o., 88.9 108.0 gea 11.4 7t+.6 764.3 228.t+ t77.4. ]32.6 98.6 97.L 1c6.3 34.4 4? 23.9 '.4

25 Another factor to be considered in determining affinities of young river carpzucker in Rio Grande and Elephant Butte Lake populations is an increase in numbers of young fish caught in the lake during 1967. Ages of 1,400 fish were determined, A total of 590 (42. 1 percent) of these were in Age Groups 0-II, including six young-of-the-year specimens.

This large sample of young fish from the lake and different growth rates found in fish from the river and lake indicate that populations are relatively discrete. This agrees with findings by Brezner (1956) that spawning occurred in Lake of the Ozarks, Missouri, and young-of-the-year fish were numenous dnring the summer. River carpsucker also spawned in Conchas Lake, New Mexico, along with upstream spawning migrations (Jester, I962al.

Scarcity of river carpsucker in Age Gnoups 0-II in 1965 and 1966 collections probably resulted fnom sampling error rather than from scarcit5l of young fish in the lake. Martin et 4. (1964) found that young smallmouth buffalo formed schools by age (or size) groups and were relatively sedentary until ttrey reached two and three years of age. It is possible that this phenomenon also occurs in the closely related river carpsucker. If so, small samples prcbably would consist largely of older, more mobile individuals rather than sedentary young.

Sental dimorphism. Grand mean lengths at time of annulus formation and grand mean anntral increments of growth were calculated for males, females, and all fish in each age group. Grand mezn lengths of males and females vary little from each other. Therefore, serntal dimorphism does not occur in terms of growth rate. Indications of dimorphism in terms of weight are shown in table g. These computations were made on the basis of length-weight relationship and are discussed in that context.

Month ly Growth

Mean gnowth which had occurred since annulus formation was computed for each age group in the portion of the composite sarnple taken during each month. Years were disregarded, and all fish taken during each month were grouped by age so that mean growth for each month is representative of that month for the entire sampling period.

AU fish taken in the gaynple fnom the Rio Grande were taken on October 16, 196?. Current-year gnowth was determined as of that date, which represents the 289th day, or 79.2 percent of the calendar year (table 10). firese data are compared with October growth data of Age Groups 0-Itr from Elephant Butte Lake (table 11). Fish in Age Group 0 achieved more growth in the river than in the lake, while fish in Age Groups I-I[I achieved less growlt in the river than in the lake.

Mean total growth since hatching (for Age Group 0) or annulus formation (Age Groups I-X) was determined for males, females, and total collections of river carp- October 16' Table 10. Growth since hatchtng or lormation of last anmrlus of 118 rlver car?sucker from the Rlo Grande' 196?. Ienglhe in mllllmeters'

Year Age L€Dgth at I*ngth at Growth Class Group Sex N Last ADnulue Caphrre 133.5 133.5 1967 0 r! 35 0.0 229,6 102.8 1966 I d 22 126.8 o 26 t23.1 229.8 106. ? d9 57 123.5 229.6 106.1 293. 1 7t.l 4 11 222.O o L2 246.2 276.6 30.3 {? 25 232.L 283.9 51.8 1964 III d' 1 927'0 360'0 33'0 g0 d I 1 32?.0 360.0 33' 0

Age 0-III from Table 11. Groq/th alnce hatchrrE or brmatlon of laet almrlue uDttl October, of rlver caDsucke! in Gnoups Rio Grande and Elephant htte Lake. Elephant hrtte Lake data taken fnom table 14, A throwh D. Iengthe in mllllmetere.

Mean Growth of Age GrcuPe OIIINI 33.0 Rlo Grande r33.5 106. 1 51.8 48.3

sucker in each age group for each month frcm the lake (table 12' A-K). Data from males and females, treated separately, were not analyzed further because of small samples.

Cumulative percent of total annual growth, monthly growth increments' and percent of aanual growth achieved during each month were computed for total collections of each age group taken during each month. These data are obviously not reliable in terms of specific lengths, increments, and percentages but appear to have considerable value in revealing trends in monthly growth of age groups. Grand mean lengths' increments' and percentages (table L2 Ll represent 1,860 fish and are considered to be more accurate than comparable data for each age group.

Grand mean percentages of annual growth and cumulative annual growth achieved during each month are shown graphicatly to reveal monthly and seasonal growth patterns of all age groups combined (figure 8). TWo peaks of gr"owth appear to oceur during the yeat, in spring and autumn. Growth is extremely slow in Jarruary and February' in- tr"ur"" rapidly in March, and reaches the highest rate of the year in April. It declines in May and, in this instance, appears to become negative in June.

It is unlikely that length of a fish actually decreases once it has been achieved. llhe apparently-negative increment appears to be caused by an increase from 37 fish in Age Groups II and Itr in May to 63 fish in these age groups in June. Fish taken in June had grown less si:rce annulus formation than fish taken in May, creating an appearance of a negative increment in grouped data. The large increase in slow-growing fish taken in June probably resulted from slower growing individuals reaching nettable

27 Table 12. Monthly growth of 1,860 rlver carpancker ln Age Groups 0-X fronr Elephaat &rtte Lake, August, 1964,thmugh December, 196?. Growth elnce formatlon of last anmrlug and monthly hcremeds ln mllllmeters.

A. Age Gnoup O l{ean total grvrtlr d t{ean total gront}r I llunber 4? 0 0 0 0 0 0 0 0 0 24 l{ean total grwtn 118.0 L2L.6 Percent tohf Brtrrth 97.O 100.0 (asguned) l{onth\y lncrenent 3.6 Percent annual grorth dur{.ng rcnth 3.O

B. Age Gmup I

l{ean total grwth 6 Q.8 141.1 Lt6.3 Lfi.t 158.9 ilean total grurth I t36.4 L*.8 t62.L L67.L l{uder d9 0 0 113 22L2U9U16 ltean total grouttr 12.6 14.9 35.5 ,&.3 W.3 9t.3 L36.t tr.r Lfr'.3 t66.4 Percent tot€I grtrth 7.6 9.0 2L.3 2t+.2 ze.t+ 54.9 81.8 92.O 98.1 100.0 l{onth{y lncrenent 2.3 20.6 4.8 7.O 44.O &4.8 fl.O rO.2 3.L Psrcent amual grorttt durd.ng mnth 1.4 t2.4 2.9 t+.2 26.t+ 26.9 tO.2 5.1 1.9

C. Age Group II

llean total grorttr d o 15.8 s6.o 66.0 41.5 37.o t+3.L 63.L 54.6 65.7 62.4 l{e,an total grwtn o r7.5 68.9 l+5.7 l+7.3 \4.3 l+5.3 6t.7 7r.o 73.9 74.t+

lfuriber d8 t7267 49 3L tA692 t+3 65 53 38 !{ean total grorth L.3 2.2 15.0 5t+.3 69.0 4t.7 t+t.3 45.O 62.9 70.9 7L.2 ?1.0 Percent total grorth 1.8 3.t 2t.t 76.3 96.9 ,8.6 58.0 63,2 6r'.3 9.6 100.0 Monthly lncrenent r.3 0.9 r2.8 39.3 t4.7 4t.3 - o.4 3.7 L7.9 8.O o.3 - o.2 Percent anrnlal grorth dur.Lng rcnth 1.8 L.3 18.0 55.2 n.7 0 O 25.L tL.2 0.t. 0 '.2 D. Age Group Iff

Uean total trorrt'tr 4 2.8 t?.7 t'6.i 9.t 4.9 36.e 29.5 ,L.6 33.o 1.4.4 49.1 Mean total grwth o 5r.6 11.8 54.2 35.2 rA.7 Le.3 9.o 62.9 \5.6

lfufrer d9 L7 166t36 t9 19 3t 25 32 28 t+9 llean total. gr"onth 0 r.3 n.7 48.6 45.t+ 33.5 43.o 40.4 9.8 48.3 53.5 52.6 Percent total grwth 0 2.t+ 33.L 90.8 84.9 62.9 80.4 75.5 95.o 9o.3 r.00.0 ilonthly lncrencnt 0 1.3 t6.4 3o.9 - 3.2 -Lt.g 9.5 - 2.6 1O.4 - 2.5 5.2 - O.9 Percent atrmral gtwth during rrcnth o 2.4 3O.7 o o L?.8 0 19.[ o 9.7 't.8 E. Age Grotrp fV

Mean total grorrth d0 o 18.9 23.3 24.O 22.7 30.6 23.4 33.6 8.1 28.3 Mean total grwth 90 o 7.7 17.8 20.1 22.8 34.7 31.4 33.3 51.' 3o.o 36.3

lfuder c9 3L 75 11 10 23 15 24 13 36 23 39 l{ean total grorrth 0 0. t 7.6 18.4 2t.? 23.5 25.o 30.6 28.0 4o.3 3r.9 32.? Percent total gtwth 0 I.2 19.1 45.? 53.3 ,e] 62.0 7r.9 69.5 100.0 ltonthly lncrenent 0 o., 7.2 10.9 3.7 1.8 t., ,.6 - 2.6 r2.3 - 8.4 0.8 Percent arurusl grwth durlng rcnth 0 r.2 t:t.g 26.6 9.2 \., 3.7 L3.9 o 3O.5 0 2.O

F. Age Group V

lteen totel grwth d0 2.9 7.6 L2.2 n.t Ll+.3 22.r 2L.O 20.6 20.6 2t+.4 25.9 Uean totel gtlrth 90 0 r4.7 L6.2 22.\ u.o 22,3 27.2 2r.9 27.t 27.2 lfunber d9 38 102 L5 L' 39 31 39 A?231+4 llean total grorth 0 0.8 7.6 13.6 L6.' 16.1 22.3 2t.t 23.3 2r.? 25.9 26.3 Percent total gorth 0 3.o 28.9 ,r.7 62.7 68.8 84.8 80.2 88.6 &..5 98.5 100.0 l{ontbly lncrenent 0 0.8 6.e 5.0 2.9 L.6 L.2 - L.2 2.2 - 1.6 l+.2 0.4 Percent anrnul grcsbh durd.ng mnttr 0 3.o 25.9 22.8 11.0 6.1 16.0 0 8.A. 16.0 T.' Table 12. (CoDtlDued).

Sex c. Age Group VI 1?.8 t4., t3.6 27.3 l,lean growth r.2 7.7 9.0 12.7 il+.2 t5.2 t5.7 total do 18.1 19.7 2l+.8 22.r Mean total grorth 90 o 5.3 11.6 14.O L6.5 2J.7 t2.4 20 L9618 Nunber d9 35 15 3 23 18 31 11 14 6.1 13.6 14.9 L9.5 14.5 L9.5 20.L 2L.L 22.8 Mean total growth 0.5 11.0 100.0 growLh 0 2.6 26.8 t+8.3 ,9.7 64.4 e5.' $,6 er.5 88.2 92.5 Percent total 0.6 1.O L.7 Monthly increment 0 0.6 )o) 4.9 2.6 1.3 4.6 - ,.o 5.o Percent anrrua1 Srowth 2L.9 2.6 l+.4 during month o 2.6 2l+.L 2L.5 11.4 5.7 2O.2 o

H. Age Group VII r4.5 16.3 rr.2 tr.2 24.8 L4.3 Mean total growth d00 14.0 17.0 llesn total grcwth 900 3.8 rt.3 7.5 Lt+.2 L2.5 12.3 26.' 16.9 n.3 ( T t+ g81O 48 Nunber d? 14 3r27 L7.3 grovLh L2.6 8.5 r5.t+ t3.9 r3.5 25.7 t7.2 L6.L Uean total 00 3.8 100.0 22.O 49.O @.0 8o.4 78.o 99.4 93.r Percent total Srowth 00 72.8 e.5 1.1 1.2 Monthly lncrenent 00 3.8 8.8 - 4.1 6.9 -r., -0.4 L2.2 - - Percent arucual gr^orth 0 6.9 during month 00 22.O 9.9 0 39.9 0

I. Age Grcup VIII

4.2 L6.3 9.t 16.0 L1+.9 Irlean total growth d00 9.7 t7.2 16.9 L4.2 Ueen total Sresth 9oo 8.0 9.6 Ll+.z I2.4 14.9 66 3l+ lfumber d9 10 9 o7 54 34 r4.2 llean total grorth 00 8.1 9.6 L6.3 L6.3 LL.5 t5.7 tr.g 18.9 growth 00 \2.9 6.2 &.2 51.4 83.1 84.1 100.0 Percent total o.2 l+.7 lilonthly increnent 00 L5 6.7 o - I+'7 4.1 3.O - Percent annual Srorth 1.1 0 during month 00 7.9 3r.5 oo 2L.7 rr.9

J. Age Group n(

llean total growth do0 9.6 8.7 ilean total grorLh 900 11.4 20.1 L6.7 15.5

Nurnber d9 9 4 0 0 400 321 Itlean total grcrth 00 10.5 15.5 t5.l+ lr.5 gmrth 67.7 1oo.o 99.4 10o.O Percent totaL 00 0.1 llonthly lncrement oo - o.1 Percent anrnral grwth during mnth 00 0.7

K. Age Group X

grorth 8.8 10.4 l,tean total d0 11.9 It{ean total grorth 9o 11.o lfunber d? 5 O 0 0 o 3L 1 grorth o 10.3 10.4 11.9 Ir{ean total 100.o Percent total grorth 0 *.6 St.,+ Uonth1y increment 0 0.1 Percent annual growLh durlng mnth o o.6

L. Composite Sample' Age Groups O through I

l,lean total grolrbh d Uean total gtorth I 2Ot d I 176 28 L3r 99 17) r55 24 162 21,2 L7l+ lfunber 92 r+g.n n.62 Mean total grorLh o.r2 L.o8 11.25 3t.cl 3t+.@ 26.L2 32.76 36.95 ie.67 i9.93 5t+.66 6t.66 e.63 97.90 100.0 Percent total gmrLh o.2o 1.80 $.77 fi.Le fi.8e B.re g.L5 t.26 Monthly lncrement o.L2 0.96 10.1? 20.62 2.22 - 7.97 6.64 4.r9 12.11 growth Percent annual 2.LO during nonth o.20 1.60 1,6.97 34.41 3.7 -t3,3 11.08 ?.0o 20.97 15.27 MJJA tvl0hltHs 0F THE YEAR Fig. 8. Mean annual growth pattern of 1,860 river car?sucker from Elephant Butte Lake, August, 1964' through December' 1967.

sizes after the sprurg period of rapid gnourth. June collections could have included a substantial number of slow-growing individuals taken from schools of relatively sedentary young fish which were not sampled earlier.

Ihe decline in growth rates during May and June coincides with, and may have resulted fnom, the peak of spawning activity.

Growth increased substantially in July and August, reached the autumn peak in September, decreased slightly in October, and was completed by the end of November.

Comparison of grorlrth rates in spring and autumn reveals a shorter growthperiod with faster gnowtb in sprlng and a longer period with slower growth in auhrmn. Separa- tion of the two periods pnobably results from a decline in growth of river carpsucker dunng spawning season. Autumn growth is terminated as a rezult of declining water temperature.

lee's Phenomenon

Leers Phenomenon (Lagler, 1956), which may be stated as f'slower growing fishes tend to live longerr', is generally evident in all samples fnom Elephant Butte Lake (see tables 5-9). It is obvious in grand mean lengths and increments when sharp declines in numbers reveal negative increments (see tables 5, 6, 8, and 9). Therefore, it may

30 be stated that Leef s Phenomenon is generally evident in river carpsucker from Elephant Butte Lake. It is most prorrounced in males in Age Groups II and VII and females in Age Groups II and VI (see table 9).

Leets Phenomenon appeared in the renge of Age Groups VI to VIII in all other sttrdies except those involving small samples and a large collection fnom Lake Texoma (Bass and Riggs, 1959). Davis (1955) compared computed lengths of the sarne year classes collected during two consecutive years and found that faster growing individuals tend to disappear from samples (interpreted as differential mortality) even during second, third, and fourth years of life. Rael (1966) compared growth rates and longevity from various shrdies, including his own, and reached a joint conclusion with this writer that Leets Phenomenon applies to separate populations of river carpzucker as well as within a given population. He felt that this accounted for at least a portion of the differences in longevit5l encountered in various shrdieg.

Growth Curves

Gnowttr curves of all fish in each age group (figure 9) support a previous state- ment that se>mal dimorphism does not occur in terms of length. Grand me'anlengths of females are consistently but only slightly longer than grand mean lengths of males.

Separate grovrlh curves for composite saynples (ta.ble 9) of each age group sometimes called absolute growth, are shown in figure 10.

Com po riso n

Grand mean lengths and annual growth increments of river carpsucker have been reported from eight waters in midwestem states, one in Tennessee, two in New Mexico, and fnom a composit" saynple representing the State of Oklahoma. Several authors used standard lengths and several reported results in English units. Ttrese data were converted to total lengths and to millimeters as necessarTf for direct comparison (table 13).

Laqgest fish and fastest growth were recorded in the composite sample from the State of Oklahoma. Mean length was 607 mm (23.9 inches) at formation of Annulus D( (Houser and Bross, 1963). Second-largest fish and second-fastest growth were reported f::om Conchas Lake, New Mexico. Mean Iength was 528 mm (20.8 inches) at formation of Annulus XV (Jester L962al. Difference between lengths of largest fish in Oklahoma and Conchas Lake was 79 mm (3.1 inches). When fish are compared at formation of Annulus D(, mean lengths of those fnom Oklahoma exceed those fnom Conchas Lake by 135 mm (5.3 inches).

River carpzucker from Elephant Brtte Lake were found to rank third in both size and growth rate among populations reported. Mean length at formation of Annulus X, the oldest attained age found, was 453 mm (17.8 inches). Fish from Oklahoma were

31 3 dg

-= I z u, z g: c z

I 67 ACE tx YEAI3 Fig. 9. Growth surves of river carpzucker fnom Elephant Butte Lake, New Mexico, August, 1964, thnougb December , L967 . Curves represent 774 males, 795 females, and a total sample of 11 871 fish.

?ro'rrrrlrryottt ol

t a 3 t a 3 a 3 a :a

AGE GIOU?S Fig. 10. Grourth curves of 11 871 river carpsucker in Age Gnoups I through X from Elephaat Butte Lake, August, 1964, through December, L967. 32 1b4 mm (6.1 inches) longer at formation of Annulus D(, and frsh from Conchas Lake were 82 mm (1.3 inches) longer at formation of Annulus X. Walburg and Nelson (1966) reported river carpsucker from Missouri River, South Dakota, prior to impoundment of Lewis and Ctark Lake, one mm shorter than those in Elephant Butte Lake at formation of Anntrlus X. Gnowth of these fish was much slower than growth of those in Elephant Butte Lake through eight years, then reached comparable length because of gmwth increments of 62 and, 27 mm (2.4 and 1. 1 inches) durrng the ninth aad tenth y"""". This suggests that rapid growth in the Missouri River dtrrrng the ninth and ienth years may be based on a small sample of dispnoportionately fast-gnowing fish. However, this is not known as mrnbers of fish used for computations were not re- 1rcrted.

at tlme 6f rnnrlue formatlon" Upper ltne ts length Tabte 13. Grand mean lenglhe and glowth lncrements of rlver carpaucker and lower llne ls lncremed br each water. $own ln milltmeters' Lcaltf

Blo Grarde 118 232 3Zl (Jeeter, nen clata) 118 11/+ 9'

Eleotrant Butte L. r2o W 326 969 96 414 t+39 ry! 448 453 (Jciter, ner date) L2OWn$zl1816t7t'

49,2 9e Conchas L., tl.ll. rE 2&. -3t+' 37s 414 t34 tr22 W2 4s1 ry2 7L 'io 10 11 7 5 (Jeeter, 1962a) +i ri2 'ss 6i 3L 3, 2t t? t3 10 '5\9 ',4

Pecos 8.. I.ll. rn 3o2 358 395 t+O4 (nttre,'1963) t[,It L55 fi 38 I

L. Texom. (kla. 91 L?2 239 3O2 36 3{L (Baas & niggs, 199) 91 81 67 $ 6t+ 15 6al State of Ck]-alrooa t35 zfl 328 37e \32 t$2 5r3 n? (ltorser a Bross, 1963) utl227tnx'.309L3915

t+t1 Des llolnes R., Ia. 74 t* 2s) 25t+ 2e4 312 332 3)2 (hchhols, 19tb) iiieflflio2820L372

Des l{olnes R.. Ia. 69 t32 r85 239 2sl 322 3t8 361 1n-narr, 1965) 69 63 53 5t+ 48 36 - 5 t+3

S81t, R.. llo. s1 160 2tg 267 295 338 394 37L (R[*eti, f9fl) 81 n5e4928t+3564

Perche Cr., llo. ?6 Lp 2t8 /12 3o5 3t+3 36e 39r 411 20 (Oavts, 1955) 76 74 66 33 3e 25 33 '4 L. Ozat*s. Uo. 7e 15o 2r3 259 42 328 3p 38L 409 W (Brezner,'1956) it ir dt t+6 33 36 22 3t 28 n

Leris & Clstk L.. S. Dek. 67 go 164 ?26 26 26 3L2 (fa:.uurg & l|elson, 1966) 67 As 5\ t?. 34 26 26

!{lgsour: R.. S. Dat(. 69 L4 180 23o 27o 3@ ltp 363 ta5 49 (tfaluurg & ilelaon, 1P66) 69605L94o3931236221

Chlckaruga L., Terut. Lrg (nschneyer et a1.r 1944) 119

33 Growth rates of river carpsucker frnom other waters in Oklatroma, Missouri, Iowa, and South Dakota were all slower than gnowth rates of carpsucker in Elephant Brtte Lake.

Grand mealr length of river carpsucker at formation of Annulus Itr in the Rio Grande is 31 mm (1.2 inches) less than grand mean length of river carpzucker at formation of Annulus III in Pecos River, New Mexico. Lengths of fish are essentially the same at formation of this anuulus in the Rio Grande, Elephant Br,rtte Lake, and the composite sample from the State of Oklahoma, Fish from all other waters are much smaller than these at three years of age.

It is concluded from these data that, in general, fastest growth of river ea{p- sucker occurs in Oklalpma near the geographic center of the range. Growth rates decline slowly in waters to the southwest and progressively faster in cooler climates to the nort}east and northwest. This is well demonstrated by comparison of growth currres selected as representative of the rarge (figure 11). Curves fall into three groups, with the composite sample fmm the State of Okla^homa comprising the fastest- growing gnoup. Ihe second-fastest-gnowing group consists of fish frpm Conchas and Elephant Ertt€ Lakes, New Mexico; Pecos River and Rio Grande, New Mexico; and Lake Texoma, Texas-Oklahoma, all located southwest of the center of the range. the slowest-growing group consists of fish from Lake of the Ozarks, Missouri, and Des Moines River, Iowa, located progressively to the northeast, and Lewis and Clark Lake, South Dakota, to the northwest.

Survivo I ond Mortolity

Martin, Auerbach, and Nelson (1964) presented a longevity study of smallmouth buffalo with results which are reciprocal to mortality rates found with a time-specific life table. Rael (1966) found longevity data preferable to mortality data because relative strength of year classes is shown by survival rates and not shown in life tables. The longevity study.was based upon a method for determining mean survival rates of fish in a population from hatching (or any age group) through subsequent age groups to the oldest attained age. Srrvival is expressed as mean number per 1,000 fish which survive into subsequent age groups. They assumed that sampling is adequate so that age-frequency in the sample is representative of age-frequency in the population.

Number of fish surviving into each age group from 1,000 fish one year younger is erpressed by the formula fu=ts*so-l t when Sn = $rrvival as number/1,000, at attained age Sn-l= Survival as number/Lr000, one year earlier Nt = Number of fish in any year class Nt+l= Number of fish in the succeeding year class

34 E E

=a t9 z ul z gl : o z a I

| 2 ! a 5 6 7 E 9 lO 11 12 t3 l1 I5 AGE IN YEARS Fig. 11. Growth curves of river carpsucker from Rio Grande, New Mexico (RG); Elephant Butte Lake, New Mexico (EB); Pecos River, New Mexico (PR); Conchas Lake, New Mexico (C); Lake Texoma, Oklahoma (T); State of Oklahoma (OK); Des Moines River, Iowa (DMR); Lake of the Ozarks, Missouri (LO); and Lewis and Clark Lake, South Dakota (L&C).

35 To determine survival rates of 1,000 fish hatched, the formula is recursive (applied sequentially) as follows: Nt*t sr= x 11 000 for number of 1,000 fish hatched which survive to Nt , enter Age Group I.

s2=p , for number of 1,000 fish hatched which survive "s, throt'gh Age Group I to enter Age Group II. N**, sr=\-*st-l for number of 1,000 fish hatched which ' survive through all age groups to attain ma:

A small error may be inherent in ft in that one fish is arbitrarily added to the sample to represent an age group one year older than the oldest group achrally represented. This hypothetical fish functions at N1..1 for computation of survival rate of the oldest age group. However, such fish might be assumed to exist in a population in such small numbers that they are not taken in samples. $rch an assumption is not completely unwarranted in view of known limitations of sampling gear which require an assumption that one or more younger age gnoups are not adequately represented in a population sarnpl€. Alsor- older fish have been taken from other waters (see table 13).

Mortality is expressed by the formula

M 1,000 S = - n

when M = Cumulative mortality as number/l,000 fish s $rrrrival rate of any given year class n =

Since this sequence of computations begins with a time-specific determination of survival, it was anticipated that sunrival rates should be reciprocal values of mortality rates as determined from traditional time-specific life tables. This was tested with hypothetical examples and found to be a eorrect assumption (Jester, 19?1b).

For this sfirdy, survival and mortality rates were determined from 1' 394 river carpstrcker taken dunng 1967 (see table 8). This annual sample was used because it is the largest, and therefore more representative of the population in Elephant Bqtte Lake than the smaller samples taken during 1965 and 1966, The larger composite sample was not used because fish could not be assigned to year classes to show relative year-class strength.

Age Groups 0 and I are inadequately represented because of limitations of gill net meshes used for sampling. Therefore, survival and mortality rates were computed for Age Groups tr through X, based on 1,000 fish which reached Age Group I,

36 rather than on 1,000 hatched. Results are shown for 624 males (table 14)' 645 females (table 1b), and a total sample of 1,394 fish (table 16). Low rates of survival and heavy mortality found for Age Groups II and III may have resulted from inadequate sampling of two and three-year-old fish. However, trends in numbers of fish in Age Groups II through IV may indicate weak year classes after 1963. High rates of surrrival in Age Groups IV and V indicate stnong year classes in 1962 and 1963. This tends to substantiate weak year classes after 1963, wtrich would result from high population density and biomass of fish four years old and older. Computation and interpretation of data beyond sunrival rates and strong and weak year classes are original work based upon survival tables constructed after the method of Martin et al. (1964).

grrvlvtlg Table 14. Mean anrlval (S) and rnortruty (M) rat€s per lr(xxt male rlver carperucker la0oAgeGroup I ln Elephad hrtte Lalce. Ftah taken durtng 196?.

Year Age Clasa N s M 0 1966 I 84 1,000 617 1966 II 20r 383 66? 1964 IU 71 333 415 19G3 w 61 527 60? 1962 v 106 893 -s... rez fr... esa

1961 VI ?9 134 866 886 1960 VII 27 114 960 1959 uu 23 40 990 195E Ix E 10 995 1957 x 2 D lbtal nrmber Wetghted gtand meane

tnElephant Table lS. Me.o aurlval (S) and mrtallB (M)mte6 perlrOoOfemale rtver ca:pancker arlvlvhg tdoAgeGloupl Butte Lake. llah tdren furtn8 196?.

Year Age Class Gloup 0 1966 I 49 1,000 660 1965 tr 197 840 706 1964 III 61 294 483 1968 Iv 58 51? 629 1962 v toz 47r 161 1961 VI 93 233 3... rao u-... azo E?8 1960 vII 46 t27 g4 1959 uu 25 56 l95E IX L1 16 986 995 195? x I 6 Itotal rumber Wetgbted grand meana

37 Table 16. Mean eur]|lval (S) "'d mortaltty (M) rat€B per 1, {D0 rtver carpsucker survtvlDg tnto Age Group I tn Elephant hrtte Lake. Flah tahen durhg 196?.

Year Age Class Grorp 1966 I 94 1,000 0 1965 II 490 318 682 1964 III 156 267 143 1968 ry t28 426 614

1962 v 209 s53 647 1961 VI 173 151 894 E..rs fr... ase 1960 vu 74 98 902 1969 VItr {8 89 961 1958 x 10 10 990 195? x 5 2 998 lotal nrmber 1' 394 Welghted grand means

Comparison of data for males (table 14) and females (table 15) reveals that males survive at higher rates than females through Age Group Itr. Survival and mortality rates are similar in Age Group IV, then change rapidly in favor of females in Age Groups V through D(. Equal rates of survival and mortality of males and females in Age Group X probably resulted from sample size.

Grand (weighted) mean survival and mortality of males (F = 162, M = 8S8) occur between Age Groups V and VI. Grand mean survival and mortality of females (S= Lg0, M = 820) occur between Age Groups VI and VII.

The total sample of 1,394 river carpsucker (see table 8) consisted of. 624 identified males, 645 identified females, and 125 fish of undetermined sex. It is noted that survival rate is lower and mortality rate is higher for Age Group X in this sample than in smaller samples of males and females. Grand mean survival and mortality for the total sample (S = L44, M = 856) occur between Age Groups VI and VII (table 16). Inter- polation of S values indicates mean life spans of 5. 89 years for males, 6, b0 years for females, and 6. 13 years for all river carpzucker which survive into Age Group I in Elephant Butte Lake.

Inadequate representation of Age Groups 0, I, and XI (if the latter exists) is discussed above. However, a curvilinear or exponential representation of survival may be computed from numbers of fishes in Age Groups II-X, and constants derived for computing the curve may be used to compute survival for the inadequately-represented groups and the number of fish which must hatch for these numbers of fish to survive to each age. Numerical survival and mortality, the number of fish which must hatch to produce these numbers, and mean longevity were computed from the number of river carpsucker representing each age group in the 1967 sample (see table 8). Methods used for computation and results are shown here.

38 Numbers of fish in Age Groups II-X were plotted against age, and a curve representing sunrival was computed (see figure 12,page 40). The formulaY = d(n, with notation S = aAo, was used in the logarithmic form: logS=loga+nlogA, to compqte the curve. Derivation of constants log a and n, and computed values of S used to establish the curve, are shown in table 17, part A. Additional points were computed to extend the curve and show numbers of fish surviving at ages of 0.5, 1, and 11 years (table 17, part B). The value of 0.5 year was used to represent time of hatching because of the occurrence of spawning in late May and early June which is approximately six months (0.5 year) before the fish enter Age Group I. Thus, the numberof fishsurviving(living) atanageof 0.Syearismorerepresentativeof the number hatched than would be a number determined for an age near zero,

The data computed to establish the curve were used to construct a table of survival and cumulative mortality from hatching to a probable mu

Annual survival and mortality rates were computed as percentages of river carpsucker from any age group uAich survive to enter the succeeding age group and those which die before entering the succeeding age group. Cumulative survival ard mortality rates are the percentages of fish hatched which survive to enter each succeeding age

Thble 1?. Conpgted nrmbers of rlver carpsucker aurvlvlng to enter Age Groups 0 (0.5 year) - )9. Ftsh collected from Elephaat Butte Lake furtDg 196?. A represente attalned age ln yeara and S rgrreeeds the mrmber of flsh tn the eample wtrtch attalned each age.

Year Computed Class A log A S los S (log A) (log s) ro962 *ffi Part A: 1965 2 0.30103 490 2.69020 0.80983 0.09062 2.82385 66? 1964 S 0.471L2 156 2.tg3l2 1.04638 0.22164 2.44224 277 4 0.60206 L26 2.10037 1.26465 0.86248 2.17248 148 1962 5 0.69897 209 2.82016 L.82L72 0.48866 1.96141 92 1961 6 0.77815 1?3 2.23805 t.74L64 0.60652 1.?8986 62 1960 ? 0.84510 74 1.86923 1.57969 0.71419 L.64477 tL4 1959 I 0.90309 48 1.68124 1.51831 0.81557 1.51910 38 1958 I o.9642t, 19 L.27875 t.22025 0.91057 1.40825 27 1957 10 1.00000 5 0.6989? 0.69789 1.00000 1.30908 20 6.55976 17.0?008 11. 50122 5.21515

Part Br 196? 0.5 9.96897-10 4.12861 L9.447

1966 1 0.00000 3.47623 2,994

1956 11 1. (X139 1.21938 r7

39 o o

eo z o .s Y=oXn, or S=oAn o logS=lo9o+nlogA o o =3A7623-216715lo9A z o o o o t o E a z o .s .9 o o z o o 0 | llttt t 6 Age os Age Gror.p Achieved

Fig. 12. Numbers of river carpsucker which survive frpm hatching to a maximum age of 11 years in Elephant Butte Lake. Computed fnom a sample of 1,300 fish in Age Groups II-X, taken during 196?.

lbble 18. Comprted mean suntl l (S) and cumulattve mortaltty (M) ratos per 13, {47 rlver carpsucker hatched tn Elephad Butte Lake. Flah tslrcn durhg 196?.

Year Age Class Group

1967 0 (0.5) 13, i147 0 1966 I 2,994 10,458 1965 II 490 667 L2.780

1964 UI 166 277 13,1?0 E..zre il...rs,zze 1963 rv r28 14E 18,299 1962 v 2@ 92 13,356

196 1 VI 1?8 62 13,385 1960 vu t4 44 13,403 1959 vlu 48 38 18,414 195E Ix 19 21 t3,42O 195? x 5 20 L3,427 1956 XI L7 13,480

lbtal nrmber 1,3(X) Wetghted gta,nd merne 2t8.2 13,229

40 Table 19. Annral and surDulatlve sun/lval (S) and mortrttty (M) ratss of rlver car?sucker from Elephant Butte Lake' ebown as pencent mortaltty. Flah tahen furtng 196?.

From To Anmal Cumulatlve Age Group N1 Age Grurp It+1 SM SM

0 L3.47 I 2,994 22.3 77.7 22.3 77.7 I 2,994 u 66? 22.3 77.7 5.0 95.0 tr 66? m 277 41.5 58.5 2.1 97.9 III 277 w 148 58.4 46.6 1. I 98.9 TV 148 v 92 62.2 3?. E 0.68 99.32 v 92 VI 62 61.4 32.6 0.46 99.54 VI 62 vu tL4 71.0 25.0 0.88 99.6? VII 4 uu 88 75.0 26.0 0.25 99.76 VIII 33 D( 27 81.8 18.2 0.20 99.80 D( 27 x 20 74.L 26.9 0.16 99.86 x 20 XI L7 85.0 16.0 0.18 99.8?

group and those which die before entering each succeeding age group. Annual and cumulative survival and mortality rates are shown in table 19.

Additional computations may be made from the mean numbers of fish surviving uihich are shown in table 18. Ttrese may be an adjunct to or replacement for percentages of fishes surviving as shown in table 19. These computations eonsist simply of fixing the number of fish hatched (SO. S) at any desired level, then determining by direct proportion the number of fish surviving to reach each age grcup (Sn) as ? remnant of the number hatched. For example if the number hatched is set at (Sg.5=) 100,000, then:

so. (s1) (s0. u ^ b) (2, ee4) (100,000) 1 -= o"^- sr =-f- =-rs,447- E %- sr. = 22,265 = number of fish which reach Age Group I, from 100,000 fish hatched.

On this basis, the estimated mean numbers of fish surviving to reach each age Brcup, from (S0. b=) 100,000 river carpsucker hatched in Elephant Butte Lake, are: st = 221265; = 4,960; 3^ = 21 060; 3, = 1, 101; S. = 684; 3^ = 461; i- = 327; S. = 24b; ;5+ o oro og = 201; 3rO:% 149; and 3.. = 126. II

Len g th -W e ighf Re/olionsh ip

Ten references to length-weight relationship were found in literature. Behmer (1965a) made an exhaustive statistical analysis and presented his findings as tabular results, Eight authors used the more traditional presentation with length-weight

4t relationships represented by an e>

Length ond Weight

LeCren Method. Empirical mean length-weight relationships at time of capture were computed for 1,884 river carpsucker from Elephant Butte Lake and 118 from the Rio Grande. Results were plotted on graphs which revealed exponential relationships which are expressed by the formula established by LeCren (1gS1): W=al,n uihen W = mean weight of fish at capture L = mean length of fish at capture a = empirical constant n = empirical constant exponent or logarithm.

Empirical constants log a and n were determined for the logarithmic form of the formula, log W = log a + n log L, by use of the procedure described for deriving these constants to constmct a survival curve (see table 17, part A). Then weights were computed for each length group of fish.

Computed weights. Computations were made for each annual sample of river carpsueker from Elephant Butte Lake, the sample from the Rio Grande, and for a composite sample including all annual samples frnom Elephant Butte Lake. Fish were grouped into 25 and 50 mm (1 and 2-inch) intenrals of total length in annual samples from the lake and the Rio Grande so that approximately 10 to 15 plots would be available for constmction of graphs to demonstrate exponential relationships.

Mean lengths and weights of fish in 25 and 50 mm (1 and 2-inch) intervals of length from annual samples were used to compute log a, n, and corrected weights for the composite sample, Thirty plots resulted from these computations.

Intervals of length, numbers of fish, mean lengths, mean weights, appropriate logarithms, and computed weights of each sample are shown in tables 20-24. Mean lengths, mean weights, and corrected weights are shown graphically to demonstrate exponential relationships and deviations of mean weights from empirical mean weights of samples (figures 13-17).

Age ond Weight

Empirical constants log a and n for each sample were applied to grand mean lengths at time of annulus formation to compute grand mean weights of river carpsucker at time when annuli are formed. Results are shown in context with grand

42 Table 20. Comprted mean length-welght relatlonsbips of 20? rlver csr?sucker at tlme of capture from Elephant Butte lake' 1965. I-engthg ln milllmetere and welghts in grams.

Comrnrted lntenal of Length N L log L w log W Iog L log W :-saz logfr w 100 3 I28.7 2.L0944 31.2 t.49457 3.t627L 4.44974 1.61325 41.0

150 2 t74.5 2.24180 L22.O 2.08643 4.67136 5.0256? 1.94182 88.8

200 2 247.0 2.39270 212.6 2.32760 5.56925 6.7260r 2.32925 2L3.4 250 I 286.4 2.45703 302.4 2.48038 6.09486 6.03?00 2.49186 310.4 300 10 318.9 2.50365 374,2 2.573r2 6.4J219 6.26826 2.609?0 407.1 638.8 350 88 381. 1 2.58106 6?9. 1 2.83194 ?.30941 6.66187 2.80637 805.4 400 8? 4t7.7 2.62088 886.0 2.94744 7.72489 6.86901 2.90602 1,074.7 450 D 468.2 2.67043 1,304. 1 3. 11531 8.31922 7.13L20 3.03127

500 0 1,8?5. 8 550 I 584.0 2.76641 1,41?. 5 3. 15152 8.71840 ?.65302 3.27319 22.34340 23.00851 58.00829 65.82078

Lake' Table 21. Computedmean length-weight relatlonahlps of 2?? river carpsucker at tlme of caphrre from Elephant Ertte 1966. Lengthe in millimeters and welghts ln gram8.

Comouted Intel:llal of w toei toeF 72 bgF w 150 1 1.63347 3.62219 4.9t722 1.37?69

1?5 0

200 0

226 3 234.0 2.36922 1?4.0 2.24065 5.30836 5.61662 2.16135 145.0 202.0 250 3 260.3 2.4t547 193. ? 2.287t3 5.524J9 5.83450 2,30632 28?.3 276 L4 291.4 2.46449 28L.2 2.4/|.502 6.03559 6. O73?1 2.45792

300 11 312.8 2.49627 359.8 2.55606 6.3?806 6.22637 2.65374 35?.9 925 3 337.7 2.52868 384.3 2.58467 6.53542 6.39346 2.65727 454.2

350 15 366.3 2.56384 510. E 2.75648 7.06717 6.57328 2.76719 685.0

3?5 50 387.7 2.58850 e23.7 2.9t677 7.54747 6.70033 2.84396 698.2

400 88 413. 1 2.61606 848.6 2.92865 7.66152 6.84377 2.92975 850.6

425 59 436.1 2.63959 1,019. 3 3.008302 ?.94068 6.9674/4 3.00300 1,006.9

450 26 458.0 2.66087 1,20r.7 3.079?92 8. 19492 7.08023 3.06924 1,1?2.8

473 3 486.0 2.68664 1,512. 3 3. 1?9637 E.54264 7.2L804 3. 14946 1,411.5 1,619.2 500 1 508.0 2. ?0586 1,503. o 3. 176960 8.59641 7. 32168 3.20929 32.95182 34. ?96439 88.95482 - 83.76709

mean lengths of each sample (seetables 5-9). Grand mean increments of weight were determined from grand mean weights at time of annulus formation and are shown in the same context.

43 Table 22. Compnrted mean length-welght relattonshlpa of 118 rlver cat?sucker at tlh€ of captrlre fiom Rlo Grande, October 16, 196?. LeDgths la mllllmetere and welghts h grams.

Ifterval Comrnrted of I€Dgtb L log L w tog W togi tosF rq,f,2 teF w 100 I tLI.4 2.06967 2r.1 1.92428 2.74082 4.28863 1.2996? 19.9 r25 2r 136.0 2.13364 33.5 1.525(X s.256?8 4.65199 t.49248 31.1 150 5 L62.6 2.18866 47.0 1.672t0 3.65111 4.76789 1.64887 4.0 175 3 194.7 2.28557 92.0 1.963?6 4.45577 5.24.L22 L.96274 91.8 200 15 216.6 2.33666 L27.3 2. 1(N83 4.9161? 5.,t4681 2.10245 126.6 225 88 296.4 2.3?181 161.0 2.20683 5.28418 5.62648 2.2L155 162.8 250 t2 261.3 2.4L1L4 2t7.6 2.38?66 5.65(N6 6.84267 2.34886 228.O

276 5 288.8 2.46060 304.4 2.48544 6. 110?5 6.06456 2.47552 301. ? 300 6 305.2 2.48458 355.0 2.65023 6.83625 6. 1?314 2.56190 356.4 325 3 331.0 2.51983 402.3 2.60455 6.56302 6.34954 2.65828 455.3 350 1 360.0 2.55680 55?.0 2.74686 7.OLS24 6.5346? 2. ?66E0 583.2 1t 25.82206 23.51858 65.9?464 60.86989

Table 23. Comprted mean length-wetght relationshlpe of 1,400 rlvercarpauckerat tlme ofcaphrrefromEl€DhantBrtteLake, 1967. Lengthe ln mllllnretere aad welghte ln grrms.

Ideral Comouted of length L tog i w r"gF log L log W r.ryrt rosF w 100 3 132.0 2.t2067 24.7 1. 392?0 2.95352 4.49682 L.4Lt32 25.8 160 2 184.5 2.26600 ?6.0 1.88081 4.26L92 5. 134?6 1.85?84 72.O 200 4 222.5 2.34788 18?.8 2.18926 5.02153 5.50996 2. 10795 128.2 260 166 284.1 2.45947 261.6 2.4L764 5.93161 6.01962 2.43602 212.3 300 289 324.5 2.5tt2l 876.2 2.51542 6.t16742 6.30618 2.61294 410. I 860 330 874.2 2.5?310 612.8 2.78732 ?. t7205 6.62084 2.80366 636.3 400 467 429.8 2.627L6 966.8 2.9853.1 7.84297 6.9019? 2.97024 933.8 450 169 461.1 2.66380 1,261.8 3.10099 8.260U2 ?.09583 3.08314 1,211.0 19.56264 L9.27947 47.9Lr24 48.08588

Sexual dimorphism, in terms of weight, is evident in all samples, although ages at which it occurs vary between samples. Females are distinctly heavier than males at formation of Annuli VI and VII in the 1965 sample (see table 5) and at formation of Annuli VI through D( in the 1966 sample (see table 6). Weights of males and females were essentially the same at formation of Annulus I and females were heavier at formation of Annulus II in the sample taken from the Rio Grande (see table ?).

Females were heavier than males at formation of Annulus III and at formation of each subsequent annulus in the 1967 (see table 8) and composite samples (see table 9). The difference between computed weights of males and females was 5.6 grams at formation of Annulus III in the composite sample (see table 9) and became progressively larger, with one exception, through formation of Annulus VII. Females were 59.4

44 Lake' Table 24. Computed meanlength-welghtrelationehips of 1,884 river carpsucker at tlme of caphrre fromElephant httte August, 1964, through December, 1967. I€ngths ln rnilllmeters aDd welght8 ln grams.

ComPuted Interval -t W }{ of Length L log L Iog W 1og L 1og W Iog L' log 1,.t+6569 10G149 3 t28.6 2.tog/{/+ 3L.2 t.t+9457 3.15277 4.1+l+972 8.2 7.t+9753 3L.4 10G149 3 L32.O 2.12057 2/4.7 t.329?0 2.95332 4.t+9682 r+.91722 L.77t+78 59.5 t5Ft7h 1 t65.o 2.21748 t3.O r.6)347 3.622t9 69.6 t5t799 2 t7l+.5 2,24rce t22.o 2.O86t+3 t+.67736 5.02567 t.84Z3O t.91359 82.0 t50-r99 2 t84.5 2.266@ 76.0 1.88081 l+.26192 5.73476 2.27607 188.8 zwug 2 Z+7.O 2.39270 2t2.6 2.3z't60 5.65925 5.7250t 2.14627 140.0 w2A9 4 222.5 2.31+?33 t37.8 2.13925 5.02!53 5.50996 2.2O89O 151.8 22?21+9 3 23t+.O 2.36922 174.0 2.21+055 5.30936 5.61652 2.1+6otl 288.5 25U299 9 285.t+ 2.t+57O3 3O2.h 2.UeO58 6.09486 6.$7AO 250-299 \56 284.r 2.t+5347 26t.6 2.1+I761+ 5.93L5t 6.oL952 2.44993 28t,8 2.34121 219.1+ 258274 3 260.3 2.415L'.1 193.7 2.2gtt3 5.52t+49 5.93t+5O 27>299 74 29L.1+ 2.t+6M9 28!.2 2.U+9Q2 6.03559 6.ow7 2.t+8tt+5 303.O 3w349 10 3t8.9 2.50365 37t+.2 2.573]-2 6,t4ztg 6.26e% 2.59349 392.2 6.3crL9 2.6L5t2 l+L2.2 3c3t+9 289 32J+.5 2.51r2t 376.2 2.575t+2 6.457t+2 3W32J+ 11 312.8 2.t+9527 359.8 2.55606 6.378c6 6.2*37 2.5695t 37t.L 6.39346 2.66t+67 t+62.o 32>3t+9 3 337.7 2.52853 384.3 2.5e467 6.53542 653.1 35U399 88 381.1 2.58t6 679.L 2.s3794 7.3O9t+I 6.66tsl 2.eU+95 6.62@l+ 2.792L8 619.7 350-399 330 371+.2 2.573tO 612.8 2.78n2 7.L72O5 35r3?L 15 366.3 2.5538t+ 570.8 2.756t+8 ?.06717 6.57328 2.?6t+66 581.7 6.7A$3 2.9)624 685.9 37>399 50 )87.7 2.58850 e8.7 2.9t577 7.5n17 40GA49 sl 4t7.7 2.62@8 885.0 2.9t+744 7.72J+89 7.86907 2,92891 848.9 884.8 40c449 t+5? l+23.8 2.62776 966.8 2.98534 7.8t+297 5.90197 2.91+681+ 822.L t+c&.l+?A 88 413.L 2.6L66 848.6 2.92e65 7.66152 6.e/{,77 2.9t50€ 425-4t+9 59 l+36.t 2.63959 t,O19.3 3.00830 ?.9468 5.967t+4 2.9821+0 960.3 tJ76.5 45Gl+99 5 46e,2 2.57Ot3 LSOt+.! 3.1L537 8.3L922 7.t3I2O 3.07063 LJ%.3 L5H+99 tr9 46L.L 2.663& \,26r.8 3.10099 8.2601+2 7.@58 3.O5L66 t+5o-Mt+ 26 458.0 2.66087 tt2f]-.7 3.vt979 8.19t+92 7.080.23 3.Ot328 1,104.8 t+7>499 3 466.0 2.6664 tt5L2.3 3.L7964 e.r+251+ 7.2r&4 3.tt7ot tJo9.2 t1485.t 5(J}-52t+ 1 5O8.0 2.70586 7,5O3.O 3,17696 8.59641 7 32L68 3,t7t99 2t2t4.7 55G5OO 1 584.O 2.7661+l r,417.5 3.15152 8.?1840 7.65302 3,3t+522

Groups 30 7r+.85786 ?7.Oe447 L94.glt+35 tsl.673?5

*Calculated with foruula W = aln, when log I'l = Iog a + n log L = - 4.56923 + 2.86091 log L

grams (2. 1 ounces) heavier than males at formation of Annulus IV' 66.5 grams (2.4 ounces) heavier at formation of Annulus V, 54.8 grams (1.9 ounces) heavier at formation of Annulus V[, and 108.5 grams (3.8 ounces) heavier at formation of Annulus vn.

45 t{5rg 3eq S{C+) 'r8>tOcd Fd c\l .r J og o o.IH : Ep o qI o. o s" o E .E JS n| ji c! ?; E cB C) :+ 3 Et cl o +, 0) +ai o oF GI 3 ':1b0 .=ij (o Pd o :r 3 H*3 crlll o a Eh :' 'o g ilO E*q5,q ]3 l-1 U) l-{

Fl{ bi fr{ rO F{59.s rvHdA t{trC) *) >tOcB .lh6: 6 f r_r C\ld ..HoH gr rH .d -, 6Etrid o-o. o E- EcB F JF E -EO'ai rx GI t|o 3+r(Dto !.i 4F to {' o .s.i .F .lo ; o9 XxB F :o t .tn; :5H -'-d J;.'. o : g .t' H* HYt'\ IDH '! o; ooo oo C'C'C' oc' a!t|r'ooo oor bi F rrrorg lrl l1tlra

46 Sgr o cd i5 o€ O5 >gQ) +r o 'i cB o oP |n s# o J o EE I ! g{ rf{ ! EpgH ?a JE or .9E oq -E +acsc) cs C6 + : Ei C6 o +rO -64-n o !fi 1I4 .PE; a(|i- o I a rr5 -llll go tk i' or Bg qt tr,.o 5H5 oo t6l aorrr0 rl b0 tiDt.n k

aI dh.a U OY!Yd S{ cd Otr .lsl'{ oiFo F{H F .s FF o:i6)!co o.€ * E!:'do"l :a 3- .Q*c.x I +icgxcs o* -o ,s.Y rq "- ?li oA r_ .qtr.rr 0)v C: o ao I .9.r ! . e:.9 oq J FT X c? l'-o € H= o > 'a s* )^\Ya\v 6ZR v d gF Fl rr.r9 rt llCtril bi r-..A

47 hriy.9 .d€h C€$ -rEP E t;:i -H x x-j I3E oE 5o

o €'H€* : .EocqeteE 8 : -$ E SE-f !t' 95.83 :p : AlE fi :8 I '0 bEA rr! a!? C-i' r rr i a age :3 S8.r€

= bi rrrr g rl llllra

FgqoH: .tf,dG) +r ,' : EE 3# -- Io J H trQ a E : t o.HE6 5 ? t I 3 Eee Ja EES raaGl - .9q a. t 3 fi 33 r$:3 a a.| E:E Oi +rO t-i} rt tl !o B€ H i: ttr?H€

o n o $g 5 rr.r9? rl tllt.n 5 s Fq

48 Differences in weight were erratic at formation of Annuli VI[-X. Females were B?.6 grams (1.3 ounces) heavier than males at formation of Annulus VIII' 83. 1 grams (2. g ounces) heavier at formation of Annulus IX, and 72.7 grams (2.6 ounces) heavier at formation of Annulus X.

Computed grand mean length-weight relationships of the composite sample of 1,8?1 river carpsucker at time of annulus formation are shown (figure 18).

Com po riso n

Brezner (1956) compared years required in four localities for river carpsucker to reach a weight of 1. ?8 pounds (800 grams). This comparison is continued here. Ages at which 800 grams of weight was reached are shown with authors and localities as follows: Davis (1955), Perche Creek, Missouri 9 years Brezner (1956), Lake of the Ozarks, Missouri 6 years Thompson (1950), Grande Lake, Oklahoma 6 years Jenkins et al. (1952), Illinois River, Oklahoma 5 years Bass and Riggs (1959), Lake Tercoma, Oklahoma 5 years Jester (I962a1, Conchas Lake, New Mexico 6 years Buchholz (1957a), Des Moines River' Iowa 9 years Walburg and Nelson (1966), Missouri River, South Dakota 8 years Walburg and Nelson (1966), Lewis andClark Lake, South Dakota 8 years Houser and Bross (1963), State of Oklahoma 4 years Jester (new data), Elephant Brtte Lake, New Mexico 1965 sample 6 years 1966 sample 6 years 1967 sample 5 years Composite sample 5 years

the largest river carpzucker was reported from Oklahoma. It was 630. 1 mm (24.8 inches) long and weighed approximately 3,814 grams (134.5 ounces) (Houser and Bross, 1963). Jester (1962a) reported two river carpsucker which weighed appnoximately 21270 grams (80.1 ounces) each, from Conchas Lake, New Mexico. They were 528. 3 and 538.5 mm (20. 8 and 21.2 inches) total length. Little (1964b) took one specimen which was 562 rnr:r- (22.1 inches) long and weighed 2,327 grams (82.L ounces) fr"om the same lake. The largest river carpsucker taken fromElephant Butte Lake was 584 mm (23 inches) long and weighed, L,702 grams (60 ounces). It is the second longest and fourth heaviest specimen which has been reported.

Condition

Hile Method. The method established by Hile (1936)r on the basis of the well- known cube law, was used to determine relative robustness of river carpsucker in Elephant Butte Lake and the Rio Grande, in terms of an index, or coefficient

49 of condition. Coefficients of condition are used here as an adjunct to age and growth shrdies and to indicate suitability of environments in these waters by comparison of values with those found in other investigations (after Cooper and Benson, 1951, and later workers).

Condition of river carpzucker has been reported for various length ranges, age groups, months, seasons, years, separate and combined sexes, and from English, metric, and combined English and metric data. Findings were standardized and converted to the metric system, insofar as possible, so that comparisons could be rnade.

Coefficients of condition were computed for river carpsucker in 10 mm (0.4-inch) intenrals of total length in the composite sample, for fish caught during each month during 1967, and for fish in each age group in 1965 and 1966 samples. Metric data were used with the formula W = KL3, for determination of K. Weight was multiplied by a constant of 105 (100,000) so that K is near unity for easier comprehension. The formula used to determine coefficients condition of was W 10b ^TL= f when KTL = Coefficient of eondition determined on basis of total length in metric units W = weight in grams L = total length in mlllimeterg

Condition ond Length

Coefficients of coDdition were computed for 1,990 river carpzucker in 10 mm (0.4-inch) intervals of total lengtb from the composite sample (table 25). K11 ranged fmm 0. ?1 to 1.39. Both minimum and maxirmm K11fs were smaller than minimum and maximum condition values of river carpsucker fmm Lake Texoma, Oklahoma (1. 08-1.45), and frcm the Des Moines River, Iowa (1. 14-2. 33). Condition of river carpsucker followed a definite trend of decline with increased length in the Des Moines River but did not follow gtrch a trend in Elephant Butte Lake nor in Lake Texoma.

Condition ond Age

Changes in condition with sfuqng€s in age could not be determined fnom condition values of river carpsucker gnouped by intenrals of length because of excessive over- lapprng of length among age groups. Therefore, effect of age on condition is considered separately fnom eondition and length.

Mean K11 was determined for aU fish in each age group taken during 1965 and 1966 (table 26). Kr" of river carpsucker in Elephant Butte Lake tends to vary with age, Highest values occurred in Age Gnoups 0-II with a decli:ning trend, second highest values in Age Groups VIII-X with a rising trend, and lowest values remaining relatively stable in Age Groups III-V[.

50 Table 25. Coefflclelrta of condltlon (K11) of length groupa of rlver carpsucker fmm Elephant Butte Lake' New Modco; Iake Texoma, Oktabma (gase afaaggs, 1959); and Dee Molnes Rlver, Iowa (hrcbbolz, 195?s). I4Dg&s ln mllllmeters.

Eleohant hrtt€ LaI€ Iake TeNona Deg Moinee River InterYaI Ktl Interval KTL IDt€rval Krl --- 38 2.33 :: 51 1.66 :: 64 1.55 76 1.80 100 1.30 89 t.4L 110 t.29 :: LOz 1.30

120 1.83 114 L.4 L.47 180 r.20 ; L.25 r27 140 1.34 140 140 1.41 150 1.39 150 :: L62 1.83 160 0.96 160 t,25 165 1.33 1?0 t.L2 170 L.26

180 180 1.35 1?8 1.05 190 L.25 190 1.45 190 1.36 200 L.25 200 1.25 20s 1.89 zLO t.24 zto r.30 220 L.22 220 1.33 2L6 1.86 230 L.25 230 L.24. 229 1.21

240 L.26 240 1.28 24L 1.22 250 1. 18 260 t.27 254 1.19 260 1.18 260 L.26 270 1. 15 270 t.2s 267 1. S0 280 t.t2 280 L.25 279 L.27 290 1. 15 290 L.2L 292 1.14

300 1. lt 300 L.24 305 L.27 310 L.L2 310 L,22 320 1. 10 320 I.25 318 L.22 330 1. 10 830 t.28 330 L.27 340 1.09 340 L.22 343 L.22 350 1. 11 350 1. 19

360 1. 15 360 L.22 356 L.21 3?0 L.22 3?0 L.2r 868 1.16 380 1.19 3E0 1.08 881 1.16 390 L.20 390 1.83 400 1.18 400 L.28 410 L.24 410 t.2s :i -l'

420 t.?A 420 1.86 430 t.25 480 t:!' 440 1.28 440 450 L.28 460 : 460 L.29 460 1.19 :t' 470 L.26

480 1.84 490 L.32 500 1.15 580 0. ?1

Table 26. Coeffrclente of condltlon (Ktf,) of age-groups of 480 rlver carpsucker from Elephant Butte Lake, Auguet, 1964, throwh December, 1966. Lengths in milllmet€rg arrd welghts ln gramg.

Coelflclente of Coudltlon of Rtverlqeqqte! l4lgeGlgup 0IUmwvvlvtrvmrxx N 326649911310142191364 w 31.? 257,3 486.8 701.2 ?85.0 917.3 L,O42.O 1,084.8 1,210.9 1,346.8 1,169.3 i 131.? 280.9 832.8 388.2 899.9 420.9 435.6 t146.0 471.3 47L.0 /U7.8 K 1.39 1.30 1.33 L.20 r.22 r.22 L.26 L.22 L.26 t.28 1.30 roaao F CIIFN{66a6OO (l' o c oooloFGaH60€H Gt@Faao(Dro I I roroa4!roo'.6:*€a o 'd FI € FFd@r0NgrdNro(Dl' 6 r(DdFIO(DHrots!d q (oca6c|tFnttF$N(Drots('| 6 €. o (DNd tst 6FdHdN(Os€N o!0HroN{H!.d(or s aotoiro)@6rtts tr!g)rDt!(Dd:l tg o ro(D6 dddNfrdF'|)H rorodqrocHrooNH th co(ooroioi.(0@ xo localo3ldro6a aI o t)i.{ B ersr6|€oNottcaN d o€adddodoo€H a {fr196@iroF l. tottloaad€t! o l- (t) c, (9 ro to 6lFNHdN10(061 N odHraNodro$od j @rD(DO@(DtlF u)d)rocaH€oa o o r[ !tol H O6NFdC'A@N al o trFdUlloldNHGAd r0|o(t€FN6|(o ro c, ro eit ts 19 qt 3I qt ! N{IF g o@ol6|10g6|aoa HtOdoo(DdoaDFd 6 6l(Da9N(DrO.OOl o odlo'i)d@o? ? E HOF .9 roor(.dF|oa€l|l a l-d|tH|O(DOdt:(Daa. ari) ooc?ostto(oc (9 FgTFrlgt$ o I o E E 9d aa(Dcaaad')rlltsto(oro 6| {.c!dHNFH6FtOH 6E ro oorooooro b6:f. tsc'c{r-€! s€d5 c6 rooo :o NON{FN@HN *t o) oFdFcNgr('tdo'isrcib:iNcidi roct@rtFoi) goE: 66|O: 35 rl.larNO6|0'Nc'6l o d6NONladdiJio{,'ii@d

52 Month ly Cond ition

Coefficients of condition were determined for males, females, and all river carpsucker taken during each month in 196? (table 27). Annual mean K11 was 1' 26 for males, L. BB for females, and 1.30 for the total sample. All groups followed the same seasonal trend, apparently associated with development of gonads. Females, found to be heavier per unit of length and possessing larger gonads, had consistently higher condition values than males. Condition values in both sexes began to increase during December, Jaluary, and February, when ovaries and testes were undergoing rapid development. Little change occurred in March. Condition values increased rapidly during April and reached peak values during May when spawning began. Condition began to decline in June when spawning was essentially completed. The decline in K11 values continued from late summer into early winter until development of gonads again became raPid in mid-winter.

Rio Grqnde Somple

Coefficients of condition were determined for the sample of 118 river carpsucker from the Rio Grande (table 28). Trends in K11 values found for fish grouped into b0 mm (2-inch) intervals of total length differed from values found for fish in 10 mm (0.4-inch) intervals of total length in Elephant Butte Lake. K11 values were lower in longer fish in the sample from the Rio Grande, while no trends occurred in condition of length groups in the sample from the lake.

Condition of fish in Age Gnoups 0-Itr from the Rio Grande followed the same trend of decline that occurred in the same age groups from Elephant Butte Lake, differing only in that K11 values of fish from the river were consistently lower than K11 values of fish from the lake.

Com po rison

Raages and means of coefficients of condition of river carpsucker have been reported in 14 shrdies from 13 localities in New Mexico, Oklahoma, Iowa, Alabama'

Table 28. coefEciente of condltion (K1fl of 50 mm length groupaandagegroupsof 118river carpsuckerfromtheRioGrande' @tober 16' 196?.

Cb,efflc,ients of Condttlon of River Carpeucker in Lngth Int€rvals 200 230 300 350 1 N 30 E 53 t7 I 557.0 w 29.8 63.9 L49.7 243.r 370.8 i 130.4 168.4 230. I 269.4 313.8 360.0 1.19 K 1.36 1.35 L.23 r.25 L.20 Coefflcients of Condltion of River Carpsucker in Age Grcup

1.36 t.25 L.26 1. 19

53 South Dakota, Nebraska, and Missouri (table 29). Both minimum and ma:rimum values of K11 of length-grcups of river carpsucker in Elephant Butte Lake are among the lowest condition values recorded in these studies.

The minimum KTL of 0.71, which occurred in Elephant Butte Lake, is the lowest K11 recorded for the species. K11 of 0.91 was reported for river carpsucker from Canton Lake, ^Oklahoma. All other minimum K1tr values reported are in a range of 1.00 to 3.09.2

The.:ma:rimum K11 of 1.39 found for river carpsucker in Elephant Butte Lake exceeds the maximurn Ktl of 1.26 found for the species in Gavinrs Point Lake, South Dakota, and is ssynparable to (1,. 05) the mu

Mean K1tr of river carpsucker frcm Elephant Butte Lake is L.20. This value is htgher than the mean K11 of 1.11 found for the species in the tailwater of Fort Randall Lake, $uth Dakota. It is comparable to C.05) mean K'1,1 values found for river carpsucker from Gavinrs Point Lake, South Dakota (K.I.f, = 1.20), Canton I-ake, Oklahoma (K1'f, = L.2Ll, and Lalre Texoma, Oklahoma (Ktf, = L.251. It is lower than mean K'1,a valuee 3anging frcm 1.30 to 1.87, which were found for river carpsucker from six other waterg.

21te antbr ts lnoll&d to qpostroo K'11 valuer lgpotd br rlver cetaancker lnon ldc of the Ozar:Le' fleourt (table 88). Other D||rlnrm K1'1 valuea raqe lnon 0. ?1 b 1.48 ad mdmn K1'1 vetrea raqe fiom 1.26 b 2. 88. Bot'h raagee arc relatlvely nsrrow and mrch lorsr la ooryertrn rtlb K11 valuer of 3.09 ard 3.48 r6pltod by Brurnot (1066).

TNble 29. Coe6olents ofcoldltioD ofrlyer carpancker sbwlng ngsa andmeenr 6f K'1,1 bom 16 studles carrled qrt oB firh boE 18 ryalers. Krl Er e LodAy lf,ldmn lfiaxlnnn Arnhor aDd lbtr El€Ehrd htte l.eke Nos Merdoo 1,900 0. ?1 1.89 t20 Jeder, Ewdall El€Ebad hrtto L.ko New Medco Lr2A:l Lr0 L.4 1.23 nr6l, 1908 Coloher Lake New Medoo %o 1.8? Jeder, 1962a Ilaa Molnea Rlver Iowa 209 1.14 2.38 1.40 hahholz, 1967a lbr lfiolneg Rlrer lowa 1.48 1.99 Bebmer, 1965a Ruthra hd !o*a 11 1.08 1.62 1.38 Crrlader and iloomaD, 1949 Ieke Tepms Oklahona 604 1.08 1.46 1.26 Bese aad Rlgga, 1959 Canbn lahe Okhbma 376 0.91 1.66 t.2t Hanoook, 1965 Fonde Alabo'ml 63 1.38 1.58 1. 39 Srlngle, 1965 GavlDs Polnt Ld.e $uth Dakota 2.217 1.16 L.26 t.20 Nel8on, 1962 Fort Randsll Irke Sotrt.h lh&ote 1,086 t.2r 1.41 1.30 $rague, 1961 Fort Randall Tallwater South Dskota 80 1.11 tblelde, 1966 Oahe Iahe Soutl Dalota 810 1.81 1.49 Fogel, 1963 Dllesrrt Rlver Nebraeka 1. {X' 1.50 lilorrts, 1965 Lake ofthe ozar*s Mlssourl 604 8.09 8.48 :i Brezoer, 1956

54 Reproduction

Spowning Seoson

Spawning seasons of river carpsucker have been reported for various periods between early April and early August in the State of Iowa (Harlan and Speaker, 1956); the Des Moines River, Iowa (Buchholz, L957a; Behmer, 1964a; Lake of the Ozarks, Missouri (Brezner, 1956); Perche Creek, Missouri (Davis, 1955); Great Salt Plains Reservoir, Oklahoma (Jenkins in Walburg and Nelson, 1966); Conchas Lake, New Mexico (Jester, l962al; Lewis and Clark Lake, South Dal

Unforttrnately, only four of these reports contained water temperatures along with dates and duration of spawning seasons. Jenkins (in Walburg and Nelson, 1966) observed river carpsucker spawning in Great Salt Plains Reservoir, Oklahoma' on June ?, 1948. Sgrface water temperafure was 75oF (23.goC). Jester (L962a) found carpsucker spawning in Conchas Lake, New Mexico, frcm early May to mid-June with a peak in mid-May. The temperature range was 65 tD TzoF (L8.3-22.2oC) with the peak occurring at approximately ?OoF (21.loC). Walburg and Nelson (1966) found evidence of spawning in Lewis and Clark Lake, South Dakota, between June 13 and July 12, 1963, with most activity about June 24. Water temperature ranged from 21 to 240C (70-760F).

Rael (1966) confirmed that the temperatures at Conchas Lake during spawning season of carpsucker applied to Elephant Butte Lake as well. He reported free- flowing milt during each month of 1965, which was confirmed by the author. Padilla (lg72l also found ripe males continuously fnom June, 1970, through May, I97L. However, the authorts observations, made between these studies, revealed that milt usually occurs from Febmary through October, and spawning takes place between early May and late June in a slightly different range of temperatures from that shown above. Spawning of river carpsucker in Elephant Butte Lake usually occurs from mid-May to mid-June in a temperature range of 67 to 74oF (19.4-23.3oC) with a peak of activity about June 1 at a temperature of approximately 70oF (21oC).

A zummary of all observations of spawning activity of river carpsueker indicates that spawuing is controlled largely by temperature. The spawning season may occur between early April and early August in a range of 18. 3 to 24oQ (65-76oF). The usual rznge of temperatures is 19. 4 to 23.9oC (67-75oF), with a spawning peak sometimes occurring at approximately 21oC (70oF).

Hobitot ond Behovior

Harlan and Speaker (1956) reported that river carpsucker are shallow-water, random spawners and that eggs are broadcast and unattended. Jenkins (Walburg and Nelson, 1966) obsenred carpsucker spawning in Great Salt Plains Reservoir, Oklahoma'

DD after dark (8:30 to 10:30 p. m. ), over fimt sand bottom, and in depths of one to three feet (0,3-1 m). Jester (1962a) obseryed spawning in Conchas Lake, New Mexico, on silty shoals, in shallow silty bays, and on silt deltas at the mouth of flowing tributaries to an undetermined point upstream. Peak spawning occurred in mid-afternoon at depths of one to three feet (0.3-1 m). Turbidity inthe spawning areas ranged fnom 80 to 150 Jackson Units, perhaps duplicating underwater light intensities equivalent to those occurring at night over firm sand bottom where water would tend to remain clear. It appeared to have been 'fstirred upff by the activities of large numbers of spawuing river carpzucker and gizzard shad which occupied the areas concurrently. Spawning was random with no nests nor care of the eggs. Both Jenhins and Jester obser:ved that spawning was a noisy performance with much slapprng and splashing at the water surface. Sawnrng habitat and behavior of river carpsucker in Elephant Butte Lake are identical to those in Conchas Lake.

Starrett (1948) suggested that river carpsucker spawn intermittently. Buchholz (1957a) found two partially spent females and reported them as supporting evidence. Behmer (1965a) developed the hypothesis, from various egg sizes present concurrently in the ovaries, that intermittent spawning probably occurs but that more sttrdy was needed. He continued his sfudy and strengthened his hlpothesis but was una.ble to establish definitely that river carpzucker spawn more than once in a season (Behmer, 1965b). fire author and Padilla (L9721examined longlhrdinal sections of numenous ovaries taken prior to and during the spawning season at Elephant Br.rtte Lake in 1971, and found neither a partially spent condition nor differential development of ova. Ova were uniform in size throughout the sections except that a few small ones occurred at random, suggesting that perhaps a few ova fail to develop. Thus, no evidence has been obsenred frcm Elephant Bltte Lake, or frcm any other water in New Mexico, to indicate that intermittent spawning of river carpzucker might occur, although the evidence is strong to indlcate the possibility of such a phenomenon in the Des Moines River.

Development of nuptial firbercles in river carpsucker is another phenomenon in which considerable variation has been found. Davis (1955) reported that carpsucker were covered with thick slime and that m fubercles Dor pearl organs were found during the spawning aeason in Perche Creek, Missouri. Huntsmar (1967) described nuptial tubercles of Camiodes and presented a frgure showing their distribution on three species, including C. carpio, fnom the Deg Moines River. the author also found nuptial tubercles on carpsucker for a period of about three months spa^nning the spawning seasons in both Conchas and Elephant Butte Lakes. Distribution of these organs appeared to be identical to that shown by Huntsman (frgUre 19).

Fig. 19. Nuptial tubercle distribution as seen in slde, ventral, and dorsal views of the head of river carpsucker (Huntsman, 1e6?).

56 Indications that river carpsucker in resenroirs may spawn in both reservoirs and tributary streams are discussed under Age-grpwth, as growth rates of the species in Elephant Butte Lake and the Rio Grande suggest that these populations are relatively discrete.

Beckman and Elrod (19?1) stated that carpsucker spawn only in perrnanent tributaries to Lake Oahe, South Dakota, and young-of-the-year concentrate in embayments at the mouths of these streams. Few were found in the reservoir proper.

Elrod and Hassler (19?1) found high catch rates of carpsucker in the Lake Oahe tailwater, and post-impoundment reductions of year-class strength and sizes of fish in comparison with pre-impoundment data, in Lake Sharlre, just downstream from Lake Oahe.

Beckman and Elrod (19?1) reported reduction in growth rate and no evidence of spawning in Lewis and Clark Lake, and cited Gasaway (1970) for reporting similar conditions in Lake Francis Case, South Dakota. However, Walburg (1971) reported taking young-of-year carpsucker in seines and trawls throughout Lewis and ClarkLake and in samples of young frsh in tailwater discharge, indicating the possibility that spawning does occur in the lake. Walburg, Kaiser, and Hudson (19?1) found river carpsucker second only to blue sucker, Cycleptus elongafirs, among all fish collected in gill nets in Lewis and Clark Lake, but eighth among nine species of young-of-year fishes collected. This could reflect low rates of survival of young fish in an established and lightly exploited or unexploited population (see $rrvival and Mortality). They also compared empirical lengttrs and weights of carpsucker in the lake and the tailwater and found faster growth and heavier fish in the tailwater.

Carpzucker caught in a trap in the North Platte River at the head of McConaughey Reservoir, Nebraska, and in the reservoir pnoper, indicate that most, but not necessarily all, spawning occurs in the river (McCarraher, Madsen, and Thomas, 1971).

Stucky and Klaassen (1971) compared growth rates, condition, and fat content of river carpsucker in the Srnokey Hill River and a mainstream impoundment, Cedar Bluff Reservoir, Kansas. Ttrey reported similar condition and fat content but faster growth in the reservoir, indicating relatively discrete populations and, therefore, probable spawning in both the river and the reservoir as were found in Elephant Butte and Conchas Lakes, New Mexico.

The author concludes, from the above and from the discussion of discrete populations under Age-Growth, that in Nebraska and South Dakota carpsucker spawn primarily in streams, and reservoir populations result fr"om immigration into the large, relatively- cold resenroirs. From Kansas southward and eastward, spawning may occur in streams and reservoirs, with most of it in reservoirs on intermittent streams in the southwestern portion of the range.

57 Sex Rotios

Brezner (1956) reported 0.95 males per female in Lake of the Ozarks, Missouri, and Behmer (1965b) found 1.25 females per male in the Des Moines River, Iowa. Males were more abundant with a ratio of 1.08 in Canton Reserrroir, Oklahoma (Buck and Cross, 1951). Females were slightly more numerous than males in the composite sample from Elepbant Butte Lake (see table 9) with a ratio of. t.027.

Differentlal mortality occurred Ir Elephant Butte Lake, as it did in Lake of the Ozarke aad Canton Resenroir, so that females outnumbered males in older age gnoups. Males outnurnbered females in Age Groups II-V and females were most numerous in Age Groups I and VI-X in Elephant Entte Lake. Nrrnbers of males declining more rapidly than nurnbers of females in older age groups indicates that females tend to live longer than males, wbich conforms to conclusions reached by Brezner (1956), Buchholz 1957a), Bass andRiggs (1959), Jester(1962a), Rael (1966)r andElrod andHassler (19?1).

Sexuo I Moturity

Grand mean increments of gnowth ehow that river carpsucker in Elephant Butte Lake grow rapidly at nearly identical rates during the frrst two years of life. Growth rate decreases in the third year, followed by a general decline with a few exceptions in older age groups. Rapid growth rates such as those shown for Age Groups I and II usually indicate that fish are immahre. A large decrease in growth, zuch as that found in Age Group III, ueually occurs concurrently with sexual mahrity (Lagler, 1956).

Examination of gonads from fish in Age Groups I through IV revealed that these statements are generally tnre for river carpsucker in Elephant Butte Lake. Sex was determined for 79 of 120 fish in Age Group I. Testes were recognized as small ttrbes (2-3 mm or 0. 1 inch diameter), appnoximately circular in cr:oss section, whitish to pale pink, and zupplied with blood by small, irregular vessels. Ovaries were slightly larger (up to 4-5 mm or 0.2 inch), somewhat flattened, reddish, supplied with blood by a single large vessel, and contained small granular-appearing eggs. No fish in Age Group I were mature.

Sex was determined for 420 of.544 fish in Age Group II. Gonads were similar to those frcm fish in Age Gnoup I except that they were larger in most individuals. Twenty-three males and two females which were caught during fall and winter months, contained gonads which appeared to be mattrre and ripening. These fish probably would have spawned during the following spring or summer.

Sex was also determined for 210 of 255 fish in Age Gnoup III. Of 118 identified males, 113 were judged to be mature, as were 89 of 92 females. Many of these fish were taken from August through December and may or may not have spawned earlier that year. However, several fish in Age Grcup If[ were taken fnom spawning areas and released milt and eggs while being removed from nets.

AU fish from which gonads were examined in Age Group IV were mature.

58 These obsenrations were interpreted to demonstrate that some male river carpsucker in Elephant Butte Lake are precocious and become sexually mahre in Age Group II, while most of them reach maturity in Age Group III. Females reach maturity in Age Group III with a few rare individuals becoming mahrre ayear earlier.

Buchholz (195?a) also found a few female river carpsucker, but no males, to be mahpe at two years of age in the Des Moines River, Iowa. He did not record mahyity of three-year-old specimens and encountered only females' all mature, in Age Groups IV and V. Thus, it appears that mahrrity occurs in river carpsucker in the Des Moines River in the same age groups as in Elephant B;utte Lake except that some males mature in Age Group tr in Elephant Butte Lake while none do so in the Des Moines River.

It appears that maturity is reached more slowly in the northwestern portion of the range of the species. Morris (1965) found that 25 percent of the males in Age Group III and 25 percent of the females in Age Group fV were mature in the Missouri River, Nebraska. Walburg and Nelson (1966) reported even later maturity in Lewis and Clark Lake, South Dakota. They found some river carpsucker mature in Age Group fV, more than half were mafure in Age Group V, and all were mature in Age Group VI[I. They suggested that mahrr$ is a function of growth rather than age on the basis of size of the smallest mature specimens observed. The smallest mature male was 223mm (8.8 inches) andthe smallest mahrre female was 218 mm (8.6inches) long in Lewis and Clark Lake. The smallest mature female from the Des Moines River was 244 mm (9.6 inches) long. The smallest mahrre male was 244 mm (9.6 inches) and the smallest mahrre female was 254 mm (10 inches) long in the Missouri River, Nebraska. Our data tend to support maturity on the basis of growth rather than age, with maturity beginning in Age Group II when grand mean lengths were 283 mm (11. 1 inches) for males and 27L mm (10.7 inches) for females at the beginning of the year (see table 9).

Fecund ity

Fecundity of river carpsucker was determined from 43 fish taken just before and dnring the spawning season in 1971 (Padilla, 19721.

Number of ova in each ovary was determined with the weight method described by Eschmeyer (1950) and techniques described by Jester and Jensen (L9721. Each ovary was analyzed separately and the numbers of ova in each ovary from individual fishes were combined to indicate the number of ova per fish. Ovaries were divided into thirds and each section was weighed to the nearest 0.01 gram. Ova in one gram fnom each section were counted to determine number of ova per gram. These data were expanded to number per section, and all data from each ovary were combined to equal number of ova per fish.

Fish examined for fecundity were in Age Groups II-V (table 30). These fish contained 18, 150 to 195,700 ova, and the weighted mean number was 105,236. Estimated mean numbers of ova per female in Age Gnoups VI-X were computed with regression

59 constants established frpm the sample. Fecundity of river carpsucker from Elephant Butte Lake was found to be greater than fecundity of fish in the same age groups in the Des Moines River, Iowa (table 31). Obviously, size of fish is a factor in this difference, as shown by comparison of fecundity and known mean lengths of fishes in both samples (tables 30 and 31).

Buchholz (1957a) apparently assumed that fecundity varied primarily with age. Jester and Jensen (L9721tested fecundity of. gizzard shad against other parameters and found closer correlations between fecundity and cornbinations of length and weight

Table 30. Fecundlty of 43 rlver carasucker ln Age Groups tr-V and eetlmat€d fecundlty for Age GrcupB Vl-X ln Elephaot hrtte Lake (comptted ft.om Padllla, 19?2).

Age h w Ova ner Fende Grotql t!. E, OZs. Range tr 2 886 13.2 626 18.5 18,150 - 38,460 28,306 m 1.6 407 16.0 8?r 80. ? 56,1?6 - 164,480 92,642 Iv t4 442 16.6 1,04? 36.9 39,165 - 191,800 110,374 v 11 462 1?.8 1,14? 40.5 58,645 - 195,?00 131,148 Mean Total Mean M€an Total Mean 8.8 43 427 16.8 983 84.6 18,160 - 195,?00 105,236 VI L72,t82 Vt through X prcJected wttl vII 204,818 age-fecundtty regf, e s slon: vuI 287,454 x F=a+bA 2?0,090 x = -23,634.1 + 32,636.14 8O2,726

Table 81. fecundlty of 19 rlver carpancker fiom the Deg Moloes Rlver, Iowa (Buchholz, 196?a).

Age TL* Ova D€r Femder GrouP mm tn g oza. Rage Mean tr I ,: 9.6 n,:, n,yt Itr rv 1 101,382 101,382 v 4 368 14.1 56,280 - L49.ltt4 100,3?9 VI 8 f2,226 - 136,600 112, ?00 VII D 96,447 - 118,4O0 108,65G

Mea.n Total Ibtel Mean IV-V 19 843 18.6 4,828 - 7.49)744 1o2.786 *r = 0.62 for TL ard ova IEr female; r = 0.83 frr log TL and log Ova per female.

Table 32. Regresslon coefBclents qnd coelficlents of determlnatlon @2; Bbowtng relatlonebtpe between fecudtty (F) aad length (L), wetgbt (W), age (A), and comblndlone of thege parametere, br 43 rlver carpsucker from Elephant Butte Lake.

Regression and Determlnatlon Coefrlcteutg of -- Coefflclents a -252,798.5 -54,51?.6 -23'634.1 -65'010.0 -228.426.? -57,737.5 555,478. ? b1 839.1 u.2 ?36.9 -2,659.6 b2 161. ? 153.2 186.6 836.2 bg 32,636. I 4,4L3.2 -5,459. ? -36,260. 1 92 0.984 0.990 0.900 0.989 0.986 0.991 1.000

60 a.nd length, weight, and age, when these were fitted to a multiple linear regression. This procedure was applied to river carpsucker from Elephant Butte Lake with the result that fecundity was correlated with age (r = 0.95' figure 221brtt less so than with either size or age or a combination of these variables (table 32). Multiple regression analysis was computed with the formula Y = a + b1X1 + bZXZ + b3X3, applied as F =s+b1L+b2W+b3Arwhen F = fecundity a = intercept b1, b2, b3= coefficients of L, W, and A L = total length of fish in mm W = weight of fish in grams A = age of fish in years Coefficients of L, W, A, and stepwise coeffi- lr rr cients of determination are shown in table 32. LtlElll Computed regressions were positive, indicat- Fig. 20. Relationship between fecundity ing increases in fecundity with increase in and length of 43 river calp- size and age of fish. Fecundity in relation to sucker from Elephant Brtte length, weight, and age is shownin figures 20-22. Lake, March-APril, 1971

E- g

f=o+bW = -5r51t.6 + l6lrw

too I wflGrr ll SRAIS ,r^r" ^i, ', Fig. 21. Relat ionship between fecund itY Fig. 22. Relation ship betwe en fecundity and weight of 43 river carp- and age of43 river carpsucker sucker from Elephant Butte from Elephant Butte Lake, Lake, March-April' 1971 61 March-April, 1971 Feeding ond Food

Feeding and food habits of the river carpsucker were reported qualitatively until 1957, quantitatively as percent occurrence until 1971, and as percent volume rn L97L-72.

Brezner (1956) guoted Forbes and Richardson (1800ts) as saying ttrat river carpsuckers are ". .. filthy feeders, swallowing a greater quantity of mud than the nearly related buffalo fishes. rr lhrck and Cnoss (1951) continued this concept with, tt... uniden- tifiable material gleaned from bottom ooze...tt. Jester (l962al followed suit with, rrCarpsucker food (and feeding) habits consist of ingesting bottom material, debris, and any invertebrates that might be included, passing the4 through the digestive system, and eliminating any substances that are not absorbed by the system. 'r He found heavy consumption of g\zzard shad eggs when tbe two species were cohabiting spawning areas. Eggs of longnose gar were also found, with no ill effects noted, in stomachs of carpsucker.in Missouri (Netsch and Witt, 1962).

Food habits of river carpsucker in the Des Moines River, Iowa (Buchholz, 1957b); Lake of the Ozarks, Missouri @rezner, 1956); Lewis and Clark Lake, South Dakota (Walburg and Nelson, 1966); T\rttle Creek Reservoir, Kansas (Klaassen and Marzolf, 1971); and Elephant Butte Lake (new data) were reported in terms of percent occurrence of various categories of items (table 33). Percent volume was reported for fish in four Oklahoma reservoirs (Summerfelt, Mauek, and Mensinger, L972) and the Lewis and Clark Lake tailwater, Missouri River, South Dakota (Walburg, Kaiser, and Hudson, 1971) (table 34).

Table 33. Percent occurretEe of food ttems from dlgeattve tracte of rlver carpeucker from f,ve localtttee.

Dee }Iotnes Rlver. Iowa Lewte & Clark I\rttle Creek Elephant Butte (Harrlaon, Lake of tlre Lake, S. Dak. Res., Kane. Lake, N. M. (hrcbbolz uryub. ta Ozarks, !,iio. (Walb'urg & (Klaaaaen & (Jecter, 195?b) Brezner, 1956) (Brezner, 1956) Neleon 1966) Mazolf, 1971) New Data) Plad matertal Vaecular planta 100 Terrestrtal plantg 10 Algae ?0 Ixatohs 7L 4E 66 Green algae 69 62 30 Bluegreen algae 56 8 Deamlds 64 63 4 Mlcrocnrstaoea 50 60 Copepoda 22 4t 38 Cladocera 7 oo 2l 20 Rotlfera 24 36 33 Trace Aquatlc lDaects 40 Dtptera (lmm. ) 41 26 4 Dff,usta 37 Trace Trace Terreatrlal arthropoda 2 o Othere 80 100 Unlonld clams 10 Flsh egge 2

62 Table 34. Perc€lrtagos of total volume of fbod ltems tn etomrcha of rlver carpancker llom iour Oklaboma Resenolrs (grmmerfelt, Manck, aDd UenslDger, t972! aid th€ lawls and Cla* Talleebr, Mleourl Rlver' 8or{t Dakota (WalbNrrg, Kalser, md Hud!o!, 1971). Food tf;#*f;Jt*t Pla.dr Algae 0.06 0.04 0.04 z'..L Fragmota 45.1? Admek 66.6 MDostrlca copepo& 3.74 6.62 1.00 10. 06 Cla&oera 0.62 3.28 1.00 0.6? Ogtracodr 19.48 1.14 0.10 Bryozoa 6.2 IDs€ats 0.8 Trtcboptera 0.02 Chlronomldae 0.72 0.10 0.60 0.60 Fragmotr 0.88 0.21 1.00 0.68 DBtrthrB tt.l Orjantc 75.06 15.12 96.60 8?.8{ lDtlrlto 0.10 0.20 0.81

Klaassen and Marzolf (gp. 9S. ) also determined availabilff of food items and indicated tbat little, if any, selection occurred. This and the other investigations cited, appear to confirm our ttvacuum cleanerrrconcept derived from literahrre and obsenrations made at Conchas Lake (Jester, L962al. Stomachs are rarely empty and all, that we and several other authors observed, contained a matrix of silt or silt and sand which appeared to represent the bottom in the area where the fish were caphrred. These soil materials and the rbrganic-mucousrt subgtance usually referred to as 'bnidentified organic materialtt constihrted 85 to 90 percent of the volume of contents of digestive tracts we observed from Conchas and ElephaJd Butte Lakes, Items reported in ta.ble 33 were contained in this matrix.

In zummary, we suggest that rthe river carpsucker is an indiscriminate omnivore which feeds largely by tsensingr organic substances on, in, or near bottom and sucking- up the material which contains the organic deposit. Occurrence of specific items in the digestive tract is probably controlled by abundance, ild plant material constittrtes the bulk of the diet. Fish eggs may be taken selectively and almost exclusively when they are available. il Ttris conforms to the observed anatomy and modes of feeding and is not contradicted by food-habits a:rd analyses cited above.

Eco logy

In accordance with the author?s views and preferences, work reported here was directed generally along the lines of ecological life history and population ecolory, or interrelationships and dynamics of fish populations. Cause-and-effect interactions between envirpnmental variables and aspects of life history and ecolory of river carpsucker are discussed in context. Srch discussions neglect many variables ulhieh operate subtly or indirectly but nevertheless exert profound influences on life histories and populations of species. So that zuch a deficiency does not develop in this report;

63 o o d E ts

6 6 ! o606 o6o6o 6o 6 @ N € 6 S O66S S66Nq ri lo (000'0I x) laaJ-artv do (ooo'ol I) :eal-arrv

64 physical, chemical, and biological factors (exclusive of fishes) are summarized under Limnotogy. population parameters are discussed under Populations to describe interactions within the fish community and their effects upon the carpsucker population.

Limnology

Physicol Foctors

Variations in volume of impounded water and surface and outlet temperatures in Elephant Bqtte Lake are shown in figure 23. Redtrctions in storage volume of 65 to 75 pereent from May to September are not uncommon.

Temperature profiles have been shown in eight reports of one to three-year investigations dating from 1935 into the 1950s. Temperature gradients form every summer and mosf winters, and fall and spring overturns always occur. During mild winters, overttrrn may persist all winter. However, a tnre therrrocline has Dever been recorded. Tlpical monthly profiles and a probably-continuous overturn during a mild winter are shown in table 35. Formation of gradients from spring to fall overturn is shown in figure 24.

Ele$edhtte Table3E. Mtd-monthteqeratur€ppfleaPc)blower($a. 1), ntddle($e.2), andrpper($a. s)tNdsof Latce, Aprll, 1969' thlougb March' 19?0.

Depth Aprtl- .hrre Sta. S Sta. I Sto. I lnm St8. 1 $a. 2 l*& 3 S&1 St8. 2 $&3 $a. 1 2 $& 28.0 2t.o 28.0 $rrface 15.5 17.0 lE.6 19.5 18.0 17.0 21.5 23.6 28.6 21.6 23.0 26.6 21.0 2E.O 1 15.5 15.5 17.0 19.5 17.0 17.0 20.6 22.0 26.6 26.6 26.0 2 15.5 15.5 1?.0 19.0 1?.0 1?.0 20.5 21.0 22.0 26.0 26.0 26.6 3 15.0 15.6 16.5 18.0 1?.0 1?.0 20.5 2L.0 22.O 21.5 24.O 25.6 4 14.5 15.0 16.5 18.0 1?.0 1?.0 20,5 2t.o 20.5 2L.0 22.0 28.6 28.6 25.6 D 14.5 15.0 16.0 18.0 1?.0 t?.0 21.0 22.O 23.0 23.6 26.0 6 14.0 16.0 16.6 18.0 16.5 16.6 20.5 22.0 23.0 25.6 24,6 7 14.0 15.0 16.5 18.0 16.5 16.6 20.0 21.0 21.0 22.0 23.0 23.6 24.O 8 13.5 14.5 16.0 18.0 16.0 16.0 20.0 20.5 21.6 28.0 28.0 28.0 9 13.5 14.0 17.0 16.0 15.0 20.0 20.6 21.6 28.0 28,0 23.0 10 13.0 18.5 1?.0 16.0 14.6 20.0 21.0 22.0 22.0 28.0 11 12.0 13.6 16.0 16.5 14.0 19.5 19.5 22.0 22.O 23.0 L2 12.0 13.5 16.5 16.0 19.0 10.0 18.5 2t.6 22.0 22.0 13 11.5 13.0 15.6 14.6 18.6 2L.6 22.0 14 11.5 18.0 15.0 14.5 18.0 18.6 21.0 22.O 15 11.6 L2.0 15.0 14.5 1?.0 18.0 11.0 11.6 14.6 14.6 1?.0 18.0 2L.O 2L.6 16 21.0 t7 10.5 11.0 14.5 14.6 16.5 16.6 20.6 20.5 20.6 18 10.5 14.0 14.6 16.6 16.0 20.0 20.0 19 10.5 14.0 14.0 16.6 16.0 20.0 20 10.0 14.0 16.0 15.6 20.0 2L 10.0 14.0 16.0 20.o 22 10.0 13.5 16.0 20. o 23 9.5 13.5 16.0 19.5 24 13.0 17.5 19.0 26 13.0 15.5 26 13.0 16.0 21 L2.0

65 Ta,ble 35. (Conttnued).

Depth SeDtember October Nonember lL sta. t sta.2 sta. g Sta. I Sa. 2 S& 3 Sta. 1 $a.2 Sta. 3 Sta. 1 $s. 2 Sta. I $rrface 28.0 26.5 26.0 24.6 24.0 25.6 16.0 15.5 14.5 11.0 10.0 8.0 1 27.0 26.5 26.0 24.O 28.0 24.O 15.0 14.0 L2.5 11.0 10.0 8.0 2 27.O 26,5 26.0 23.O 23.0 23.5 14.5 13.5 11.5 11.0 10.0 8.0 3 27.0 26.6 26.0 29.0 28.0 14.0 13.5 11.5 11.0 10.0 8.0 4 27.O 26.6 26.0 23.0 22.6 13.5 13.5 11.0 10.5 8.0 D 2?.O 26.5 26.0 23.O 22.5 13.5 13.5 11.0 9.6 8.0 6 27.0 26.0 26.0 23.0 22.0 13.5 13.5 11.0 9.5 7 26.0 26.6 26.0 23.0 22.0 13.5 t2.6 11.0 9.5 8 25.5 26.5 26.0 23.0 22.O 13.5 t2.5 11.0 9.5 9 25.5 26,0 23.0 22.O 13.5 L2.6 11.0 9.6 10 24.6 25.0 28.0 21.0 13.5 12.5 11.0 9.6 11 24.0 24.5 23.0 13.5 12.0 11.0 9.0 L2 23.5 24.0 23.0 13.5 12.0 11.0 9.0 13 23.O 23.5 28.0 13.5 11.0 9.0 L4 23.0 23.5 23.0 13.5 11.0 15 22.0 23.0 23.0 13.5 11.0 16 22.0 22.0 23.0 13.5 11.0 t7 2L.6 2L.0 28.0 13.5 11.0 l8 2L.0 13.5 11.0 19 2L.6 13.5 11.0 20 2L.O 11.0 2L 20.5 22 20.6 29 20.0 December Jganeri Febnrarry Sta" 1 sa. 2 Sta. 3 Sta. 1 $a. 2 St& 3 $4. 1 Sta. 2 $8. 3 St& I lla. 2 Sta. 3 $rrface 10.0 9.5 9.0 8.5 6.0 6.0 7.5 6.0 6.0 10.0 9.0 8.0 1 10.0 9.5 8.0 7.5 6.0 4.0 7.5 6.0 5.0 ?.6 8.0 7.0 2 10.0 9.0 8.0 7.O 4.0 4.0 7.0 6.0 5.0 7.O 6.5 6.5 3 10.0 9.0 8.0 6.5 4.0 4.O ?.0 o.o 5.0 ?.0 6.5 6.5 4 10.0 9.0 8.0 6.5 4.0 4.O ?.0 6.5 5.0 6.5 6.0 6.5 5 10.0 9.0 6.0 4.0 4.0 6.5 o.o 5.0 6.5 6.0 6.0 6 10.0 9.0 6.0 4.0 4.0 6.5 5.5 5.0 6.5 6.0 6.0 ? 10.0 9.0 6.5 4.0 4.0 6.0 o.o 5.0 6.5 6.0 6.0 I 10.0 9.0 o.o 4.0 4.0 6.O o.o 5.0 6.5 6.0 6.0 I 10.0 9.0 5.5 4.0 6.0 5.5 5.0 6.5 6.0 6.0 10 10.0 9.0 5.5 4.O 6.0 o.o 5.0 6.5 6.0 6.0 11 10.0 8.5 o.o 4.0 6.0 o.o 6.5 6.0 L2 10.0 8.5 o.o 4.0 6.0 o.o 6.5 6.0 13 10.0 8.5 5.5 4.0 6.0 o.o 6.5 6.0 t4 10.0 8.5 5.5 4.0 6.0 o.o 6.5 6.0 15 10.0 8.5 o.o 4.O 6.0 5.5 6.6 6.0 16 9.5 5.5 4.0 6.0 o.o 6.0 6.0 '17 9.6 5.5 5.0 6.0 5.5 6.0 6.0 18 9.5 5.5 6.0 6.0 6.0 19 9.6 5.6 8.0 6.0 20 9.6 5.5 6.0 6.0 21 9.6 D.O 6.0 6.0 22 o.o 6.0 6.0 23 5.5 6.0 6.0 24 o.o 6.0 6.0 25 6.0 6.0 26 6.0

66 physical variables of color, Secchi disc visibility, turbidity' and specific gravity-- recorded monthly from April, 19?0, through March, 19?1 -- are shown as typical examples of these conditions during the eight years of our investigations (table 36) (Padilla, et al., 1971).

Chemicol Foctors

Monthly and quarterly chemical analyses made on gurface-water samples taken from April, 1g?0, through March, 19?1, are also shown as typical examples of conditions from 1964 to L972 (tables 3? and 38) (Padilla et al., 1971).

lomperoluro in oC lo l2 l4 16 20 22 21 26 28

ob ! To 6o d .t +g oa

Fig. 24. Development of temperature gradients from spring overturn in March until fall overturn in September, 1969. Bottom of each line represents maximum depth of Elephant Butte Lake at mid-month. *Denotes apparent densitY currents. 6T o o t a rErr3rr!'Er qlo 2. o B e to lr N o o 6 F' rC 6 'Err!rr!.rir E ltt I E IHHF c lltllE.lle.l?! E a dddd t o o C) ca HN666a@OUtO!FrON HNNd6d (ON d H I Nd F d F N g g) Or g! rO N o! f, tl lO lO { aa qt 02ddNNNd E € d 6 F , 16€\lOO16t-!.t+CrOaad ? c N HCaOild6l € 6 o F 6 H(0roooclooutd€(0 c 9gce9Q9S9e9e99gg a N@<.NCaOc|Nc)tl.@@dddNiH qlr b GadHdd ! o o N {|ocDorH@@c?.oH(0d { ooo@F6AG)aA{o)F@ rl o q) o Fts1J:ll:t@rOlo(A@(90N o SaNao6a6|HHHdCl6aGa E I I o 4 Fd6tNN{{.d(oHFF E o6NCaaagr('rorog)gro oA rddi cl t'l N6(ONNITTOON@(OCO 5 a

{) l) ao ti Fgeee$s!3A$e

68 Table 3?. lfionthly chemlcal determlnottong tn rng,/l (except pH) frcm three flxed etatlona ln Elephad Butt€ ltke.

Chemlcal Sta. Sta. 2 s& Alkaltntty: 11.0 Phemlphthaleln 4.0 5.0 8.0 30.0 15.0 8.0 9.0 6.0 r42.o Met\yl orange 125.0 186.0 160.0 162.0 148.0 t42.O 166.0 169.0 lterebre: 0.0 Itydrcxlde 0.0 0.0 0.0 t52 18.0 0.0 0.0 0.0 22.O Carbonate 8.0 10.0 16.0 60.0 0.0 124.O 18.0 12.0 120.0 Blcarbon&te 11?.0 L2.6 196.0 102.0 0.0 0.0 14?.0 16?.0 194.0 Totd hardneoe t12.0 206.0 210.0 2L4.O 166.0 196.0 206.0 220.0 148.0 Calclum hardnees 156.0 160.0 156.0 150.0 146.0 188.0 L41',.O 180.0 2.4 Dlssolved oxygen 10.3 9.5 9.3 10.0 11.1 9.6 5.2 2.8 0.0 Free carbon dlo:dde 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 llydrcgen anlide 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 pH ?.6 ?.6 1.4 ?.6 7.4 ?.6 8.3 8.8 8.1 July. l9?0 Aucust. 19?0 SeDtsmber. 19?0 $a. I $a. 2 $a.8 Sa. 1 t€,.2 Sta. I $8. I lla. 2 t*8. I Alkallnlty: Phenolphtbaletn 10.0 13.0 1.0 3.0 8.0 8.0 3.0 Lz.O 13.0 Metbyl orgstre 169.0 15?.0 164.0 162.0 r12.O 168.0 189.0 1E5.0 176.0 lterefore: Hydroxtde 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Cst'bonds 20.0 26.0 2.O 6.0 16.0 16.0 6.0 24.O 26.0 BtcarboDate 149.0 131.0 152.0 156.0 166.0 152.0 183.0 161.0 160.0 Total hanlnega 22.8.0 216.0 216.O 194.0 1&L 0 176.0 214.O 206.0 182.0 Calclum her6eaa 118.0 136.0 14,r.0 150.0 1,t16.0 120.0 t.14.o 166.0 96.0 Dlgaolved oryger 4.9 7.4 6.5 7.6 7.6 10.0 5.3 ?.6 6.0 Free carbon dflodde 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Ifdrcgen anlf,de 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 pH E.5 8.6 8.8 E.2 8. I 8.2 ?.8 8.6 8.9

October. 1970 libvember. 19?0 December. 19?0 $o. 1 S8. 2 Sta. 3 Sta. I $a. 2 t[&8 $a. 1 S&2 ffr.3 Alkallntty: Phercphthaleln 0.0 lr.0 0.0 4.6 26.O 6.6 4.0 9.0 6.8 MetbS'l oralge 186.0 183.0 208.0 189.4 153.6 164.4 200.0 161.6 152.6 therebre: Hydrcdde 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Carbonate 0.0 22.0 0.0 s.2 10.0 Lt.2 8.0 18.0 11.6 Btcalbonat€ r85.0 141.0 208.0 180.2 148.6 t43.2 192.0 148.6 141.0 Total har$ese 294.O 2U.0 286.0 2L0 182.0 268.0 192.0 260.0 918.0 Calctum har&eaa 170.0 114.0 L24.O 64 84.0 94.0 162.0 1?6.0 164.0 Dlsolved or(ygon 10.0 10.0 tt.z 8.0 48 10.0 8.8 4.0 10.0 Free calbon dtorddo 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 gdrcgen anlfide 0.0 0.0 0.0 o.0 0.0 0.0 0.0 0.0 0.0 pH 8.5 8.5 8.5 8.6 8.6 8.5 8.6 8.5 8.6

Jalrarv. 1971 F€bnr'n/. l9?l Mr.roh. 19?1 $r" 1 $a. 2 tl& 3 Sla. I Sts. 2 $4. 3 $a" 1 $a. 2 Sta. I Alkaltnlty: Phemphtheleln 6.6 1.6 19.0 2.4 .L6 6.8 6.2 8.2 9.8 Metbyl orange t79.4 170.0 1?3.4 166.4 166.2 16?.4 t?8.2 188.2 t87.2 lterefore: IIydrcride 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Carbomte tt.2 s.2 38.0 4.8 9.2 18.6 10.4 10.4 19.6 Btcartonat€ 168.2 166.8 135.4 160.6 16?.0 158.8 167.8 166.8 16?.6 Total hartheaa 294.O 262.0 2tO.0 332.0 362.0 264.O 812.0 264.0 266.0 Calclum har$esa 160.0 146.0 158.0 240.0 238.0 230.0 170.0 164.0 146.0 Dieeolved oxygen 11.0 13.0 14.0 10.0 L2.0 18.0 12.0 L2.0 16.0 Free celbon d[oxtde 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Hydrcgen sulf,de 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 pH E.6 8.6 8.5 8.4 8.7 8.8 8.4 8.7 9.0

69 Table 88. Quarterly phystcal and chemtcal determlnatlone from Elephant Butte Lake. Conoentratlone la mg/l €xcept as noted.

June. 19?0 Sedemb€r. 19?0 December. 19?0 March. 19?1 Cbemical Analyela Stt. 1 $a" 2 Ste. 3 $a. 1 *t. 2 ffa. 3 Sa.1 $s.2 $a.3 $a. 1 $a.2 $& I Dlssolved oxJ6en 5.2 2,6 2.4 6.3 7.6 5.0 8.3 ,L 0 10.0 10.0 t2.0 13.0 Free carbon diodde 0.0 o.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 flkaltnfry Phemlphthaletn 9.0 6.0 11.0 1.0 5.0 2.O ,L 0 9.0 6.8 2.4 4.6 6.8 Metbyl orange 165.0 169.0 14?.0 126.0 172.0 180.0 200.0 161.6 L62.6 165.4 166.2 L67.4 Iterefore: Wdrodde 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Carbonate 18.0 Lz.O 22.0 2.0 10.0 ,L o 8.0 18.0 11.6 4.8 s.2 13.6 BlcalboDate r47.O 167.0 120.0 124.0 162.0 1?6.0 152.0 143.6 41.0 160.6 157.0 163.8 lotal (Yers€Dat€) har&ess 206.0 220.0 194.0 198.0 224.0 218.0 294.0 260.0 318.0 332.0 852.0 264.0 Calclum hardnesa 144.0 180.0 148.0 152.0 150.0 186.0 162.0 1?6.0 164.0 240.0 2S8.0 230.0 Alumln:m 0.18 0.18 0.28 0.26 0.32 0.4 0.26 0.21 0.26 0.16 0.19 0.24 Barfum 9.0 11.0 18.0 16.0 20.0 15.0 6.0 7.0 8.0 Lz.O 12.5 14.5 Bonon 0.02 0.03 0.2 0.0 0.0 0.o8 0.05 0.05 0.0? 0.0 0.0 0.25 Bltonlne 0.0 0.01 0.02 0.08 0.05 0.36 Trace 0.0 Trace 0.02 0.0 0.0 Chlorlde 39.5 3?.6 38.0 8?.0 4.6 54.6 55.0 58.0 46.0 40.0 3?.0 35.5 NaCl 61.9 61.9 82.7 61.1 73.4 89.9 91.0 88.0 74.0 66.0 61.1 58.6 Chlorlne 0.0 0.0 0.01 0.o2 0.02 0.1 Trace 0.0 Trace 0.03 0.0 0.0 Chrcmate 0.06 0.06 0.08 0.07 0.06 0.1 0.07 0.06 0.09 0.02 0.06 0.06 Color @laffmrm- cobalt untte) Aparent 510 60 30 60 266 60 50 60 15 25 50 Tnre 5E 20 28 86 509 820 10736 Copper o.22 0.2 0.08 0.35 0.41 0.8 0.45 0.5 0.6 0.,15 0. 39 0. 4 Cyanide 0.08 0.0 0.0 0.0 0.0 0.0 Detergentg 0.06 0.08 0.0r 0.03 0.03 0.04 0.08 0.02 0.02 0.04 0.o2 0.(X Flourlde 0.06 0.0? 0.20 0.66 0.77 o.zl 1.0 1.10 1.10 L.26 0.90 0.8S Hydrazlne 0.0 0.0 0.01 0.0 0.01 0.1 0.03 0.62 0.03 Tlace 0.0 Trace Hydrcgen arlfide 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Ilon (total) 0.05 0.08 0.16 0.62 0.1 0.L2 0.16 0.05 0.05 0.1 Ferroua -:'o _:'o 0.03 0.0 0.16 0.05 Tlace 0.02 .01 .02 .0? Ferrlc 0.0 0.16 o.4t 0.o5 0.L2 0. 14 .04 .03 .03 Manganeee 0.4 1.4 0.6 0.0 0.0 0.0 0.5 0.26 0.5 8.1 0.7 1.1 Nltmgen Amonium 0. 15 0.3 0.8 0. 1 0.18 0.85 0.2 0.8 0. ? 0.16 0.2 0.3 Nttrtt€ 0.0 Ttace Trace 0.0 0.0 0.03 0.0 Trace 0.0? 0.02 0.02 0.02 Nltrate 18.0 0.0 8.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Phercls 0.0 0.0 0.02 0.0 0. 0 0.0 0.0 0.0 0.0 Trace Trace l}ace Phosphate Tbtal 0.8 1.8 0.3 0.8 1.2 2.3 0.45 0.5 0.5 o.2 0.3 0.5 O'rtho 0.1 0.0 0.1 0.5 0.1 0.5 0.25 0.3 0. I 0.1 0.1 0.3 Foly (meta-) 0.1 1.8 o.2 0.3 1. 1 1.8 0.20 0.2 0.2 0.1 0.2 0.2 Selenlum 0.0 0.01 0.01 Trace Tlace 0.03 0.0 Trace Trace 0.04 0.0E 0. 1 SlUca 11.0 11.0 1?.0 14.0 13.0 18.0 0.0 1.0 1.0 8.1 10.0 14.0 Sllver 0.05 0.05 0.5 0.03 0.04 0.07 0.06 0.03 0.06 0.05 0.05 0.05 tltlfate 89.0 89.0 90.0 110.0 126.0 180.0 160.0 180.0 106.0 120.0 100.0 98.0 Tanntn and llgntn (as taDric actd) 0.35 0.4 0.6 0.4 0.8 1.0 L.2 1.16 t.zL 0. I 0.1 0.3 TDS (as NaCl) 300.0 285.0 262.0 290.0 31?.5 862.5 338.0 315.0 278.0 342.6 282.6 282.5 I\rrbidtty (Jack8on urtts) 0.0 9.0 28.0 14 2E LOz 19 25 2S 346 pH G+ - bn corc.) 8.3 8.8 8. 1 ?.8 8.6 8.9 8.5 E.6 8.5 8.4 8,7 8.8 $eclflc gravtty 1.00r 1. (x)1 1.00r 1.001 1.001 r.0,01 1.001 1.001 1.001 1.001 1.001 1.001 Speclflc condrctance (m mhos,/cm) 0.66 0.?0 o.77 0.74 0.?0 0.62 0. ?5 0.65 0.65

70 B io log ico I Fo ctors

Coliform bacteria. Most probable numbers (MPN) of coliform bacteria were monitored monthly from 1964 to 1971 to give an indication of domestic pollution which enters Elephant Butte Lake from approximately one-half million people wtro live in the Rio Grande watershed in New Mexico, MPN of total coliforms @srobacter. aerogenes and Escherichia coli) is usually small (table 39), suggesting that intensity of domestic pollution is low. Partitioning of E. coli to determine proportion of total coliforms vihich is definitely of fecal origin, shows that fecal pollution is slight even when total coliform counts are relatively high (table 40). Numbers of E. coli shown here could result entirely from cattle and wild homeothermic animals living adjacent to the lake. MPN of total coliforms increases to levels such as those occurring in September and October, 1969, when water storage is small and when large amounts of terrestrial vegetation are inundated by rising water. S

Plankton. Density and biomass of net plankton are consistently low (table 41). Zooplankton is proportionately high in all samples (table 42), which indicates a rapid hrrnover rate and heavy consumption ofphytoplankton by gizzard sbad (Jester and Jensen, 1972). 3B. L.'J*"*, and C. Sanchez, Jr., 19?0. Collfom bacterta tD Elephatt Brtte Lake, New Mexlco. Paper preaoted to Arlzoe-New Mexlco Ch4pter, Amerlcan Ftsberloo Sootety.

Table 39. Moat prcbable nrmber (MPN) of collbrrn bacterta per 10O ml of water 8t $auols l, 2, and I lr El€Fhant htte Lalce, Aprll, 19?0, thrilgh Uerlh, lg?1.

Colt$ms per lfi) ml H2O Dudry tfiontbs of StatfoDAMJJASONDJfM FPN -

1 0.0 23.0 9. 1 8.6 0.0 3.6 0.0 0.0 o.0 2 8.6 0.0 9. 1 9, 1 3.6 0.0 3.6 9. I 3.6 3 23.0 9.0 23.0 7.8 43.0 9. I 9. I 9.6 8.8 lbble ,10. MPN of total coltbrm baoterla and Erohertohrts colt per 100 ml of ryater |a Ef€pb8d htt€ lrke, S€pt€mber- @ber, 1969.

MPN Coltbrne oer 100 ml H2O Set|oa I *otbr 2 Ss$ou I bd lbtal -8. olt lbtd E. oolt fred E. oott SeptemDer 20 3 6.2 3 28 t{ October ?5 0 240 8.2 2g 0 Ilotds 96 3 2tt8.2 s.2 51 1a

Teble 41. Volunsr of let plenkton 6mrd lr Elophsnt Drtte LaLe, June, 19?0, thtoug! Itarch, 19?1.

Mtlltlttera ol plankton per cublc meter of water drrlDs nod,ha of - $atto[ MeaDt 1 2.7 8.0 4.2 3. I 1.6 3.6 2.6 0.8 1.E 4.4 2.8 2 3.8 ?.6 8. I 1.5 6.2 6.4 2.8 L.1 8.2 8.7 4.2 3 E.2 t4.4 10.0 11. I t1. 1 9.6 t4.4 8.9 9.6 0.9 7.5 Welghted rneana 4. I 6.{ 6. I 3.0 8.7 5. 1 8.7 1.6 2.6 8.6 {.0

7t NrO 6r!:rO O cooo r4t61 6too e !.ooo do Foo o oooo daD Noo 6a NOirc @do IDNC) H

o)(o ott6|N N aoooo oN o)oo (', NO('tO to(0 iooo o) oco0 lo s!oo ro doNo Fdol (od N cr

Ga or 6r o) 14) uir toooo roro ooo d t-ONO od !too (D dooo s'{ doo gr oooo CO CA o rllN N O)

(o{. o|oaa o NOOO cDo oi!000 0 NOOO .DH (DT9N (o HOOO @F 6rOO (D lod(') {. r|. ot oooc

{ro oilo.o o @o{o dtg !|€O t- 9?OOO oiti. ioao ro 6aooo oro ooo ro !.ooc IgH O H ttd ir 6t

q, oo oe{ N o€No o(D tfcc oll 1r!0NO x raN FON tr NOOO OH b.CO ('l oooo q rDd N (D Fd d or o e fir$ a!roo 6) groNo 6a rt@ dNO !t (oooo a 6|rd 30ro 6 oooo g) oit Glcto cr oooo cl trH(D c ca ol Aq a o F tl 6r i.aa utOti qr odco N ON NOO N oo@o E (DC (')O@ ts ddoc oirF ooo o oooo tgd (D E .f lOTa N gl t c a cE Eg li NrO OOH @ {.€oo r0(D 6aco o NOOC lrro doca F HOOO irj gtoo o icco E l''d N O c (0d i €l a a iq) F<. (orO O lifitQO ga q)d dtcc o ocoo oi €ad Noc o docc €6| OOO ('| dooo E Fd d (D cl odgr qt a o k o A N(O tsaDO 6 NONO 6l €r H (ooo ro do{ro o |'r

c.i o gBsiusis €6 F BFFB$s" FEgEus;EggHFes

72 Benthos. Uhland (in Padilla, et 4. , 19?1) analyzed 5t feet2 (4.75 m2; of bottom samples to deterrnine incidence, densit5r, volume, and distribution of benthos by depth and type of substrate. He found a sparse benthic fauna in terms of both density and variety (table 43). Distribution varied with depth and proportions of silt and sand in the zubstrate (tables 44-461, A crawfish, Orconecteg causeyi Jester, varies' apparently in a three-year cycle, from sparse to abundant (.3 to >30 per 24-hour gill-net set) while other benthos appears not to have varied significantly from quantities shown here, from 1964 to L972.

Table 43. Numbera, welghta (gram!), and volumea (ml) of bedhlc ottErl8m6 and percentagee of total sarrple comPoeed of t-t tt -.r -.tt "-t " Perc€d Peroert Percelrt Orgrnt36" Number Itrnb€r Wetght Welgbt Volume Volume Tendpedldae 825 76.4 0.63 85.4 0. E6 77.8 Ougocbreta 9E 22.8 0.10 13.7 0.25 22.7 Hlnndlnea 4 0.0 Trace Traoe Trace Trsc€ l{ematoda 3 0.? Trace Trace Trace Trace Peychodldae 1 o.2 Trace Trace Ilace Ilac€ lbtd 4S1 0. ?3 1. 10

Table 44. Depth-frequency dldrtbutlon of bed,hoe ghowa ag mean nurnber per squane bot (ca. O. 1 -2) of 481 ortirnlsms ln Elephant Bntte Lake, Ocbber, 1969, thrc.gh AprU, 19?0.

Interval Sample of DeFh 8[ze Orgedlms oer &uare Foot t-r 6]r 0 I 7.0 0.0 2.0 9.0 I I 8.2 1.0 0.0 9.2 6 I 19.7 3.0 0.0 22.1 I 6 2.6 1.8 0.0 8.8 L2 18 2.6 1.6 0.2 4.2 15 l0 L.4 3.? 0. 1 6.2 IE I 11.8 0.9 0.2 t2.g 2l 1 ?.0 0.0 1.0 8.0 24 2 lE.0 5.O 0.0 23.0

Grad meane 6.4 1.9 o.2 8.6

Table 46. lfean nrnber of 431 bedhlc otTontlm! p6r BqurlE bot (ca. 0. f n2; of bottom oonpoaedof varlous prcpor'ttolrof atlt. Elephant Butte Lake' @tober' 1969, througb Aprtl' 19?0. ht6nal Sa4le Percent $ze srlt (fL 2) 0 L2 6.8 2.2 0.0 ?.8 10 I 22.0 8.0 0.0 25.O 20 t 3.0 2.O 0.0 6.0 30 4 t2.7 1.E 0.5 15.0 40 3 1.8 1.8 0.0 2.6 50 3 3.0 0.0 0.3 3.3 60 I 21.0 0.0 0.0 21.0 ?0 6 3.3 2.7 0.2 6.2 EO l3 3. 1 0.9 0.3 4.3 90 7 12.6 4.1 0.0 16. ? 0-49 44.6 10.3 0.5 55.4 50-99 43.0 7.7 0.6 61.6 Total 8?.6 18.0 1.3 106.9

73 Table 46. Mean mrmber of 431 boutbtc organlams per square bot (ca. 0. f m2) compoaed of vartouaploportlone of sand. Elephant Butte Lake, October 1969' through Aprll' 19?0.

Idelral Somple Percent $ze trbot Sand Othere 81 6.6 2.O 0.2 ?.8 10 3 1?.3 0.3 0.0 1?.6 20 2 4.0 0.0 1.0 5.0 80 3 1.8 2.7 0.0 4.O 40 I 19.0 6.0 0.0 24.0 60 2 1.6 1.0 0.0 2.6 60 0 ?0 4 7.O 2.0 0.0 9.0 80 1 0.0 2.0 0.0 2.O 90 2 0.0 0.0 0.0 0.0

0-49 47.2 10.0 t.2 58. { 5(F99 8.5 6.0 0.0 13.5 1lotal 66. ? 16.0 t.2 ?1.9

Populolions

Vorious Droinoges

Populations of river carpsucker are mentioned frequently in published literahrre but usually are dismissed with brief general statements. Eschmeyer, g! al. (19441 reported taking ?7 specimens in Chickamauga Reser:voir, Tennessee. Patriarche and Campbetl (1957) reported Carpiodes carpio as I'present'r in Clearwater Lake, Missouri. Bonn and Holbert (1961) mentioned the species as ttcommonrt in L,avon and Bonham Park Lakes, Texas. Starrett and Fritz (1965) stated that the species was trcommonrr in Lake Chatauqua, Illinois, that none are taken by anglers, a few are taken commercially, and they gave the size of the largest specimen. Population estimates were published by Behmer (1969) for the Des Moines River, Iowa, and Jester (1971a) for Elephant Butte Lake, New Mexico. Other than the latter two citations, most carpsucker population data are contained in multilithed state fishery reports. Ttre status of river car?sucker in lakes and streams in the South Canadian, Pecos, and Rio Grande drainages, in New Mexico, is strmmafized from such literafure.

South Canadiaa drainage. Ttre South Canadian River rises in an alpine canyon in the Sangre de Cristo Mountains (southern Rockies) just west of Raton Pass, on the New Mexico-Colorado boundary. It flows southerly for approximately 150 miles (240 km) before entering Conchas Lake (see figure 2). All of the headwater streams a.nd impoundments are trout waters. The prevalent catostomid is the white sucker, Catostomus commersoni 1f,acLp6ae1, downstream to the vicinity of Mills Canyon, approximately 50 miles (80 km) upstream from Conchas Lake. The author has collected river carpsucker at Mills Canyon but they apparently are not common. Between Mills Canyon and Conchas Lake, carpsucker become abundant. During a three-year study of Conchas Lake, the author found the species to be third to gizzard shad arrd white crappie in relative density. It was approximately equal to gizzard shad in terms of relative biomass during two years and was second during the third

74 year. Drring 1961, collections in experimental gill nets included 3' 002 fish weighing 2,676 pounds (1,213. I kg). Carpzucker numbered 260 and weighed 543 pounds (246.3 kS), This was appnoximately nine percent of the total number (relative density) of fish and 20 percent of the weight (relative biomass). Drnng 1959 and 1960' carpsucker constituted 15 and 16 percent of the number and 34 and 33 percent of the weight of fish taken (Jester, L962a). In a periodic check, Little (1964b) took 450 fish including 153 (34 percent) river carpsucker which weighed 430 pounds (195 kg) (60 percent).

Ute Lake was impounded on the South Canadian River in 1963, on El Llano Estacado (the Staked Plain), 60 miles (96 km) downstream from Conchas Lake. It is similar to Conchas Lake, in that both are dimictic, morphometrically oligotrophic, and are subject to essentially the same climate and weather. Ute Lake has a mar

Pecos drainage. The Pecos River also rises in the Sangre de Cristo Mountains' southwest of the headwaters of the South Canadian River and east of the Rio Grande. Many trout streams in the Pecos Wilderness (Santa Fe National Forest) contribute water, and the Pecos is an important trout stream in the headwaters (Harrison, 1965). The fish fauna is poorly known from the lower limit of the trout fishery to U, S. Highway 66 (I-40), some 80 miles (130 km) further south in east-central New Mexico. From this point near the western edge of the Staked Plain through the desert of southeastern New Mexico, numerous fishery investigations have been completed.

Little (1962) reported that carpsucker comprised 11 percent of the number of fishes in samples from the Pecos River between Highway 66 and Alamogordo Reser- voir, Ttrey comprised 7. 1 percent of the number and 34 percent of the weight of fishes in the reservoir (Little, 1964c).

Two additional main-stream irrigation reservoirs are located on the Pecos River downstream from Alamogordo Dam. McMillan Reservoir, the upstream member of this pair, yielded 4t percent river carpsucker by number and 34 percent by weight in population samples (Little, 1964d).

Little (1963a; 1964e) also reported percentages of numbers and weights of each species taken from the river between McMillan Reservoir and Avalon Reservoir (the downstream member) during a seven-year period. Percentages of these fishes that were river carpsucker are: L957 1958 1959 1960 1961 L962 1963 Percent N 31.6 15.4 21.4 ,T ,6 39.2 24.8 L4.7 Percent W L4.L LA.2 23.8 4.7 24.3 23,9 8.5

75 Navarre (1960) summarized the catch for 1955 through 1959 (fnom Morley, 1956; Navarre, 1958a, Navarre, 1959) taken in abarrier and trap which was installedacross the river between the reservoirs i:r an attempt to reduce rrroughrt fishes. The trap was designed to take all fishes which crossed the barrier in either direction. Carpsucker catches were as follows: 1955 1956 1957 1958 1959 Number 32,803 11,400 5,943 820 3,411 Weight, pounds 4,982 2,198 3,436 330 1,811 Weight, kg 2,260 997 1,559 150 82L Percent W 11.9 11.3 4.6 0.9 35.4

Little (1963b) operated the trap for 10 days in L962. He took ?1 carpsucker weighing 45 pounds (20.4 kg). This was 48 percent of the number and 40 percent of the weight of fishes trapped.

The Pecos River below the McMillan-Avalon reseryoir complex is used heavily as a source of irrigation water. Chemical concentrations are high with total (Versenate) hardness ranging up to 2,960 and chlorides up to 15r 000 mg/1 (Little, L964al. This portion of the river extends some 70 miles (112 km) through Chihuahuan Desert to the New Mexico-Texas state line. Little (9. g:!. ) sampled fish populations at 24 stations during one year. His catch of river carpsucker consisted of 618 fish, which weighed 952 pounds (432 kg). This catch ranked second in number (25 percentz 4L.4 percent gizzard shad) and first in weight by a wide margin (34 perceutz L8.2 percent gizzard shad).

Five reports (Little; 1959; 1960; 1964f; 1965; Navarre, 1958b) included population data from two tributary streams and two small impoundments in the lower Pecos drainage. Total collections from these waters consisted of 27,885 fish which weighed 81297 pounds (3,764 kg). Carpsucker numbered 1,380 (5 percent) and weighed 2,099 pounds (952 kg or 25 percent).

None of these authors attempted to estimate density or biomass on an areal or total basis. However, their relative densities and biomasses demonstrate that river carpsucker definitely should be classified as t'common" in the South Canadian and Pecos drainages.

Rio Grande drainage. The Rio Grande rises in the Sangre de Cristo Mountains of south-central Colorado. It flows acnoss New Mexico from north to south before becoming the Texas-Mexico border. The Pecos River is a major tributary to the Rio Grande in West Texas. Ttrus, both drainages empty into the Gulf of Mexico. The South Canadian River rises near the headwaters of the Rio Grande-Pecos system but drains into the Gulf via the Arkansas and finally the Mississippi. ltre Rio Grande is the westerrr-most drainage in which the river carpsucker is endemic to the fauna.

Headwaters and tributaries in Colorado and northern New Mexico are mountain trout streams containing native Rio Grande cutthroat, Salmo clarki virginalis Cope, and introduced rainbow, brown, brook, and Dolly Varden. The main stream of the Rio Grande in New lVbxico contains few native species of game fishes. It flows

76 throughadeepgrogefor approximatelyl00 miles (160 km), beginning near theColorado boundary. The portion of the river in the gorge and for a short distance downstream has been used as a rainbow and bnown trout fishery for about 60 years (Jester, 1963a).

South of the gorge, the river follows a series of increasingly wider valleys. From Albuquerque southward, low semi-arid and arid hills and rct€h, arroyo-cut, desert plains--in the Sonoran Life Zones--bound ttre river. The portion from Albuquerque downstream has been stocked with ltwarm-watertt species since the 1880rs (Huntington and Hill, 1956). TVo main-stream reservoirs are located in the Chihuahuan Desert of southwestern New Mexico, near the town of Truth or Consequences. These are Elephant Butte Lake and Caballo Lake, which is approximately 20 miles (32 km) further downstream. These impoundments support a vast irrigation system in approximately 150 miles (240 km) of the Rio Grande Valley in southern New Mexieo and the vicinity of El Paso, Texas-Juarez, Chihuahua (Huntington and Hill, 1956; Rael and Ozmina, 1965).

The river carpsucker is known to inhabit the Rio Grande as far north as the village of Rinconada, Rio Arriba County, which is near the mouth of the Rio Grande Gorge approximately 120 miles (192 km) south of the Colorado boundary. 1he species was characterized as rtpresenttt in this area as only two specimens were observed during a year of sampling (Jester, 1963a).

Basic sun/eys of numerous series of irrigation drains and the main stream of the Rio Grande fnom Albuquerque downstream revealed that the carpsucker is one of the dominant species inthe lower 250 miles (400 km) of the drainage in NewMexico (Huntington and Navarre, L957; Huntington and Jester' 1958).

Two population anal.yses, made prior to our investigations of catch per unit of effort and mark-and-recapture data, showed that the carpsucker is also one of the more abundant fishes in Elephant Butte Lake. Huntington and Hill (1956) collected 14,813 fish, including 2,405 carpsucker or 16.2 percent of the fish taken. Approxi- mately half of the sample (7,84I fish) was taken in gill nets. Of these fish, 2,381 were car?zucker, which was 30.4 percent of the number of fish netted. Only gizzard shad were more numeroug,

Rael and Ozmina (1965) also collected with (experimental) gill nets. Their sample consisted of 2,843 fish, which weighed 2,784 pounds (1,263 kg). The number of carpsucker was 478 or 16.8 percent of the sample, uihich is approximately one- half the percentage of carpsuckers taken in gill nets by Huntington and Hill some 10 years earlier. The 478 specimens weighed 715 pounds (324 kg) and constituted 26 percent of the sample weight. Gizzard shad were much more numerous at 41 percent of the sample but made up only 8.5 percent of the weight. Smallmouth buffalo were slightly more numerous (17 percent) than carpsucker and constituted a greater portion of the weight (26 percent carpsucker: 35 percent buffalo). Otrr investigations of carpsucker population density and biomass were more prolonged, intensive, and sophisticated than these analyses and are discussed separately.

77 Two estimates of carpsucker biomass in the Rio Grande between the two lakes were made following rotenone treatments in L95? and 1960. Huntington and Jester (1958) estimated 1,709 pounds (776.8 kg) per mile (1.6 km) on the basis of twelve 0.l-mile (0. 16*m) samples. Three years later, Regan (1961) estimated 1,200 pounds (545.5 kg) per mile (1.6 km). The Rio Grande was estimated to be 10 m (33 feet) wide, as was the Des Moines River when Behmer (1969) estimated 1,760 pounds (800 kg) per mile (1.6 km). Behmer used the Schnabel (1938) Method and stated that his estimate was conservative because of inadequate distribution of marked carpsucker in the population. Obviously, the Rio Grande estimates were conservative as they depended upon recoverT/ of dead fish, which was facilitated by closure of the outlet in Elephant Butte Dam. However, closeness of the estimates (table 47) in streams of the same size tend to validate the estimates, with the limita- tion that all were somewhat eonservative. Rotenone was applied to the Rio Grande with the objective of destroying all fishes, and Reganf s estimate was made three years after the first treatment. Thus, 11 200 fish per mile (1.6 km) represents a three-year population development which resulted from immigration of carpsucker into the river from one or both lakes.

Caballo Lake, along with the Rio Grande, was treated with rotenone, in 1960. Regan (op. cit. ) estimated that 315 pounds of carpsucker per acre (351. kg/ha) were killed. This weight represented 45 percent of the biomass of fish in the lake. In post-rotenone investigations, Regan (1961) did not find the carpsucker in the river, Dixon (1963) failed to collect the species in Caballo Lake, and Ozmina (1965) reported only five carpsucker in a collection of ?r 331 fish from the lake. In 1972, carpsucker are known to be numerous in the Rio Grande and sparse in Caballo Lake.

Regan (1960) also took 15 carpsucker in a collection of 55 fish from an irrigation drain at Hatch, Dona Ana County, New Mexico, 55 miles (88 km) downstream from Caballo Dam.

E le ph o nt Butle Lo ke

Our investigations of the river carpsucker in Elephant Butte Lake included annual analyses of relative density and biomass in population samples, catch per unit of effort,

Trrble 4?. Egttmates of rlver catasucker populailone tnthe Dee ltfiolnes Rlver, Iowa, ln 19G9, and the Rto Grande, New Mexlco, between Elephant Butte and Caballo Lakee h 195? aDd 1960.

Des Molnee Rtver Rlo Grande Behmer, 1969 Huattngton and Jester, 1958 Regan, 1961 Number per kllometer 1, ?33 hectare 1, ?33 rntle 2,779 acre 69? Wetght kllograme per kllometer 500 486 341 kilograms per hectare 500 486 34r pounds per olle 1, ?60 1, ?09 r.2oo pounde per acre 43 430 302

78 and estimates of population density from mark-and-recaphrre data. These parameters are discussed in terms of interactions with other populations and changes in water storage from 1964-65 tD I97L-72. All population data used in this paper were taken in experimental gill nets, described under Methods. Samphng periods were eight arurual segments of April through March, 1964 to L972. Samples were taken during at least three weeks of almost every month during the eight-year period.

Relative densitv and biomass. These parameters are defined as the number and weight of one species or group of fish as percentages of total number and weight of all fish taken in experimental gill nets during a sampling period. Commercial fishes' including river carpsucker, comprised 20.9 percent of the relative density during all segments. Densities were above the mean during three of the first four segments (1964-68), and below the mean and declining during four subsequent segments (1968-72). Relative biomass followed a similar but slightly more erratic trend, varying about a mean of 50. ? percent and declining from earlier to later segments (table 48). Varia- tions in relative density and biomass of game and forage fish groups are included to indicate interactions among the three groups.

Interactions amorg species within the commercial-fish group must also be considered to indicate the status of the river carpsucker among species which cohabit a portion of the lake bottom and apparently compete for benthos produced in the cohabited area. Distributionof river carpsucker is limitedto depths <11 m(35 ft.)' which com- prise approximately 35 percent of the bottom area of the lake, most carp occupy this area) and smallmouth buffalo inhabit the entire lake bottom. Thus, changes in relative density and biomass of buffalo and carp are partially reflected by changes in these parameters of carpsucker. This is shown by the slight increase and relative stability of combined relative biomass of buffalo and carp in 1968-72, corresponding to a decrease and relative stability of carpzucker during the same period (table 49). Com- bined relative biomass of buffalo and carp (not shown) was L6.4, 22.7, 27.2, and23.7 percent, compared with 28.3, 22.8, 2L.1, and 24.8 petcent carpsucker during the four segments. The general decline in relative density and biomass of buffalo; ac- companied by variations in these parameters of carpsucker, carP, game' a.nd forage fish populations; suggest certain effects of selective commercial harvest of buffalo (1963 to the present) on interactions between and within groups. Interactions are

Table rl8. Reladve denstttea and blomaeBee of grcups of f,shee ttr potrrlatlor aanplee taken from Elephant &rtte Iake durtng elgbt annal aegtnelrta' 1984 to 19?2.

Game flgh N 16.5 tL.2 22.2 20.1 19.9 16.1 L2.S 8.6 16. ? w 22.3 32.0 4E.8 4.1 4L,2 36.1 27.6 24.6 84.4

Forage fleh N 42.5 65.9 68. r 67.2 60.8 69.6 ?3.6 7E.9 68.4 w 6.5 9. 1 9. 1 LO.2 14. I 19.4 21.r 27.O 14.9

Commerclal fleh N 40.6 23.2 19. ? 22.7 19.3 15.8 14. r L2.6 20.9 w 71.2 58.9 42.7 46.7 44.7 46.6 48.8 48.6 50. ?

79 Table 49. Relatlve deusttleg and blonaaseg of commerolal f,ahea ta pprlatlon samples tako from Elephad Drttc Lake drrlry etght allrlral segD€nta' 1964 b 1572.

$ectes Carp N 9.8 6. 1 3. 1 4.7 4. 1 6.0 4.6 4.0 6.3 w 8.? 7.6 4. 1 6.4 6.6 10.1 9.2 s.2 1.f tuallmorth bufialo N 18.9 9.9 1.2 6.2 8. I 2.7 3.8 2.8 6.9 w 36.2 36.6 22.6 16.7 9.9 12.6 18.0 14.6 20.9

Rlver carpeircker N 16.9 7.8 9.4 12.8 12.L 6.6 6.2 6.2 9.8 w 26.8 L4.7 16. 1 22.6 28.3 22.8 2t.t 24.8 22.r diseussed below under topics where independent parameters allow clarity of interpretation which is not afforded by relative values.

Catch per net-unit. Relative density and biomass of species or groups may be affected by changes in populations of other species or groups, thus indicating changes in populations which may not have occurred. Stability or real changes in populations must be determined by use of indices or estimates of abundance (Jester, 19?1a).

One method of establishing indices of abundance is to compute catch rates per unit of sampling effort. Jester (gp. gi!. ) devised catch per net-unit as a method for determiqing numbers and weights of each species caught per unit of effort in experimental gill nets. A net-unit consists of a 25 by 10-foot (7.6 x 3m) panel of one size gresh set fcr 24 consecutive hours. Catch per net-unit consists of mean number (Cfl or weight (Cyy) of that species caught per net-unit, in net-units in which the species is taken. Cn should vary with density and C1y with biomass of a population when samples are representative and size of the lake is constant. Variations in catchability between species preclude determination of relative size of populations by parallel comparisons of Co and C* during one sampling period. However, linear or chronological comparisons of these data may be made to show changes in each population, then parallel comparison may be made to show relative changes between populations.

Elephant Butte Lake is subject to a^n annual fillilg and dewatering cycle which follows a similar pattern each year, so that annual Co and C* values should be comparable linearly. However, mean annual area and volume vary considerably because of erratic precipitation and snowpacks in the watershed. Ttrus, the annual cycle is consistent but annual mean area and volume are not, so that C1 and C,,, are affected from year to year by crowding or dilution of populations. During the eight annual segments, from 1964 to L972, the area of the lake was smaller than the eight- year mean during three years and larger than the mean during five years. Crowding was more pronounced (drastic) than dilution, so it may be assumed that three years of crrowding and five years of dilutionjend to neutralize effects of these factors on eight-year mean values of Co and C*. Therefore, trends in Ca and Cy may be interpreted as reflecting trends in populations during the eight-year period.

80 Ea and 6* of commercial, game, forage, and all fish are shown in table 50, where decreasing commercial and forage fishes, and increasing game fishes imply interactions among these groups. The increase in game fishes is attributed partly to introduction of species and partly to utilization of resources which became available as a rezult of reduction of biomass of commercial fishes due to harvest of buffalo. Reduction of forage fishes is attributed to increased predation by larger populations of game fishes (Jester, 1971a).

Interactions between species of commercial fishes are also evident (table 50) in that carpsucker and carp tended to replace a portion of thre buffalo removed by commercial harvest. Again, parallel comparison of C1 and C* values may not be used to determine extent of this replacement because of variations in catchability between species. However, it may be concluded from trends in Ca and C* that the buffalo population has been reduced and that carpsucker and game fish populations have increased in response to reduction of buffalo. Carp density and biomass remained relatively stable through six years and appear to have increased in 1970-72. This increase may be more apparent tErn real because of the effect of an extreme drawdown on catch rates in l97l-72. C1 of total fish doubled from 1970-71 to L97l-72, and total commercial fish, carp, a:rd forage fishes 4so doubled, indicating that little real change occurred in these species and groups. C1 ofgame fisheq-increased by only 63 percent, which probably indicates a decline in density, while C* approximately doubled, injic2li* little change in biomass. Smallmouth buffalo failed to double Gn * 59Vo; Cw + 75Vo), also indicating possible declines in density and biomass. Cn and Cy of river carpsucker, alone among the groups and species shown intable 50, increasedby substantially more than 100 percent (Cn + L2\Voi C* * Li|Vol, implying real increases in density and biomass.

In the discussion of relative density and biomass above, it was suggested that competition among river carpsucker, carp, and smallmouth buffalo exerted substantial influence on density and biomass of the three populations in the portion of the lake < 11 m (95 ft. ) deep. It was estimated (Jester, I97Lal that during the first six segments (1964-?0), buffalo were reduced by 30,100 fish and 54'400 kg (119,759 lbs.) on these shoals by commercial harvest, and that carpsucker responded by increasing 161 percent (48,600)of thenumberand63percent (3?,050kgor81,512 lbs.)of the weight of buffalo removed fi:om shoals. Carp density a:rd biomass remained relatively stable. Although it will be shown by population estimates that changes in buffalo are rtrendsrt pnobably best described by two lines and changes in carpsucker were sigmoid; in density of buffalo, carpsucker, and carp are best described in terms of simple lin,ear regressions of Co and C* over time during the eight annual segments. Trends in C1 and Cys are represented by the formula: i=u+bXn, when: i = d1 or Ey "ooort Xn = ordered rank of years since sampling was started a = intercept b = coefficient of slope. Raw data, coefficients of slope, and its are shown for buffalo (table 51), river carpsucker (table 52), and carp (table 53). Trends and interactions indicated by these data 81 o A 5oa 9o6 I 6 F,o6' BFA dHe :6a Esra Q) iduj dF:.d dl:d da'd irid 6iddi ddo' (t: dBs, Nsg dd-i.3s R s3 se} se o a q) E {. u0o ON rO $Ne 5.oe S€S Po:6' SoA 8N- o 6lGA 3l did idd ddd ii.f' Gis.io' iic; aa { N8e caBK c N idci@ Eqe Se9 $s B= c

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82 Table 51. Computed trende ln 9o d C* of anrtlmoutl hffalo durlng elght years tn Elephad hrtte l,al

Year Y (No. ) 0.q)gxD Y =en 196S5 I 0.50 0.009 o.428 1965-66 2 0.53 0.018 0.419 1966-67 3 0.23 o.o21 0.410 196?-68 4 0.50 0.036 0.401 1968-69 D 0.24 0.0,15 0.392 1969-?0 6 0.29 0.064 0.388 19?0-?1 7 0.84 0.063 0.374 L97L-72 8 0.54 0.072 0.366

Y Gs) 0.015xn ti =Uw 1964-65 1 0.4(X) 0.015 0.388 1965-66 2 0.660 0.080 0.403 1966-6? 3 0.309 0.045 0.418 196?-68 4 0.558 0.060 0.433 1968-69 5 0.239 0.0?5 0.448 1969-?0 6 0.307 0.090 0.463 197G71 7 0.41? 0.105 0.4?8 L97r-72 8 o.729 0.120 0.49S

Table 52. Cogfutedtrends tn^-!n aod E* of rlver carprucker qfig etgbt yeare ln Elephant Butte Iake. Computed as as ? = bxn, ruten iiFil = 1.0?5 + 0.080Xa @bove) and ?@w) = 0. ?645 + 0.039:h @low).

Y€ar Y (No.) 0.080xn Y=Cn

1964-65 1 t.20 0.080 1.105 1965-66 2 0.96 0.0,60 1. r35 1966-6? 3 0.88 0.090 1. 185 196?-6E 4 1.9? 0.120 1.195 1968-69 D 1.19 0.160 t.226 1969-?0 6 0.91 0.180 1.256 1970-?1 7 0. ?9 0.210 1.285 t97L-72 E 1. ?8 0.240 1.315

196,1-66 I 0.910 0.039 0.804 1965-66 2 0.7L2 0.0?8 0.843 1966-6? 3 0.688 0.11? 0.882 196?-68 4 1.586 0.156 0.921 1968-69 5 0.852 0.195 0.960 1969-70 6 0.691 0.284 0.999 1970-?1 7 0.610 0.278 1.038 L97t-72 8 1.548 0.312 L.077 are_shown in figures 25-30. These figures also show trends with effects of drawdown on Cn and Cw deleted by computation of regressions without data collected during 1964- 65, 1967-68, and L97I-72, when water levels were extremely low (tables 54-56).

Line I (figure 25) indicates that density of buffalo declined under pressure of commercial harvest while the corresponding biomass has increased (figure 26\. When effects of severe drawdown on catch rates are eliminated (Line II, both figures), it appears that both density and biomass declined at approximately the same rate b = -0. 025). The positive Cry-regression reflects samples taken at random frpm the entire area of the lake and may not conform to changes which occurred on shoals which buffalo cohabit with carpsucker.

83 All Yoor lll Drowdorn Dololod (lll Y=o*bX Y=o+bX C I .60 r- C D .50 r-a a - .ao b Ao a .30 r-9 o I .20

r96a-65 t965-66 1966-67 196748 1968{9 1969-70 1970-71 r97t-72 Yoort

Fig. 25. Tlend is Eo of smallmouth buffalo during eight years in Elephant Butte Lake. Line I disregards drawdown and Line II was computed without data from years in which extremely low levels occurred (represented by @;.

Yoorr Drordorn (lll .80 4ll lll Drlorod Y=oibX Y=o+bX t.70 =o.373+O.Ol5X =o.at5-o.o25x g r=o.23 r=-o.39t : .60 tC t .so - B:.rc .ro !o ' .2o

t96a-65 1965-66 196647 t967-68 t968-69 1969-70 t97O-71 l97l-72 Yoorr

Fig. 26. Trends ir Er of smallmouth buffalo during eight years in Elephant Butte Lake. Line I disregards drawdown and Line II was computed without data from years in which extremely low levels occurred (represented by @1. ae Y a + trXnr rryhen trenda h 6a ard Ew of carp^dlrlng elgbt yeare in Elephanthrtte.I4rke. ComErted = Table 63. Qomprted + 0.086xn {b; J. A-55. q ofix; (above) and y(Cw) = o.w6s + 0.0?% (above)and ?(ew) = o. oe8 @elow)'

0.317 1 0.36 0.0?1 1964-65 0.388 2 0.71 0.Lu 1965-66 0.459 3 0.33 0.213 1966-6? 0.630 4 0.85 0.2u 196?-68 0.601 5 0.87 0.866 1968-69 0.672 6 0.65 0.428 1969-?0 0. ?43 7 0.60 0.497 19?0-?1 0.814 l'g?t-?2 8 1.15 0.668

Y (ks) 0.036:h Y =Cw I 0.15? 0.086 0.1&{ 1964-65 0.1?0 2 0.266 0.o72 1965-66 0.206 s o.229 0.108 1966-6? 0.242 196?-68 4 0.169 o.t4 0.180 o.278 1968-69 5 0.158 0.216 0.314 1969-?0 6 0.246 o.262 0.850 19?0-?1 7 o.267 0.28E 0.3E6 LSTl-72 I 0.5?6

occ{rred ln Table s4. comtrrted treods tn 6o ana C* of amallmouth buffalg not lrcludtng year: r*tpt ortrlgldrew&wa q' ! 0' 485 0' 025xn ElePbsnt Butt€ l,ahe' comprted as Y = a + bXn' rvhen?1Co1 = 4a6-- o' 025xn (above) and YGw) = - (below).

o.420 1 0.026 1964-65 0.396 2 0.63 0.060 1965-66 0.370 1966-6? 3 0.23 0.0?5 0.846 196?-68 4 0.100 0.320 1968-69 6 o.24 0.126 0.296 1969-?0 6 o.2s 0.150 o.270 19?0-71 7 0.34 0.176 0.245 ts?L-72 8 0.2(X) Y 0s) 0.02D(D Y=Cw 0.465 1964-65 1 0.025 0.436 1965-66 2 0.660 0.060 0.410 1966-6? I 0.309 0.076 0.885 196?-68 4 0.100 0.360 1968-69 5 0.239 0.126 0.836 1969-?0 6 0.30? 0.160 0.810 19?0-71 7 0.4t7 0.175 0.286 t97l-72 E 0.200

Trends in density and biomass of carpsucker and car? appear to have responded to redtrction of buffalo by relative increases in both density and biomass. Line I (figUres 27 and 28) indicates that carpsucker increased in terms of both parameters and, when effects of drawdown are eliminated, a decrease in car?sucker appeared to occur but at a slower rate than the decrease in buffalo (b = -0. 015 and -0.011 for Line 2, both figures, compared to b = -0.025 for buffalo)' thus resulting in an increase in ratio of carpsucker to buffalo. Population estimates discussed below tend to substantiate real increases in density and biomass of carpsucker indicated by Line I. High catch rates ofboth buffalo and carpsucker durrng the three years shown, indicate

6b All Yror (ll Drordorn Dololod llll Y=o+bX Y=o+bI =1.o75+o.o30x =t.ol9-o.o5x r=OJ7 r=-0.208

(,a

C D I za a A a I 0 I

.90

.80

t96a-65 1965-66 1966-67 1967-68 1968-69 1969-70 1970-7r l97r-72 Yoorr 31g. 27. Trends inEo of river carpsucker during eight years in Elephant Butte Lake. Line I disregards drawdown and Line II was computed without data fnom years in which extremly low levels occurred(represented by @ ).

r.50

All Yrorr (ll Drordorn Dololod llll (,' : Y=o+bX Y=o+bX E D =o.765+O.O39X =ot62-oollx a r=O.21 r=-O.519 zo o t.* l9 o (, .9O

.70

1964-65 1965-66 1966-67 1967-69 1968-69 1969-70 1970-71 l97l-72 Ycorr Fig. 28. Trends in d* of river carpsucker during eight years in Elephant Butte Lake. Line I disregards drawdown and Line II was computed without data from years in which extremely low levels occurred(represented by @ 1. 86 Teble 55. Comprted trends ln 6o rod Ea, olrtver car,pcucker not tnch'rbg yeara lF whlch extreme-dra*ty *TT{b ElephantButteLeke. Comp[tedas Y = a + bXn, whenY(eil = 1.019 - 0.015Xn(above)eDdY(Cw) = 0.?62 -0.011Xn (below).

196.1-65 1 0.016 1.004 1965-66 2 0.96 0.030 0.989 1966-67 I 0.88 0.045 0.9?4 1967-68 4 0.060 0.959 1968-69 5 1.19 0.0?6 0.94 1969-?0 6 0.91 0.090 0.929 19?(F?1 I 0. ?9 0.105 0.914 L97L-72 8 0.120 0.899 Y (ls) 0.011x! Y=Cw 1964-66 I 0.011 0.761 1965-66 2 o.7t2 0.022 0.740 1966-67 3 0.688 0.088 0.725 196?-68 4 0.0114 0.71E 1968-69 5 0.862 0.066 0.707 1969-70 6 0.691 0.066 0.696 19?0-?1 7 0.610 0.077 0.685 t97L-72 8 0.088 0.674

Table 5i6. Cornprted trends b Ep and dw of cata ryt_trctudfng years ln crhtch erdreme dracr&wn occurred tn Elephad hrtte Lake. Conputed ag Y = a +bXn, cfrenV(Cd =0.498 +0.(X)D(a (a,bove) andYPw) = 0.280 - 0.fir0lh @e!ow).

Year Y (No. ) 0. fil?Xn Y=Cn 1964-65 1 0.00? 0.606 1965-66 2 0.71 0.014 0.512 1966-6? 3 0.88 0.02r 0.519 1967-68 4 0.028 0.526 1968-69 5 0.37 0.036 0.538 1969-?0 6 0.65 0.M2 0.640 19?G7r 7 0.60 0.(N9 0.547 L97L-72 8 0.066 0.664 a4 Y G8! 0.000xn Y =cw 196,t-65 I 0.firo 0.230 1965-66 2 0.266 0.000 0.280 1966-6? 3 0.223 0.000 0.230 196?-68 4 0.0(X) 0.280 1968-69 6 0.158 0.000 0.280 1969-?0 6 0.26 0.firo 0.2s0 19?O-?1 7 0.267 0.(X)0 0.230 L97r-72 I 0.000 0.230

that drawdown does have zubstantial effects on 6n and Cw of both species, with a greater effect on carpsucker than on buffalo. This differential effect is discussed in the section on harvest methods.

Carp also appear to have increased substa"ntially (Line I, figures 29 and 30) in response to decreases in density and biomass of buffalo. However, it was found that both parameters of the carp population remained rather stable during the first six years (Jester, 1.971ra), and it should be noted that drawdown apparently had little effect on C1 and Cw of carp except in L97L-72. Most of the slope of Line I resulted

8? Drordorn Drlrrod (lll too Y=otbX Y=o+bX .90 =O246+0O7lX =O.498+O.OO7X r=O.O88 C r=o.62 !l .so :a !16-- =r-I 26,0o 3L ^ .5o at 3m- 30

t964-65 t965-66 196$7 196748 t96S69 11169-70 1970-71 r97l-72 Ycon Fig. 29. Tlend in do of carp dtmng eight years in Elephant Butte Lake. Line I disregards drawdown and Line II was computed without data from years in which extremely low levels occurred (represented by@). t .60 All Yoorr (ll Drowdown Drbtcd (lll I Y=o+bX .= 50 Y=o*bX 33 =O.O98+OO36X =O23O+O.OOOX t40 t451 r=O.OO = E:30 a -20 (,€ .lo

t964{5 1965-66 1116647 1967 S8 1968-69 1969-70 11r70-7r llr7l-72 Ycorl Fig. 80. Tlends in Ew of carp during eight years in Elephant Butte Lake. Line I disregards drawdown and Line II was computed without data from years in wtrich extremely low levels occurred (represented by @). fnom catch rates achieved during the last two segments (especially 1971-721 a';nd' magnitude of the trends_may be more apparent than real. If it is assumed that drawdown did affect Cn and C*, as it reasonably should, then density of carp increased only a slight amount O = 0.00?) (Line I figure 29) and biomass was stable (b = 0.000) (Line II, figure 30).

Population estimates. Srnallmouth buffalo and river carpsucker have not been found in digestive tracts of predaceous fishes, and cary are eaten only by flathead catfish in Elephant Butte Lake. Stable water level during spawning season is not necessarTr for spawning zuccess of buffalo or carpsucker because of the random nahge of their spawning activity. Therefore, reduction of buffalo and its effect on carpzucker and carp populations appear to be the most important factors contributing to changes in populations of commercial fishes. One exception might be that spawning success of carp may have been enhanced by stable water levels (Jester' L97la). Marked buffalo and carpsucker have been recaphrred in adequate numbers to produce acceptable population estimates to indicate interactions between the two populations as a re$rlt of selective harvest of buffalo.

Commercial fishing for 1,941 days from August 1, 1963, through March 31' 19?2 resulted in a catch of LL2,62? buffalo weighing 203,L24W (446r 871 lbs. ).

Tags were attached to 21480 buffalo between June 1, L964, and March 3L, L972, The 1?6 tags (?. LTol recovered from 87,193 fish caught in experimental and commercial nets were used for monttrly estimates of population density. Monthly estimates were combined to determine eight annual mean densities for 1964-65 through l97l'72. The smallest buffalo taken consistently were approximately 250 mm (10 in. ) total length and in Age Group tr, Thus, estimates used are anmal mean densities of buffalo > two years old. Estimated mean number during the first segment was 843,613 fish. Estimated mean number during the last segment was 620,748. This difference represents an estimated net reduction = 2221865 fish (26.4 percent) weighing 245,654 kg (540,448 lbs. ). Reduction exceeded the number and weight of fish caught probably because of (1) intensive harvest of the most fecund sizes of ripe fish from spawning sites (reducing reproductive potential disproportionately)' and (2) tendency of carpsucker to replace buffalo which are removed or fail to occur.

Padilla (L9721found that ?0 percent of the female buffalo in a sample taken for fecundity studies were in Age Groups V and VI and that fish in these age gnoups eon- tained 66 percent of the ova in the sample, Moody (1970) showed that fish in these age groups constihrted a large portion of the commercial halrrest. It follows that harvest of large numbers of five and six-year-old buffalo from concentrations of fish at spawning sites, which has occurred annually at Elephant Butte Lake, could, and probably did, reduce spawning success so that reduction of population density was greater than the number of fish harvested over a period of years.

Population densities of river carpsucker were also estimated monthly from mark- and-recapture data, Tags were attached to 31581 carpsucker. One hundred and forty- two tags 14.IVol were recovered from 8,178 fish, most of which were caught in experimental gill nets. Annual mean population estimates were computed for seven segments from 1965-66 through I97L-72 (figpre 31). These estimates are also limited to fish 89 CO loI (0 o)

5o) 6 a{ ; .4 Et* t\ -9=C]t C{ TQX q:- E'A r cd ll fa\O; 0 Y++ o\ 6,F ;i A- Fl iq .EE s'r E EC) 6toll 6 6E 1R \o !!x gE o\ jsR ?:- cl *rl SE i :8 lo I H€ a \o rOa O+. 6L Ioo 9 o N,o vt rO .if n I o o\ .tt -F c F{op >r i.3 o a tsds pd,\7 dt{l'{ o ;= o5 hg. ocl Eg>c) iHl \o o€ \o -sl o\ 9T qhali €EOCB A- EEcdk r'l \o o\ if^raT 0 op- o oQ I OH x Ea c tr5 .9 0 ,3.E et o OOCteOogrc)OOO 'j G =99\€l\arr.li(t6l bi

90 > Z5O mm (10 in. ) long, or > two years old. Estimated mean density of carpsucker increased from 1?,400 during 1965-66 to 103,419 during L97I-72, an increase of 86,000 fish or 594 percent. Biomass increased by 67, 193 kg (147,824lbs. ).

Population interactions. Buffalo and carpsucker feed by ingesting large quantities of bottom materials and apparently assimilate anything with nutritional value (Jester' 1g?1a). Carp use many of the same items with less ingestion of bottom materials (Sanchez, 19?0). Buffalo, carpsucker, and carp distributions are strongly associated with take bottom. Buffalo occur in relatively uniform densities at all depths, while carpsucker and carp usually intrabit silt, sand, ild gravel shoals at depths <11 m (Bb ft. ). This suggests interspecific competition between carpsucker' carp, and that portion of the buffalo population which occupies depths < 11 m (35 ft. ). Estimates of population density indicate that buffalo are dominant and that competition probably occurs in approximately 35 percent of the bottom area of the lake (Jester, 197la).

Aszuming that 35 percent of the buffalo cohabited shoals with carpsucker and carp, and that population rednction was relatively uniform throughout the lake, we estimate that density was reduced by ?8,000 buffato and biomass was reduced by 86,000 kg (189, 100 lbs. ) in carpsucker and carp habitat. Carpsucker responded by increasing 110 percent (86,000) of the number and 78 percent (67,200 kg or 147,800 lbs. ) of the weight of buffalo removed from shoals. It was estimated two years earlier that carpsucker had replaced 161 percent of density and 68 percent of biomass of buffalo removed from shoals (Jester, L97la). Buffalo increased by 51' 178 fish (17r 900 = 3570 on shoals) and carpsucker increased in size to reduce the percent number and increase the percent weight of replacement, dunng the ensuing two years.

Two large increases in numbers, in September, 1966, through 1967-68' and in Lg71-72 (figure 31), are attributed to high rates of survival of carpsucker spawned during 1964 and 1965 and spawning of these large year classes in 1968 and 1969 in Age Groups III-V, including Age Grogps III and IV which Padilla (1972) found to con- tain 6? percent of the ova in his sample of ripe females. Removal of.32,842 buffalo weighing 65,554 kg (114,219 lbs. ) during 1963 and 1964 may have reduced competition sufficiently to allow increased survival of carpsucker to the extent necessalT to establish such strength of year classes.

Summary of population parameters. Reduction of buffalo is indicated by decreases in mean relative dgrsity and biomass of commercial fish (table 48); mean relative density and biomass, Cpl and Cw of smallmouth buffalo (table 49, figures 25-26, and table 54); and armual estimates of population density; along with annual decreases in mean numbers and weights per day of buffalo--from 169 fish weighing 348 kg (766 lbs. ) in 1963 to 36 fish weighing 62 kg (136 lbs. ) in 1971--taken by the commercial fisherman.

Relative density a4d biomass of river carpsucker declined less than these values for buffalo (table 49), Cn and C* either increased or remained relatively stable (figures 26-27), and estimates of population density revealed a large increase in the number of carpsucker.

91 C""p declined in relative density and changed little in relative biomass (table 49) while dn and C* remained stable except for 1971-72 (figures 29-30). Death of carp from a few minutes to eight days after tagging and only 17 recaptures from >2,400 tagged fish prevented computation of density estimates, apparently as a result of a high rate of mortality among tagged carp.

Mean relative densities and biomasses indicate that carpsucker exceeded buffalo and that buffalo exceeded carp during the eight-year period (table 49). Mearr Cn also indicates that carpsucker were most numerous but that carp were more numerous tban buffalo, and Cyy indicates greater biomass of carpsucker, followed by buffalo, and then carp (table 50).

Estimates of population density and total catch of the three species in experimental and commercial nets demonstrates that buffalo acfually were first, carpsucker second, and carp third in both density and biomass of commercial fishes. Estimated mean density of buffalo was 541,200 during seven years fmm 1965-66 to L97L'72. Estimated mean density of carpsucker was 56,300 during the same period. Total catches of the three species in experimental and commercial nets consisted of L15' 870 buffalo (207,2g5 kg or 456,049lbs. ), g,2gO carpsucker (7,570 kg or 16,654lbs. )' and ?,5b0 carp (6, L24kg or 13,472Lbs.1. Experimental gill nets are selective for carpsucker and carp and against buffalo because most carpsucker and carp in the lake are susceptible to small meshes and many buffato are too large to be caught readily in meshes < three-inch square. Conversely, commercial nets are selective for buffalo and against carpsucker and carp. If catch rates of carpsucker and carp are proportional, catches of.9,290 carpsucker and 7,550 carp and mean density of 56'300 carpsucker indicate a mean density of 45' 800 carp / x- -56,300. N=4b.8oo\. \7,550 9,290 I If catch rates of buffalo and carp are proportional, catches of 115,870 buffalo and ?, Sbg carp and mean density of.54Lr200 buffalo indicate a mean density of 35' 200 carp t l- EAa onn ^ \ / N --54L,200. f,r = 85.2ool. \2, sso 115,870 / Comparison with carpsucker should provide the best estimate of carp density(45' 800 carp) because of similarity of size and configuration (and, thus, netability) of the two species.

On the basis of the above, it appears that considerable competition occurs among buffalo, carpsucker, and carp in shallow water. Declines in density and biomass of buffalo were aceompanied by increases in density and biomass of carpsucker in this habitat. Stnaller quantities of carp remained essentially stable, indicating that existing habitat was more favorable to the other species. It also appears that unexploited populations of the three species would result in dominance of smallmouth buffalo over river carpsucker and carp, as was the case when sampling was started in 1964.

Length-frequency. Jester (19?1b) found that length-frequency of fish in Age C"o.rps O-tt co,rta be used as supporting evidence for validation of the scale method for determining age and growth of river carpsucker in Elephant Butte Lake and the Rio Grande. 92 Eleven age groups (0 to X, inclusive) and five peaks of length-frequency were found in a sample of 1,397 carpsucker taken from Elephant Butte Lake during 1967 (figure 32). Histograms representing these data show that (1) lengths of fishes in older age groups overlap to obliterate peaks of age-frequency in the population and (2) frequency peaks skewed toward larger, older fish demonstrate size and age struc- ture of an unexploited population of long-lived fishes. Assuming that the sample is reasonably representative, length-frequency appears to show that recruitment of young fishes is controlled essentially by natural mortality of older fishes and that such a population is static. Increased survival and recruitment would depend upon e>

A length-frequency histogram representing a sample of carpsucker firom the Rio Grande upstream from Elephant Butte Lake appears to show four peaks which conform to frequency of fish in four age groups (figUre 33). These data are skewed toward smaller, younger fish, indicating an expanding population. This expansion probably represents recovery from a dry period when the Rio Grande ceases to flow and consists of small infrequent pools or becomes completely dry,

Movement

Davis (1955) analyzed movements of several species of fishes, including river carpsucker, in Perche Creek, Missouri. Eleven of 63 (1?.5 percent) carpsucker which were marked and recaptured had moved and 52 had not moved after periods of high water. Seven fish were recaptured 1. 0 to 2.5 miles (1.6 to 4 km)' or an average of 1.6b miles (2.6 km), upstream from the release site dunng spring, an average of 248 days after they were marked. One carpsucker was recaptured in summer, 2.5 miles (4 km) downstream, 62 days after it was marked. Two others were recaptured in the fall, one of which was three miles (4.8 km) upstream and the other three miles (4.8 km) downstream, 181 days after they were marked.

Rael (1966) analyzed movement data from 23 marked and recaphrred carpsucker in Elephant Butte Lake. Ten fish moved 1.0 to 2.8 miles (1.6 to 4. 5 km) during time lapses of 69 to 117 days and 13 fish were recaptured at release sites atter 7 to 339 days. Rael concluded that some carpsuckers tend to be sedementary and others to move, which would also appear to be the case in the Missouri stream.

Patterson and this writer extended a method described by Martin et al. (1964)' for analyzing fish movement, ild Patterson (1968) applied it to smallmouth buffalo in Elephant Butte Lake. Movements of 98 river carpsucker, including the 23 fish recaptured by Rael (op. cj!. ), were aaalyzed with this method. A grid composed of quarter-sections was superimposed on a map of the lake (figure 341. Mark and recapture sites were identified by numbers assigned to quarter-sections, and distance that fish moved was deterrnined to the nearest half mile by counting the number of quarter-sections crossed or entered along the shortest possible route between mark and recaphrre sites. Ttre deeper, downstream portion of the lake is identified as rrBrr, frArt and the shallower, upstream portion is identified as with the division line

93 .L o I ..llll---

f.aquancy SGola

" -rlhl,--

Y,rr-lll.-

't-Id.r* xS o o q o o o o o o o o o o cF o o o o o 9 0 9 0 0 0 C' 0 0 0 0 0 C' C' 0 0 0 :: : :::::::l ::i::l 3 ; l:: :: :; : :::: : :: :: s Fig. 32. Length-freguency of 1,397 river carpsucker from Elephant Butte Lake, L967. Upper histogram shows frequency of occurrence of 10 mm length groups in the sample. Lower histograms show contributions of each age group to length-frequency in the total sample.

94 a o T tl ill

i I = 123.5 annulus L O = 127.0 caPture ! TI = 232.L annulus L T = 225.8 capture

L III = 327.0 annulus I(EY L II = 280.8 caPture

7l cl Ago Group I ,'' ot attulo. Foroction

6\.t ar. o'out Ct ot coPlura sr frtoulNcY

o 00 0 oo oo0o0 o0 9oo ooo oo o9 o9o o FG.G' -rr .i. oo'! Qrn e o ii ai.o9 G| at n Cr!??6 G. n Gr ai Gr Gr o Ct !t at o at !t

Fig. 33. Length-frequency of 118 river carpsucker from the Rio Grande, October 16, 1967. Upper histogram shows frequency of occurrence of 10 mm lenglh groups in the sample. Lower histograms show contributions of each age group to length-frequency in the total sample.

95 A

Fig. 34. Elephant Butte Lake shouring qtrarter-section grid, downstream section (a), and upstream section (b) used for analysis of migration and movement of river carpsucker. Tnnsi contour represents the approximate mean shoreline

96 for these 'halves" established at Kettle Top Butte. Bona fide seasonal migrations trAf r frBr', should involve large numbers of fish moving between and or between the shallow, upstream area and the deep, downstream area.

Fishes recaptured in relation to month and area of marking are shown in table 57. Little interchange between fish marked and recaphred in areas A and B indicate that seasonal migrations do not occur and directions of movements between and within A and B indicate no more than upstream and downstream shifts and considerable random movement of individual fishes. Of fishes marked in winter and spring, 22 were recaptured downstream (i 0.5 mi. or 0.8 km), 20 were recaphrred upstream, 3 across the lake, and 8 at sites where they were marked. Slightly more of the fishes marked in summer and fall were recaphrred upstream (19) than downstream (15), 4 hadcrossed the lake, and ? were recaptured at sites where they were marked. These movements indicate a slight shift downstream during colder weather and a slight shift upstream during warmer weather.

Movements of carpsucker in relation to month and area of recapfure are shown in table b8. Again, a net difference of only six fish were involved in an interchange between areas A and B, indicating that migrations do not occur, Directions in which fish moved within and between areas A and B prior to recaphrre also indicate possible seasonal shifts with considerable random movement of individual fishes, which conforms to Rae|s (1966) earlier observation in Elephant Butte Lake and to implications of Davist (1955) data from Perche Creek, Missouri.

Distance between mark and recapture sites (called distance moved), elapsed time, and mean distance moved per day were computed for marked and recaptured carpsucker

!n whtch they were marked, area l[ rvhlcb they Table S?. Number of mark€d rlver carpsucker recaphrr€d' monf.b and erea Butte Seaeons were recaptured, ald dtrection they had moved between marklng ad recapture tn Elepbent lakei summarlzed below.

N Mr*ed tr Recanfrred ln Ptrec!&4]&Yd- 4 B g 10 E 2 7 I 4 2 1 I 2 2 2 I 4 3 6 1 3 1 5 l6 16 l6 8 2 t

14 10 l4 4 9 I I I 8 6 2 t2 t2 L2 I 3 6 1 1 I I

5 4 I 6 I 1 2 7 4 3 5 2 1 4 l1 1l I 2 7 1 1 4 3 1 4 1 2

E M.M 8? 30 7 36 1 t3 L4 2 6 J.A 22 22 2t 1 8 6 2 11 I 2 1 s -N 23 19 4 l9 4 7 I 1 D-F 16 t2 4 13 3 *Markedand rcaptured lnA =downstreamI of lake;B = upstream *' IXrectlona rroved: U = upstream, D =downstream, A = acrogs. and N = no movemetrt.

97 Table 58. Number of marked rlver catpeucker recapdfed, oDea ln whlch they were mer*ed, snnth and area ln whtch they were r€captured' and dlrectlon tbey had moved between nerklng ard recaphrre tD Elephant Butte Lake.+ Seaeona gummarlzed below.

lrtonthe N Mar*ed ln Recaohred ln Dlrectlon ltfioved R€captured Recapfired AB J 2 2 F M 4 4 1 4 A 16 l5 16 I I 3

M 11 8 3 8 5 2 1 3 J L2 I 3 l1 6 4 2 J 29 27 2 29 7 L2 10 A 6 6 I 6 4 2

s I 729 5 4 o 4 813 I 1 N 2 22 1 D 2 112 1 I lbtal 98 83 89 3? 15

M-M 81 27425 6 L2 10 4 6 J -A 41 1L646 I LI 18 2 l0 s -N 15 L2314 1 I 6 1 D-F 5 324 1 2 3 *Markedand recapfrued tnA =downstream I of lake; B = upatream |. Dtrecttons moved: U = upstream, D -downstr€am, A = acnoag, artd N = ur mveme[t.

Table 59. lfiovement of rlver ceSpaucker tn Elephart Butte Lake, summartr€d fiom 98 marked and recapturled flsh taken durtry 1964 thrcugh 19?2. Dtetanceg moved ln mllee aDd (ktlometers), elapaed tlne ln daye, and nean dlgtaDce per day ln feet and (meters).

Elaoeed fime Mean Dletance Int€nral Mlnlmrm Marlmrm Mean Mlnlmum Maxl'rqrn Mean Day 0 1.5 0.6 222.5 16.1 (0.0) (2.41 (1.0) (4.6)

38 2 8.5 2.8 14 1564 508.2 25.6 (e.2) (5.6) (4.6) (e.0)

4 5.5 4.8 1969 642.2 46.8 (6.4) (8.8) o.7l (14.8)

6 7 6.4 2L 2266 ??5.6 48.6 (s.6) (11.2) (10.2) G3.8)

8.6 9.5 9.0 123.0 388.3 (18.6) (16.2) (14.4) (ru.8)

10 10 11 10.6 562 933.0 69.4 (16.0) (17.6) (16.8) (18.1)

L2 L2 t2 12.0 1(x)6 1006 1006.0 63.0 (0.0) (1e.2) (1e.2) (1e.2)

0-12 98 0 t2 2.9 484.1 86.2 (0.0) (1e.2) (4.6) (10. ?) grouped into two-mile (3.2 km) intervals of distance moved (table 59). Seventy-five fishes (76.5 percent) were recaptured less than four miles (6.4 km) from the site

98 where they were marked, including individuals which were free to move for 1,564 and 1,885 days between marking and recapture. The longest distance moved was 12 miles (Lg.Z km), by a fish which was free to move for 1,006 days. Mean minimum distances moved per day were short, ranging from 15. 1 to 386.3 feet (4.6 to 117. 8 m). These distances seem to imply slow directional movement intermixed with considerable random movement along the way, or perhaps all-random movement which results in directional movement over a period of time. Recaphrres both upstream and downstream from release sites during any given season tend to substantiate the latter pattern. Implications of shifts will be discussed under management, in terms of seasonal concentrations of earpsucker in upper, middle, and lower thirds of the lake.

Diseose ond Porosifes

Fungus, a nematode, two copepods, and two cestodes constitute the parasites reported for the carpsucker. Bucbholz (195?a) found the copepods, Argulus 9!. and Lernaea S. , to be rather common as ectoparasites and cestodes, @l!l3!s .9Il,. and Biacetabulum infrequens, as endoparasites in specimens from the Des Moines River, Iowa.

Light infestations of a fungus, Saprolegnia parasitica, occurred on carpsucker in Conchas Lake, New Mexico, mostly during the latter portion of the spawning season and for approximately 10 days thereafter. A nematode, Philometra sp., was found on 12 percent of the specimens taken during three years frnom the same lake (Jester, I962al. This worm was about 2.5 inches (63.5 mm) long and occupied subcutaneous canals on opercles, lips, and snouts.

Obsenrations made at Elephant Ertte Lake have added little to the above. EtP- rolegnia parasitica was observed on carpsucker during spawning season and on recaptured fishes which had been caught in gill nets within the previous 10 days. Two specimens of Argulus q. and three of Lernaea cnrinacea were observed as ectoparasites on carysucker caught from 1964 to L972; extremely light infestations at worst.

Monogemenf I'rough Status of river carpsucker as an important fishr was discussed in the introduction of this paper. Brezner (1956) commented that carpsucker had little economic value because most specimens weighed less than four pounds (1.8 kg), and offered no management recommendations because Lake of the Ozarks, Missouri' contained few carpsucker, which apparently were of little importance to the sport fishery. However, he did note that carpsucker were reported as caught and marketed by commercial fishermen in the upper portion of the Mississippi drainage.

Limited experience with marketing of carpsucker from Elephant Butte Lake and research in progress at New Mexico State University on acceptibility of flavor

99 a^nd aroma of several "rough" or 'tcommercial" species, indicating that caprsucker have a greater commercial potential than one would surmise from the sparse literature. It appears that the carpsucker has been neglected from the commercial viewpoint much as we found that it has been neglected until recently in efforts to manage reservoir sport fisheries (several papers in Hall, 1971). In view of an increase in per capita consumption of fish (Fish Farming Industries, 1972) and an apparent commercial potential, management of river carpsucker is considered herein from a commercial viewpoint. However, we hasten to add that both commercial and "rough" fish management consist of manipulating harvest to control population density and biomass, and the difference is largely one of degree.

Econom ic Volue

The Southern Division of the American Fisheries Society established values of fishes for the purpose of assessing damages from pollution-caused fish-kills. River carpsucker were valued at $0. 15 per pound ($0.33/kg) (SFI, 19?1). However, such a value could represent an approximate mean made up of small unsaleable fishes, fishes which are discarded for lack of a local market, and fishes which are sold at prices acceptable for commercial harrrest. It is known that carpsucker have been harvested for commercial purposes from upper Missouri River reservoirs during 1968 to 1972, but we do not know the prices received nor the specific market areas.

River carpsucker from Elephant Butte Lake occasionally have been sold to markets in southern California for the same price as comparable-sized smallmouth buffalo (B.C. Sparkman, commercial fisherman, Elephant Butte, New Mexico, personal communication). However, the fish is relatively unknown to the public and the name rrcarpzuckern apparently zuggests fbarpt'to many people, Thus river carpsucker weighing less than three pounds (1.4 kg) rrfleeced'r weight, have been sold for approximately $0.25 per pound FOB ($0.55/kg) under the name rrcoldwater buffalor'. In our opinion, rboldwater buffalort is not necessarily a misnomer as it makes a definite distinction between carpsucker alrd c&rp, recognizes the taxonomic and ecological similarity between carpsucker and buffalo, describes a distinction between extremes of the range of the two catostomids, and makes a necessary psychological distinction to allow development of an economic entity.

Research in progress at New Mexico State University has shown that flavor and aroma of river carpsucker are acceptable and flavor is rated above average in comparison with 'rfish in general'f. A taste panel, without knowing the species, ranked smallmouth buffalo, river carpsucker, and carp behind channel catfish, in that order, but differences between any and all of the four species were non-significant (Mrs. June L. Wisdom, M. S. candidate in home economics, personal communication). These findings indicate that river carpsucker have a potential economic value at least equal to similar size-classes of smallmouth buffalo, although it is obvious that this potential will be reached only by marketing the fish under an acceptable name such as rfcoldwater buffalo" or as processed products such as filets, sticks, or patties.

100 Horvesl Methods

Experiments with gill nets, seines, trawls, and traps revealed that gill nets are the most effective gear for catching river carpsucker in Elephant Butte Lake. Addi- tional experiments were made to determine methods for improving efficiency of gilt nets so that harvest rates may be increased and controlled. Effects of mesh sizes, color of nets, and seasonal concentrations of carpsucker are discussed singly and in combination, followed by an analysis of effects of changes in population density and size of the lake on catch rates.

Mesh Sizes

Numbers and weights of 16 species and groups of game, commercial, forage, and total fish caught in each mesh size in experimental gill nets were recorded from April 1,, 1968, through March 31, 1971. Percent of total number and weight of fish in each category, caught in each mesh, was computed to reveal selectivity of mesh sizes. Computations were made for three annual samples and for a composite sample of fish caught during the three-year period. Only minor changes in percentages of fish caught in each mesh occurred between years, so that the composite sample is representative of the entire period (table 60).

Total catch of river carpsucker consisted of 11 750 fish which weighed 48' 569 ounces (3,036 lbs. or 1,380 kg). Ninty-two percent of the number and 93 percent of the weight were caught in 3, 4, and 5-inch (?.6, 10.2, and12.?-cml stretch meshes. Four inches (10. 2 crn) was the most effective single mesh, taking 58 percent of the number and 60 percent of the weight of carpsucker.

Four and five-inch (10.2and 12.?-cm) stretch meshes were selected as the best combination of mesh sizes to combine with color and seasonal concentrations to increase efficiency of gill nets for selective harvest of carpsucker. These two meshes caught ?0. ? percent of the number and 76. ? percent of the weight of carpsucker' tended to maximize harvest per unit of effort of larger carpsucker, and avoided catches of large numbers of game and forage fishes which were caught in three-inch (7.6-cm) mesh.

Color of Gill Ners

Methods for collecting and analyzing data to determine effects of color of gilt nets on catch rates of fishes in Elephant Butte Lake were described by Jester et al. (19?0). Nine colors were tested, and numbers and weights of fishes caught were compared with numbers and weights collected in white control nets. Effects of all colors on catch rates of nine species and one group are contained in a manuscript in press (Jester, 19?3). Two colors, brown and clear monofilament, offer advan- tages for harvesting river carpsucker and are summarized here.

Brown experimental gill nets were selective for river carpsucker, caught as many buffalo and carp as white nets, and were selective against gizzard shad, channel

101 Table 60. Nrmber, welgbt, and percent number and weigbt of ffshes caugbtin2-thtrough 6-lnch (5.1- through 15.2-cm) stretch

2-i.Dch (5. 1-cm) 3-inch (7.6-cm) srcclesardGroune N W N W N WN w -- percent -- -- pelcent -- Gane Black and whlt€ crappleg 40 97 31. ? 16.4 49 2LL 38.9 35.8 Largemoutb boes 43 63? 18.5 E.6 53 1,340 22.8 L8.2 Whlte bass ?05 2,O54 52.5 14.4 245 2,73L t8.2 L9.2 Walleye 65 2.22L o.7 13.1 89 4.67L 11. 1 9.8 Qhnnnel ssfflsh ?63 5,293 47.8 26.4 5t2 5,990 32. t 29.9 Flatbead catflsh 3 47 3.0 0.4 38 4,478 38.0 57.7 librthen plke I 27 38.8 33. ? 2 53 66. ? 66.3 Total 1,620 14,3?6 39.9 L4.2 988 L9,474 24.3 19.2

Commerclal $nallmouth bufialo 17 666 2.5 2.6 84 3,500 12.5 13.2 Rlver carpsucker t28 8,138 ?.8 6.5 377 7,9O7 2L.5 16.3 Carp 73 719 7.9 5.0 422 4,O42 46.5 26.1 Tbtal 2L8 4,583 6.5 5. 1 883 15,4149 26.4 1?.1

Forage Glzzard ahad 16,054 35,868 85.6 ?0.0 2,6t4 L4r7t,4 13.9 29.2 Blueglll 145 258 85.8 74.2 2L ?8 L2.4 22.8 Warmouth 38 80 66. ? 40.0 t7 98 29.8 49.0 Iongear gunflsh 778 943 99.2 93.3 o 15 0.6 1.6 Greeneunflsh 73 181 98.6 98.5 1 2 1.3 1.5 Total 1?r 088 36,7?5 86.1 ?0.5 2,658 14,93? 13.4 28.6

Grand Total 18,926 55,734 69.4 22.8 4,529 49,860 16.6 20.4

Table 61. l.frrmberE and wetghts of flahes caught in 25 repllcatlone ofpalred brown and qAlte erQ€rlmental glll nets. Catch rates ilr whtte nets are valud at untty (1.00) and catch rateE ahown are tbose h brtwn nets aa ratlos ofmrmberg and welghts caught ln brown n€ts to thoae caught tn whlte nete. Only valuee wblch are atgnlflcantly dlfferent at .05 and .01 levels are shown" Welghta ln ounces and ftllograme).

Secles or \4,hlte Nete Brown Neta Catch Rstee Group NW NW NW Smallmouth buffalo 8?8 24 990 (24.e1 (28. t) Rlver carpaucker 1?56 106 3084 1.58 1. ?8 (4e.8) (86.0) Carp 7l 1016 47 602 (28. E) (1?. r) Gtzzard ehad 573 1490 331 929 0.68 0.62 (42.2' (26.3) Walleye 27 1859 33 2t40 (52.71 (60.7) Channel catflah 103 994 63 ?68 0.61 (28.21 (22.3',) Flatlead cetfleh 2 297 0 0 (8.4) (0.0) Whtte baee 1(r E?8 24 271 o.23 0.31 (24.s| (t.7t Largemouth boes 6 158 3 31 (4.6) (0. e) Other gunflsh DO 81 84 117 (2.3) (3.3)

Total 9406 E902 0.68 (266.71 (262.41

L02 19?1. Weight ln ouncea' meshes of whlte erperlmental glll nete in Elephant Butte lake, April t, 1968, throryh March 31,

6-inch(15.,,!cm) NWNWN @ =. percent -- -pelceDt" -- L2 2.4 2.0 L4 123 11. 1 20.8 20 t47 r5.9 24.9 3 L,441 9.5 19.5 59 L,622 25.4 22.0 56 2,32E 23.7 31.6 22 4.6 13.0 2M 4,75L 15.3 33.0 u25 2, E53 9.3 20.0 62 1,85? 4.5 6.8 220 13, ?48 27.4 29.0 250 19,6?0 31.2 41.3 36 3,208 1,219 2.2 6. 1 190 4,333 11.9 2L.6 95 3,189 5.9 15.9 36 ,-.-ttu__, tr__o t1_u n:1'o r1-o 11_t ':1" -:' ':ltt 1: 11,80? 4.8 11.6 698 26,86 r7.2 26.0 561 29,470 13.8 29.0 193

8,335 19.8 31.5 247 5,9?5 36.9 22.6 189 ?,994 28.2 30.2 133 0.3 0.5 l,016 29,060 58.0 59.8 223 8,208 r2.7 16.9 6 258 1,792 2.0 11.6 389 6,762 36.6 43.7 72 2,096 7.8 13.6 t9 10,385 4.7 11.5 1,602 42,787 41.9 46.2 484 18,298 14.5 20. L 158

0. ? o:T 87 374 0.5 l'-* : '::' 3 10 1.8 2.9 -:' :" 2 22 8.5 11.0 t 0.1 0.1 -l : 7 0. 1 0.01 93 407 0.5 0.8 11 21 0.2 0.1 4 1.3 9. I 2,393 68,660 8.8 26. 1 1,056 47,796 3.9 19.6 856 22,Lgg

catfish, and white bass. They caught as rnany walleye, flathead catfish, largemouth bass, and other sunfish as white nets, w?rich poses no major problem as eatches of these fishes are usually small (table 61).

Clear monofilament experimental gill nets were selective only against channel catfish and small sunfish on a year-round basis. However, selectivity was strong seasonally, and catch rates of smallmouth buffalo and river carpsucker were high during warrner weather when plankton blooms reduced mean Secchi disc visibility to ?3. b cm (30 in. ) (table 62). Catch rates of carpsucker and carp were reduced in comparison with catch rates in white nets during colder weather when mean Secchi disc visibility was 104.5 cm (41 in. ).

These findings demonstrate that efficiency of gill nets for selective harvest of commercial fishes, especially river carpsucker, may be increased on a year-round basis by use of brown nets and during the warmer months by use of clear monofilament nets.

Seo sono I Concentrotions

Seaso_nal concentrations of river carpsucker were determined from catch per net-unit (C1 and C*) in two to six-inch (5, 1 to 15.2-cm) mesh white experimental nets and in five and six-inch (L2. ? and L5.2-cm) mesh brown commercial nets. These

103 Table 62. NumberB and welghts of flehee ceught tn 25 repllcatlore ofpalred clear monofilament and whtte €t(t)€rtmeDtsl gul neta drrlng June-Auguat and September-March. Catch rates tn whtte n3ts are valued at udty (1. 00) aDd catch rateg ehowa are tboae tn clear mmfllameut nets as ratlos of num.bers rnd welghts curgbt tn clear nets to thoae calght b whtte Det8. Only valuea whtch are aigntflca^dty dtfferent at . 06 8od .01 levels are showD. Welght ln ouaces and (ktlograms).

gedember Throuah Maroh qslsb84geq Secie8 or Clear Netel -@ ClearNets2 w NW N w N w w Smallmouth bulfalo n 54 30 1110 1. ?6 2.04 T 351 9 33? (16.4) (31.5) (10.0) (e.6) Rlver carlrsucker 84 921 55 1409 L.62 1.53 31 851 20 666 .66 .6? (26. r) (40.0) (24.L| (16.1) CarT ?1 820 69 868 22 888 15 181 .68 .47 (23.3) (%.3) (11.0) (5.1) Glzzard ghad 548 1448 762 t7u2 1.88 1.20 369 1016 248 642 .68 .63 (41.1) (4e.4) (28.8) (18.2) Walleye 9 510 L2 ?68 t.47 7 397 L2 690 1.69 (14.5) (21.6) (11.3) (le.6) Channel catflah 80 680 52 349 .65 .DO 36 602 16 248 .4 .4L (1?. e) (s. e) G?. r) (7.0) Flathead catfish 0 0 I 64 0 0 1 15 (0.0) (1.6) (0.0) (0.4) Whtte baee 130 ?36 127 1206 1.64 32 24 23 11? .72 .49 (20. e) (34.2) (6.8) (3.3) Iargemouth baea 1 49 6 74 6 191 2 19 (1.4) (2.1) (5.4) (0.5) Other onflgh 69 97 28 4t .40 .42 28 36 9 20 .35 .66 (2.8) (1.2) (1.0) (0.6) Total 5?55 LL32 ?600 1.19 L,32 4072 360 2835 .66 .?0 (163.2) (215.6) (115.5) (80.4) 110 repllcatlone. 215 repllcatlons. data lend themselves best to analysis of -Cn and dw in four- and five-inch (12. ? and 1b.2-cm) meshes of both white and brown nets along with analysis of a one-year experiment carried out to determine feasibility and cumulative selectivity of fishing with four- and five-inch (10. 2 and 12.7-cm) stretch mesh, brown, commercial gill nets in thirds of Elephant Butte Lake where seasonal concentrations of carpsucker occur. Integrated effects of mesh sizes, color, and seasonal concentrations are shown below.

Brown Commercio I Nets

lVbximizing efficiency of gill nets for selection of certain fishes and against others involves utilizing all factors known to produce such selectivity so that the most efficient combination contains cumulative effects of the separate factors. Four and five-inch (12,7 and 15.2-cm) stretch meshes were found to be selective for river carpsucker and against game and forage species, Brown nets were found to have the same effects. It was also noted that carpsucker do not migrate up-and-down-lake but tend to shift so that population density in thirds of the lake changes discernably during various seasons. Thus, seasonal concentrations in defined thirds of the lake are shown by comparison of seasonal catch rates in both white and brown nets. Cumu- lative effects of mesh sizes, color of nets, and seasonal coneentrations of fish are shown by catch rates in four and five-inch (12. ? and 15. 2-cm) stretch mesh, brown,

L04 commercial nets set in sections of the lake where concentrations of carpsucker occur during each season.

Feasibility of use of these commercial nets depends upon cumulative effects of selectivity factors, high catch rates of target species, and ability to concentrate fishing effort in areas where concentrations of target species occur.

Cumulative effects of selectivity of mesh sizes and color were determined as percent of number and weight of species and groups of fishes caught (table 63). River carpsucker made up 58 percent of the number and 56 percent of the weight of fishes caught, and carpsucker, buffalo, and carp, combined, resulted in 85 percent of the number and 81 percent of the weight consisting of commercial fish. Ttre remaining 15 percent of number and 19 percent of weight consisted of. (L2Vo number, 1970 weight) game and (370 number, <170 weight) forage fishes. Dtrring 1971 and L972, the commercial fisherman used six- inch (15.2-cm) stretch mesh white commercial nets and caught 81.8 percent commercial fish by number xd 72.8 percent by weight, along with no forage fish. Therefore, four and five-inch (10. 2 and 12.7-cm), brrown commercial nets were more selective against game fish and for commercial fish with river carpsucker as the primary target, than were six-inch (15. 2-cml stretch mesh white nets with smallmouth buffalo as the primary target.

Catch rates of carpsucker in four and five-inch-mesh (10.2 and 12.7-cm-mesh), white and brown nets are comparedintable64. Grand mean eo and dw were derived from all carpsucker caught during all seasons from all areas of the lake and, therefore, show substantial increases in catch rates in brown nets over catch rates in white nets. Seasonal catch rates in upper, middle, and lower sections of the lake are shown separately and reveal seasonal concentrations of carpsucker along with catch rates achieved in each section during each season.

Priorities for fishing to achieve maximum efficiency for harvesting carpsucker and other commercial fish, with minimum catches of game and forage fishes, are shown (table 65) for upper, middle, and lower sections of Elephant Butte Lake (figure 35).

Table 63. Number, w€lght' ard perceut of total number and wetght of specles and groupa of flrheg caug[t ln bro*n 4- a'"t 5-trch stretch-meech gtll nete la Elephant hrtteLak€, Sepember, 19?0, thFoughAugust, 19?1. Welghte tnpdrtdE and Gilograma).

Gmrpa aad gecleo Commenctal Rlver carpancker 1,135 2,161 (982) 5?.8 56.1 Smallmuti hffalo 2L7 489 (2221 11.1 t2.T Carp 320 453 (206) 16;3 11. ? Ilotal 1.672 3, 104 (1,411) 86.2 80.6

Game 231 736 (8S4) 11.8 19. 1

Forage 59 l3 (6) 3.0 0.3

Ilotal 1,962 3,858 (1,751) 100.0 100.0

105 Table 64. Seasonal conceqtratlona of rlver carpsucker la upper (U), mtddle (M)' md lower (L)thtrde of Elephant hrtte lake' sbown by catches per net-ualt lD 4- ad 5-trch etretch-lt€ah; whlte and brcnm g{ll neta, Septenber, 19?0' througb Auguet, f9?1. Ew tD ounces.

en andEw |n & and S-Inch Str€tch Meabee ln -- WhlE nets Brcqg nete sectton = - Season of Iake Net-unlts En Ew Net-untts en ew Srlry U 36 0.9 27.0 36 2.L 69.9 M 42 1.4 41. I t2 2.4 76.4 L 202 0.? 2t.L 60 2.6 ?5.8

$rmmer U 40 0.9 26.2 24 0.04 L.7 M tL2 2.6 13.2 72 4.8 14?.9 L 216 1.8 39.0 72 2.L 64.1

Fall U 52 0.6 20.7 L2 0,2 4.4 M 72 0.9 26.1 24 0.6 16.5 L t72 0.7 1?. E 84 t.7 61.0

Wtnt€r U 58 0.4 26.3 t2 0.3 8. 1 M 76 0.4 tt.2 24 L.2 31. ? L 154 0.3 9.5 48 2.0 82.6 Tbtd L,292 Gra.od means 1.48 23.25 2.lE 63.35

Table 66. Prlorltt€s for fleblng upper (U), mlddle (M), and lower (L) tblrds of Elepbant htte ldre ln order to maxlmlze harrest of rlver carpenrcker by utiltztDg seaso1al co[centratlola of flsh and moat aelectlve m€sb slzo8 and color of commerclal gtll neta.

Prtorltleal SectloDB

(March - Dlay) U

$rmm€r ML 1 M (Jue - Auguat) 2 L

Fall ML I L (Sopt€nber - November) 2 M

Wtnter UML I LM (Deoemb€r - Febnuty) 2 U lsrbleot to the followhg condltlons: 1. Nete: (a) 4- and S-lrch stretch meah O) bFqn 2. Set: (a) bottom 4 u n (36 1t.) (b) preferrrbly 4 e n 1zo tt.) 3. Ma:dmum elf,ciency br 1 or Doae aeaao[s but leaa than year-rould: (a) 3 moaths: $lmm€r' M L @) 6 noatbs: Sprlrg' L M U; $rmmerr M L (c) 9 months: Sprhg' L M U; Slrmmer' M L; Fall, L M.

Effects of Populotion ond Lole Sizes on Horvesl

Changes in catch per net-unit as indices of changes in population density and biomass were discussed under populations._ Population changes were found by minimizing effects of crowding and dilution on Cn and Cw. Analysis of these data may

106 McRAE

ELE BUTTE DAM

Fig. 35. Boundaries of upper (U), middle (M), and lower (L) sections established for analysis of seasonal concentration of river carpzucker in Elephant Butte Lake. Inner contour represents the approximate mean shoreline during 1964 to 1rg71.

107 also be used to show effects that population and lake sizes had on catch rates by con- sidering, rather than minimizing, annual mean population parameters and areas of the lake, Changes in density and biomass of river carpsucker were sufficiently similar over a period of years to indicate that either may be considered a function of the other so that either catch rate may be compr.ted to refle"1 shanges in both. Q *as chosen arbitrarily for this paper.

Separate and combined effects of estimated annual mean btal popolation density and annual mean surface area of the lake on catch per net-unit (Cn) were computed with the stepwise multiple regression formula

Y = a + bt X1 + b2X2' aPPlied as Eo=t+b1P+b2A.

Effects of population and area on catch rates of carpsucker and buffalo (buffalo not shown) were computed. Chtnges in Cn of carpsucker were more sensitive thanchanges in Cs of buffalo in response to charges in surface area (A). This indicated an interaction caused by greater changes in density of carpsucker per unit-area than changes in density of buffalo because area of carpsucker habitat (< 11 m deep) changes at a different rate thgr buffalo habitat (entire lake bottom). To account for this difference in sensitivity of Cn, the stepwise multiple regression model was modified to include the interaction of density per unit-area. The model became:

y = a + b1 X1 + bZXZ + b, X3, applied as

En = a+ b1 P +b2 A + b3 D, when:

En = catch per net-unit

P = &rnual mean population (x 11 000) A = arrnual mean surface area (x 100 acres) D = density as thousands of fish per 100 acres inhabited by b2, bB = coeffieients of P, A, and D.

Density was computed on the basis of estimated percentages of the area constituting carpsucker habitat in five percent intervals of various ranges of area. Thus, thousands of P . o _ ... carpsucker _ (76 earpsucker habitat) (100's of acres) fA

Estimated values of rrfff for existing mean surface areas (A) were

A < 80 (8,000 acres) .25 80 - 94.9 .30 95 - gg,g .35 > 100 .40

108 Cots were taken from table 50, population estimates were taken from figure 31, mean surface areas were computed from daily areas recorded by the U. S. Bureau of Reclamation, and density was computed from these data as shown above. Stepwise coefficients of determination 1R2) were computed to reveal percentages of change in Ca which were caused by independent variables P, A, and D, separately and in all possible combinations. Independent variables P, A, and D, and dependent variable C1 for project segments 1965-66 through L97I-72 (table 66) were us_ed to compute rrarr ard coeffieients of P, A, and D shown in table 6?. Values of R2 show that area had the greatest single effect on Ca, that population and area had an effect equal to area and density, and that combined changes in population, area, and density account for about 6? percent of the change in C1 from year to year. Mean surface area had the largest effect, singly and in all combinations, which shows that drawdown could be used or capitalized upon to achieve high rates of selective harvest of carpsucker for either commercial purposes or I'rough fishrr control efforts.

Potentiol Horvesl

Potential harvest of river carpsucker from Elephant Butte Lake is dependent upon catch per net-unit and number of net-units used for fishing during a given period of time. Catch per net-unit, in turn, depends upon population parameters and area of the lake. Estimates of potential Co and number and weight of carpsucker harvest may be made with the multiple regression method used above for analyzing effects

Table 66. Catchratee andestlmrted anmal mean populations of rlver carysucker, annral mea^n gur{ace erea, and denatty of carpancker per 1(X) acreg lnhablted tn Elepha.d ertte IaI

Year 6o P(x1000) A(x100) o=f 1965-66 0.96 LI.4 83.6 0.69 1966-6? 0.88 22.7 91. ? 0.83 1967-68 1.9? 45.2 71.7 2.64 1966-69 1. 19 59.4 83.5 2.87 1969-?0 0.91 66.0 113.0 1.46 l9?G7l 0. ?9 ?5.8 100.6 1.89 L97t-72 1. ?8 103.4 61.4 6.71

Table 6?. Effect8 of poprlatlon alze, area of the lake, denslty as an hteractlon of poFlatlon md area' aad comblratloo of theae parsmetera on Ea of rlver carpancker tn El4hant hrtte Lake durbg r€v€lr years, 1966- 1912. *

Independent Varlablea Affectlng Cn P-A P-D a 0.8870 3.1441 0.8286 2. E534 1.1061 2.5046 2.7rgt b1 0.0068 0.0033 -0.0099 0.0021 b2 -o.0222 -0.0210 -0.016? -0.0194 b3 0.1612 0.2793 0.0650 0.0241 92 0.138? 0.6809 0.4929 0.6722 o.6240 0.6?13 o.6725 *Cn=a+blP+b2A+bgD.

109 of population density and surfac e areawhen a factor is applied to extrapolate En in bro'*m commercial nets during the same period of time. Thus, (from table 67) : cnwhite = 2.7L9L +0.0021 P- 0.0194A +0.0241D, and : + 0. 0021 P 0. 0194 A + 0.0241 D) (f), or Cn bro*o _ Q.7I9I - co (f) (cn b"ot, = white)' a ratio of to e during the same time period, which The factor, f, is e' brown o white may be derived as

E.n Drown -n brown , or simPlY tr-- ",---- En En white white c,= ". b* , when C' represents grand means for a specific time. 1 = dn white was 2. 18 for the year September, 1970, through August, 1971 (table 64). en .brown En in nets used to derive coefficients of P, A, and D were 0. ?9 during 1970-71 white (table E* represents seven months of the 19?0-?1 and 1. ?8 during Lgll.-lz 66). n ,^*^..*brown year and five months of the I97L-72 year. It follows that =cnwhite =W=r.20

C brown 2' 18 Therefore , f ='n - + 1.82, and cn white l'2o

(1' 82) (co co b"o*r, = *thit")' : Then, may be computed for any desired range of surface areas for any given ' en ,,_-^_-__brown population of carpsucker or vice-versa. : shown here (table 68) are daily means for one year. The carp- Computed e' b"o*r, sucker population is assumed to be L00,000 fish, and two four-inch (10.2-cm) mesh and two five-inch (12.7-cm) mesh, 150 by l0-foot (45.7 by 3m1 nets are set at random in carpsucker habitat (4 nets = 24 net-units/day). Selected surface areas from 6,000 to 12,000 acres are shown in the table.

110 Mean daily- E- for seasons and sections of the lake may be computed as propor- ^n = tionat to annualE-, seasonal E- i" proportional to annual C For example, nnn"" if four nets were set in middle and lower sections of the lake during summer (first priority, table 65) and the area of the lake were 6,000 acres:

3 C n summer n summer : =-. t Wnen c n annual n annual

C n annual = 3.51 (table 68) c n annual = 2. L8 (table 68)

C 3.45 or the mean of C-- from middle and lower sections during n summer = n A9,+t1 summer (#) (table 68). (co (co t- ro-*"") (3.51) (3.45) n summer = - "orro"t) 2.L8 e n rnnual = 5.56. Mean daily catch would be (5.56 fish/net-unit) (24 net-units/day) = 133. 4 fish/day. These fish, at a mean weight of.29.1ounces, would weigh 31882 ounces (243 pounds or 110.3 kS).

Table 68. Co fn rvUte ogerlmedal and brown 4- ard 6-tnch gtretcb meah conmerclal gfll neta ft.orn a poprlatbn of 100,000 rlver carpsucker tn Elephad &rtte Lake cihet meaD surface aree varles frrn 6r @0 to 12r 000 aorea. ProJected dally catch le based upoa 24 net-unttg ln t*o 4-lnch a.nd two 5-lnch meah, 160 bS' 10-bot netc get per day.

Dallv Catch A D Cn n'htte Eo boowo ad (acres) (100) P ^N fA P.ezl@o *6t*1 €a)Fa uroun) lba. (Ig) 60 6.7 1.93 3.61 E4.24 153 (60.6) 70 6.7 1. ?1 3. 11 74.U r86 (61.8) 60 4.2 1.48 2.85 64.56 11? (58.2) 90 3.7 L.27 2.31 66.4 101 (45. e) 100 2.6 1.05 1.91 46.84 83 (3?. ?) 110 2.9 0.85 1.65 3?.20 68 (80. e) L20 2.1 0.65 1. 18 28.s2 62 (23.6) lMean wetht of carpaucker caugbt tn br.oum commerclal nets waa 29.1 ouno€a (table 6a). Wetght of dally calch wae conputed as (29.1)(N), tben converted to pouDds ald kllograme.

111

Iifero ture Cifed

AFS. 1945. A list of common and scientific rrames of the better known fishes from the United States and Canada. Trans. Amer. Fish, Soc., Vol' 75. AFS. 1948. A list of common and scientifrc names of the better known frshes of the United States and Canada. Amer. Fish. Soc. Spec. Rrb. No, 1. AFS. 1960. A list of common and scientific names of fishes from the United States and Canada. Amer. Fish. Soc. Spec. Pub. No. 2. AFS. 1g?0. A list of common and scientifrc names of fishes from the United States and Canada. 3d. Ed., Amer. Fish. Soc. Spec. Pub. No. 6. Al-Rawi, T. R. 1965. Reading of scales of river carpsucker, Carpiodes carpio. Unpub. M. S. thesis, Iowa State Univ., Ames. Bailey, R.M., ffidM. O. Allum. L962. Misc. Pub. Mus. Zool., 119:80, Univ. of Michigan, Ann Arbor. Bailey, V. 1913. Life zones and cr"op zones of New Mexico. North Amer. Fauna No. 35, U. $. Dept. Agric., Washington, D. C. Bass, J. C., and C. D. Riggs, 1959. Age and growth of the river carpsucker, Carpiodes carTio (Rafinesque), of Lake Texoma. Proc. Okla. Acad. Sci., Vol. 39. B41

113 Brezner, J. 1956. Some aspects in the life history of the northern river carpsucker, Carpiodes carpio @afinesque), in the Niangua Arm of the Lake of the Ozarks. Unpub. M.A. thesis, Univ. of Missouri, Columbia. Buchholz, M. M. 195?(a). Life history of the river carpsucker (garpiodes. c. carpio) in the Des Moines River, Boone County, Iowa. Unpub. M. S. thesis, Iowa State Coll. (Univ. )' Ames. Buchholz, M. M. 195?(b). Age and growth of river carpsucker in Des Moines River, Iowa. Proc. Iowa Acad. Sci., Vol. 64. Buck, H. , and F. L. Cross. 1951. Early limnological and fish population conditions of Canton Reserrroir, and fishery management recommendations. Rept. Okla. Fish and Game Coun., Oklahoma City. Multilithed. Carlandern K. D. 1956. Appraisal of methods of fish population study, Part I. Fish growth rate studies: Techniques and role in surveys a:rd management. Trans. 21st N. Amer. W1dlf. Conf., Wldlf. Mgt. Inst., Washington, D.C., pp.262'274, Carlander, K. D. ,' &d E. B. Moorman. 1949. Management of small ponds for fish production. Proj. 3?, Quart. Rept. Iowa Coop. Wldlf. Fish. Resch. Units' pp. 54-83. Cooper, E. L. , and N. G. Benson. 1951. The coefficients of condition of brook, brown, and rainbow trout in the Pigeon River, Otsego County, Michigan. Prog. Fish-Cult., 13(4):181-192. Davis, J. T. 1955. Contribution to the ecology of fishes of Perche Creek, Missouri. Unpub. M. A. thesis, Univ. of Missouri, Columbia. Dixon, J. R. 1963. Periodic check and marked-fisherman creel census of Caballo Lake. D-J F-22-R-4, New Mexico Dept. Game and Fish, Santa Fe, Multilithed. Eddy, S. 7957. How to know the freshwater fishes. Wm. C. Brown Co. o Dubuque, Iowa. Elrod, J. H. , and T. J. Hassler. L97L. Vital statistics of seven fish species in Lake Sharpe, South Dakota, 1964-69. In Hall, G. E. (Ed. ). Reservoir fisheries and limnology. Amer. Fish. Soc. Spec. Pub. No, 8. Eschmeyer, P. H. 1950. The life history of the walleye in Michigan. Michigan Dept. Cons. , Inst. Fish. Resch., Misc, Bull. No. 3. Eschmeyer, R. W. , R. H. Stroud, and A. M. Jones. L944, Studies of the fish population Acad. Sci' on the shoal areas of a TVA mainstream reservoir. Jour. Tennessee ' Vol. 19. Fish Farming Industries, L972, Whatts ahead for catfish? 3(3):10-12. Mount Morris, Illinois, Fogel, N. E. 1963. Report of fisheries investigations during the fourth year of impoundment of Oahe Reservoir, South Dakota, 1962. D-J F-1-R-L2, South Dakota Game, Fish, and Parks, Pierre. Multilithed.

LL4 Gasaway, C.R. 1970. Changes inthe fish population in Lake Francis Case in South Dakota in the first 16 years of impoundment. Tech. Paper 56, Ihrr. Slort Fish, and Wldlf. , It. S. Dept. Interior. Hall, G. E. (Ed. ). 1971. Reservoir fisheries and limnology. Amer. Fish. Soc. Spec. Pub. No.8. Haacock, H. M. 1955. Age and growth of some of the principal fishes in Canton Reservoir, Oklahoma, 1951, with particular emphasis on white crappie. Okla. Fish and Game Coun. Pnoj. Rept., Part 2' Oklahoma City. Multilithed, Harlan, J. R. , and E. B. Slreaker. 1956. Iowa fish and fishing. Iowa State Cons. Comm. , Des Moines. Harrison, J. S. 1965. Basic survey of the upper Pecos River drainage. D-F F-22-R-5, New Mexico Dept. Game and Fish. Santa Fe. Multilithed. Hile, R. O. 1936. Age and growth of the cisco, Leuchichthyes artedi (Le Sreur) in the lakes of the northeastern highlands, Wisconsin. Bull. U. S. Bur. Fish. ' 48(1935): 209-317. Hile, R. O. Lg4L. Age and growth of the rock bass, Ambloplites mpestris (Rafines$re)' in Nebish Lahe, Wisconsin. Trans. Wis. Acad. Sci., Arts, and Lett. r 33:189-33?. Houser, A. , &od M. G. Bross. 1963. Average growth rates and length-weight relationships of fifteen species of fish in Oklahoma waters. Rept. No. 85, Okla. Fish. Resch. Lab., Univ. of Oklahoma, Norman. Multilithed. Hubbs, C. L., and K. F. Lagler. 1949. Fishes of the Great Lakes region. Cranbrook Inst. of Sci., Bloomfreld Hills, Michigan Huntington, E. H. , ffid A. W. Hill. 1956. Population study of fish in Elephant Butte Lake. D-J F-11-R-1, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Hlntington, E. H. , and D. B. Jester. 1958. Fisheries investigations in District No. 3. D-J F-11-R-3, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Huntington, E. H. , and R. J. Navame. 195?. Fisheries investigations in District No. 3. D-J F-11-R-2 New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Huntsman, G.R. 196?. Nuptial tubercles in carpsuckers (9-arpiodes.). Copeia (212457-458. Hutchinsor, G. E. , and H. Idffler. 1956. The thermal classification of lakes. Proc. Natl. Acad. Sci. , Yol. 42. Jenkins, R. M. , E. M. Leonard, and G. E. Hall. L952. An investigation of the fishery resources of the Illinois River and pre-impoundment study of the Tenkiller Reservoir' Oklahoma. OkIa. Fish. Resch. Lab. Rept. No. 26, Univ. of Oklahoma, Norman. Multilithed. Jensen, B. L., and D. B. Jester. 19?0. Investigations of commercial fishery potential of nough fish species. Comm. Fish. 6-11-R-2, New Mexico Dept. Ga"ure and Fish' Santa Fe. Multilithed. Jester, D. B. L962(al, Fisheries study of Conchas Lake. D-J F-22-R-3, New Mexico Dept. Game and Fish, Santa Fe. Multilithed.

115 Jester, D. B. 1962(b). A pre-impoundment sfirdy of Ute Reservoir, New Mexico. D-J F-ZZ-R-3, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Jester, D. B. 1g63(a). Basic surrey of the upper Rio Grande drainage. D-J F-22'P"'4, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Jester, D. B. 1963O). Rehabilitation of Ute Lake watershed, New Mexico. D-F F-19-D-5, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Jester, D. B. 19?1(a). Effects of commercial fishing, speeies introductions, and drawdown control on fish populations in Elephant Butte Lake, New Mexico. In Hall, G. E. (Ed. ). Reservoir fisheries and limnology. Amer. Fish. Soc, Spec. Pub. No. 8. Jester, D. B. 19?1(b). Age and growth of the river carpsucker. Unpub. Ph. D. thesis, Colorado State Univ., Fort Collins. Jester, D. B. 19?3. Variations in catchability of fishes with color of gill nets. Trans. Amer. Fish. Soc., 102(1) or 102(2). In press. Jester, D.8., and B. L. Jensen. L972. Life histolT and ecology of the gizzatd shado Dorosoma cepedianum (Le Sueur) with reference to Elephant Butte Lake. Ag. Exp. Sta. Resch. Rept. 218, New Mexico State Univ., Las Cruces. Jester, D.B., T.M. Moody, C. Sanchez, Jt., md D.E. Jennings, 1969. Game fish reproduction and rough fish problems in Elephant Butte Lake, Nerv Mexico' D-J F-22-R-9, New Mexico Dept. Game and Fish, santa Fe. Multilithed. Jester, D.8., R.R. Patterson, D.E. Jennings, T.M. Moody, andC. Sanchez, Jr. 1,970. Effects of color of gill nets on catch rates of fishes. Ag. Exp. Sta. Bull. 564, New Mexico State Univ., Las Cruces. Johnson, G. V. , and D. E. Kidd. L9?0. An investigation of primary productivity using the C14 method and an analysis of nutrients in Elephant Butte Reservoir. Ann. Narrative Rept., Univ. of New Mexico, Albuquerque. Klaassen, H. E. , and G. R. Marzolf. 19?1. Relationships between distributions of benthic insects and bottom-feeding fishes in T\rttle Creek Reservoir. In Hall' G. E. (Ed. ). Reservoir fisheries and limnology. Amer. Fish. Soc. Spec, Pub. No. 8. Koster, W.J. 1957. Guide to the fishes of New Mexico. Univ. of New Mexico Press, Albuquerque. Lagler, K. F. 1956. Freshwater fishery biology. 2d Ed. Wm. C. Brown Co., Dubuque, Iowa. LeCren, E. D. 1951. The length-weight relationship and seasonal cycle in gonad weight and condition in the perch (Percal fluviatilis). Jour. Animal Ecol, 20(2lz20l-2L9. Lee, RosaM. Mrs. T.L, Williams),'LgzO. Areviewof themethodsof ageandgrowth determination in fishes by means of scales. Ministry of Agric. and Fish. , Fish. Invest. , Set. n, 4(2lzL-32. Little, R, G. 1959. Berrendo Creek rehabilitation. D-J F-22-R-1, New Mexico Dept. Game and Fish, Santa Fe. Multilithed.

11_6 Little, R. G. 1960. Rehabilitation of Carlsbad Municipal Lake. D-J F-22-R-2, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1962. Basic surveys of waters in Units A and B of District 4, D-J F-22-R-3, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1963(a). Periodic check of the frsh population between McMillan and Avalon Reservoirs. D-J F-22-R-4, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1963(b). Routine periodic check of Pecos River Fish Barrier and Trap No. 1. D-J F-ZZ-R-4, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1964(a). Resurvey of the Pecos River (short title). D-J F-22-F''4, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1964(b). Periodic check of Conchas Reservoir. D-J F-22-R-5' New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R.G. 1964(c). Routine periodic check of Alamogordo Reservoir. D-J F-22-R-5, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1964(d). Periodic check of McMillan Resenroir' D-J F-22-R-5, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1964(e). Periodic check of the fish population between McMillan and Avalon Reservoirs. D-J F-22-R-5, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1964(0. Periodic check of lower Black River D-J F-22-R-5, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Little, R. G. 1965. Routine periodic check of Carlsbad Municipal Lake. D-J F-22-R-6, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Martin, R.E., S.I. Auerbach, and D.J. Nelson. L964. Growth and movement of smallmouth buffalo, Ictiobus bubalus (Rafinesque), in Watts Bar Reservoir' Tennessee. Oak Ridge Natl. Lab., O* Ridge' Tennessee. McCarraher, D, B. , M. L. Madsen, ild R. E. Thomas. L97L. Ecolory and fishery marragement of McConaughy Reservoir, Nebraska. In Hall, G. E. (Ed. ). Reserrroir Fisheries and limnology. Amer. Fish. Soc. Spec. Pub. No. 8. Mendenhall, W. 1963. Introduction to statistics. Wadsworth Pub. Co., Inc., Belmont, California. Moody, T. M. 19?0, Effects of commercial fishing on the popqlation of smallmouth buffalo, Ictiobus bubalus (Rafinesque), in Elephant Butte Lake, New Mexico. Unpub, M. S. thesis, New Mexico State Univ., Las Cmces. Moody, T.M., C. Sanchez, Jt., B.L. Jensen, and D.B. Jester. 1970. Investigations of commercial fishery potential of rough fish species. Comm. Fish. 6-11-R-1. New Mexico Dept. Game and Fish, Santa Fe, Multilithed. Morley, W. H. 1956. Pecos River Fish Barrier and Trap No. 1. D-J F-10-R-1, New Mexico Dept. Game and Fish, Santa Fe. Multilithed.

LL? Morris, L.A. 196b. Age and growth of the river carpsucker, Carpiodes carpio, in the Missouri River. Amer. Midl. Nat., 73:423'429. Navarre, R. J. 1958(a). Pecos River Fish Barrier and Trap No. 1. D-J F-10-R-3' New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Navarre, R. J. 19b8O). Biological and chemical study of Willow Lake and Black River. D-J F-10-R-4, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Navarre, R. J. 1959. Pecos River Fish Barrier and Trap No. t, D-J F-10-R-4, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Navarre, R. J. 1960. Pecos River Fish Barrier and Trap No. 1. D-J F-22-R-1' New Mexico Dept. Game and Fish, Santa Fe' Multilithed. Nelson, W. R. 1962. Report of fisheries investigations during the seventh year of impoundment of Gavins Point Reservoir, South Dakota, 1961. D-J F-1-R-11' South Dakota Game, Fish, and Parks, Pierre. Multilithed. Netsch, N. F., and A. Witt, Jr. 1962. Contributions to the life history and ecology of the longnose gar (Lepiososteus.osseus) in Missouri. Trans. Amer. Fish. Soc., 9L(3'1225L-262. Odum, E. p. 1959. Fundamentals of ecology. 2d Ed. W. B, Saunders Co. , Philadelphia. Ozmina, D. J. 1965. An evaluation of the physical, chemical, and biological factors of Caballo Reservoir following rehabilitation. Unpub. M. S. thesis, New Mexico State Univ., Las Cruces. padilla, R. L972. Reproduction of carp, smallmouth buffalo, and river carpsucker in Elephant Butte Lake. Unpub. M. S. thesis, New Mexico State Univ. , Las Cruces. padilla, R. , W. R. Uhland, G. L. Wisdom, and D. B. Jester. 1971. Investigations of commercial fisheries potential of rough fish species. Comm. Fish. 6-11-R-3' New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Patriarch€, M. H. , and R. S. Campbell. 1957. The development of the fish populations in a new flood-control reservoir in Missouri, 1948 to 1954. Trans. Amer. Fish. Soc., Vol. 87. patterson, R.R. 1968. Age, growth, and movement of smallmouth buffalo, Ictiobus bubalus (Rafinesqtre), in Elephant Butte Lake, New Mexico. Unpub. M. S. thesis' New Mexico State Univ., Las Cmces. Purkett, C.A., Jr. L957. Growth of fishes in the Salt River, Missouri. Trans. Amer. Fish. Soc., VoI. 87. Rael, C. D. 1966. Age-growth, length-weight relationship, condition, and movement of the river carpsucker, Carpiodes carpio (Rafinesque), in Elephant Butte Lake, New Mexico, Unpub. M. S. thesis, New Mexico State Univ., Las Cruces. Rael, C, D., and D.J. Ozmina. 1965. A study of game fish reproduction and rough fish problems in Elephant Butte Lake. D-J F-22-R-6, New Mexico Dept. Game and Fish, Santa Fe. Multilithed.

11-8 Regan, D. M. 1960. Periodic check of Garfield Drain. D-J F-22-R-1, New Mexico Dept. Game and Fish, Santa Fe. Multilithed, Regan, D.M. 1961. Rehabilitation of Caballo Lake and the Rio Grande between Caballo Lake and Elephant Brtte Dam. D-J F-19-D-3, New Mexico Dept. Game and Fish, Santa Fe. Multilithed. Regan, D. M. 1963. Periodic check on the Rio Grande between Elephant Butte Dam and Caballo Reseryoir. D-J F-22-R-4, New Mexico Dept. Game and Fish. Multilithed. Ricker, W. E. 1958. Handbook of computations for biological statistics of fish populations. Bull. No. 19, Fish. Resch. Bd. Canada. Romer, A. S. 1955. The vertebrate body. 2d Ed. W. B. Saunders Co., Philadelphia.

SFI. 19?1. $$ vatues of fish. Sport Fishing Institute B;nll. No. 227, Auglst. Washington, D. C. Sanchez, C. , Jr. 19?0. Life history and ecolory of carp, Cyprinus carplo_Linnaeus' in Elephant Butte Lake, New Mexico. Unpub. M. S. thesis, New Mexico State Univ., Las Cmces. Schnabel, Zoe E. 1938. The estimation of the total fish population of a lake. Amer. Math. Monthly, 45(6):348-352. Shields, J. T. 1956. Report of fisheries investigations during the third year of impoundment of Fort Randall Reservoir, South Dakota, 1955. D-J F-1-R-5, South Dakota Game, Fish, and Parks, Pierre. Multilithed. Sprague, J. W. 196L. Report of fisheries investigations during the seventh year of impoundment of Fort Randall Reservoir, South Dakota, 1959. D-J F-1-R-9, South Dakota Game, Fish and Parks, Pierre. Multilithed. Starrett, W. C. 1948. An ecological study of the minnows of the Des Moines River, Boone County, Iowa. Unpub. Ph. D. thesis, Iowa State Coll. (Univ. ), Ames. Starrett, W. C. , and A. W. Fritz, 1965. A biological investigation of the fishes of Lake Chatauqua, Illinois. Ill. Natl. Hist. Surv., Urbana. Stucky, N. P. , and H. E. Klaassen. L97L, Growth and condition of the carp and the river carpsucker in an altered envirpnment in Western Kansas, Trans. Amer. Fish, Soc., L00(21:276-282. $rmmerfelt, R. C. , P. E. Mauck, and G. Mensinger. 1972. Food habits of river carpsucker and freshwater drum in four Oklahoma reservoirs. Proc. Okla, Acad. Sci. 52. In Press. Swingle, W. E. 1965. Length-weight relationships of Alabama fishes. Ag. Exp. Sta. Zool.-Entomol. Ser. Fish, Vol. 3, Auburn Univ., Auburn, Alabama. lbompson, W. 1950. Investigation of the fishery resources of Grand Lake. Oklahoma Game and Fish Dept., Fish Mgt. Rept. No. 18. Oklahoma City. Multilithed. U. S. Dept. Commerce. 1970. Climatological data, N. M. annual summary, 1970. 74213. NOAA, Asherville, North Carolina.

119 Van Oosten' J. 1953. A modification in the technique of computing average lengths fnom the scales of fishes. Prog. Fish-Cult,, 1b(2):8b-86. Walburg, C. H. 1971. Ioss of young fish in reservoir discharge and year-class sunrival, Lewis a.nd Clark Lake, Missouri River. In Hall, G. E. (Ed. ). Reservoir fisheries and limnolory. Amer. Fish. Soc. Spec. Pub. No. 8. Walburg, C. H. , G. L. Kaiser, and P. L. Hudson. 1971. Lewis and Clark Lake tailwater biota and some relations of the tailwater and reservoir fish populations. In Hall, G. E. (Ed. ). Reservoir fisheries and limnology. Amer. Fish. Soc. Spec. Pub. No. 8. Walburg' C.H., &od W.R. Nelson. 1966. Car?, rivercarpsucker, smallmouthbuffalo, and bigmouth buffalo in Lewis and Clark Lake, Missouri River. Resch. Rept. 69, Bur. Sport Fish, and Wldlf. , It. S. Dept. Interior. Woodbury, A. M. 1956. Uses of marking animals in ecological studies: Introduction. Ecolory 37:665.

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