Montana State Library Records Digitization Project COVER SHEET This page is not part of the original document and was inserted for formatting purposes fWWM 3 33.*/ '- 85 -► SAMPLING STATIONS 1 Dam Section 2 Hosford 3 Birney 4 Ashland 5 Viall 6 S-H 7 Orcutt 8 Keogh WYOMING Figure 3. Tongue River sampling stations. 10 fO 1- c: +-> •i- (T3 3 to en c E 1- O r— (UJ) U0I(DA3|3 11 ,Y SMBH^^-- Figure 5. Sampling Station 1, Corwin Springs Figure 6. Yankee Jim Canyon between stations 1 and 2. 12 Figure 7. Near Station 3 above Livingston, Figure 8. Station 4 at Livingston, 13 Figure 9. Station 5 at Grey Bear Fishing Access, Figure 10. Aerial view of Yellowstone River above Miles City. 14 :eK t£P&*Z'> Figure 11. The Yellowstone River about 10 miles upstream from Miles City. Figure 12. Yellowstone River at Gl endive during early winter. 15 No. 18. Figure 13. Aerial view of the Intake diversion, sampling station Figure 14. Yellowstone River at Intake diversion, 16 IKtttuxL SAMPLING METHODS AND MATERIALS Sampling methods used to collect aquatic macroinvertebrates on the Yellowstone River included kick nets (figure 15), Water's round samplers (figure 16), and Hester-Dendy multiple plate artifical substrates. The kick net, essentially a Surber Sampler on a pole, consisted of a modified Turtox bottom net 10" deep with dimensions of 8" x 8" , a six-foot wooden handle used to hold the net perpendicular to the current, and wire frame 17" x 16" attached to the bottom lip of the net frame perpendicular to the net opening in such a way that the wire frame rested on the stream bottom. The area within the frame was 272 in2 (0.175 m^) . When the area with- in the frame was disturbed, bottom organisms were carried into the number 20 (0.70 mm) mesh net. Net material was added to each side of the wire frame to minimize side washout of organisms. This technique can be used as lonq as the water is shallow enough to wade. The bottom outlined by the frame is merely stirred with the foot. This sampler was used at the Glendive and Intake sampling stations during 1975 only. Water depth, and current speed at six-tenths total depth, were determined in the center of each sampling site. A timed (2-minute) kick sample without the 17" x 16" frame was taken at many stations during 1974 in the Yellowstone and Tongue rivers to determine relative abundance of organisms. A Water's round sampler was used to take six samples per month at ten of the 20 sampling stations in the Yellowstone River from August to November 1975 The Water's sampler is 19.5 in (.495 m) in height and encloses an area just'slightly less than one ft? (143.14 in2 or 0.093 m2) . The area to be sampled, randomly selected, is approached from downstream. After forcing the sampler into the bottom, the investigator reaches down through the open top and stirs the bottom with his hand. Water current carries the orqamsms into the trailing, 20-mesh net. All organisms were preserved in the field in 70-percent ethyl alcohol. Hester-Dendy multiple-plate artificial samplers (Hester and Dendy 1962), Fullner 1971, Parsons and Tatum 1974) were used occasionally during 1974 but their use was discontinued when they proved to be unsatisfactorily colonized. In the laboratory, all organisms were nicked from bottom detritus and gravel under a dissecting microscope. Immature invertebrates were identified to genus and species (and, less commonly, only to family) using appropriate taxonomic keys. Adult insects were used whenever possible to confirm species identifications. Experts (identified on page 4 ) were consulted when difficulties were encountered. 17 Figure 15. Kick net and other data collecting gear. Figure 16. Water's round bottom sampler. 18 Measurements were made to determine velocity and depth preferences of invertebrates. All velocity measurements were made with a Price model -AA- type current meter at six-tenths total depth. Discharge at the Miles City and Sidney stations on dates sampling was preformed is shown in Table 1 (USGS 1976). Table 1. Discharges of the Yellowstone River at Miles City and Sidney during sampling periods (cfs). Date Miles City Sidney August 6, 1975 20,200 21,200 August 7, 1975 18.500 20,300 September 9, 1975 9,890 10,100 September 17, 1975 8,440 8,980 October 9, 1975 8,000 9,730 October 15, 1975 8,850 10,300 November 7, 1975 8,620 10,400 November 11 , 1975 10,300 10,100 CONVERSIONS: 1 cfs = .0283 m3/sec SPECIES DIVERSITY CALCULATIONS Aqgreaations or communities of aquatic orqanisms are subjected to almost continual stress due to environmental changes, some natural and others caused by society. It is a generally accepted axiom in ecology that a gross environmental stress exerted upon a diverse biological community (one consisting of a large number of species) results in a simplication of the system through a reduction of species diversity (i.e. number of species) (Cairns 1969). Slobodkin and Sanders (1969) developed the stability-time hypothesis to suggest the kinds of animals that must live in low- and high- diversity places: all places of high diversity would have stable or predictable environments, and all places of low diversity would either be places of unpredictable hazard or would be short-lived. This theory was tested in one widespread, stable environment—the ocean floor. Although this investigation is far from complete, the theory appears to hold. In low-diversity areas, the dangers of species extinction are great. Populations of opportunistic animals must frequently be decreased by weather to prevent it, and the possibility still exists of breeding failure. The loss of several consecutive year-classes means extinction even for long-lived 19 animals. But such year-class failure is less likely in stable climates, and a series of failures is unlikely. Extinction is thus more probable as environmental stress increases. The actual number of species present in any place is a product both of the loss of species by extinction and of their replacement with new species. In a few specialized organisms, such as birds, a limit to the number of species that can accumulate is set by a restricted number of possible niches. For most other kinds of animals and plants, the number of possible niches is much larqer than the number of existing species. The patterns of diversity presently evident arc the products of different environments of the earth (Colinvaux 1973). The use of species diversity indices to analyze biological communities originates from efforts to apply information theory to complex biological problems. Workers who have explored the theoretical use of diversity indices in biology, suggested refinements, or attempted studies include Brillouin (1960), Lloyd and Ghelardi (1964), Wilhm and Dorris (1966, 1968) Lloyd et al . (1968), Margalef (1968), Pielou (1969), Wilhm (1967, 1970abc, 1972), and Cairns and Dickson (1971). Several indices have been generally acceDted: mean diversity (d), equitability (Em), redundancy (R), evenness (J'), and richness (SR). FORTRAN computer programs for calculating species diversity indices are available from the following sources: Wilhm (1970b), Cairns and Dickson (1971), and Orr et al . (1973). MEAN DIVERSITY (d) In general, the fundamental objective of information theory is applied to biology is to provide insight into community structure. The biological information theorist asks how much new knowledge or "information" about the species composition of a community can be obtained by drawing individuals at random. If the community is composed of only one species, then no new composition information is obtained after the first drawing. But if the community is composed of numerous species, possibly with each individual being a different species, then much new information is gained with each drawinq. Information theory attempts to quantify the information contained in the community in terms of "bits" of information per individual. Mathematically stated, "information" equals the uncertainty of correctly predicting the identity of an individual randomly chosen from a community. Where uncertainty is high, information per individual is high. The mean amount of uncertainty of prediction of any individual's identity equals the mean number of bits of information per individual, and this number is referred to as the species diversity index. Mean information per individual is commonly measured usinq the function developed by and named after Shannon and Weaver (1964). The formula for the Shannon-Weaver function is: s. d - -£ (N./N) loq2(N./N) i=i where d = mean number of bits of information per individual, or the species 20 diversity index. s = number of taxa in the sample N. = number of individuals in the taxon l N = total number of individuals A few of the authors cited earlier in this section and Hurlbert (1971) have criticized the Shannon-Weaver function as improperly used in many studies. However, the U.S. Environmental Protection Aqency (1973) has provisionally accepted and recommended the function for aquatic macrobenthos studies. The index, d, possesses features that make it a useful method for summarizinq communitv diversity. The index is dimensi onless and expresses the relative importance of each species in the community. As sample size is increased, the d of the progressively pooled samples increases rapidly at first and then levels off. Since diversity of progressively pooled samples asymptotically approaches the diversity of the population, and since diversity of individual samples are hiqhly variable, it is preferable to report the diversity of the pooled samples. Diversity had leveled off by the fifth pooled sample in most of the areas sampled by Wilhm (1970abc). The range of d varies from zero to any positive number. A value of zero is obtained_when all individuals belong to the same species. The maximum value of d depends on the number of individuals counted and is obtained when all individuals belong to different species. The d usually varies between three and four in clean-water stream areas and is usually less than one in polluted stream areas (Wilhm 1970abc). A low diversity index indicates a larqely monotypic community dominated by a few abundant organisms. Often the total number of species is low. In addition, a low diversity index often suggests that deqraded environmental conditions exist which favor the proliferation of a few tolerant species and the removal of less tolerant forms. A high diversity index indicates a heterogeneous community in which abundance is distributed more evenly among a number of species. The total number of species is generally high. EQUITABILITY (Em) As measured by Marqalef ( 1 9B7 ) and Krebs (1972), equitability (E ) is a retio of the observed d to a maximum theoretical diversity (dmax) computed as though all individuals were equally distributed amonq the species. Maxi- mum diversity here is measured simply as loq9 s; therefore E = d/loq0 s m c As equitability increases, the species become more evenly distributed and their distributions conform more closely to perfect theoretical distri- butions. Equitability may range from 0 to 1, except that in samples containino only a few specimens with several taxa_represented , values of E greater than 1 may occur. The estimates of E™ and d improve with increased sample size, and samples containing fewer than TOO specimens should be evaluated with caution if 21 at all (U.S. EPA 1973). An improved equi tabi 1 ity formula is presented below and must be used with tables presented in Lloyd and Ghelardi (1964) and U.S. EPA (1973): where s1 = tabulated value Em2 ^ Because a table is required to calculate Em? it is not easily applied to computer operations. Equi tabi 1 i ty has been found to be sensitive to even slight levels of environmental degradation. Equi tabi 1 i ty levels below 0.5 have not been encountered in southeastern U.S. streams known to be unaffected by oxygen- demanding wastes, and in such streams Fm2 values are generally between 0.6 and 0.8. Even sliqht levels of degradation have been found to reduce Em2 below 0.5 and generally to a range of 0.0 to 0.3. REDUNDANCY (R) Redundancy (R), as measured by Wilhm and Dorris (1968) and Cairns and Dickson (1971), gives the relative position of the observed diversity index (d) between theoretical maximum and minimum diversities (d and d . » It is calculated as follows: max minj- R = ^max " ? d - d . max mm Theoretical maximum and minimum diversities are calculated as follows: d = (1/N) [log9N!-s logo (N/s)f| max L ^ ~c J dmin = (1/N) {log2N! - log2 [N-(s-l)] !} Redundancy measures the repetition of information within a community, thereby expressing the dominance of one or more species, and is inversely proportional to the wealth of species. It is maximal when no choice of species exists and minimal when there is a greater choice of species. EVENNESS (J1) If the numbers of individuals, Nj, N?, . . . Ns, in each of the s species are portrayed in histogram form, s is the range of data or the width of the histogram. The shape of the histogram is best described in what may be called its "evenness." Thus, the distribution has maximum evenness if all the species abundances are equal; the greater the disparities among the different species abundances, the smaller the evenness. Evenness (J1) is calculated as follows: (Pielou 1969): log? s Eqloff and Brakel (1973) calculated evenness for a population of aquatic macroinvertebrates in a stream receiving large inputs of domestic sewage. Above the outfall, evenness values ranged from 0.6 to 0.7 and diversity was 3.0 and greater; below the outfall, evenness dropped to 0.4 and below and diversity decreased to less than one. The number of species and evenness appeared to be inversely related along the stream except at the outfall, where both decrease. The evenness index has not been widely used in aquatic studies. SPECIES RICHNESS (SR) A further component of diversity, richness, was calculated in the computer proqram furnished by Orr et.al. (1973), but no reference to it could be found in the literature. It was calculated as follows: SR = d - d/log2 N Species richness is more commonly calculated by summing the total number of species present in a sample. 23 /T#e (MtraducUavi ta Uutaal j1) in contrast to headwater and large rivers where P/R < 1 (figure 17). Large rivers tend to be turbid with heavy sediment loads, the culmination of all upstream processes. These systems, which possess plankton communities, could be characterized by their food chains: FPOM--bacteria--collectors (figure 17). Fish populations generally show a downstream transition from cold-water invertivores to warm-water invertivores and from piscivores to planktivores. A more autecological approach to distribution of aquatic invertebrates in aquatic ecosystems investigates the distribution and abundance of stream- dwelling invertebrates as regulated by such factors as current speed, temp- erature, substrata, vegetation, and dissolved substances (Hynes 1970); others are competition, zoogeography, and food. Temperature and water chemistry usually exert the greatest influence on the composition of living communities considered over large areas, but because of feeding and respiratory requirements, it is largely current that determines how local communities actually are composed (Jaag and Ambuhl 1964, Chutter 1969). In fact, some macroinvertebrate species are confined to fairly narrow ranges of current speed. As an example, in the case of the net-building caddisflies (e.g., Hydropsyche, Cheumatopsyohe, Parapsyche) , the nets require a definite current in order for them to function properly (Philipson 1954). Many organisms must function in proximity to a specific current but cannot tolerate being actually in it. There is often great variation in current velocity for an insect living on top of a rock compared with one living under that rock, yet both may have current requirements. Because of the impossibility of taking measurements at most places macroinvertebrates inhabit (such as under rocks), current velocity is usually measured at some reproducible depth, e.g., mid-depth, six-tenths of total depth, or near the bottom (Hynes 1970). There are unmistakable high-current specialists (e.g., Baetis, Simulium, and Hydropsyche), while some organisms find optimum habitat at low velocities (e.g., Gammarus, Hyalella, Trioorythodes) . Each species prefers a certain range of current velocity. 27 Figure 17. Relationships between detritus, producers, and consumers in different order streams--stream continuum. Reproduced with permission from Cummins 1975b. 23 ^~~ I 29 In every turbulent flowing system, marginal effects develop in the boundary layers. Close to the substratum, movement of the water gradually slows due to friction, and a boundary layer is formed in which the flow is strongly retarded, until, close to the substratum, it is stagnant (Jaag and Ambuhl 1964). The thickness of this boundary layer depends, among other things, on the velocity of the current above and the shape and roughness of the substratum. Extremely flattened organisms (e.g., Epeorus, Rhithrogena) make use of the boundary layer to avoid the current. Many species that live in flowing water (e.g., most Plecoptera) can be maintained only in such water, since they either possess no ventilating organs or have changed or lost the function of those organs in the course of their evolutionary development. They are extremely sensitive to still water and quickly die in it. Macrodistribution of aquatic invertebrates can be explained with increasing difficulty as habitat gradually changes moving downstream. Cummins (1975a) described food as the ultimate determinant of macroinvertebrate distribution and abundance in nondisturbed running waters. The current regime, velocity, and turbulence set the limits on the range of sediment particle sizes present as well as controlling such features as the growth of periphyton and macroDhytes and accumulation of particulate detritus. The size of particles present decreases in a downstream direction (Macan 1974, Hynes 1970), resulting in community variation in primary producers, macroinvertebrates, and fish. These community changes may be generally placed into three categories or habitat subsystems: (1) erosional zone, (2) intermediate zone, and (3) depositional zone. Each zone has a characteristic physical-chemical makeup and a characteristic fauna. 30 SxMutq aitctatuM MACROINVERTEBRATE DISTRIBUTION A checklist of the macroinvertebrates found in the Tongue and Yellowstone rivers is presented in table 2. This list is as complete as possible and utilizes all published sources available, as well as data gathered during this study. Distributional records were taken from Stadnyk (1971), Gaufin et al . (1972), and Thurston et al . (1975). For specimens for which a precise species identification was not possible, the most probable species (considering the most recent available distribution data) is listed in parentheses. In the order Diptera, several genera are listed under the family Chironomidae; this is the only place these genera will appear in this report because of unconfirmed identifications. Identifications of this group are difficult both to make and to confirm. YELLOWSTONE RIVER Mayflies The distribution of all mayflies (Ephemeroptera) known to occur in the Yellowstone River (37 species variously distributed) is presented in figure 19. Four species were collected throughout the study area, and a fifth species {Ephemerella inevmis) was missing only from the lower two sampling stations. In this figure and in several others, stations 7-12 are shaded and represent the probable location of the transition zone between the salmonid and nonsalmonid zones. This transition zone also corresponds to the inter- mediate zone between the erosional and depositional habitat subsystems outlined by Cummins (1975b) for large rivers. The number of mayfly species found at each station is illustrated in figure 20. Station 5 yielded the largest number of species (19) and stations 19 and 20 the fewest with 10 species. No pattern of mayfly distribution is apparent throughout the transition zone. Longitudinally, the community exhibits a gradual shift from mountain fauna to prairie fauna more adapted to slower flow, warmer temperatures, and a silty substratum, but the number of species is reasonably constant along the entire river. A mature Heptagenia elegantula nymph is shown in figure 21. 31 TABLE 2. Checklist of the aquatic macroinvertebrates of the Tongue River (t) and the Yellowstone River (y). Phylum Arthropoda Order Ephemeroptera Family Siphlonuridae y Ameletus (oregonensis McD.?) y Isonychia (sicca campestris McD.?) Family Baetidae y t Baetis insignificans McD. y t Baetis parvus Dodds y Baetis (propinquus Walsh) y Baetis tricaudatus Dodds y Centroptilum sp. A y t Dactylobaetis cepheus Traver & Edmunds y Pseudocloeon sp. A Family 01 igoneuriidae y Lachlania powelli Edmunds Family Heptageniidae y Epeorus (Iron) albertae (McD.) y Epeorus (Iron) longimanus (Eaton) y Heptagenia elegantula (Eaton) y t Rhithrogena undulata (Bks.) y t Stenonema terminatum (Walsh) y Stenonema prob n. sp. Family Ametropodidae y Ametropus (neavei McD.)? Family Leptophlebiidae y t Choroterpes albiannulata McD. y t Leptophlebia gravastella Eaton y Paraleptophlebia bicornuta (McD.) y Paraleptophlebia heteronea (McD.) y t Traver ella albertana (McD.) Family Ephemerel 1 idae y Ephemerella (Attenuatella) margarita N. y Ephemerella (Caudatella) h. heterocaudata McD. y Ephemerella (Caudatella) hystrix Traver y Ephemerella (Drunella) doddsi Needham y Ephemerella g. grandis Eaton y t Ephemerella (Ephemerella) inermis Eaton y Ephemerella (Serratella) tibialis McD. y Ephemerella (Timpanoga) h. hecuba (Eaton) Family Tricorythidae y t Tricorythodes minutus Traver y Tricorythodes sp. A Family Ephemeridae y Ephemera sp. A Family Polymitarcidae y Ephoron album (Say) Family Caen idae y t Brachycercus (prudens McD.?) y Caenis latipennis 32 TABLE 2 (continued). Family Baetiscidae y t Baetisca sp. A Order Trichoptera Family Rhyacophil idae y Rhyacophila bifila Bks. Family Hel icopsychidae y Helicopsyche borealis (Hagen) Family Glossosomatidae y t Glossosoma sp. A y Glossosoma traviatum Bks. y Glossosoma velona Ross Family Psychomyiidae y Polycentropus cinereus Hagen y Psychomyia flavida Hagen Family Hydropsychidae y Arctopsyohe grandis Bks y t Cheumatopsyche sp. A y Cheumatopsyche analis (Bks.) y Cheumatopsyche campy la Ross y Cheumatopsyche lasia Ross y Cheumatopsyche enonis Ross y t Hydropsyche sp. A t Hydropsyche near alhedva Ross y Hydropsyche cockerelli Bks. y Hydropsyche corbeti Nimmo y Hydropsyche occidentalis Bks. y Hydropsyche oslari Bks. y Hydropsyche separata Bks. Family Hydroptilidae y t Hydroptila sp. A y Hydroptila waubesiana Betten y Agraylea multipunctata Curtis y Ochrotrichia potomas Denning y Neotrichia sp. A Family Leptoceridae y Athripsodes sp. A y Leptocella sp. A y t Occetis sp. A y Occetis avara (Bks.) y Occetis disjuncta (Bks.) y Triaenodes frontalis Bks. Family Lepidostomatidae y Lepido stoma n. sp. y Lepidostoma pluvialis Milne y Lepidostoma veleda Denning Family Brachycentridae y Amiocentrus aspilus (Ross) y t Brachycentrus sp. A. y Brachycentrus americanus (Bks; y Brachycentrus occidentalis Bks. 33 TABLE 2 (continued). Order Hemiptera Family Corixidae y Callicovixa utahensis (Hung.) y Cenocovixa audeni (Hung.) y Sigara alternata Say y Tviohooorixa bovealis Sailer Family Naucoridae y Ambrysis mormon Mont. Family Veliidae y t Rhagovelia distinota Champion Family Gerridae y Gerris remigis Say Family Nepidae y Ranatra fusca P.B. Order Qdonata Family Gomphidae y t Gomphus sp. A y t Ophiogomphus sp. A Family Agrionidae t Calopteryx sp. A Family Coenagrionidae t Argia sp. A y t Amphiagrion sp. A y Enallagma sp. A t Enallagma ebrium (Hagen) t Ischnura sp. A Order Coleoptera Family Dytiscidae y Oreodytes sp. A Family Dryopidae y Heliohus sp. A Family Elmidae y t Dubiraphia sp. A y t Miorocylloepus pusillus (LeConte) y Optioservus quadrimaculatus (Horn) y t Stenelmis sp. A y Zaitzevia parvula (Horn) Family Gyrinidae y Cyrinus sp. A Order Diptera Family Blepharoceridae y Agathon sp. A y Family Ceratopogonidae Family Chironomidae Subfamily Tanypodinae y Ablabesmyia sp. A y Clinotanypus sp. A y Cryptocladius sp. A y Prooladius sp. A 34 TABLE 2 (continued). Family Limnephil idae y Hesperophylax '■ 'isus Bks. y Limnephilus taloga Ross Order Plecoptera Family Nemouridae y Nemoura (Prostoia) besametsa Ricker y Nemoura (Zapada) oinctipes Bks. y Paraleuctra sara Claassen y Capnia (Capnia) confusa Claassen y Capnia (Capnia) gracilaria Claassen y Capnia (Capnia) limata Frison y Capnia (Utacapnia) distincta Frison y Capnia (Utacapnia) poda Nebeker & Gaufin y Eucapnopsis vedderensis Ricker y Isooapnia missourii Ricker y Isooapnia vedderensis (Ricker) y t Brachyptera (Taenionema) fosketti Ricker y Brachyptera (Taenionema) nigripennis Bks. y Brachyptera (Taenionema) pacifica (Bks) Family Pteronarcidae y Pteronarcella badia (Ha gen) y Pteronarcys calif ornica Newport Family Perlodidae y Arcynopteryx (Skwala) parallela (Frison) y Isogenus (Cultus) aestivalis (N & C) y Isoqenus (Cultus) tostonus Ricker y t Isogenus (Isogenoides) frontalis colubrinus Hanen y Isogenus (Isogenoides) elongatus Hagen y Isoperla fulva Claasen y Isoperla mormona Bks. y Isoperla longiseta Bks. y Isoperla patricia Frison Family Chloroperl idae y Alloperla (Suwallia) pallidula (Bks) y Alloperla (Sweltsa) coloradensis (Bks) y Alloperla (Alloperla) severa Hagen y Alloperla (Triznaka) signata (3ks) Family Perl idae y t Acroneuria abnormis y Acroneuria (Hesperoperla) pacifica Bks. y Claassenia sabulosa (Bks) Order Isopoda Family Asellidae y Asellus racovitzai racovitzai Williams Order Lepidoptera Family Pyralidae y t Cataclysta sp. A 35 TABLE 2 (continued). Subfamily Chironominae y Chironomus sp. A y Cryptochironomus sp. A y Microtendipes sp. A y Paralauterborniella sp. A y t Rheotany tarsus sp. A y Stiatochironomus sp. A Subfamily Diamesinae y t Diamesa sp. A y Monodiamesa sp. A Subfamily Orthocladi inae y Brillia sp. A y t Cardiocladius sp. A y Cricotopus sp. A y t Eukieffeviella sp. A y Metrioanemus sp. A y t Orthocladius sp. A y Tvichocladius sp. A Family Dolochopodidae Family Empididae y Hemerodromia sp. A Family Muscidae y Limnophora sp. A 36 1 2 3 4 5 6 7 Sc 8 mp 9 ing 10 St II atio 12 n 13 14 15 16 17 18 19 20. Baetis (propinquu.- Ephemerella hyst p x Epeorus longimanus Ephemerella heterocaudata hecuba Baetis trioaudatus Pseudocloeon sp. Ephemerella tibialis Ephemera sp. ■ .imerella doddsi Ephemerella grandis Paraleptophlebia heteronea Epeorus albertae Paraleptophlebia bicomuta Ephemerella margarita Stenonema prob. n. sp. Ameletus (oregonensis ?) Ephemerella inermis Baetis insignifiaans parvus Heptagenia elegantula Rhithrogena undulata Leptophlebia gravastella Daatylobaetis cepheus Trioorythodes minutus Tricorythodes sp. A Choroterpes albiannulata Traverella albertana Brachycercus (prudens ?) Stenonema terminatum Caenis latipennis Ephoron album Baetisca sp. Isonychia (campestris ?) Centroptilum sp. Lachlania powelli Ametropus (neavei ?) S a Irr Zc oni ne d T ran Zo sitio ne n No nsa Zor mo le lid Figure 19. Ephemeroptera of the Yellowstone River. 37 o Q. 0 B -C n u 0 *^ u - - • — ' a (/) 0) — ■ o > E o; saioads jo jaqoin^ 38 Figure 21. Mature nymph of the mayfly (Heptagenia elegantula) , Stoneflies The longitudinal distribution of the stoneflies (Plecoptera ; in figure 22 differs considerably from that of the Ephemeroptera (figure 19). Thirty-seven species were identified in the study area. Data available for this order are probably the most accurate because of the work of Stadnyk (1971) and Gaufin et al . (1972). Only one species was collected at every station. Most of the fauna are probably adapted to the conditions found in the upper river. Twelve species drop out in the transition zone, and five could be classified as prairie stream forms. Aaroneuria abnormis probably washed out of the Tongue River, where it is abundant, and was collected only at station 15. The number of Plecoptera species decreases steadily downstream (figure 20). Generally the nonprairie stoneflies appear to have habitat requirements similar to those of the salmonid fishes. Caddisfl ies Caddisfly (Trichoptera ; distribution in the Yellowstone River is presented in figure 23. The present list contains 36 species; more will probably be collected if additional studies are performed. Distributional patterns are less distinct than with the Ephemeroptera and Plecoptera. In most cases caddisfly larvae cannot be identified to species; adult males are necessary. The present distribution data are incomplete because all stations were not sampled with equal frequency. For example, station 9, sampled more intensively, 39 Sampling Station 9 10 II 12 13 14 15 16 17 18 19 20 Para 1 ' Nemoura besametsa Isoperla fulva fusa 'a poda Pteronarcys californica Alloperla coloradensis Isocapnia vedderensis Alloperla severa Euaapnopsis vedderensis Alloperla pallidula Acroneuria pacifiaa Nemoura oinctipes Alloperla signata Isoperla mormona Arcynopteryx parallela Braohyptera nigripennis Isogenus tostonus Pteronarcella badia Isogenus elongatus Claassenia sabulosa Alloperla sp. Braohyptera pacifiaa Isoperla patricia Isocapnia missourii Capnia sp. Capnia limata Acroneuria abnormis Isoperla longiseta Braohyptera fosketti Isogenus frontalis Braohyptera sp. Isogenus s p . Isoperla sp. Salmonid Zone Transition Zone Nonsalmonid Zone Figure 22. Plecoptera of the Yellowstone River. 40 Sampling Station 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 Cheumatopsyche pettiti Amiocentrus aspilus Hesperophylax incisus Lepidostoma pluvialis ■ phila bifila ;topsyche campy la Limnephil idae Athripsodes sp. Psychomyia flavida Heliaopsyche borealis Arctopsyche inermis Lepidostoma veleda Brachycentrus ocaidentalis Hydropsyche cockerelli Agraylea multipunotata Cheumatopsyche analis Lepidostoma n. sp. Potomyia flavida Triaenodes frontalis Brachycentrus amevicanus Hydropsyche oslari Polycentropus cinereus Ochvotvichia potomas Glossosoma velona Hydropsyche ocaidentalis Hydroptila sp. Oecetis avara Oecetis disjuncta Cheumatopsyche enonis Neotrichia sp. Limnephilus taloga Leptocella sp. Hydropsyche corbeti Hydropsyche separata Cheumatopsyche lasia Salmonid Zone Transition Zone Nonsalmonid Zone Figure 23. Trichoptera of the Yellowstone River. 41 had the largest number of species. Generally caddisfly distribution is similar to that of the Plecoptera with a steady downstream decline in species. The genera Hydropsyche (figures 24 and 25) and Cheumatopsyche are abundant throughout the river, but dominate in the lower 10 stations. Other Orders The distribution of the remaining aquatic orders is given in figure 26. The order Diptera is widely distributed throughout the river, with the family Chironomidae being the most abundant and diverse. Protanyderus margarita, a Diptera species previously unreported from Montana, was captured at several stations. Representatives of the remaining orders illustrated no distributional trends and, with the exception of the Oligochaeta, were never abundant. TONGUE RIVER The distribution of macroinvertebrates found in the Tongue River, shown in table 3, is complex and not easily explained. The fauna is similar to the Yellowstone fauna in many ways, but there are several differences. The stonefly Aovoneuvia abnovmis, the elmid beetle Stenelmis sp. and the mussel Lampsilis sp. are abundant in the Tongue but rare in the Yellowstone. Odonates are more abundant and diverse in the Tongue River. INSECT EMERGENCE MAYFLIES Emergence times were determined for only 13 species of mayflies (figure 27), generally the species common in the lower reaches of the Yellowstone River. Most mayfly adults emerge at dawn or dusk and live from a few hours to a few days. Emergence of mayfly adults in the lower river is concentrated in the June-September period. Adult Ephovon album emerged so late in the summer that many adults, influenced by cold morning temperatures, were observed fluttering on the beaches, unable to fly. One of the largest mayfly emergences observed occurred in late August 1974 at Huntley (station 11), where adult Traverella albertana (figure 28) were emerging. The adults were so thick on the water surface (probably hundreds of thousands of insects were involved) that carp were surface feeding on them. It was a wet day, and the adults hovered over the wet highway from Huntley to Miles City. The conspicuous emergences of Tricorythodes minutus (figure 29) and Ephoron album also involved large numbers of individuals. STONEFLIES The emergence of adult stoneflies, occurring from March to August (figure 30), covers a longer time span than does that of mayflies. Three species, 42 Figure 24. Larvae of the Caddisfly Hydropsyche. Figure 25. An adult of the genus Hydropsyche. 43 DIPTERA Ceratopogonidae Dol ichopodidae SP- Hemerodromia sp. Protanyderus sp. Athevix sp. Simuliwn sp. Dicranota sp. Hexatoma sp. Holorusia sp. Tipula sp. Lirnnophova sp. Chironomidae ISOPODA Asellus sp. LEPIDOPTERA Cataclysta sp. HEMIPTERA Rhagovelia sp. Ambry sis sp. Callicorixa sp. Cenocovixa sp. Trichoeovixa sp. Sigava sp. Gevvis sp. Ranatra sp. COLEOPTERA Oreodytes sp. Cyrinus sp. Dubiraphia sp. Microcylloepus sp. Optioservus sp. Stenelmis sp. Zaitzevia sp. Helichus sp. 2 i 3 Sampling Station 7 8 9 10 II 12 13 14 15 16 17 18 19 20 Salmonid Zone Transition Zone Nonsalmonid Zone Figure 26. Aquatic invertebrates of the Yellowstone River. 44 Sampling Station 8 9 10 II 12 13 14 15 16 17 18 19 20 ODONATA ■ hus sp. Ophiogomphus sp. Amphiagrion sp. Libel lul idae AMPHIPODA Cammarus s p . Hyalella sp. ACARI Hydracarina MOLLUSCA Ferrissia sp. Gyraulus sp. Lampsilis sp. Lymnaea sp. P7zi/sa sp. TURBELLARIA Phagocat.i sp. OLIGOCHAETA /ifais sp. Ophidonais sp. Salmonid Zone Transition Zone Nonsalmonid Zone Fiaure 26. (Continued 45 TABLE 3. Macroinvertebrate fauna of the Tongue River, Montana. Station No. 1 2 3 4 5 6 7 3 c o +-> o ■o ■o Ol s- >> c +J oo o Ol (O i — +-> -C 4- c ^ cr> E l/l s_ -C i o Ephemeroptera Baetis spp. X X X X X Baetisca sp. X Brachycerous sp. X Choroterpes sp. X X Dactylobaetis sp. X Ephemerella sp. X X X X X X X Heptagenia sp. X X X X X Leptophlebia sp. X X X Rhithrogena sp. X X X X X X Stenonema sp. X X Traverella sp. X X X X X Tricorythod.es sp. X X X X X X X Trichoptera Braohyoentrus sp. X X X X X X X Chewmatopsyche sp. X X X X X X X X Glossosoma sp. X X Hy dropsy che sp. X X X X X X X X Eydroptila sp. X X X X X Mystacides sp. X X X Oecetis sp. X X X X Plecoptera Aoroneuria sp. X X X X Brachyptera sp. X X X X X Isogenus sp. X X X X X X Coleoptera Dubiraphia sp. X X Microcylloepus sp. X X X Stenelmis sp. X X X X X X X Mollusca Ferrissia sp. X X X Gyraulus sp. X Lymnaea sp. X X Lampsilis sp. X Physa sp. X X X Pisidium sp. X X Sphaerium sp. X 46 IABLE 3 continued. Station No. 1 2 3 4 5 6 7 8 c o -a -a CD s- >> c: +-> oo o CD ro +-> -C 4- c o en E l/) S- -C n D O Taxa ro O l/> i S- ai Q zn CD • 00 o ±z. Odonata Argia sp. X X Calopteryx sp. X X X Enallagma sp. Ischnura sp. X Gomphus sp. X Ophiogomphus sp. X X X X X X Lepidoptera Cataclysta sp. X X X X Turbellaria Dugesia sp. X X X X X X Hemiptera Corixidae X X X X X Ehagovelia sp. X Uiptera Chironomidae X X X X X X X X Cardiooladius sp. X X Diamesa sp. X X Eukiefferiella sp. X X Orthocladius sp. X X Rheolany tarsus sp. X Si mul iidae Simulium sp. X X X X X X X Tipul idae Hexatoma sp. X X X X X 01 igochaeta X X 47 s is ■•■is '.- aepheus ■ ' ■ odes mii 'bum ■if icons powelli J A Sampling Months Figure 27. Emergence of mayflies from the Yellowstone River, 1 974-76 . iiuutf Figure 28. Adult Mayfly (Tvaverella albertana) . 48 Figure 29. Adult Mayfly (Trioorythodes minutus). Capnia limata Brachyptera fosketti Brachyptera pacifica Isogenus colubrinus Isogenus elongatus Alloperla signata Isoperla longiseta Isogenus tos tonus Isoperla patricia Pteronarcys calif ornica Pteronarcella badia Isoperla mormona Alloperla pallidula Claassenia sabulosa J J A Sampling Months Figure 30. Emergence of stoneflies from the Yellowstone River, 1974-76. 49 Capnia limata, Bvachyptera fosketti, and B. pacifica, emerged when the river was still essentially covered with ice. Stoneflies are not as abundant as mayflies and spend less time in flight; they are therefore less conspicuous when emerging. The most spectacular stonefly emergence is that of Pteronarays oalifoimioa, the giant stonefly or the "salmonfly" of fly fishermen. This species is confined to the upper river where adult insect sampling was less intense. A small yellow stonefly, Isoperla longiseta (figure 31) emerges in large numbers in the lower river. Figure 31. Adult stonefly (Isoperla longiseta), CADDISFLIES The emergence patterns of caddisflies are presented in figure 32. Emergence and flight times ranged from May to September. Caddisflies and stoneflies can live for several weeks as adults; therefore, the presence of an adult does not necessarily signify recent emergence. The list of species presented in figure 32 is much larger than either the mayfly or stonefly lists (figures 27 and 30) because the fauna is rich and because adult caddisflies, readily attracted to lights, are easily collected. 50 Agraylea multipunatata Polycentropus cinereus Potomyia flavida Hydropsy che coakerelli Glossosoma velona Brachycentrus oacidentalis Chewnatopsyahe lasia Hydropsyahe oorbeti Lirrmephilus taloga Arctopsyohe grandis Hydropsyahe oacidentalis Chewnatopsyahe oampyla Psyahomyia flavida Rhyacophila bifila Oecetis avara Hydropsyahe oslari Chewnatopsyahe enonis Hydroptila waubesiana Lepidostoma pluvialis Bvachyoentvus amerioanus Chewnatopsyahe analis Glossosoma tvaviatwn Lepidostoma veleda Tviaenodes frontalis Hesperophylax inaisus Hydropsyahe separata Oahrotriahia potomas Oecetis disjuncta Miarasema aspilus J ' J A S Sampling Months Figure 32. Emergence of caddisflies from the Yellowstone River, 1974-76. 51 The family Hydropsychidae dominates the caddisfly fauna of the Yellowstone River. Representatives (13 species) of this family are all net spinners and include the genera Cheumatopsyche , Hydropsyche, and Avatopsyche. One species, Hydropsy ohe corbeti, was not known to be present in the United States until collected in the Yellowstone River. BOTTOM FAUNA POPULATION Bottom samples taken during the fall of 1974 were designed to survey the bottom fauna and to test equipment. The data (available in Newell 1976 or in the files of the Montana Department of Natural Resources and Conservation, Helena) are, therefore, semiquantitative and difficult to compare with later sampl ing. Quantitative bottom fauna sampling began in the summer of 1975. No sampling is possible in the lower river during the winter because of ice cover. Shortly after the ice is removed, spring runoff begins; bottom samples from this period would be of little value. The data gathered by Schwehr (see Report No. 8 in this series) were added here to compare the density of invertebrates of the midriver (stations 5-11) to that of the lower river (stations 12-20). Field data from samples taken at stations 15, 17, and 18 are presented in Newell 1976 and are on file at the Montana DNRC. In August, bottom fauna population estimates ranged from about 50/m2 at station 9 to about 2,000/m at station 5 (figure 33). Station 19 exhibited the lowest mean, 250/m2. Generally, there was a gradual downstream decrease in mean population size. September population estimates (figure 34) exhibited a greater range, from 20/m2 at station 19 to 8,500/m2 (station 5). Estimates from the lower river were much lower than those from upper river stations. In October, less variation in range was observed (figure 35). The minimum population estimate was 250/m2 at station 18 and the maximum was 400/m2 (station 11). The trend again was a gradual downstream decrease in the density of organisms. In November samples, data from stations 1 and 3 were also available (figure 36). Population estimates at stations 1 and 3 were similar and were much higher than for the remaining sampling stations (range 4,500-12,000/m2) The trend was a decrease in population downstream. The percentage composition of all invertebrate orders collected in 1975 is presented in tables 4-7. The mean percentage composition of each order is found in table 8. Ephemeroptera dominate the fauna in August, and Trichoptera begin to dominate in September and October; the Diptera became dominant in November. Plecoptera and others are a minor portion of the fauna. Figure 37 graphically illustrates the longitudinal changes in percentage composition of invertebrate orders. 52 10,000—1 Ji E Z 100- 10- Range # Mean — I 1 1- II 15 17 Sampling Station 18 19 Figure 34. Population estimates for September 1975, mean and range of six Water's samples at each station. 54 10,000-] Range # Mean <, Mayflies (Ephemeroptera) Caddisflies (Trichoptera) Stoneflies (Plecoptera) 100 -i -A True Flies (Diptera) --D Others (see table 8) 80- 60 - A A 40 - V A '^ \>-.. \ A-/.. A <► / / \ / ./ .* **»\ •* 20- ▲ V / 7*%^/ //D— ^ r\ t — — ■' X a/ ^ u — ' T T 1 1 i 1 i T i T 7 9 II 15 Sampling Station 17 19 Figure 37. Mean percentage composition of invertebrate orders from Water's samples taken August-November 1975. 57 TABLE 4. Percentage composition of benthos from the Yellowstone River using Water's samples, August 1975. Station Order 5 7 9 11 15 17 18 19 Ephemeroptera 24.4 40.1 67.4 84.7 52.3 49.7 68.8 75.2 Plecoptera 6.7 25.7 17.4 0.8 2.8 0.6 Trichoptera 4.3 22.4 5.8 8.6 31.9 48.7 30.1 19.7 Diptera 63.2 11.8 9.5 5.6 9.9 1.6 5.1 Coleoptera 1.4 3.1 Odonata 0.5 01 igochaeta 0.6 TABLE 5. Percentage composition of benthos from the Yellowstone River using Water's samples, September 1975. Station Order 5 7 9 11 15 17 13 19 Ephemeroptera 18.2 71.1 50.4 50.7 37.4 30.1 37.8 28.8 Plecoptera 3.1 5.0 1.7 0.1 0.2 2.0 Trichoptera 21.2 1.7 0.9 18.7 48.1 52.1 57.1 46.6 Diptera 56.5 21.8 47.0 30.3 14.2 14.6 3.0 19.2 Coleoptera 0.9 0.2 0.1 Hemiptera 0.04 Turbellaria 0.04 Odonata 1.4 01 igochaeta 3.2 4.1 Acari 0.1 TABLE 6. Percentage composition of benthos from the Yellowstone River using Water's samples, October 1975. Station Order 5 7 9 11 15 17 18 19 Ephemeroptera 8.3 35.6 50.8 26.1 35.0 19.8 22.9 21.8 Plecoptera 7.8 13.4 2.9 0.2 0.2 Trichoptera 12.2 12.0 14.1 29.9 39.7 47.4 17.9 44.8 Diptera 71.2 38.7 32.0 44.0 23.3 12.9 29.3 27.0 Coleoptera 0.1 0.2 0.1 0.2 0.5 Odonata 0.2 01 igochaeta 1.6 19.8 29.7 6.0 Acari 0.3 0.1 0.2 58 TABLE 7. Percentage composition of benthos from the Yellowstone River using Hater's samples, November 1975. Station Order 1 3 5 7 9 11 15 17 13 19 Ephemeroptera 14.5 25.4 33.4 22.9 24.8 12.7 7.4 19.6 4.3 Plecoptera 1.4 1.6 8.3 13.8 4.3 1.7 0.4 4.5 1.0 Trichoptera 62.3 43.5 26.3 20.3 16.5 24.7 24.5 29.4 10.8 Diptera 21.1 29.4 29.6 40.6 53.8 54.2 48.4 35.9 75.4 Coleoptera 0.1 0.7 2.4 0.3 0.4 01 igochaeta 0.1 0.1 0.8 6.2 19.7 10.6 8.6 Acari 0.5 0.1 TABLE 8. Mean percentage composition of benthos from the Yellowstone River using Water's samples, August-November 1975. Station Order 1 3 5 7 9 11 15 17 13 19 Ephemeroptera 14.5 25.4 21.1 42.4 48.4 53.8 34.4 26.8 37.3 32.5 Plecoptera 1.4 1.6 6.5 14.5 6.7 0.4 1.2 0.1 1.8 0.3 Trichoptera 62.3 43.5 16.0 14.1 9.3 19.1 36.1 43.2 33.6 30.5 Diptera 21.1 29.4 55.1 28.2 35.6 26.6 25.4 19.4 17.1 31.7 Coleoptera 0.1 0.8 0.7 0.1 1.0 Hemiptera 0.01 Turbellaria 0.01 Odonata 0.1 0.1 0.4 01 igochaeta 0.1 0.1 2.0 10.7 10.2 3.7 Acari 0.5 0.1 SPECIES DIVERSITY Species diversity indices were calculated from Water's samples taken during August-November 1975 in order to begin a monitoring study of the Yellowstone River. Mathematical indices are one way of condensing long species lists to a single mathematical value that can be compared with those from other stations and other time periods. Four diversity indices, based on data collected for this study and presented in raw form in Newell 1976, are graphed and presented in figures 38-41. The Shannon-Weaver index (d), apparently the most sensitive to community changes, is presented in figure 42. The Miles City and Sidney stations exhibited the greatest seasonal change. The Glendive and Intake stations were constant and similar (tables 9-12). 59 4. On 3.0- E 2.0H b 1.0- 1 Range • Pooled ! I I. On .5- * \ \ I. O-i .5- + 1 1 i I.0-. o .5- i 1 1 17 Sampling Station 1 i 19 Figure 38. Species diversity: range of six Water's samples and all six pooled, August 1975. 60 4.0- Range # Pooled 3.0- 1 ; • 1 > 1 1.0- I.0-. .5- I.O-i .5- * t + 1 \ I 1 1.0- o .5- i 1 I 1 "I- 19 15 17 Sampling Station Figure 39. Species diversity: range of six Water's samples and all six pooled, September 1975. 61 4.0- Range # Pooled 3.0- Diversity ro b i T • • • i.o- i i I. O-i -° .5- ■ O-i 5 .5- * t ♦ 1 I * I. On .5- 1 1 17 Sampling Station 19 Figure 40. Species diversity: range of six Water's samples and all six pooled, October 1975. 62 4.0-1 3.0- 52 2.0- 1.0- I.O-i .5- I.O-i .5- 1.0-1 o .5- t I ♦ I 1 1 t i t A I "I 1 1- 3 15 17 Sampling Station Range Pooled 1 * * I 18 19 Figure 41. Species diversity: range of six Water's samples and all six pooled, November 1975. 63 4.0 -1 3.0 - 2.0- 1.0- — ■ — - Miles City — • - Sidney ..<>... Intake -A— ■ - Glendive Aug. Sept. Oct. Nov. Figure 42. Seasonal changes in Shannon-Weaver diversity indices (the result of pooling six Water's samples each month at each station during 1975). 64 TABLE 9. Species diversity, range of six Water's samples and all six pooled, August 1975. Station Index 5 7 9 11 15 17 13 19 Max 2.79 3.11 2.95 3.17 3.22 2.70 2.27 2.43 Mean Diversity (d) Min 1.24 1.66 2.19 2.58 2.16 1.51 1.59 1.69 Pooled 2.22 3.43 3.25 3.08 3.19 2.15 2.12 2.49 Max .72 .22 .94 .36 .50 .65 .52 .49 Redundan :y (R) Min .27 .00 .02 .01 .24 .23 .33 .14 Pooled .49 .08 .28 .26 .32 .44 .45 .30 Max .78 .96 1.00 .92 .89 .90 .81 .95 Evenness (J1) Min .18 .83 .12 .70 .65 .62 .68 .76 Pooled .53 .88 .75 .74 .73 .62 .61 .75 Max .52 .72 1.00 .65 .63 .60 .50 .60 Equitabi lity (Em) Min .18 .52 .45 .36 .31 .27 .29 .39 Pooled .24 .47 .43 .36 .38 .29 .28 .35 TABLE 10. Species diversity, range of six Water's samples and all six pooled, September 1975. Station Index 15 17 18 19 Max 2.50 1.86 1.35 2.33 Mean Diversity (d) Min 1.84 1.38 0.83 1.69 Pooled 2.49 2.14 2.09 2.49 Max .55 .59 1.00 .49 Redundancy (R) Min .33 .25 .43 .14 Pooled .39 .43 .43 .30 Max .72 .87 .95 .95 Evenness (J ' ) Min .55 .61 .53 .76 Pooled .62 .62 .63 .75 Max .33 .49 .58 .60 Equitabi lity (EnJ Min .26 .30 .20 .39 Pooled .25 .27 .32 .35 65 TABLE 11. Species diversity, range of six Water's samples and all six pooled, October 1975. Station Index 15 17 13 19 Mean Diversity (d) Max Min Pooled 2.50 1.84 2.41 1.86 1.38 2.14 1.85 0.83 2.09 2.33 0.99 2.42 Redundancy (R) Max Min Pooled .55 .33 .39 .59 .25 .43 1.00 0.43 0.48 1.00 .38 0.00 Evenness (J ' ) Max Min Pooled .72 .55 .62 .87 .61 .62 .95 .53 .63 1.00 .62 .73 Equitability (E ) J m Max Min Pooled .33 .26 .25 .49 .30 .29 .75 .20 .32 1.00 .31 .39 TABLE 12. Species diversity, range of six Water's samples and all six pooled. November 1975. Station Index 1 15 17 IS 19 Max 2 .88 2 .82 1.96 2.45 2.24 1.97 Mean Diversity (d) Min 2 .01 2 .18 1.41 0.84 1.06 0.24 Pooled 2 .64 2 .81 2.00 2.11 2.46 1.30 Max .53 .44 .64 .32 1.00 .91 Redundancy (R) Min .31 .32 .26 .33 .36 .32 Pooled .43 .39 .50 .51 .33 .56 Max .72 .70 .80 .74 .75 .76 Evenness (J') Min .49 .59 .54 .32 .61 .15 Pooled .58 .62 .54 .53 .71 .46 Max .32 .31 .35 .36 .39 .36 Equitabil ty ErJ Min .28 .25 .29 .13 .28 .03 Pooled .23 .25 .23 .23 .33 .14 66 The Shannon-Weaver index was near or below 3.0 for most stations. Generally an index above 3.0 illustrates a healthy, unstressed community, while an index below 1.0 is indicative of a monospecific community under stress. The index range of 1.0-3.0 seems to illustrate a community under some stress (Wilhm 1970bc). Stresses upon certain Yellowstone communities might be due to large amounts of inorganic sediments and nondiverse, uniform riverbottom substrate types in some areas. FEEDING MECHANISMS It is interesting to note that Egglishaw (1964), Macan (1974), and Cummins (1975a) all believe that the microdistribution of a species is deter- mined more by food preferences than by any other factor. Current distributes allochthonous detritus and periphyton which in turn determine invertebrate distribution (figure 43). In attempting to determine if faunal zonation occurs in the Yellowstone River, aquatic genera found in the Yellowstone River were grouped according to feeding mechanisms (table 13). A grouping of organisms into zones is difficult. It is necessary to go to a lower taxonomic level than family in describing distribution; e.g., the family Chironomidae is listed under all four feeding mechanism categories and is found at all 20 stations. Four genera in the shredder category confined to the upper river represent, at least in part, the erosional habitat of Cummins (1975a). Genera found in the collector and scraper categories are variously distributed along the entire river, thus obscuring the importance of the intermediate and depositional zones for faunal zonation. It may be necessary to graph the abundance of each genus or each species in order to separate the fauna into habitat zones. More information on feeding habits of individual species is necessary before this can be done. CURRENT AND DEPTH REQUIREMENTS FOR INVERTEBRATES DATA COLLECTED Data from the current-depth studies at Gl endive and Intake are summarized in table 14. In general, current and depth means are similar for both stations and all sampling times. Taxa and number of individuals varied greatly, however. At Glendive the mean number of taxa increased from 3.9 in August to 9.0 in November; a similar trend was evident in the Intake samples. The mean number of individuals increased from 9.1 to 149 at Glendive and from 37.9 to 65.8 at Intake. More taxa and more individuals were captured in the October and November samples at both stations than during August and September. December samples would have been valuable, but were unavailable because the lower river froze on November 30, 1975. Population estimates from 24 samples at each station are shown in tables 15-18. In August (table 15) the fauna was dominated by Traverella and Hydropsyahe. There was a large difference in the total number of individuals collected at Glendive (1222) and Intake (5199). 67 MACROMOVEMENTS~«- Optimal range of physical and chemical factors (current, sub- strate, temperature, light, dissolved oxygen) Suboptimal range of physical chemical factors MICROMOVEMENTS [orientation with respect to flow and turbulence) MICROHABITAT SELECTION [food quality, quantity) LOW FOOD Reduced feeding and increased movement Increased respiration (reduced growth) HIGH FOOD Increased feeding and reduced movement Decreased respiration (increased growth) Mortality increased LOW NUMERICAL AND/OR BIOMASS DENSITY Mortality decreased t HIGH NUMERICAL AND/OR BIOMASS DENSITY Figure 43. Proposed relationships between invertebrates and the factors that determine their distribution and abundance (from Cummins 1972). 68 C CD ■I- > ■r- c/1 O O •i- »r- +-> a +-> ZJ O CO co mji w i" o ui o T T i i c i i " OU3r- i— I— r— i— r— C0000100O00OOO , — , — , — M, — CM CM CM I I I I I I I I I i— CNJi— CO r— r-i— i— i— I I I I I C» CO CO CS OV O ?( O +» T3 3 4^ ca -ti O . . Cl, o Cl, £ sx ^ "^ ^ Si O Sjr-i gj'ti ?h 3 +> +i +* v> :aco-^^cqfcia:co K <» ca ^ Cu co ca co a •** B *^ <» « Cl, (3 a: cq fei Cl, O « Sn ca rii ?, co co^^; 3i +> ^h H^; ft;* ■=c •i- O Q. •i- "O co >> -— CD CO i— •■- a; -o i— •!- CO T- cd cd c -o E ro s- a» •<- o Q.-0 CD OVi— c O •<- E co i— O Q. CD -C Q- E •■- +J CD C i- Q. CD -C CD -i- CD co Q- co -C X CO LxJ O O CD CD CO "3 -o -a -r- -a JC >, E T- D. CO O C O Q. C O o o o •>- CO S~ i- CD >>-a •■- co axua -O CD -r- ■a aii- (1) S-+J S_ (O CD CD CD S- i— SZ +J .— •■- CD O M- -O CD CD Cl N co co 69 TABLE 14. Mean (upper number) and standard deviation (bottom number) for four variables measured in the invertebrate/current investigation in the Yellowstone River Date. Depth ft Current ft/sec m/sec Number of Taxa Number of Individuals GLENDIVE August 7 1.8 0.9 .55 .27 1.202 0.575 .366 .175 3.9 1.6 9.1 8.2 September 17 1.2 0.9 .37 .27 0.744 0.613 .226 .186 6.5 2.4 21.7 11.1 October 9 1.4 1.0 .43 .30 0.786 0.570 .239 .173 10.9 2.2 126.9 86.6 November 7 1.6 0.9 .49 .27 1.029 0.678 .313 .206 9.0 3.8 149.0 133.9 INTAKE August 6 1.3 0.6 .4 .18 1.653 0.782 .505 .238 4.8 1.8 37.9 32.4 September 9 1.4 1.0 .43 .3 0.970 0.623 .295 .189 6.0 1.7 28.9 12.2 October 15 0.8 0.6 .24 .18 1.124 1.031 .342 .314 8.5 2.9 84.0 53.1 November 11 1.6 0.9 .49 .27 1.477 0.921 .450 .280 7.0 3.2 65.8 44.8 70 TABLE 15. Population estimates from the August 6 and 7, 1975, invertebrate- current samples (24 pooled samples from each station). Taxa Gl endive Intake Baetts insignif icons 17 6 Baetis parvus Braahyoercus s p . Choroterpes sp. Dactylobaetis sp. Ephemerelta sp. 34 80 0 11 6 74 17 11 11 0 Heptagenia sp. Isonychia sp. Ehithrogena sp. Traverella sp. 57 11 11 193 28 40 210 3,111 Tricorythodes minutus 63 734 Hy dropsy che spp. Leptocella sp. 569 28 751 6 Isoperla sp. 6 46 Chironomidae 119 114 Simul iidae 11 23 Dytiscidae 0 6 Oligochaeta Totals 6 11 1,222 5,199 Means of 24 samples 51 217 71 TABLE 16. Population estimates from the September 9, 1975, invertebrate- current samples (24 pooled samples from each station). Taxa Gl endive Intake Baetis insignificans 28 102 Baetis parvus 28 108 Braahyoercus sp. 34 17 Caenis sp. 6 0 Choroterpes sp. 23 57 Daatylobaetis sp. 28 97 Ephemerella sp. 0 0 Ephoron sp. 28 17 Heptagenia sp. 131 14 Isonychia sp. 0 6 Ametropus sp. 0 6 Traverella sp. 74 682 Tricorythodes minutus 279 347 Tricorythodes sp. 0 57 Stenonema sp. 0 6 Cheumatopsyche sp. 63 23 Hy dropsy che sp. 779 1,763 Leptocella sp. 0 6 i4croncuris sp. 0 6 Isoperla sp. 6 6 Micro ay lie opus sp. 6 0 Ranatra sp. 6 0 Certopogonidae 6 0 Chironomidae 1,314 239 Simul iidae 6 51 01 igochaeta Totals 119 28 2,964 3,638 Means of 24 samples 124 152 72 TABLE 17. Population estimates from the October 9 and 15, 1975, invertebrate- current samples (24 pooled samples from each station). Taxa Glendive Intake Baetis insignif icons 1,772 1,490 Baetis parvus 142 182 Brachycercus sp. 28 11 Caenis sp. 0 6 Centroptilum sp. 11 0 Choroterpes sp. 46 11 Dactylobaetis sp. 791 301 Ephemerella sp. 0 6 Heptagenia sp. 1,879 943 Isonychia sp. 0 6 Rhithrogena sp. 0 742 Stenonema sp. 6 0 Tvaverella sp. 165 642 Tricorythodes minutus 267 91 Tricorythodes sp. 11 0 Unknown 6 0 Gammarus s p . 6 6 Hyalella sp. 0 6 Brachycentrus sp. 11 0 Chewnatopsyche sp. 199 51 Hydropsyche sp. 9,845 4,448 Hydroptila sp. 0 6 Oocetis sp. 11 0 Gomphidae 17 0 Isogenus sp. 6 80 Isoperla sp. 6 23 Corixidae 23 0 Dolochopodidae 0 6 Empididae 11 0 Chironomidae 1,973 2,314 Simuliidae 11 154 Stenelmis sp. 6 0 Ferrissia sp. 23 0 Lymnaca sp. 6 0 Oligochaeta Totals 2,776 1,104 20,037 12,640 Mean of 24 samples 835 527 73 TABLE 18. Population estimates from the November 7 and 11, 1975, invertebrate- current samples (24 pooled samples from each station). Taxa Glendive Intake Baetis insignificans 751 Baetis parvus 17 Braohycercus sp. 6 0 Caenis sp. 11 0 Dactylobaetis sp. 63 40 Ephemerella sp. 63 0 Heptagenia sp. 956 427 Leptophlebia sp. 6 6 Rhithrogena sp. 80 330 Stenonema sp. 11 0 Traverella sp. 51 11 Tvicorythod.es minutus 97 34 Trioorythod.es sp. 6 6 Cheumatopsyche sp. 927 114 Hy dropsy che sp. 10,608 4,846 Hyalella sp. 6 0 Brachyptera sp. 256 239 Isogenus sp. 6 142 Corixidae 46 0 Chironomidae 1 ,905 1,758 Empididae 6 0 Ceratopogonidae 0 6 Simuliidae 0 6 Dytiscidae 11 6 Ferrissia sp. 17 11 Lymnaea s p . 11 0 Oligochaeta Totals 4,374 529 20,245 8,938 Mean of 24 samples 844 375 74 In September (table 16) ■ were again abundant, as were Chironomidae. Totals were comparable for Glendive (2964) and Intake (3638). and Chironomidae again dominated in the October samples (table 17). Number of taxa and total number of individuals greatly increased at both stations. November samples showed Hydropsyche and Chironomidae dominant (table 18). Totals were high at Glendive (20,245) but considerably reduced from October at Intake (8988). All 48 samples taken each month were pooled to illustrate which orders dominate the fauna (table 19). The fauna was dominated by Trichoptera and Ephemeroptera with Diptera third. Ephemeroptera monthly percentages ranged from 11.7 to 73.6 while Trichoptera percentages varied from 21.1 to 56.3 percent of the total. The October and November samples contained more infor- mation than the August-September samples, probably due to summer emergence losses and the presence in August and September of very small larvae and nymphs, most of which passed through the collecting net. Mean population estimates varied from 138/m2 (August) to 681 /m2 (October). Percentage com- position of orders at each station is shown in table 20. Results obtained with the kick net were compared with results of the Water's sampler (figures 44 and 45). The Water's sampler is 19.5 in high; thus only kick samples taken in depths less than 19.5 in were compared. Results were similar, but the number of organisms obtained with the kick net was always lower than numbers obtained with the Water's sampler. Several kick samples were taken at the water's edge in water too shallow to sample with the Water's sampler, tending to expand the range and reduce the mean. Results from the two samplers followed the same trend over time at both stations, and a line joining the means of both methods is almost parallel. ENVIRONMENTAL REQUIREMENTS Multiple regression analyses were performed on the current-depth data with current and depth as independent variables and number of taxa and number of individuals as dependent variables. Three models were applied: 1) untransformed; 2) semilog transformation (of dependent variables); and 3) log-log transformation. The detailed results of these analyses, for all three models, are reported in Newell 1976 and are on file with the Montana DNRC. The general results are given in tables 21 and 22. Number of taxa and number of individuals yield similar results when regressed against current velocity. Figures 46-48 show how these regression equations can be used to predict the numbers of individuals at any particular current or depth. The deviation of the data from the regression line is demonstrated in figure 48, for example, where the regression coefficients (r) are 0.774 for current and 0.808 for depth. 75 (O crv i_n co co o CM c ro co o o ro co O OJ CO «* s: r-~ ro CM ID r» «d- -Q &? ^ CO CM CM CO O S- a> -O E re CD en io ro ro 00 en o > ro ^a- rji <* CO O o r-. r— o +-> <* *d- CO CO <7> 1 — CM CO :z O h- en CO ro *3" o CM CO co «3" t~^ CTl CM -Q ** CM <* O ro ^ o i_ ai -O o « 4-> CO LO CTi o r~. 1^ o fO LO r~- co CO CO f-» oo o +J ld i_n i — ^3- 00 CO CO o h- CT> (T3 Q. \D ^- co CO 1 — CM CM CO CU (C r-» ro «* O ro (/I +-> CO co CO o 1— CM CM 1 CO CO ro CM ro -Q ** CM O «* O o +J CO 3 Dl fD 3 lt> ■^i- CM r^ i — CO CO cC re CM LO ID co I— CM ro +J r~- ro CM «d- O t— >3- 1 CO re S- cu re re co +-> s- re +-> to O- ai S- cu re c o +j CU re -t-> re s_ Q. +-> re -C o cu O) O Q. s- o CO h- s: cc E JZ O 0) o S_ LxJ CO o o +J en a> O -C <1J O- j= a: CL S- ■fj o UJ h- Q_ O O o 76 Range Mean 1,000- 100- 10- — I 1 1 1 — Aug. Sept. Oct. Nov. Water's — I 1 1 1 — Aug. Sept. Oct. Nov. Kick net Figure 44. Comparison of sampling methods, Water's and kick net at Glendive using kick samples taken in depths less than 19.5 in. 77 Range Mean 1,000- 100- -Q E 10- Aug. Sept. Oct. Water's Nov. — I 1 1- Aug. Sept. Oct. Kick net Nov. Figure 45. Comparison of sampling methods, Water's and kick net at Intake using kick samples taken in depths less than 19.5 in. 78 1,000—j £ 100- 10- ln y = 3.898 + 0.. ! r = 0.644 % 0.5 1.0 1.5 Current Velocity (ft/sec) 2.0 2.5 Figure 46. Current/invertebrate relationships, Yellowstone River, Glendive, October 9, 1975. 79 500- 2 100— 5 50- 10- Current o Depth • In y - 3.594 + 0.512x r = 0.635 In y = 3.335 + 1.006x r = 0.676 _ 0'» 0 • 0 • LA ~i ■ i • i ■ r~ 0.5 1.0 1.5 2.0 Current Velocity (ft/sec) 2.5 3.0 0.5 1.0 1.5 Depth (ft) 2.0 2.5 Figure 47. Current/depth/invertebrate relationships, Yellowstone River, Intake, October 15, 1975. 80 Current o 500- 100— 50- 10- Depth In v = 3.470 + 1.039x r = 0.774 In v = 3.255 + 0.843x r = 0.308 eS • n ■ i ■ i 0.5 1.0 1.5 Current Velocity (ft/sec) 2.0 2.5 1.0 2.0 3.0 Depth (ft) 4.0 5.0 Figure 43. Current/depth/invertebrate relationships, Yellowstone River, Glendive, November 7, 1975. 81 TABLE 20. Percentage composition of invertebrate orders derived from kick samples taken at Glendive (17) and Intake(lS) in 1975. Auqi iSt September October November Order 17 18 17 18 17 18 17 18 Ephemeroptera 39.8 81.6 22.2 41.7 25.6 35.1 10.5 14.8 Trichoptera 48.9 14.6 28.4 49.3 50.2 35.6 57.0 55.2 Plecoptera 0.5 0.9 0.2 0.2 0.05 0.8 1.3 4.2 Diptera 10.6 2.6 44.7 8.0 10.0 19.6 9.4 19.7 Hempitera 0 0 0.2 0 9.1 0 9.2 - Coleoptera 0 0.1 0.2 0 0.05 0 0.1 0.1 Odonata 0 0 0 0 0.1 0 0 0 Amphipoda 0 0 0 0 - 0.2 0.1 0 Mollusca 0 0 0 0 0.1 0 0.1 0.1 Oligochaeta 0.5 0.2 4.0 0.8 13.9 3.7 21.6 5.9 Mayfl ies Mayfly (Ephemeroptera) species diversity (d) was great, with as many as 15 species present in some current-depth samples. Because Ephemeroptera nymphs are much easier to identify to the species level, current preferences were obtained for several abundant species. These data provide some insight into niche separation in the mayfly community and how separation and current preference change throughout the life cycle of several species. Densities of Tvaverella albertana and Tricorythodes minutus are presented in figure 49. In this figure and in figures 50-54, the exact nature of the invertebrate/current relationships is not clear from the daU; the following conclusions record only how the data were interpreted by the author. Peak densities in August at Intake for Tvaverella albertana occurred at about 2.25 ft/sec. Nymphs of T. albertana were more abundant in August than in any other month. This species emerges in September and October, and nymphs do not reappear in any number until November. At the Intake station during the October samples, peak population densities were determined for several species (figure 50). Heptagenia elegantula were more abundant in slower currents and most abundant at 0.5 ft/sec. Traverella albertana was abundant near 2.5 ft/sec as in the August samples. Baetis insignificans was also most abundant at 2.5-3.0 ft/sec, but there was no way to determine at what velocity this population would reach its peak. A similar situation exists with Rhithrogena undulata, although the population seems to reach its greatest density at about 2.75 ft/sec. In November, H. elegantula and B. insignificans exhibited low densities at Intake, but peak densities appear to have occurred at 1.5 ft/sec and 2.5 ft/sec, respectively (figure 51). Some current preferences were apparent for mayflies at the Glendive station (figure 52). A population extreme was evident for H. elegantula (0.5 ft/sec). In the November samples (figure 53), the highest density of H, elegantula occurred at about 1.5 ft/sec. 82 TABLE 21. Synopsis of regressional analysis on the current-depth3 data (against number of taxa) showing significance for the three models for both sampling stations. Depth & Model Depth Current Current Date Sta. ns ns NS NS NS NS NS NS NS NS NS * NS NS NS NS NS * ** ** ** ** ** ** NS NS NS NS NS ** NS NS NS NS NS NS ** * •• • ** ** * NS * NS ** ** NS Aug. 17 NS Aug. 17 NS Aug. 17 NS Sept. 17 NS Sept. 17 * Sept. 17 * Oct. 17 * Oct. 17 ** Oct. 17 ** Nov. 17 ** Nov. 17 ** Nov. 17 NS Aug. 18 NS Aug. 13 ** Aug. 18 NS Sept. 18 NS Sept. 18 NS Sept. 18 •* Oct. 18 ** Oct. 18 ** Oct. 18 ** Nov. 18 ** Nov. 18 ** Nov. 18 NOTE: NS = not significant at p = .05 * = significant at p = .05 ** = highly significant at p = .01 aCurrent in ft/sec, depth in ft 83 TABLE 22. Synopsis of regression analysis on the current-depth3 data (against number of organisms) showinq significance for the three models for both sampling stations. Model Current Depth & Current NOTE: NS = not significant at p = .05 * = significant at p - .05 ** = highly significant at p = .01 aCurrent in ft/sec, depth in ft 84 / /' /■ ■ * i ^ i O o « s s* -Ks o a +2 V Sn ■^ w P rO r-^i to CI CK lTi « o r-i riT t^i -t-5 ■ Sh S, ^ 51 « •^ S, *. CT>i— S|DnpiAipu| jo jaquunfyj 85 1 1 1 1 1 < 1 i i i '" A ■ + 1 r J * ■ ♦ "^ 1* \ ••■••. ■ /\ a \ V *\ \ ' ' \ *M \ < \ / \/ \ ** /'• \jf • \ ■ / \ /• 'A \ • J 3 < 1 1 • f \ v~- \ 0 c < ♦\" \ . • ; +s +» < 3 C S A \ K < J t-J s • V* \ <3 ;< . \ A ♦ J R ~ - 3 * \ « < 0 R 3 •*a ! - " j \ \ R V O -i if <$• Cc 0 S, *H a • J ^ U -U H J +s EX i! "^ 5 0) - -i *H tc c a ft: e "i 1 — I--. - 1 1 1 1 ' 1 ' 1 o ^ > if) o — o O O siDnpiAjpui jo JsqujnN 86 <► • 4- <► ^ o c ^ O O ft • « • • ♦J :. - ■-: UQ OJ — £ c c .£ *- ^ -a t cu -c (O o m CL != O. QJ o 03 S- S|DnpiAipu| jo J9qujnN 87 Cn CO t-i ft •^ r* +i -w +i Pi, 05 o s- en 3 r— sionpiAjpui jo jaqoinN 88 en i- ■r- (U E CU sionpiAjpui jo jaqwnN 89 +i a +i -w hj t> < SX C », \ x s ^ \ . -.. N ■ • **«. \ V • *• :\. \ /: "X->.. \\ \ l\ X » • -^ ••-. vo* :\ \ ^~~—^^ V / \ ---~«^ ••-. i-. n : \ ^--^^^ ••. > . \ . " ^X^ . • N t ^V \ ■ • \ \ \ '•■•:, \ \ ; \ » \\\ ■■•; \ \ X* :•• \ « VW". \ » ^-^_ m w _ — _ fN^ — ' — : XV ^*-**^^^ X 'G i 1 1 1 r-1 *■ ro O O eouDpunqv 9*UD|8y 90 All of the data on mayfly current preference were pooled and are presented in figure 54. Several characteristics are evident. Current preference seems to change with different periods in the life cycle of a species. Greatest population densities for Heptagenia elegantula changed from 0.5 ft/sec in October to 1.5 ft/sec in November. Populations of Baetis insignif leans exhibited a similar trend but at higher velocities. The two samples of Traverella albertana, however, were similar (near 2.5 ft/sec). Figure 54 gives some insight into niche separation of six species of Ephemeroptera. Each of these species had its highest densities at slightly different current velocities, thus reducing interspecific competition for food and resting areas. The remaining mayfly species were present in numbers too small to illustrate current preference and made up an insignificant part of the fauna in the lower Yellowstone River. Stonefl ies Stonefly (PlecopteraJ nymphs were not common in the lower Yellowstone River, and little information on current preference was obtained. At Intake, however, Plecoptera were found only at the fastest currents. Caddisflies Caddisfly (TrichopteraJ larvae, Hydropsyehe in particular, exhibited a distinct current preference, with the greatest number of larvae found at the fastest currents sampled. Larvae could not be identified to species, although at least three species of Hydropsyehe have been collected at Glendive and Intake. Samples taken in August and September were not significant (p=.05) when relating numbers of individuals to current. Samples taken in October and November at both stations were highly significant. Regression lines varied little from October to November at Glendive and at Intake (figures 55 and 56). There is some evidence that Hydropsyehe reached its greatest densities at about 2.5 ft/sec at Intake in October (figure 55) and November (figure 56). 91 300-1 100 — 50- 10- Glendive o Intake So ■¥*■ tt 1 In y = 0.146 + 3.314x r = 0.906 In v = -5.909 + 4.470x r = 0.716 r ^ i ^ 0.5 1.0 1.5 Current Velocity (ft/sec) 2.0 2.5 3.0 Figure 55. Distribution of Hydropsyche larvae at various currents during October 1 975. 92 300^ 100 — 50- 10- Glendive o In y = -6.837 + 7.171x r = 0.783 Intake • In y = -8.590 + 5.277x r = 0.687 <& 0.5 i ■ i ■ r 1.0 1.5 2.0 Current Velocity (ft/sec) 2.5 3.0 Figure 56. Distribution of s --'/< larvae at various currents during November 1975. 93 1*k{hic& o^ (Atfrfvi withdMXwaU It is difficult to predict the effects of flow reduction on the invertebrate fauna because of the large number of species involved and the inability to discuss the environmental requirements and tolerances of a group as large as the Ephemeroptera or Trichoptera. Even within genera there are large variations in tolerance. The need to know environmental requirements of a species is complicated in- the west because few western species have been intensively examined. Roback (1974) lists the habitat requirements of many aquatic insects in terms of chemical concentrations, but few western species are listed. Because of these problems, the following evaluation of effects of reduced flows will be general. The three levels of development projected for the Yellowstone Impact Study (see Report No. 1 in this series) were not considered in this impact assessment because of the lack of specific invertebrate data and because this invertebrate study was completed before the final projections were available. CHEMICAL Attempts to explain the distribution of species in terms of chemical differences have not had much success except where conditions are extreme (Macan 1974). At present in the Yellowstone River, dissolved oxygen concentrations are sufficiently high to sustain invertebrates and fish. Dissolved oxygen could influence invertebrate communities if reduced flows are so low that the BOD of domestic sewage or decaying organisms taxes the reaeration capacity of the river. With reduced flows, increased concentrations of nutrients could result in an increase in peripnyton growth, especially of the present dominant alga Cladophora. A large mat of Cladophora would increase the diversity of benthic habitats, probably resulting in a larger standing crop of benthic organisms and a shift in benthic species composition (Percival and Whitehead 1929). SILT The Yellowstone River carries large amounts of suspended material, mostly inorganic in nature. There is sufficient current to remove much of this material, and silt deposits are not frequent along the river. The high spring runoff is one factor that keeps the river flushed of inorganic sediment. 95 The macroinvertebrate fauna of the lower Yellowstone is predominantly silt tolerant. Genera known to be silt tolerant include: Isonyahia, Tricorythod.es y Caenis, Traverella, Braahyaercus , Stenonema, Dactylobaetis , and Ephoron (Berner 1959, Jensen 1966). It is not known how much silt the benthic fauna of the lower river can tolerate. Sampling station 20 has the lowest gradient, greatest silt concentrations, and lowest benthic diversity of all sampling stations. If station 20 is used as an example of what could happen at other stations if a high level of development is achieved, the result will be a fauna poorer in numbers and species. TEMPERATURE Reduced flows, resulting in a shallower river, would probably result in higher summer water temperatures. These increased temperatures, besides affecting dissolved oxygen levels, would affect invertebrate growth, emergence, egg hatching, and metabolism. The net effect would probably be a reduction of the fauna. Another factor associated with temperature is ice. In the lower Yellowstone River, a solid ice cover lasts for several months (figure 57). Ice cover at Glendive lasted from late December to April during the winter of 1974-75 and from late November to mid-March during 1975-76. Surface ice can act in several ways to kill invertebrates (Brown et al . 1953). Low flows would permit thicker ice conditions, freezing of large areas of shallow water, and increased gouging and molar action during the time of ice break-up (figure 58). CURRENT AND BOTTOM HABITAT Bottom samples taken at Glendive and Intake during 1975 revealed that invertebrate densities are directly proportional to current velocity up to velocities of 3.0 ft/sec (no samples were taken at velocities greater than 3.0 ft/sec). Flow reductions in the Yellowstone would result in reduction in current velocities across the river channel because of its "U" shaped configuration. A general reduction in velocity would result in a faunal reduction because of most species' preference for swift currents. Minshall and Winger (1968) found that a reduction in flow caused a large increase in the percentage of organisms drifting, exposing a greater number of invertebrates to predation1 by fish which could result in species extinction in a section of stream. It is possible to relate invertebrate densities to discharge if mean current velocities across the river at several points are known. The Bureau of Reclamation's Water Surface Profile (WSP) Computer Program (U.S. Department of Interior 1968) utilizes current and depth measurements from several transects to compute area and mean current velocity in several subsections of all transects at any desired discharge. At the Intake station, the WSP Program was used to predict mean current velocities in 15 subsections (shown in figure 59) at three discharges (table 23). The mean current velocity was placed in the regression equation obtained from kick samples in November 1975 (sampling 96 Figure 57. Yellowstone River at Terry during late winter. Figure 58. Ice jam during late winter at Glendive. 97 data available in Newell 1976 or in Montana DNRC files), selected because it was the last month bottom samples were obtained. The population was summed for all subsections. At a discharge of 9000 cfs (about mean low summer discharge), the population estimate is approximately 209,000 for a bank-to-bank, one-meter-wide strip of river bottom at Intake (table 23). This number decreases to about 190,000 at 8,000 cfs and approximately 172,000 at 7,000 cfs, about a ten-percent reduction in population with each 1 ,000-cfs reduction in discharge. TABLE 23. Invertebrate population estimates utilizing data from Intake station 18, subsections from WSP (Water Surface Profile), and regression equation from November kick samples. at 9000 cfs at 8000 cfs at 7000 cfs Sub- Mean Population Mean Population Mean Population Section3 Current Velocity (ft/sec) Estimate Current Velocity (ft/sec) Estimate Current Velocity (ft/sec) Estimate 1 0 0 0 0 0 0 2 1.02 0 0.91 0 0.81 0 3 2.53 20,819 2.32 18,640 2.15 16,704 4 3.42 39,563 3.17 34,306 2.96 30,433 5 2.94 30,156 2.72 26,560 2.54 24,070 6 2.09 25,868 1.90 22,825 1.73 20,923 7 1.88 16,600 1.70 14,940 1.58 14,110 8 2.13 11,931 1.94 10,721 1.77 9,683 9 2.56 15,217 2.35 13,487 2.18 12,277 10 2.39 16,600 2.66 19,297 2.49 17,430 11 2.85 17,983 2.68 16,254 2.45 14,352 12 1.97 10,894 1.79 9,856 1.62 8,819 13 0.72 3,216 0.62 3,009 0.50 2,801 14 0 0 0 0 0 0 15 0 0 0 0 0 0 TOTALS 208,847 189,895 171,602 aShown in figure 59 Population estimates at 7,000, 8,000, and 9,000 cfs are graphed in figure 60; a diagramatic representation of loss of habitat due to water with- drawal is shown in figure 59. Stage at 9,000 cfs is 1985.30 ft at cross-section 5 (opposite the boat launch at Intake). Stage decreased to 1985.15 ft at 8,000 cfs and 1984.90 ft at 7,000 cfs. Thus the river drops only a few inches as dis- charges decrease by 1000 cfs, and only a small percentage of the river bottom is exposed. All of these calculations apply to transect 5 at Intake; the river bottom figuration changes at other locations, as do current and population. 98 2010—1 2000- 1990- 1980- 200 400 600 Width of River Channel 800 1000 feet Figure 59. Cross section No. 5 at Intake, showing water depth at various flows and the 15 subsections used in WSP calculations. 1,000,000' 100,000- 10,000 Calculated • Hypothetical O Low Flow 1975 4000 5000 6000 7000 Discharge (cfs) 8000 9000 Figure 60. Invertebrate population estimates at various discharges, cross-section No. 5 at Intake. 99 When population estimates derived at 7,000, 8,000, and 9,000 cfs are plotted against discharge, the following regression equation results (figure 60) log population = 4.9384 + 0.000042 discharge (cfs) This equation permits a prediction of population of invertebrates at any dis- charge. One should remember that a regression equation is a mathematical tool that may or may not predict a future biological event. Population estimates may continue decreasing linearly as the regression equation indicates. In this case the regression line is probably roughly accurate. Because of the channel morphology in the Intake area, decreases in discharge result in decreasing currents across the entire channel, and little bottom habitat is exposed in the process. However, at some low discharge, large amounts of river bottom would be exposed with resultant loss of habitat and a dramatic decrease in fauna. The effects of reduced current velocity and of loss of bottom habitat are separable in their effect on fauna. Reduced current velocities (due to lowered streamflow) could adversely affect bottom fauna even before a significant loss in bottom habitat occurred. Using the regression equation (figure 60), population estimates in a one-meter-wide strip at Intake can be calculated for lower discharges: 6000 cfs 156,000 organisms 5000 cfs 141,000 organisms 4000 cfs 128,000 organisms 3000 cfs 116,000 organisms 2000 cfs 105,000 organisms 1000 cfs 96,000 organisms These estimates, based on data gathered in November, are higher than estimates would be based on data gathered later in the winter or in the spring, because of natural mortality and drift out of the study area. As flows decrease, other factors--ice and silt--would undoubtedly result in a higher-than-normal mortality of invertebrates. With decreased discharges, ice cover would tend to be thicker than normal, thus freezing larger-than- normal areas of river bottom and resulting in a greater amount of molar action during spring ice break up. Low discharges and reduced currents during the spring would permit greater amounts of silt to accumulate, resulting in a detrimental effect to bottom-dwelling organisms. Evidence confirming the "stream continuum" theory is apparent, although not in large quantities. One major problem with implementing this theory in the west involves stream order. With the multitude of tributaries to every stream a large creek might be of order 10 to 15 by the time it reaches a larger river. The Yellowstone River could conceivably be of order 20 or more, although this has never been calculated. Some of the basic tenets of the theory are evident. The invertebrate fauna in stations 1-8 is dominated by shredder-type organisms. The fauna in the middle and lower river is dominated by collector organisms, e.g., the Trichoptera family Hydropsychidae, which build small nets to collect small food particles and 100 organisms carried along by the current. Scraper or grazing organisms are found throughout the river, and silt-tolerant organisms become abundant in the low-gradient portions. Faunal zones, both for fish and bottom-dwelling organisms, are broad and not distinctly defined. Throughout the upper half of the river, the salmonid community gradually decreases, as does the Plecoptera fauna. Ephemeroptera, however, exhibit a gradual shift in species composition from one community to another with the exception of several adaptable species that are present throughout the entire river. 101 ScCrtUHO/ity The invertebrate fauna of the Yellowstone River is rich in numbers and species. The number of species and the population are greatest in the upper river (stations 1-5), and both decrease downstream. The invertebrate fauna is dominated by mayflies (Ephemeroptera) , caddisflies (Trichoptera) , and true flies (Diptera). The stonefly (Plecoptera) fauna is diverse but not abundant, and there is a steady decrease in number of species downstream. The mayfly fauna is composed of a mountain fauna and a prairie fauna, although several species are found throughout the river. In the lower five sampling stations, mayflies are the most diverse order. Caddisflies are abundant and diverse throughout the Yellowstone River. The caddisfly family Hydropsychidae dominates the invertebrate fauna in the lower half of the river. True flies, in particular the midge family, Chironomidae, are abundant and diverse throughout the river. The invertebrate fauna of the Tongue River is similar to but distinct from the fauna of the lower Yellowstone River. Baseline species diversity calculations showed that the Shannon-Weaver index was near or below 3.0 for most stations. Generally an index above 3.0 illustrates a healthy unstressed community, while an index below 1.0 is indicative of a monospecific community under stress. The index range of 1.0- 3.0 seems to illustrate a community under some stress. The current preferences of many species and genera were examined. For most species, increasing current (up to 3 ft/sec) means a larger population. At present, dissolved oxygen concentrations in the Yellowstone River are high enough to sustain invertebrates and fish. Lack of dissolved oxygen could influence invertebrate communities if reduced flows are so low that domestic sewage or decaying organisms tax the capacity of the river. With reduced flows, increased concentrations of nutrients could result in an increase in periphyton (alga) growth which probably would result in a larger standing crop of benthic organisms and a shift in benthic species composition. Increased water temperatures as a result of reduced flows would affect invertebrate growth, emergence, egg hatching, and metabolism. The net effect would probably be a reduction of the fauna. A reduction in flow which results in a reduction of current velocity will result in a faunal reduction because most species prefer swift currents. Flow reduction also decreases the river stage, exposing large amounts of 103 river bottom with a resultant loss of habitat and a dramatic decrease in fauna. The effects of reduced current velocity and of loss of bottom habitat are separable in their effect of fauna. Reduced current velocities (due to lowered streamflow) could adversely affect bottom fauna even before a significant loss in bottom habitat occurred. Because of the shape of the Yellowstone River channel, flow reductions would result in corresponding reductions in water velocity. 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L. and T. C. Dorris. 1966. Species diversity of benthic macro- invertebrates in a stream receiving domestic and oil refinery effluents. American midland naturalist. 76:427-449. 1968. Biological parameters for water quality criteria. Bioscience. 13:477-481 109 MONTANA DEPARTMENT OF NATURAL RESOURCES & CONSERVATION Helena, Montana I th r< *yoLc Of MOHTMU iM" Montana State Library Records Digitization Project COVER SHEET This page is not part of the original document and was inserted for formatting purposes