The food of rainbow trout, brown trout and brook trout fry and fingerlings from five southwestern Montana streams

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1 The food of rainbow trout, brown trout and brook trout fry and fingerlings from five southwestern Montana streams by James P Fry A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of Master of Science in Fish and Wildlife Management Montana State University Copyright by James P Fry (1960) Abstract: Samples of rainbow trout (Salmo qairdneri), brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) fry and fingerlings were obtained for stomach analysis during the spring and summer of 1959 from five Southwestern Montana streams. An attempt was made to secure samples from the time trout began to feed until they reached a length of approximately 4 inches. Stomachs from 356 rainbow trout, 356 brown trout and 116 brook trout were examined. The predominant food of all three species of fish was the larva of Tendipedidae, although Baetidae was nearly as abundant in the brook trout stomachs.

2 THE FOOD OF RAINBOW TROUT, BROWN TROUT AND BROOK TROUT FRY AND FINGERLINGS FROM FIVE' SOUTHWESTERN MONTANA STREAMS by JAMES P. FRY -5/ A THESIS Submitted to the Graduate' Faculty in p a rtia l fulfillm en t of the requirements for the degree of Master of Science in Fish and W ildlife Management at Montana State College Approved: ining Committee Dean, Graduate/Division Bozeman, Montana June, 1960

3 Table of Contents Page Abstract o... 3 Introduction Methods Description of Study Areas Results a ID Rainbow Trout TO Brown T r o u t Brook T r o u t Discussion... ^. 29 Summary L iterature Cited

4 - 3 - Abstract Samples of rainbow tro u t ('Salmo q a ird n e ri), brown tro u t (SaImo tru tta ) and brook trout (Salvelinus fo n tin a lis ) fry and fingerlings were obtained for stomach analysis during the spring and summer of 1959 from five Southwestern Montana streams. An attempt was made to secure samples from the time trout began to feed u n til they reached a length of approximately 4 inches.. Stomachs from 356 rainbow trout* 356 brown trout and 116 brook trout were examined.. The predominant food of a ll thr.ee species of fish was the larva of Tenddipedidae, although Baetidae was nearly as abundant in the brook tro u t stomachs. r

5 4 Introduction Very few workers have reported substantial information on the food of tro u t less than 4 inches in length. Clemens (1928) studied the stomach contents of 155 small brook trout (Salvelinus fo n tin a lis ) and seven small rainbow tro u t (.Salmo q a ird n e ri). Ricker (1930) examined stomachs from 41 small brook tro u t, while Hazzard and Madsen (1933) studied the food of 48 small cutthroat tro u t (Salmo c la r k i). The present study was in itia te d during the spring of 1959 in which juvenile rainbow tro u t, brown trout (Salmo t r u t t a ), and brook trout were collected for stomach analysis from five Southwestern Montana streams. An attempt was made to secure samples from the time trout began to feed u n til they reached a length of approximately 4 inches. The f i r s t collection was made April 22 and subsequent collections were secured a t about 2 week in terv als term inating September 22. Stomach analyses were made on 356 rainbow tro u t, 356 brown trout,- and 116 brook tro u t. Results compare the food of the d ifferen t species in re latio n to location and date of capture. The w riter is indebted to Dr. C. J. D. Brown, who suggested the study and assisted in preparation of the manuscript. valuable aid in the id e n tific a tio n of in sects. Dr. R. C. Froeschner gave Mr. A. C. Fox, Mr. Jack Heaton and my wife, Gayle R. Fry, provided assistance in the fie ld. The Montana State College A gricultural Experiment Station furnished some financial aid and equipment.

6 -5 - Methods C ollecting was accomplished during the daylight hours (8:00 a.m. to 7:30 pom,). The time required for each collection was 1-3 hours. Early in the season tro u t fry and fingerlings (usually less than 3 inches in length) were captured with a 4-foot "common sense" seihd (one-eighth-inch mesh) operated by one person. Later in the season, when fish were usually in excess of 3 inches, an 8-foot seine (one-fourth-inch mesh) was employed. This was operated by two persons and was effective in fa s te r, deeper water, where many of these fish were found. An e le c tric sh o ck er-(d.c.) was used for procuring the la s t collection from the Madison River. All specimens were immersed in a solution of 10-percent formalin immediately a fte r capture. A few fish were observed a fte r immersion and none was seen to reg u rg itate food. Also, no regurgitated food was found in the collection ja rs a fte r preservation. Fish were placed in a fresh solution of 10-percent formalin, I or 2 days a fte r capture, and then stored for la te r study. Water temperatures were taken a t the time of each fish collection. Turbidity was determined only on those collection dates when the water was noticeably turbid= Where numbers perm itted, 20 fish of each species, from each c o lle ction, were randomly selected and th e ir stomachs examined= When less than 20 specimens were present in a co llectio n, a ll were examined. Each specimen was opened on the ventral side and the esophagus and stomach were re moved for analysis. The organisms found were determined to fam ilies,

7 -6 - whenever possible, and counted. All Diptera larvae were id en tified to family, however pupae and adults, were placed in the category of m iscellaneous D iptera. I t is probable that a large proportion of thosb place^ in th is category belonged to the family Tendipedidae. Organisms, exclusive of te r r e s tr ia l insects and fish-,- were c lassifie d using Ward and Whipple's Fresh Water Biology (Edmondson, 1959). T errestrial insects were id en tified using An Introduction to Entomology (Comstock, 1957)....Weights or volumes were not determined because of the small quantitie s present. Description of Study Areas Five collecting stations.w ere established as follow s:. Madison River drainage - North Meadow Creek, Madison River proper, South Fork of the Madison River, Duck Creek; G allatin River drainage - Trout Creek. Stations were generally located in the shallow, protected portions of streams. With few exceptions fish were captured in slow moving water, less than 2 feet deep, where bank vegetation was submerged or overhung into the stream, q-r where aquatic vegetation was abundant. The sm allest fish were captured in very shallow water, usually in association with sand or s i l t bottoms. Collections were most readily obtained from areas where spring-seeps entered the stream..as the season progressed and fish became larg er, they were also captured in deeper, fa ster water. Larger fish were found more commonly beneath undercut banks or in pools, rath er than in shallow sandy areas. North Meadow Creek This statio n included about 800 lin eal feet of re la tiv e ly straig h t

8 stream, which had an average width of 17 feet. The average depth was 9 inches and the velocity ranged from 0.0 to 2.5 feet per sgtipnd. The maximum water temperature was 69 F. on June 23 and the minimum was 50 F. on September 22. There was no noticeable tu rb id ity and water levels re mained re la tiv e ly stab le. with small areas of sand. The bottom was predominantly gray,el and rubble A few small spring-seeps were present and these were choked with w atercress (Rorippia isla n d ica ). Stream banks were bordered with scattered willows (Salix s p.), grasses, and sedges that overhung into the water. The surrounding area was f la t pastureland. Madison River This statio n included a re la tiv e ly stra ig h t portion of stream along the north bank of the riv e r. I t was approximately 900 feet long and about 10 feet wide except at the lower end where i t included a small is land. Here the width was approximately 200 feet. The average depth was 10 inches and v e lo c itie s ranged from 0.0 to 4.0 feet per second. The maximum water temperature was 71 F. on July 25 and the minimum was 60 F. on June 23. There Was no noticeable tu rb id ity. Water levels varied considerably due to irreg u lar releases from Hebgen Reservoir, which was lo cated one-fourth mile upstream from the statio n. Bottom m aterials consisted largely of boulders, rubble and gravel with areas of sand and s i l t adjacent to the island. Some s tr ic tly aquatic vegetation was present and, in addition to th is, grasses and sedges along the edges of the island were inundated during periods of high water. cut and bordered with grasses and sedges. The North riv e r bank was sharply The surrounding area was a

9 8 steep, rocky canyon p a rtly covered with conifers= Ch August 15, an earthquake made access to th is statio n im practical. As a re s u lt, the la s t collection was made 10 miles below the original collecting statio n and 5 miles below a landslide that dammed the riv e r, The water level was reduced about 2 feet from normal and the flow in th is area was lim ited to water from a few springs and some seepage through the landslide. tu rb id ity. The water temperature was 54 F. and there was noticeable Fish.were collected from remaining pockets of water beneath a bridge. South Fork of the Madison River This statio n contained parts of two large meanders of the riv e r, and was about 1,000 feet in length. I t included about 8 feet of stream along each bank except for several pools over 3 feet deep. These were not in cluded in the statio n because collecting methods were not effective in deep water. The average depth was 10 inches and v e lo cities ranged from 0.0 to 3.5 feet per second. The maximum water temperature was 56 F. on July 25 and the minimum was 43 F. on June 23. There was no noticeable tu rb id ity except on September I, a fte r the earthquake, when i t was 70 p.p.m. Water levels did not vary appreciably. Bottom types included gravel and several large areas of sand in the r i f f l e areas and s i l t in the backwater areas. Water buttercup (Ranunculus sp.) was abundant in the smaller backwaters and on some sheltered sandy areas. Tall grasses, sedges, rushes, and willows lined the riv e r banks. Some of the banks were undercut, as much as 5 feet. The surrounding area was a re la tiv e ly f la t

10 - 9 - valley floor, largely covered with willows, and conifers were predominant a t higher elevations. Duck Creek This collecting statio n included a 150-foot section of re la tiv e ly stra ig h t stream with an average width of 35 feet and an average depth of 11 inches. V elocities varied from 0.0 to 3.0 feet per second. The maximum water temperature was 69 F. on July 25 and the minimum 54 F. qn September I* There was no noticeable tu rb id ity except on September I, a fte r the earthquake, when i t was 64 p.p.m. Water levels remained re la tiv ely stab le. The bottom was predominantly gravel with a few large dep o sits of sand. S ilt was present in the backwater areas. Dense beds of water buttercup covered Jthehsandy areas and c a tta ils and rushes were present along a few gradually sloping banks. Most banks were sharply cut and bordered by overhanging grasses and sedges. A portion of th is statio n was beneath a highway bridge. The surrounding area included gently ro llin g fo o th ills near one edge of the Madison River valley, where vegetation was predominantly coniferous fo rest and sagebrush p ra irie. Trout Creek This statio n included about 1,500 feet of meandering stream with an average width of 5 fe e t, and an average depth of 8 inches. The velocity ranged from 0.0 to 2.5 feet per sedond. The maximum temperature was 60 F. on July 21 and the minimum was 45 F. on April 22. T urbidities were p.p.m. during June and July but were not measured in August, when no noticeable tu rb id ity was present. Holton (1952) reported the occurrence I

11 of flash floods in th is stream, which caused considerable washing of the stream banks and scouring of the bottom. No such floods occurred during the course of th is study. Bottom m aterials included small gravel in r i f f l e areas,, and sand and s i l t in pools. Areas of sand and s i l t in creased noticeably from April to August. The water source was irrig a tio n runoff and spring seeps. Watercress was the chief submerged aquatip p lan t. This was confined to the sandy areas in early summer but choked a large portion of thev stream by autumn. Overhanging banks were predominant and were lined with willows and sedges. In the f a l l, sedges formed a canopy over portions of the stream in the upper end of the statio n. The en tire statio n lay in a small ravine, surrounded by f la t farmland. Results A to ta l of 829 trout fry arid fingerling stomachs were examined. These came from the following lo c a litie s :. North Meadow Greek - IOS1ra in bow tro u t, 120 brown tro u t; Madison River - 80 rainbow tro u t, 79 brown tro u t; South Fork of the Madison River - 88 rainbow tro u t, 92 brown trout.; Duck Creek - 80 rainbow tro u t, 65 brown tro u t; Trout Creek brook tro u t. Only four stomachs were empty and these were not included in the to ta ls. Rainbow Trout No attempt was made to distinguish between rainbow and cutthroat tro u t, however cutthroat tro u t were rare in the collection areas and there is l i t t l e pro b ab ility any were taken ini the collections.

12 11 North Meadow Creek (Table I ). The most abundant organisms in the rainbow trout stomachs were the larvae of Tendipedidae0 The number of these organisms per stomach ranged from 58 to 90 percent of the to tal in a ll collections except on September 22, when i t was only 30 percent. They occurred in percent of the stomachs in a ll collections but the one taken on July 24 where they occurred in only 80 percent. Miscellaneous Diptera were,next in abundance in a ll collections except the one procured July 24. The number of these organisms per stomach ranged from 5 to 21 percent of the to ta l. The percentages increased as the seaspn progressed with a consequent increase in size of fish, however the number of stomachs in which they occurred, in each collection followed no apparent pattern. A. large number of aphids occurred in the July 24 and September 22 collectio n s. This may be accounted for by rain s during and ju s t preceding collecting on those dates which probably washed them into the stream from overhanging vegetation. Other organisms which included over 5 percent of the to ta l number of items per stomach were: Baetidae, Dytis'cidae, Hydroptilid a e, Tipulidae larvae, and Dixidae larvae. Madison River (Table I I ). Lake dwelling Cladocera and Copepoda comprised a major portion of the food in three collections. Copepoda was the predominant food in the July 9 co llectio n, where i t comprised 80 percent of the to ta l number of items per stomach and was found in 17 of the 20 fish examined from th at collection. I t was followed in abundance by Cladocera, with 13 percent ( found in 13 fish ). In the August 10 collection, Cladocera was the most abundant organism. I t constituted 65 percent of the to ta l number of organisms per stomach, followed by Copepoda with 26 percent.

13 Table I, The food of rainbow trtput from North Meadow Creek (1959) exp resse d as number of item s p e r stomach and p ercen tag e occurrence. June 23 July 14 July 24 Aug. 10 Sept. 4 Sept. 22 Total fish Range in to tal length (inches). I. 0-1.I Oo9 1o6 I *2.4 I I Average length (inches).,...,. I. O' I.? ,.4 Item CU Cn CD O) CU P 4-3 A C CD CU A CU CU CD 4-> CCU CD CD 4-3 Ph C CD m CU CD O O1 W 8 s O l -. 0 CM 1 2 H CU CL, O CO CL, 0 CO 0 I 3 % cu s a, Aquatic Nonid td & Oligochaeta Ostracoda Copepoda Isopoda ooooooooo Amphipoda Ephejneroptera Baetidae ' Epheftiere llidae Tricorythidae Plecoptera Nemouridae Coleoptera Dytiscidae '19; Elmidae 00*0000* Trichoptera Psychomyiidae Hydropsychidae Hydroptilidae Q Limnephilidae Brachycentrid ae misc. Trichop L Diptera.Tipulidae Psychodidae Dixidae *00* Simuliidae U Tendjbpedidae Stratiomyidae

14 13- Table I (continued). June 23 July 14 July 24 Aug. 10 Sept. 4 Sept. 22 CU 0 Cn U) CU Item H -P CU A fh fh Q 0 0 <D <u O -Q Xi % S I 0 I s a.- s Ck S Ck 3. Ck. 3 Ck 3 - Diptera cont, Musidae : misc^--diptera IOD Acari "9", p lan t m aterial unidentified T errestrial ' Thysanoptera Thripidae Homoptera Aphididae Gicadellidae Lepidoptera Micropterygidae. Hymenoptera Formicidae umber Total ercentage ercentage umber ercentage 'ercentage

15 14- Table I I. The food of rainbow tr o u t from the Madison R iver (1959) exp ressed as number of item s p er stomach and p ercen tag e occurrence. July 9 July 25 Aug. 10 Aug. 24 Total fish Range in to ta l length (inches) I I Average length ' (inches) ) CU o O") CO CO CO 0 -P -P Item A C A C A C A C _Q CU O 0) I S I S S 0,.,2 O,- 2 2 a, Aquatic Cladocera ", Copepoda Ephemeroptera BsstidsG « Plecoptera Nemouridae Trichoptera Hydropsychidae Hydroptilidae Limnephilidae Glossosomatidae Diptera Simuliidae Tendipedidae...- O raise. Diptera A c sri 0«'oooooo 0* unidentified T errestrial Homoptera Cicadellidae Total

16 Bo th organisms occurred in 95 percent of the stomachs from that collection. Copepoda was second in abundance in the July 25 collectio n, being present in 40 percent of the stomachs. The presence of these plankters was not surprising since the collecting statio n was only a short distance downstream from Hebgen Reservoir. They undoubtedly inhabited the reservoir and passed over the spillway at Hebgen Dam. They were completely absent from the August 24 co llectio n following the earthquake, which was procured 10 miles downstream from the collecting statio n, ju s t below a landslid e which dammed the riv e r. Except for these plankters, Tendipedidae larvae and miscellaneous Diptera were the predominant food organisms in a ll except the collection taken on August 24. Miscellaneous Diptera exceeded Tendipedidae larvae in abundance on July 25 and August 10. was the predominant food organism in the fish taken on August 24. Baetidae This family occurred in a ll fish, and the number of organisms per stomach comprised 74 percent of the t o ta l. In th is collection Tendipedidae larvae in cluded 11 percent and also occurred in a ll fish. I t was followed in a- bundance by'; Simuliidae larvae, miscellaneous Diptera and Hydroptilidae, respectively. South Fork of the Madison River (Table III). Tendipedidae larvae occurred in a larger percentage of the stomachs than did other organisms in a ll collections from th is statio n and were also the most abundant organisms in the stomachs except for the collection taken on July 25, where Cladocera comprised 50 percent of the to tal number of organisms per stomach. Cladocera occurred in only 6 of the 20 stomachs from that collection and one of these contained 188 of these organisms. Cladocera con-

17 Table I I I The food of rainbow tro u t from South Fork of the Madison R iver (1959) expressed as number of item s per stomach and p ercentage o ccurrence. June 23 July 11 July 25 Aug. 10 Sept. I Total fish Range, in total length (inches) I Average length "»» I. Or CD CU CU CD CD CTl Cn CD CD -P -P -p -P -P A C <L> CD CD CU CD CD CD CD CD CD -Q P 6 P I CD I 9 S D CD 2 CU 2 CU 2 CU, 2 CU. 2 CU. Aquatic Hirudinia Cladocera ,25 15 Ostracoda Copepoda Amphipoda Ephemeroptera Heptageniidae Siphlonuiidae Baetidae Ephemerellidae Plecoptera Nemouridae...<, S Trichoptera Hydroptilidae Limnephilidae Brachycentridae misc. Trichop Diptera Simuliidae Tendipedidae misct Diptera , Acari cues 20 Gastropoda T errestrial Homoptera Aphididae Total

18 stitu te d 10 percent of the to ta l number of organisms per stomach on July 11, but occurred in only three of the 20 stomachs from that collection. Miscellaneous Diptera were of minor abundance except in the July 11 and July 25 collections when they made up 11 percent and 17 percent re spectively of the to ta l number of organisms per stomach. They occurred in 75 percent and 50 percent of the stomachs, respectively. Baetidae was present in a ll co llectio n s, and it s numbers per stomach ranged from I to 9 percent of the to ta l. I t occurred in percent of the stomachs. Hydroptilidae and Lirtinephilidae were present only in the collection taken on September I, where each comprised 7 percent of the to ta l number of organisms per stomach. Hydroptilidae occurred in 8 of the 20 stomachs from th at collectio n, and Limnophilidae in 12. Duck Creek (Table IV). Tendrpedidae larvae were the most abundant food organisms in the July 9 and July 25 collections. They were present in a ll co llectio n s, with the number per stomach ranging from 19 to 63 percent of the to ta l. These percentages decreased as the season progressed. Miscellaneous Diptera were predominant in the August 11 and September I collectio n s. They were present in a ll collections and th e ir numbers per stomach tanged from 26 to 55 percent of the to ta l. Baetidae occurred in a ll collections with a range of 3-13 percent of the to ta l and occurred in percent of the stomachs. A v ariety of te r r e s tr ia l insects occurred in a ll co llectio n s, but were never very abundant. Limnephilidae occurred in eight of the 20 stomachs from September I and constituted 9 percent of the to ta l number of items per stomach in that collection, but was not as abundant in the other collections from th is stream.

19 Table IV. The food of rainbow tro u t from Buck Creek (1959) expressed as number of item s per stomach and percentage occurrence. July 9 July 25 Aug. 11 Sept. I Total fish Range1in total length (inches) CO t ' 1.9 I Average length (inches CU CU CU CU S CU CU CU Item fh C H C A C A C CU CU CU CU CU CU CU CU I S I S I A CU ; s.s A. S A 2 A 2 A Aquatic Cladocera...; Ostracoda Copepoda Ephemeroptera Baetidae ' Leptophiebiidae Ephemereilidae Hemiptera Corixidae Coleoptera Dytiscidae JO Trichoptera Hydroptilidae Limnephilidae raise. Trichop Diptera Tipulidae Simuliidae Tendipedidae Musidae... '' 0.05,5 OilO 5 raise. Diptera fish eggs plant material unidentified =05 5

20 Table IV, continued. July 9 July 25 Aug. 11 Sept. I Item Number Percentage Number Percentage Number Percentage Number Percentage T e rrestria l Collembola Entomobryidae Thysanoptera Thripidae : '05 5 Hbmoptera Aphididae C icadellidae Hymenoptera Platygasteridae Total

21 Brown Trout North Meadow Creek (Table V). Tendipedidae larvae were the predominant food organisms in small brown tro u t stomachs from a ll collections from th is statio n, where th e ir numbers per stomach ranged from 41 to 87 percent of the to ta l. Percentages were smaller as the season progressed. These larvae occurred in percent of the fish except in the September 22 collectio n, where thgy occurred in only 80 percent. M iscel- laneous Diptera were second in abundance in most collections and the < number per stomach ranged from 5 to 21 percent of the-total. The percentage increased as the season progressed, but decreased to 11 percent on September 22. They occurred in percent of the fish, but th eir occurrence followed no apparent p attern. Aphids occurred in large numbers in the July 24 and September 22 co llectio n s, as they did in the rainbow tro u t from th is stream. These collections were taken during and ju st a fte r ra in s. Hydroptilidae was abundant in a ll collections but those procured on June 23 and July 14. I t constituted 5-19 percent of the to ta l number of items in a ll collections but the la tte r two mentioned. Baetidae was present in a ll collectibns with 2-8 percent of the to ta l. Madison River (Table VI). The food of small brown tro u t was sim ilar to that of rainbow tro u t, at th is statio n below Hebgen Dam. Planktonic Cladocera and Copepoda were present in a ll collections except the one procured on August 24. Cladocera was the most predominant food organism in the stomachs of fry and fingerlings taken July 9 and August 10. I t made up 67 and 77 percent of the to ta l number of organisms per stomach, re spectively. Copepodk occurred in large numbers in the June 23 and July 9

22 -21 Tjafcle V. The food of brown tro u t from North Meadow Creek (1959) expressed as number of item s p er stomach and percentage occurrence. June 23 July 14 July 24 Aug. 10 Sept. 4 Sept. 22 Total f i s h Range in total length (inches). I I I , I Average length (inches) Item <D <D CD <D CD CD CD CD CD -P -P -P -P -P -P Jh Ui 0) CD <p CU CD CD CD 0) CD CD CD -Q O O h I S. I I 8 0) 8 I 8 S IX S Oh S Oh. S Ph S Oh S. Oh Aquatic Nemata T Oligochaeta Ostracoda Isopoda Amphipoda Ephemeroptera Heptageniidae Siphlonuridae Baetidae Ephemerellidae Tricorythidae IO Plecoptera Nemouridae Coleoptera Hydrophilidae Elmidss oooosooo Curculionidae Trichoptera Psychomiidae Hydropsychidae Hydroptilidae Limnephilidae Brachycentridae misc. Trichop Diptera Tipulidae Psychodidae Pixidae

23 Table V (continued). June S23 July 14 July 24 Aug. 10 Sept. 4 Sept 22 Item CD ' CTi CTi CD CD CD -P C /- P a CU CD CU CU CU CD ' Fh S -P - P -P C A to C Li C A Q A 0) CU' CU CU CD CU CU CU CU CU CU X) -Q -Q A A A t CU CU o g. CD I CU. CT S S O.. S CU S CU S CU. S CU % CU Diptera cont... Simuliidae I Tendipedidae ' IOQ Heleidae ' Stratiomyidae Musidae misc. Diptera Acari Gastropoda fish eggs plant m aterial. " unidentified T e rrestria l Homoptera Aphididae , cr C icadellidae Hymenoptera Formicidae... 1, Total

24 Table VI The food o f brown tr o u t in the Madison R iver (1959) expressed as number o f item s p er stomach and percentage o ccurrence. June 23 July 9 July 25 Aug. 10 Aug. 24 Total fish Range in to ta l length (inches) :2.4 I I Average length (inches) Item cn Cn CU CD CD -p -P -P -P -P M C C N C A C C <u. cu 0) CD OJ CD CD CD CD CD I S I M 0) H 3 CD % H CD s a,. S' a, s a. S Ph S Ph CD CD CD CD CD A quatic' Cladocera Copepoda Ephemerbptera Heptageniidae Baetidae raise. Ephem Hemiptera Corixidae Trichoptera Hydropsychid^e Hydroptilidae Limnephilidae Diptera S im u liid a e Tendipedidae ; raise. Diptera Gastropoda unidentified T e rrestria l Homoptera Aphididae Cicadellidae Hymenoptera Fbrmicidae raise: Hymenop Total

25 co llectio n s, comprising 25 and 26 percent of the to ta l, respectively, however i t was found in only a few fish. As in the case of rainbow tro u t, both Gladocera and Copepoda were abseltt from the August 24 collection, which was procured downstream from a landslide that dammed the riv e r. Miscellaneous Diptera were the most predominant food items in the June 23 and July 25 collections and were next to Cladocera and Copepoda in abundance in the July 9 collectio n. The numbers of miscellaneous Diptera per stomach ranged from 38 to 75 percent of the to tal in the la tte r three co llectio n s, and were followed in abundance by Tendipedidae larvae with 2-22 percent of the to ta l in the same co llectio n s. In the August 10 collectio n, Tendipedidae larvae were next in abundance to Cladocera, when they constituted 6 percent of the tota^ number of organisms per stomach, followed by miscellaneous Diptera with 5 percent. Baetidae was the most predominant food in the August 24 co llectio n. I t was present in a ll the stomachs in th at collection and the number of these organisms per stomach constituted 67 percent of the to ta l. Baetidae was followed in abundance by Tendipedidae, Simulidae, Hydropsychidae, miscellaneous D iptera, and Hydroptilidae respectively in that collectio n. South Fork of the Madison River (Table VII). Tendipedidae larvae were the most predominant food organisms in the July 11 and September I co llectio n s. They appeared in a ll co llections from th is location. The numbers of these items per stomach decreased from 59 percent of the ^totiai on June 23 to 13 percent on August 10, and increased to 42 percent on September I. They occurred in percent of the stomachs. Baetidae was present in a ll collections from th ii statio n and i t s numbers per

26 Ja b le V II. Th^ food of brown tro u t in the South Fork of the Madison R iver (1959) expressed as number of item s per.stom ach and percentag e occurrence. June 23 July 11 July 25 Aug. 10 Sept. I Total fish Range in to tal length (inches). I. 1-2.I I I I I Average length (inches) Item 0 CD (0 " 4-) A C 0) 0 I i 0 CD (0 4-> M C 0 0 I I & CO 4-> : f-i C 0 0 S a, 0 CD 0 0 -Q O S S S P. 0 CD 0 4-> A C 0 0 I I Aquatic Hirudinia Cladocera Ostracoda Copepoda... 0,10 5 Oi 05 5 OJfcv' Amphipoda Ephemeroptera Siphlonuridae ; Baetidae Leptophlebiidae Ephemerellidae Plecoptera Nemouridae Coleoptera H aliplidae Dytiscidae Trichoptera Gloss olseiha tida e Hydroptilidae Limnephilidae ; raise. Trichop ,08 8 Diptera. Tipulidae Simuliidae Tendipedidae ;50 70 Heleidae raise. Diptera Acari

27 Table VII (continued). June 23 July 11 July 25 Aug. 10 S ep t. I Item Number Percentage Number Percentage Number Percentage Number Percentage Number Percentage Aquatic," fcpnt. Teleostei Cottidae... unidentified T e rrestrial Homoptera Cicadellidae Total V '

28 stomach ranged from 8 to 35 percent of the to ta l. I t was the most predominant food in the July 25 collection. This item occurred in percent of the stomachs from th is station,. Cladocera was the most predominant food in the August 10 co llectio n, where i t constituted 66 percent of the to ta l number of items per stomach. I t was also present in the July 25 collection with 14 percent. on each of these two dates. I t occurred in only five of the 20 stomachs Other organisms constituting over 10 percent of the to ta l number of items per stomach on one or more dates were: EphemerelIidae, Hydroptilidae, and Limnephilidae. Duck Creek (Table VIII). Stomachs from collections taken on June 23, July 9, and September I contained predominantly Tendipedidae larvae. numbers per stomach constituted from 30 to 59 percent of the to ta l. The Miscellaneous Diptera were present in a ll collections and were the most predominant food items in the July 25 co llectio n. Their numbers per stomach ranged from 6 to 36 percent of the to ta l and they occurred in percent of the stomachs. Cladocera constituted 22 percent of the to ta l number of items per stomach on July 25, but occurred in only one of the nine fish in th at collectio n. Baetidae was present in a ll collections and the number per stomach ranged from 10 to 32 percent of the to ta l. I t occurred in percent of the stomachs. The only instance where small tro u t stomachs contained a re la tiv e ly large number of fish was the July 9 collection from Duck Creek. Seven of the 20 brown tro u t stomachs in th is collection contained small sculpins (Cottus b a ird i). which were approximately 8 m illim eters in length. r

29 Table V III. The food of brown tro u t in Duck Creek (1959) expressed as number of item s per stomach and percentage occurrence. June 23 July 9 July 25 Sept. I Total fish Range in to ta l length (inches). I I I Average length (inches) P Item A C Q). CD CD CD Cn U) CD CD A -P C CD CD CD CD CD CD CD CD I S I S I S I S Z Ph S Ph. S Ph S Ph A -P C A -P C Aquatic Oligochaeta Cladocera Ostracoda Copepoda Amphipoda Ephemeroptera Siphlonuridae Baetidae Ephemerellidae Plecoptera Nemouridae Hemiptera Corixidae Coleoptera Haliplidae Dytiscidae... OilO Trichoptera Hydroptilidae Limephilidae..= misc. Trichop ,06 6 Diptera Tendipedidae misc, Diptera ' Teleostei. Cottidae T e rrestria l Homoptera Aphididae , 22 Total r'

30 Brook Trout Trout Creek (Table IX). Tendapedidae larvae were abundant food items in a ll brook tro u t collections and were the most predominant organisms in stomachs from the June 4, July 21 and August 18 co llectio n s. The number of organisms per stomach ranged from 20 to 48 percent of the to tal and these organisms occurred in percent of the stomachs in a ll coir lectio n s. Baetidae was also abundant and was the mbst predominant food in the June 30 and August 15 co llectio n s. The number of these organisms per stoma,ch ranged from 11 to 45 percent of the to tal and th is item occurred in 75-IOO percent of the stomachs. Copepoda was the most abundant food organism ^aken in the April 22 co llectio n, where i t included 39 percent of the' tdta], number of items per stomach. Cladocera constituted 18 percent in th is collection. Hydroptilidae occurred in a ll collections except those taken on April 22 and June 4, and ranged from 2 to 6 percent of the to ta l number of organisms per stomach in the various co llectio n s. The percentage increased as the season progressed. Simuliidae occurred in these same collections and constituted 2-10 percent of the total.number of organisms per stomach. The percentage of th is item also increased as the season progrssed. Aphididae was abundant in the collections taken on August 5 and August 18 but no reason for th e ir presence was evident. Discussion Although foods from the d ifferen t streams varied considerably, Tenddpedidae larvae were abundant in a ll rainbow trout collections and'made up 40 percent of the to tal number of organisms per stomach. The remaining

31 3 D " Table IX. The food of sm all brook tr o u t in Trout Creek (1959) expressed as number of item s p er stomach and percen tag e o c c u rre n ce. Apr. 22 June 4 June 30 July 21 Aug. 5 Aug. 18 Total fish Range in to ta l' length (inches) I. 1-2.I I Average length (inches) I M rh I I Number Percentage Number Percentage Number Percentage Number Percentage Number Percentage Number Percentage Aquatic Nemata I Hirudinia '0 Cladocera Ostracoda Copepoda Ephemeroptera Heptageniidae Baetidae ' Plecoptera Nemouridae : Coleoptera Haliplidae Dytiscidae Hydrophylidae Curculionidae TrTchoptera Hydroptilidae Limnephilidae Diptera Tipulidae Simulidae Tendipedidae Heleidae Stratiomyidae Rhagionidae Musidae misc. Diptera

32 Table IX (.continued) Item A pr. 22 Ju n e 4 Ju n e 30 J u ly 21 Aug. 5 Aug. 18 CU -Q CD CU CU CU CU CU' CJ) CU CU CU CU CU CU C CU A CU A CU I C I C CU K S O A A CU I CU S I A A CU CU S Oh S PU. 2 CL 2 CL 2 CL, 2 CL, A CU e: CU A, CU C CU A c a r i G a stro p o d a f i s h p la n t m a t e r ia l T e r r e s t r i a l O rth o p ter a L o c u s t id a e H om optera A p h id id a e \80 C i c a d e l l i d a e F u lg o r id a e H ym enoptera I F o r m ic id a e A ra n eid a T h o m isid a e Total

33 percent was divided about equally among miscellaneous D iptera, Baetidae,' Copepoda, Cladocera and miscellaneous food. As the season progressed and fish consequently grew la rg e r, there was a greater v ariety of organisms in the stomachs. Id y ll (1942) studied the food of 15 rainbow tro u t and 20 cutthroat tro u t, up to 4 inches in to ta l length, from the Cowichan Riyer System in B ritish Columbia. He found Tendipedidae was the predominant food of both fish, co nstituting 7.6 percent and 64 percent of the total number of items per stomach, respectively. He found Plecoptera was second in importance in rainbow tro u t (12 percent) and Ephemeroptera in cutthroat tro u t (16 percent). Hazzard and Madsen (1933) determined the food of 48 cutthroat tro u t (I inches in to ta l length) from a trib u tary of Jackson Lake, Wyoming. They reported Tendipedidae larvae to be the predominant food, making up 20 percent of the to tal number of organisms per stomach, while Copepoda and Diptera pupae and adults were present in large numbers. A cari, Oligochaeta and Ostracoda were also quite numerous. These la tte r occurred in the rainbow tro u t of the present study but we^e of minor importance. Te'ndipedidae larvae contributed 32 percent of the to ta l number of organisms per stomach in brown trout (Figure l) with miscellaneous D iptera, Baetidae, and miscellaneous foods each with about equal amounts. The number of Cladocera per stomach in brown tro u t included 21 percent of the to ta l, while Copepoda included only 4 percent. Idyll (1942) examined : stomachs of 35 brown tro u t, up to 4 inches in to tal length and found that Tendipedidae constituted about 70 percent of the to ta l number of organisms per Stomach, followed by Ephemeroptera with 15 percent. Clemens (1928)

34 Rainbow Trout Cladocera Copepoda - ybaetidae / misc. X 12% / Diptera / 13% Tendipedidae 40% Total fish Average length inches Average number of organisms per stomach - 27 misc. 15% Brown Trout Total fish Copepoda 4% Cladocera Baetidae Tendipedidae ^ 32% Diptera, 14% Average length inches Average number of organisms per stomach - 23 Copepoda Acari-*-> 4% Hydroptilidae Simuliidae Aphididae 8% misc. 14% Tendipedidae \ 31% Baetidae Brook Trout Total fish Average length inches Average number of organisms per stomach - 17 Figure I. Percentages of the to tal number of items found in the stomachs of rainbow tro u t, brown tro u t and brook trout fry and fingerlings.

35 i-34-~ studied the food of seven brown tro u t (2-3 inches in to ta l length) from Oneida County, New York apd found the predominant foods were Trichoptera and Ephemeroptera. Although numerous differences occurred between the foods of rainbow tro u t and brown tro u t, only four were very noticeable. Considering a ll c o lle c tio n s, Ciadocera was le s s abundant in rainbow trout than in brown t tro u t, while Copepoda was less, abundant in the la tte r. In several collectio n s from Duck Creek and the South Fork of the Madison River, Baetidae was more predominant in brown trout than in rainbow tro u t, while Tendi- pedidae larvae were more predominant in the la tte r. Changes in diet composition throughout the season were generally quite sim ilar in both species of fish. Although the most abundant food in small brook tro u t was Tendipedidae larvae, Baetidae was nearly as predominant. Together, thebe constituted over h alf the to ta l number of organisms per stomach. Most of the other food was comprised of: Aphididae, Simuliidae larvae, H ydroptilidae, Acari and Copepoda. Clemens (1928) found that Tendipedidae (larvae and pupae) were the predominant food organisms, followed by Ephemeroptera, in I55 brook trout up to 4 inches in length. Ricker (1930) analysed 41 brook trout (0.8-4.O inches in to ta l length) stomachs from Ontario, in which Tendipedidae made up 39 percent of the to ta l volume of organisms per stomach. He found Cladocera, Copepoda and Ostracoda to be quite important for fish O inches long. Results from Trout Creek (Table IX) agree with th is. The foods of small brook tro u t were somewhat d iffe re n t from those of

36 rainbow tro u t and brown tro u t. Baetidae comprised a much larger portion of the food in stomachs of brook tro u t than in the other two species. Cladocera,and. miscellaneous Diptera'. were less abundant in brook tro u t, while Aphididae, Simuliidae larvae, Hydroptilidae and Acari were more abundant. These differences might be explained by the lower elevation of the stream and difference in h ab itat where brook tro u t were collected. As the season progressed, and small trout grew larg er, th eir stomachs contained a greater v ariety of organisms. Larger tro u t, no doubt are able to capture and swallow bigger organisms and they range over more of the stream, where a greater v ariety of organisms are found. Summary 1. Samples of rainbow tro u t, brown tro u t and brook tro u t fry and fingerlings were obtained for stomach analysis from five southwestern Montana streams. 2. Collections were secured a t about two-week in te rv a ls, from about the time tro u t began to feed u n til they reached a length of approximately four inches. Samples were procured from April 22 to September Where numbers perm itted, 20 fish of each species, from each stream for each date were randomly selected for stomach analysis. 4. A to ta l of 356 rainbow tro u t, 356 brown tro u t and 116 brook tro u t were examined. 5. The most abundant organisms in the stomachs of rainbow troyt fry and fingerlings were the larvae of Tendipedidae, which made up 40 percent of the to ta l number of organisms per stomach in th is fish.

37 Miscellaneous D iptera, B aetidae, Copepoda, Cladocera and m iscellaneous food were about equally abundant in rainbow tro u t stomachs' and comprised the remaining 60 percent of the d ie t. 7. Tendipedidae larvae constituted 32 percent of the to ta l number of organisms per stomach in small brown tro u t, and was the predominen food. 8. Miscellaneous D iptera, Baetidae, and miscellaneous foods comprised about, equal portions of brown tro u t d ie t. Cladocera exceeded Copepoda in abundance in these stomachs. 9. Considering a ll co llectio n s, Cladocera was le ss abundant in stomachs of rainbow tro u t than in brown tro u t, while Copepoda was more; abundant. Baetidae was more predominant and Tendipedidae larvae were less predominant in stomachs of brown tro u t than in rainbow tro u t in several co llectio n s. 10. Changes in d ie t composition throughout the season were sim ilar in rainbow tro u t and in brown tro u t. 11. Aphids were abundant in the stomachs of rainbow tro u t and brown tro u t collected in North Meadow Creek during and a fte r rain s. 12. Cladocera and Copepoda were abundant in rainbow tro u t and brown tro u t stomachs collected, from the Madison River statio n, a short distance downstream from Hebgen Reservoir. 13. ' Tendipedidae larvae were the most abundant food items in brook tro u t stomachs, however Baetidae comprised nearly as many organisms per stomach. 14. Cladocera ; and miscellaneous Diptera ^ere less abundant,. in brook tro u t than in the other two species, while Aphididae, Simuliidae

38 larvae, Hydroptilidae and Acari were more abundant. 15/ '.As the seasdn progressed and fish became larg er, there was a greater v ariety of organisms in the stomachs of a ll three species of fish. L iteratu re Cited Clemens, W. A The food of tro u t from the streams of Oneida County, New York s ta te., Trans. Am. Fisheries Soc., 58s *, Hazzard, A.; S. and M. J. Madsen Studies of the food of the cutthroat tro u t. Trans. Am. Fisheries Soc., 63s Holton, G. D A tro u t population study in a small creek in G allatin County, Montana. Jour. JAIildl. Mgt., 18 (I ) s Id y ll, C Food of rainbow, cu tth ro at, and brown tro u t in the Cowichan River system, B. C. Jour. Fish. Res. Bd. Canada, 5 (5)s '' ; Ricker, W. E' Feeding habits of speckled trout in Ontario waters. T rans. Am. Fisheries Soc., 60s

39 MONTANA STATE UNIVERSITY LIBRARIES O f 946f t b f