Utilization of Mayflies and Caddis Flies by Some Mississippi River Fishes• DAVID TOWNSEND HOOPES Departmentof Zoologyand Entomology Iowa State Universityo/Science and Technology,Ames, Iowa ABSTRACT At samplingstations in the MississippiRiver near Keokuk,Iowa, during 1958mayfly naiads, Hexagenia spp., comprised over 50 percent by volume of the food of channel catfish (Ictalurus punctatus),freshwater drum (Aplodinotusgrunnlens), mooneyes (Hiodon tergisus), goldeyes(Hiodon alosoides),and white bass (Roccus chrysops),and over 40 percent of the food of paddlefish(Polyodon spathula) and white crappies (Pomoxis annularis). These naiads were also eaten by shovelnosesturgeon (Scaphirhynchusplatorynchus). Larval caddis flies, Potamyia ]lava, comprised over 60 percent of the food of the shovelnosesturgeon and between 10 and 20 percent of the food of mooneyes,goldeyes, and white crappies. The Hexagenia naiads found in the stomachsare the same kinds that ordinarily create a problem in the river communitiesbut the nuisancespecies of caddis flies (Cheumatopsychecampyla and Hydropsycheorris) are not usually significantin the diets of the fish studied. INTRODUCTION METHODS Or INVESTIGATION Large emergencesof caddis flies and may- The fish examinedduring this study were flies occur at many places along the im- collectedin Pool 19 of the MississippiRiver pounded waters of the upper Mississippi in the vicinity of Burlington and Keokuk, River during the summermonths. At timesof Iowa, and in the tailwatersimmediately below peak emergencehordes of winged adults in- Lock and Dam 19, Keokuk, Iowa (Table 1). vademany of the river towns,creating health, The problemof acquiringthe large numbers of fresh samplesnecessary for this studywas transportation,economic, and nuisanceprob- overcomeby enlistingthe aid of severalcom- lems. Many of the river towns are planning mercial fishermen and fish markets in the to developprograms designed to either elimi- vicinity of Keokuk and Burlington. The nate these insects or to control their numbers. quantities,in percentage,of eachfood organ- The initiation of any programwhich might ism with relation to the total stomach con- alter the numbers and distribution of the tents of each fish speciesmay be presented aquatic immature forms shouldbe seriously in a radial diagram where each of the five consideredonly after a thoroughinvestiga- radii is 100 percentand the pointson these radii are connected to form a characteristic tion of their presentdistribution, ecological figure (Figure 1). Although a number of importance,and biology. Such a study was speciesof mayfliesand caddisflies were iden- initiatedat Keokuk,Iowa, in 1957 assistedby tifiedduring the stomach-analysiswork, only a grant from the National Science Founda- relativelyfew were importantin the dietsof tion. This paper reportsthe degreeto which the fish examined.A comparisonof all anal- mayflyand caddis fly aquaticstages were util- yses made for each fish speciescollected izedas foodby severalspecies of fishas de- showed that little seasonal variation in food termined by the collection,examination, and habits occurred relative to the utilization of analysisof stomach-contentmaterial. caddisand mayfly iramatures. •JournalPaper No. J-3685of the IowaAgricultural UTILIZATION OF MAYFLIES AND CADDIS FLIES and Home EconomicsExperiment Station, Ames, Iowa. Project No. 1373, Iowa CooperativeFisheries Mayfliesof the genusHexagenia form an ResearchUnit, sponsoredby the Iowa State Conser- importantsource of food for the paddlefish vation Commissionand Iowa State University of Scienceand Technology,with the cooperationof the during the winter, spring,and early summer U.S. Fish and Wildlife Service.This phaseof the months.Naiads of Hexageniacomprised 46 project was aided by a grant from the National percent of the total food content of the 64 Science Foundation. paddlefishexamined. Cladocerans, copepods, 32 USE OF •N[AYFLIES AND CADDIS FLIES BY RIVER FISHES 33 Diptera, and Odonata.The total stomachcon- tent of 136 mooneyesincluded 66 percent Hexagenia naiads and 17 percent Potamyia fiava larvae. ImmaturePlecoptera, Diptera, and Odonatacomprised the remainder.The FRESHWATER CHANNEL MOONEYE WHITE BASS DRUM CATFISH food habitsof the goldeyeare almostidentical to those of its more abundant relative, the mooneye.Hexagenia naiads comprised 56 per- centof the contentsof the 44 goldeyestomachs collected;Potamyia fiava larvaemade up 19 percent. Immature Zygoptera and Odonata , 3 3 3 3 and fish formed the bulk of the remaining GOLDEYE PADDLEFISH WHITE SHOVELNOSE contents. The stomach contents of 143 channel CRAPPIE STURGEON catfishcontained 68 percentHexagenia naiads F•cuI•E L--Utilization of mayflies, Hexagenia spp. and subimagosbut only 3 percentPotamyia (1); caddisworms,Hydropsyche orris (2); Cheuma- topsyche campyla (3); Potamyia fiava (4); and fiava larvae.Mayfly subimagosappeared only other organisms (5); as food By fish, Mississippi in channel catfish stomachs collected between River, near Keokuk and Burlington, Iowa, January June 24 and July 16 and their presenceal- 1958 to November 1958. ways coincidedwith periodsof peak mayfly emergence.The remainderincluded immature and algae were also significantfood items, Plecopteraand Diptera, clams, snails, and primarily in the late summerand fall months. algae.Hexagenia naiads comprised 54 percent Shovelnosesturgeon depend largely upon of the total stomach content of the 56 white caddislarvae throughoutthe year. In the 74 basscollected. The larvae of Potamyiafiava sturgeonexamined the total content was 68 formed9 percentof the contentand immature percent Potamyia fiava larvae, 7 percent Odonataand Zygoptera,Hemiptera, amphi- Cheumatopsychecampyla larvae, 17 percent pods, crayfish, and fish were also present. Hexagenianaiads, and 8 percentother mate- The food of 83 white crappiesincluded 42 rial which included immature Plecoptera, percentHexagenia naiads and 11 percent Po- Tasn•; 1.--Fish collectedin the MississippiRiver at Burlington and Keokuk, Iowa, in 1958 /or [ood-habits study Numbers Total lengths Species Collection dates with food Gear of fish in inches• Paddlefish January and February 17 Gillnet 29.0-54.5 April 24 Seine July and Auglist 10 Seine October and November 12 Seine Shovelnose sturgeon April 44 Trammel net 17.5-24.0 June and July 10 Hoop net October 2O Trammel net •Iooneyes April 36 Seine 8.5-14.5 July and August 33 Seine October and Noveu, ber 67 Seine Goldeyes July and August 39 Seine 10.0-15.5 October 4 Seine Channel catfish April 14 Seine 9.5-21.5 June 39 Trot line July and Auglist 68 Trot line October 9 Seine White bass April 8 Seine 8.0-14.5 July and August 35 Seine October and November 14 Seine White crappie April 4 Seine 6.6-12.3 July and August 76 Seine October 2 Seine Freshwater drum April 4 Seine 8.5-14.5 July and August 18 Seine October and November 11 Seine XShovelnosesturgeon were measnred in standard lengths. Paddlefish were measured from the tip of the bill to the end of the dorsal portion of the caudal tilt. Total lengths of all other fish were measured from the anterior of the head (mouth closed) to the longest ray of the cattdal fin (lobes co•npressed)while the fish lay on its right side. 34 DAVID TOWNSEND HOOPES tamyia ]lava larvae. The remainder of the lated to H. orris and C. campylaboth biologi- content was composedchiefly of immature cally and taxonomically,has. little importance Diptera, Odonataand Zygoptera,Hemiptera, as a nuisancespecies because it doesnot enter and fish. Seventy-fivepercent of the total cities or residential areas in large numbers stomach content of the 33 freshwater drum but is relativelysignificant as a sourceof food examinedwas comprised of Hexagenianaiads. for manyof thefish, especially the shovelnose Immature Coleoptera and Odonata, snails, sturgeon. and fish constitutedthe bulk of the remaining 25 percent. ACKNOWLEDGMENTS The stomachanalyses show that, with re- The author wishesto extend his appreciationto the spectto mayflies,the nuisancespecies are the •nany co•n•nercialfishermen and fish-houseoperators, same as those which are important as fish whose interest and assistancemade this study pos- sible. Thanks are due the personnelof Lock and Dam food in their immaturestages. With regardto 19 and the Corps of Engineers, U.S. Army, for caddis flies, however, the problem species providing laboratory space and assistanceand to the (Cheumatopsychecampyla and Hydropsyche City of Keokuk for lodging during the periods of field investigation.The author is indebted to Dr. Ken- orris) are apparentlynot significantas food neth D. Carlander for guidance and critical co•mnent organismsin the fish examined.In this case in preparation of the paper and to Calvin R. Freon- anothercaddis fly, Potamyiatiara, closelyre- ling for field assistance. .