TI-]E UNIVERSITY OF MAIíITOBA Popr.rlation Dynamics and Feeding trcblogy of chaoborus f lavicans (trreigen) (Diptera : chaoborid'ae) i.n Relation to gþaobelge Prod'ucLivity in I¡iest BIue Lake by V]ALTER LYSACK A"TI.IESTS SUBÍ".IITTËD To TT{B FAiULTY OF GR¿\DUATÈ STUDIES IN P,\RTIÀL FUi,FILtIlEi{T OF TFIE REQUIREI'itrl'11-s FoR T}iE D]IGREE OF MÀSTER OF SCIET'TCE DBPARTì,IEI.IT OF ZOOLOGY TVII.ÍNTPEG, Ì\LANITOBA AUGUST , I97 6 .,POPULATION DYNAMICS AND FEEDING ECOLOGY t)F CHAOBORUS FLAVICANS (MEIGEN) (DIPTERA:CHAOBORIDAE) IN RELATION TO CHAOB.ORUS PRODUCTIVITY IN I,.¡EST BLUE LAKE'' by I¡IALTER LYSACK i':-- t,, ], A disse¡tation submitted to the FaculÊy of Graduute Sturlies of the University of Munitobu in partial fulfillment of the requirements of the degrce of : MASTER OF SCIENCE o tsze Pernrissio¡r hus l¡ecn gratttcd to ttre LIBRARY Ol'l TtlU UNIVUR' SITY OF MANITOllA to tr:nrl or u:lt copies of this tlissertation, to the NATIONAL LIBRARY OF CANADA to nticrofilm this rtissertutio¡t and to lend or setl copies of the filnr, and UNIVURSITY MICIIOFILMS to publish un ubstruct of this dissortution Thc autlrcr reserves other publication rights, und ncitlrcr tlre dissertation nor extensivs cxtracts t'runr it tnuy be printed or otl¡er- wise reprorluce¡l without rhc author's writtcn pennissiolt TABLE OF CONTENTS PAGE INTRODUCTION 1 LITERATURE REVIEW B General Biology of Chaoborus sp. I Population Dynamics and Productivity 13 of Chaòborus 13 Vertical Migration of Chaoborus Larvae 1B Respiration and Feeding Ecology of Chaoborus Larvae ..;.. 22 METHODS AND }ÍATERIALS ....... 27 Description of StudY Area 22 Life History, Population Dynamics and Production of C. flavicans . .. .. - - - - 27 Respiration and Feeding of C. f l-avicans . -.... 33 Calculations ..... 36 RESULTS ...... 38 Life History and Population DynamJ-cs of C. fl-avicans .. Production of C. ftavrcang in West BIue Lake. - 50 Respiration and Feeding of C. flavicans . -.... 61 DISCUSSION ;.... 73 Life History and Populati-on Dynamics of C. flavicans in West Blue Lake 73 Growth, Feeding and Respj-ration of C. flavicang in Vüest BIue Lake . - -.86 Productivity of C. flavica4q in West Blue Lake. -106 (i) PAGE LITERATURE CITED APPENDICES 1 33 (ii ) LIST OF FIGURES FIGURE PAGE t. Map of West Blue Lake showJ-ng sampling stations 28 2. Head capsule length . 31 3. Vertical distribution of C. flavicans farvae during :19 r97 4 89 ¿. Temporal changes in density of C. Flavicans larvae at three stations during I974-75 40 Temporal changes in benthic density of C. flavicans larvae during L974 42 6. Diel vertical migration of C. flavicans larvae 43 7. Head capsule length histograms of C. flavicans Iarval instars, 1974 45 B. Instar succession of C. flavicans larvae, L974.... 46 9. Temporal chang,es in emergence rate of C. flavicans adu]ts ..... ..... 48 l_0 . Horizontal distribution of adul-t emergency across station 1 49 lr. Presence or absence of C. flavicans and amphipods at station I transect 51 L2 Growth curve (irrespective of instar) of overwintered L973-74 generation and L974-75 generation of 9. flavicans 13. Instar-specific growth curves 53 (iii ) FIGURE PAGE 14. Growth in terms of carbon content of C. flavicans l-arvae and pupae, I975 55 15 Al-len curve production of L974-75 generation of C. flavicans larvae ..... 56 16. Effect of temperature on O, consumption rate of C. flaïicans l-arvae and pupae . 65 L7. Effect of body sj-ze on O, uptake per unit weight of pupae C. flavicans larvae and at five temperatures.. 66 \': :': 1B Food selection by C. fl-avicans instars I - IV ...... 6B 19 Effect of food concentration on ingestion rates of --C. flavicans 69 20. Feeding intensities of C. flavicans ... 72 AI. Rearing tanks .......¡.. ...134 81. Transparent PVC feeding chamber .....136 82. Rope cradle 83. Feeding chamber suspended in the water . I 38 CI. Effect of predator density on ingestion .. .....143 ir': i:-,l (iv) LIST OF TABLES TABLE PAGE 1. Temporal changes in pelagic densities (no. *12) of C. flavícans during Lg74-75 41 2. Pechen-Shuskina production of the L97A-75 generatj-on of C. flavicans in West Bl-ue Lake . 57 3. Carbon'and ca]oric conversions of pechs¡ -Shuskina production 62 4. P/B ratios . ....: 1i' 5.FeedingcurVeparametersandsignificancetests7o :.: : l -.1 l:: : : . : . (v) LIST OF APPENDICES APPENDfX PAGE A. Rearíng Tanks !.... 133 B. Feeding Chambers 13s c. Trial Feeding Experiment 139 D. Benthic Densitìes of Chaoborus Larvae, Lg74 ....... 144 Iì Depth=i,veighted Peaks of Vertical Migration of q. f-l-avicans, D. pulicaria and C. bicuspidatus 14s F. Emergence and Sex Ratio of C. fl-avicans Adults 148 G. Numbers of C. flavicans and Amphipods Caught in Submerged Traps at Station I H. Dry Vüeights of C. flavicans Larvae and Pupae ...... 150 I. Instar-specific Growth Data 1 51 J. Cal-orific Content of C. -----:-------llavicans Larvae an<l Pupae. 153 K. Carbon Content of C. f l-avicans 156 L. HatchÍng Success of C. flavicans Eggs 1 59 M. C. flavicans Respiration Data N. Allen Curve Product.ion ¡¡rår o. Feeding Experiment Results 165 D Authors of Species................................ 171 (vi ) ' /r CI(tIOIILEDGI 1Ij]JTS I v;ish to e::press ml/ sincere gratitucle to Dr:. F. J. 'rfa::cl , professor , I)epartrqent of Zoology , tlnive::sit;r of i l'larritoba , for his valuat¡}e counsel ancl suppo::t ciurinc¡ thís stucly. I greatl-y app::eciate the a<lvice an<l cr-i-tical reviev¡ r of the nantrscr-ì-pt by Dr:. I(. !¡. Stev¡ar:t , profc^ssor, Department : of 7,crologlz , tJníversitlz of tfanitoba , I)l:. O. A. Saether t (lanacla S¡re'cial ì:hanks ar:e clrre to Dr. Ii. Pata-1-as for aclvice and encour:agerrent. l\ssistance in tl'¡e fie-l-cl by i'fr. and l,i::s. ¡\. T'ernov¡ski is g::eatl¡r app::erciateci. I r+oulcl like to thanll nl1 parents ancl l1::. llrs. J. IJoocl for encouragenent an<l l"n suppor:t This v¡orll ::eceive<l support frotir g::ants to Dl:. IJarcl fron the i,Iatic>na.l- P,esea::ch Council of Canacla (.A260¿t) ancl fr:or.r thc Depar:trient of I'Iines, Resou::ces aucl Lnvironr,rental t-.--l r^1.- iianaqer,rent, P::clrzj-nce of-c ilanítolla lvii) ABSTRACT The life cycle, population dynamics, respírat,ion and feeding ecology of Chaoborus flavicans (Meigen) (Diptera: Chaoboridae) in West Blue Lake vrere examined over a two year period. The new generation began in early Juty. La'rvae gre\¡r into fourth instars before winter. Fourth inst.ars over- wintered in the mud in a st,ate of diapause, emerged next spring ancl metamorphosed into pupae. Adults emerged, mated end producecl floating egg rafts during fate June and early July. Larval abundance declined rapidly after'they hatched and remained low for the rest of the season. Younger instars remained nearer the surface while older instars moved to deeper daytime clepths an<1 exhibited more extensive diel ver- tical migrations. DeVelopmental times of C. flavicans instars I-IV r¡rere: 10, 12, 12, and 142 days respectively. Biweekly weight increments were larger in successive instars. Maximum dry weights of instars I-IV rtrere: 0.0193, 0.0493r 0.1543 and 0.9354 mg. respectively. Caloric content per unj-t weight (5.864 kcal. gr*.-1dry weight) was not clifferent among larvae and pu¡>ae. Carbon content.per unit weight of instars I-IV and pupae was: 661.3, 602.Bt 623.6, 468.1r and 389.8 ug. C mg:lclry weight respectively. Net productivity of C. flavicans larvae was 1982 rng. dry weight mî2year-I (1.09 x 10 ug. c mlzyear-l rr .625 kcal. mî2year-l) according to the Allen curve ancl 2074 mg. dry weight mî2y"tt-laccording to the (víii ) Pechen-Shuskina formula. oxygen uptake rates of fourth instars and pupae in- creased exponentíally with temperattlrêo In younger instars, oxygen uptake rates increased linearly with temperature. i- r'i Oxygen uptake per unit weight was significantly higher in pupae than in Larvae. Ig silu incubation experiments showed that cliversity in size and type of prey increased in suc- cessive instars. First instars fed on rotifers and nauplii ancl second instars added larger Cyctgps ,bicuspidatus Thomasi to their diet. Third instars began feeding on small Daphnia pulicariâ. Leydig. Fourth instars pt"f"tt"d g. bicuspiclatus and consumecl all other types of prey. Feeding rates of aII instars were lower in the hypolimnion than ín the epilimnion. Feeding intensity increased. with foocl concentration and tem- perature an<l clecreased as Iarvae grew o1cler. 1ix) INTRODUCTION ..'l Research at Vüest Blue Lake is aimed at quantita- ::i'..' : tively describing energy exchanges and pathways in this freshwater ecosystem. To help attain this goal, informa- ,,:1.: . tion about food web components is required. Life cycles , ; i,,,''. : 1 population dynamics, productivity and feeding parameters ", are pertinent in describing an organismts place in the food web and j.ts contribution to the productivity of the whole ecosystem. Chaoborus larvae play an important roLe in fresh- water ecosystems. They contribute significantly to the total biomass and productivity of the ecosystem. Chaoborús larvae exert significant predatory pressure on freshwater zooplankton. In t,urn, Çhqgborus larvae are an import,ant ^food source for amphipods and fish. Ch?oborus larvae occur in large numbers. Densities of over 501000 m.-2 are reported (Borutzky 1939, Bonomi L962) . Chaoborus larvae can attain a dry weight of I.3 mg. (Parma L97L). Parma (1971) estimated biomass of benthj-c Chaoborus.Iarvae to be 57.5 kg.