, INTERNATIONALE VEREINIGUNG v ä FÜR THEORETISCHE UND ANGEWANDTE LIMNOLOGIE ^

INTERNATIONAL ASSOCIATION 3 OF THEORETICAL AND APPLIED LIMNOLOGY

ASSOCIATION INTERNATIONALE ' DE LIMNOLOGIE THEORIQÜE ET ÄPPLIQUEE

Verhandlungen • Pröceedings • Travaux

Cöngress in Munichr1989

Volume 24 • Part 5 -

Edited for,the Association by V. Sladecek and A'.SladeSkovd

World List Abbreviatipn: Verh. int. Ver. L i m n o l .

DIN 1502 Abkürzung: Verh. I n t e r n a t . Verein. L i m n o l .

Stuttgart 1991 v

E. Schweizerbart'sche Verlagsbuchhandlung , (Nägefe u. Qhermiller)

INTERNATIONALE VEREINIGUNG FÜR THEORETISCHE UND ANGEWANDTE LIMNOLOGIE

INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY

ASSOCIATION INTERNATIONALE DE LIMNOLOGIE THEORIQUE ET ÄPPLIQUEE

Verhandlungen • Proceedings • Travaux

Congress in Munich 1989

Volume 24 • Part 5

Edited for the Association by V . Sladecek and A . S ladeckovä

World List Abbreviation: Verh. i n t . Ver. L i m n o l .

D I N 1502 A b k ü r z u n g : Verh. I n t e r n a t . Verein. L i m n o l .

Stuttgart 1991 E. Schweizerbart'sche Verlagsbuchhandlung

(Nägele u. Obermiller)

Contents of Part 5

XII. Ecology of Aquatic Organisms. 2. Algae and Macrophyta (continued)

V A N DER D O E S , J. & K L I N K , F. J. : Excessive growth of Lemnaceae and A z o l l a in ditches observed by false colour teledetection 2683

K O K , C . J . & V A N D E L A A R , B. J.: Influence of p H and buffering capacity o n the decomposition of Nymphaea a l b a L . detritus i n laboratory experiments: A possible explanation for the inhibi t ion of decomposi­t ion at low alkalinity 2689

V A N D E N B R I N K , F. W . B., M A E N E N , M . M . J . , V A N DER V E L D E , G . & D E V A A T E , A . B.: The (semi-) aquatic Vege­

tation of still waters w i t h i n the floodplains of the rivers Rhine and Meuse i n The Netherlands: Historical changes and the role of inundation 2693

V A N V I E R S S E N , W . & H O O T S M A N S , M . J. M . : O n the or ig in of macrophyte population dynamics during lake recovery aftereutrophication 2700

H O O T S M A N S , M . J. M . & V A N VIERSSEN, W . : Computer simulations of macrophyte population dynamics during lake recovery after eutrophication 2703

C O O P S , H . & SMIT, H : Effects of various water depths o n Scirpus m a r i t i m u s L . : Field and experimental ob-servations 2706

C L E V E R I N G , O . A . & v. G U L I K , W . J . M . : The establishment of Scirpus lacustris ssp. lacustris and S. m a r i t i m u s i n the northern Delta area, The Netherlands 2711

G A C I A , E . & BALLESTEROS, E. : T w o methods to estimate leaf product ion i n Isoetes lacustris L . : A critical assess-ment 2714

V I A R O L I , P. & F U M A G A L L I , I.: Regeneration of dissolved reactive silica during decomposition of recalcitrant plant tissues in temporary shallow-water environments 2717

B R E E N , C . M . & S T O K M A N N S , C . - H : Observations o n the growth and production of Cyperus papyrus L . in a sub-tropical swamp 2722

XII. Ecology of Aquatic Organisms. 3. Animals

M E I S T E R F E L D , R.: Vertical distribution of Difflugia b y d r o s t a t i c a (Protozoa, Rhizopoda) 2726 O C A N A , A . & P I C A Z O , J. S.: Study on nematode species encountered i n the Monach i l River (Granada,

Spain): Response to organic pol lut ion 2729 W A R N E R , B. G . & C H E N G A L A T H , R.: H a b r o t r o c b a angusticollis (Bdelloidea, Rotifera): A new paleoecological

indicator in Holocene peat deposits i n Canada 273 8 D E M A N U E L , J.: Distr ibution of Brachionidae (Rotifera: Monogononta) i n Spanish reservoirs 2741 E S P A R C I A , A . , A R M E N G O L , J., V I C E N T E , E . & M I R A C L E , M . R.: Vert ical distribution of Anuraeopsis species as

related to oxygen depletion in two stratified lakes 2745 W A L Z , N . & R O T H B U C H E R , F . : Effect of food concentration on body size, egg size, and population

dynamics of B r a c h i o n u s a n g u l a r i s (Rotatoria) 2750 C A R M O N A , M . J. & SERRA, M . : Comparative total protein and demographic patterns of mictic and amictic fe-

malerotifers 2754 R O T H H A U P T , K . O . : The influence of toxic and filamentous blue-green algae on feeding and population

growth of the rotifer B r a c h i o n u s r u b e n s (Abstract) 2760 M A T V E E V A , L . K . : Can pelagic rotifers be used as indicators of lake trophic State? 2761 B O N A C I N A , C , B O N O M I , G . , D i C O L A , G . & M O N T I , C : A n improved model for the study of population

dynamics in Tubifex tubifex (Oligochaeta, Tubificidae) 2764 V I J V E R B E R G , J . & K O E L E W I J N , H . P.: Size dependent mortal i ty and production of D i a p h a n o s o m a b r a c h y u r u m

( L I E V E N ) in an eutrophic lake 2768 H E R Z I G , A . & A U E R , B.: The feeding behaviour of Leptoäora k i n d t i and its impact on the Zooplank­

ton Community of Neusiedler See (Austria) (Abstract) 2772 SIEBECK, O . & B Ö H M , U . : U V - B effects on aquatic animals 2773 D U N C A N , A . & DOS SANTOS, L . C : C o h o r t analysis i n three species of D a p h n i a in the London reser­

voirs 2778 G E R R I T S E N , J. J.: The influence of phosphorus-limited grown algae on grazing of D a p h n i a m a g n a

(Abstract) 2783 G A B R I E L , W . & T A Y L O R , B. E . : Opt ima l resource allocation in cladocerans 2784 G I A N I , A . : The nutritive value of different algae as food for two D a p h n i a species 2788

X X X V I

F U H L E N D O R F , D . C : Measuring seasonal patterns of food l imitat ion in D a p h n i a - an experimental study . . . . 2792 B E R B E R O V I C - J U N G E , R.: Starvation resistance of two coexisting D a p h n i a species under temperature con-

ditions simulating vertical migration behaviour (Abstract) 2794 G L I W I C Z , M . Z . : F o o d thresholds, resistance to starvation, and cladoceran body size 2795 W O L F , H . G . & W E I D E R , L . J.: D O life-history parameters of D a p h n i a as determined i n the laboratory cor-

rectly predict species successions i n the field? 2799 T O L L R I A N , R.: Some aspects i n the costs of cyclomorphosis i n D a p h n i a c u c u l l a t a 2802 R I N G E L B E R G , J.: The relation between ultimate and proximate aspects of diel vertical migration i n D a p h n i a

hyalina 2804 L E H T O V A A R A , A . & S A L O N E N , K . : D i e l vertical migration of D a p h n i a longispina in a humic lake wi th steep

thermal and oxygen stratification (Abstract) 2808 G O R B I , G . , PARIS , G . M . , M O R O N I , F . & B A C H I O R R I , A . : Differences i n population dynamics of D a p h n i a m a g n a

clones 2809 B A C H I O R R I , A . , ROSSI , V . , B O N A C I N A , C . & M E N O Z Z I , P. : Enzymatic variability of a colonizing population of

D a p h n i a o h t u s a K U R Z (Crustacea, Cladocera) i n Lake O r t a (Italy) 2813 ROSSI, V . , R O Z Z I , M . C . & M E N O Z Z I , P. : Life strategy differences among electrophoretic clones of Heterocypris

i n c o n g r u e n s (Crustacea, Ostracoda) 2816 C H A P M A N , M . A . , G R E E N , J . D . & N O R T H C O T E , T . G . : The enigma o t D i a p t o m u s c o n n e x u s (Copepoda) i n M a -

honey Lake: O n e or two populations? (Abstract) 2820 H A R T M A N N , H . J.: In situ predation on planktonic ciliates by copepods, measured w i t h diffusion exclosures

(Abstract) 2821 F E R R A R I , I., F A R A B E G O L I , A . , P U G N E T T I , A . & S T E L L A , E . : The occurrence of a calanoid Australasian species,

Boeckeila t r i a r t i c u l a t a ( T H O M S O N ) , i n fish ponds of N o r t h e r n Italy 2822 M A L Y , E . J.: Dispersal ability and its relation to incidence and geographic distribution of Australian

centropagid copepods 2828 B U R N S , C . W . & X u , Z . : Ut i l i za t ion of cyanobacteria (blue-green algae) as food by freshwater calanoid co­

pepods (Abstract) 2833 V I L L A L O B O S , L . & Z U N I G A , L . : Latitudinal gradient and morphological variability of copepods in Chi l e :

BoeckellagracilipesDADAY 2834 W Y N G A A R D , G . A . : Evidence of food l imitation i n a subtropical copepod population 2839 E L G M O R K , K . : Winter reproduction strategies i n freshwater cyclopoids 2844 H A L V O R S E N , G . : The ecology of Cyclops a b y s s o r u m t a t r i c u s K O Z M I N S K I i n N o r w a y (Abstract) 2847 V A N D E N B O S C H , F . & G A B R I E L , W . : The impact of cannibalism on the population dynamics of cyclopoid

copepods 2848 SANTER, B . : The role of food l imitation i n summer diapause of cyclopoid copepods (Abstract) 2851 A D R I A N , R.: The feeding behaviour of Cyclops kolensis and C v i c i n u s (Crustacea, Copepoda) 2852 G R O S S N I C K L E , N . E . : Comparative feeding study of the Opossum shrimp, Mysis r e l i c t a , in Trout Lake,

Wisconsin, U S A , Lake Pääjärvi, F inland, and Lake Jonsvatn, N o r w a y 2864 Y O U N G , L . B . & H A R V E Y , H . H . : The influence of lake p H and crayfish size on carapace elemental compo-

sition in O r c o n e c t e s spp. and C a m h a r u s spp 2869 C H A I S E M A R T I N , C : Respiratory rates and adenylate energy charge in healthy and parasitized muscles of cray­

fish (A u s t r o p o t a m o b i u s p a l l i p e s ) 2873 S C H M I D T - H A L E W I C Z , S. & B A U E R , J.: Response of the macroinvertebrate Community in N T A - , phosphate-

and copper-charged freshwater ponds 2877 A L L A N , J . D . , F L E C K E R , A . S. & K O H L E R , S. L . : D i e l changes in epibenthic activity and gut fullness of some

mayflynymphs 2881 Z W I C K , P.: G r o w t h and emergence of L e u c t r a p r i m a (Plecoptera): Habitat - species interactions 2886 N E U M A N N , P. : The egg development of Brachyptera s e t i c o m i s (Insecta, Plec.) (Abstract) 2891 R U P P R E C H T , R. & F R I S C H , S.: The sensitivity of N e m u r e l l a p i c t e t i i (Insecta: Plecoptera) to acidity 2892 M A L M Q V I S T , B . : Stonefly functional responses: Influence of Substrate heterogeneity and predator interac-

tion 2895 A U R I C H , M . , W A G N E R , R., R E D E R , E . & V E I T H , R.: Defensive behaviour of the larva of A p a t a n i a fimhriata

(PICTET) (Abstract) 2901

M U O T K A , T. : Life history patterns of R h y a c o p h i l a o b l i t e r a t a in northern Finland (Abstract) 2902 J A C K S O N , J . K . & R E S H , V . H : Use of cellulose acetate electrophoresis to examine population gene-

tics of the caddisfly Helicopsyche borealis 2903 E R L A N D S S O N , A . : G r o u p dynamics i n the water cricket Velia caprai (Hemiptera) 2908 G I S L A S O N , G . M . & J Ö H A N N S S O N , V . : Effects of food and temperature on the life cycle of S i m u l i u m

v i t t a t u m Z E T T . (Diptera: Simuliidae) i n the River Laxa, N-Iceland 2912

X X X V I I

R E I D E L B A C H , J . : Studies on population dynamics of blackflies (Diptera: Simuliidae) i n a grassland stream (Abstract) 2917

SMIT, H . , K L A R E N , P . & S N O E K , W . : Lipiniella a r e n i c o l a S H I L O V A (Diptera: Chironomidae) on a sandy flat i n the Rhine-Meuse estuary: Dis t r ibut ion, population structure, biomass and production of larvae in relation to periodical drainage 2918

H E I N I S , F. : The relation between oxygen regimes and distribution patterns of the larvae of Ch i ronomi­dae (Abstract) 2924

C U R E , V . : Structure and ecological role of phytophilous chironomids from some Danubian ecosystems in Romania 2925

S A V A G E , H . M . , R E J M Ä N K O V Ä , E . , A R R E D O N D O - J I M E N E Z , J . L , R O B E R T S , D . R. & R O D R I G U E Z , M . H . : Prel iminary

l imnological and botanical characterization of larval habitats for two primary malarial vectors, A n -opheles a l b i m a n u s and A n . p s e u d o p u n c t i p e n n i s , in coastal areas of Chiapas State, Mexico (Abstract) . . . . 2930

W O L F , B. A . M . : Some aspects of the nutrit ional ecology of a detritus-feeding Diptera larva: Ptychoptera p a -l u d o s a (Abstract) 2931

Y A M E O G O , L . , C A L A M A R I , D . , G R U N E W A L D , J . & F A I R H U R S T , C . P.: The aquatic monitoring and bioassay com-

ponent of the W H O Onchocerciasis C o n t r o l Programme in West Afr ica 2932 A L O I , J . E . & B R Ö N M A R K , C : Effects of snail density on snail growth and periphyton 2936 J O K I N E N , E . H . : The malacofauna of the acid and non-acid lakes and rivers of the Adirondack M o u n ­

tains and surrounding lowlands, N e w Y o r k State, U S A 2940 D O R G E L O , J . : G r o w t h , food and respiration i n the prosobranch snail Potamopyrgus j e n k i n s i (E. A .

S M I T H ) (Hydrobiidae, Mollusca) 2947 Y I P P , M . W . : The relationship between hydrological factors and distribution of freshwater gastropods i n

H o n g K o n g 2954 R I C C A R D I , N . , M A N G O N I , M . & P I V A , A . : The elemental (C , H , N , O , S) and biochemical composition of

Unio m a n c u s (PFEIFFER) and A n o d o n t a cygnea L 2960 T O K E S H I , M . : Aggregation, habitat characteristics and species coexistence (Abstract) 2964 F R A N C E , R . L . & W E L B O U R N , P . M . : Abundance of R a n a c l a m i t a n s tadpoles in Canadian Shield lakes 2965 M E I L I , M . : In situ assessment of trophic levels and transfer rates i n aquatic food webs, using chronic

(Hg) and pulsed ( C h e r n o b y l 1 3 7 C s ) contaminants 2970

XIII. Sediments

C U R T I S , P . J . : P and Fe release f rom anoxic Precambrian Shield lake Sediments mediated by addition of Fe(II)-insoluble and Fe(II)-soluble bases 2976

R O W A N , D . J . & K A L F F , J . : The l imnological implications of catchment sediment load 2980 C A R A C O , N . F. , C O L E , J . J . & L I K E N S , G . E . : Phosphorus release from anoxic Sediments: Lakes that break

therules 2985 N O R T O N , S. A . , V E R T A , M . & K A H L , J . S.: Relative contributions to lake sediment chemistry by atmo-

spheric deposition 2989 E K H O L M , P. , Y L I - H A L L A , M . & K Y L M Ä L Ä , P. : Avai labi l i ty of phosphorus in suspended Sediments

estimated by chemical extraction and bioassay 2994 H U P F E R , M . & U H L M A N N , D . : Microb ia l ly mediated phosphorus exchange across the mud-water interface . . . 2999 K J E N S M O , J . : Bio-geochemical composition of recent Sediments from the mixo- and the monimol imnion of

Lake Svinsjoen 3004 H O R I , R. , H j . I K H S A N , S. B I N , W O O D , A B D . K . BIN & A B U B A K A R , M D . Y . B I N : Neut ron activation analysis of

the sediment of Kelang River , Malaysia 3009 SAGER, M . : Detection of environmental mobilities of nutrients and heavy metals in Sediments 3012 O S B O R N E , P . L . & T O T O M E , R. G . : Sediment deposition in Lake K u t u b u , Papua N e w Guinea 3018 T A T U R , A . , D E L V A L L E , R. & P A Z D U R , M . : Lake Sediments in maritime Antarctic zone: A record of land-

scape and biota evolution: preliminary report 3022 G O L T E R M A N , H . L . : Influence of FeS on denitrification in shallow waters 3025 D E G R O O T , C.-J.: The influence of FeS on the inorganic phosphate System in Sediments 3029 K O Y A M A , T . : Biochemical reduction process in the lake sediment-water interface. O n the basis of

laboratory experiments 3036 M A R X S E N , J . & F I E B I G , D . : Measurement of bacterial production in stream-bed Sediments (Abstract) 3044 T O M A S Z E K , J . : Oxygen consumption by bottom Sediments 3045 W A S M U N D , N . : Microautoradiographic determination of the viabil ity of algae in deep sediment layers (Ab­

stract) 3050 A N D E R S E N , F . 0 . & J E N S E N , H . S.: The influence of chironomids on decomposition of organic matter and

nutrient exchange i n a lake sediment 3051

X X X V I I I

I W A K U M A , T . & O T S U K I , A . : Role of chironomid larvae in reducing rate of nutrient release from lake sediment: Evaluation by a mathematical model 3056

S C H R O E D E R , F., K L A G E S , D . & K N A U T H , H . - D . : Contributions of Sediments to the nitrogen budget of the Elbe

estuary 3063 K E R N E R , M . : The coupling of microbial respiration processes w i t h i n the two-dimensional spatial structure

of an intertidal mud flat sediment of the Elbe Estuary 3067 W I L T S H I R E , K . H . : Experimental procedures for the fractionation of phosphorus in Sediments with emphasis

on anaerobic techniques 3073

XIV. Received too late for Classification

H E R R M A N N , J . : Bioindication of nutrient and organic pol lut ion by benthic stream invertebrates - pitfalls and problems (Abstract) 3079

M U N A W A R , M . , L E P P A R D , G . G . & M U N A W A R , I. F.: Ecotoxicology of stressed environments: Structural and functional strategy 3080

W A R D , J . V . & S T A N F O R D , J.: Benthic faunal patterns along the longitudinal gradient of a R o c k y Mountain river System 3087

O V E R B E C K , J.: Plenary lecture: Initial, present and future aim of l imnology 3095

Societas Internationalis Limnologiae: Twenty-Fourth Congress, Munich/Federa l Republic of Germany, 1989 3102

Officers and list of members 3137 Contents of volume 24 (completely) (1)

Verh. Internat. Verein. L i m n o l . 24 2 8 4 8 - 2 8 5 0 Stuttgart, Dezember 1 9 9 1

The impact of cannibalism on the population dynamics of cyclopoid copepods

Frank van den Bosch and Wilfried Gabriel

Introduction

Predation is one of the key factors in the dynamics of Zooplankton communities ( K E R F O O T 1980) . Therefore, it is important to improve the knowledge on the popula­t ion dynamics of predacious species. Intraspecific preda­tion (cannibalism) may strongly determine the demog-raphy of a population and thereby influence the whole Community structure. It has been supposed that can­nibalism, which is a widespread phenomenon (POLIS 1981) , can be advantageous i n cyclopoids ( G A B R I E L & L A M P E R T 1985) , especially to overcome periods of food limitations ( G A B R I E L 1 9 8 5 , V A N D E N B O S C H et al. 1988) . In

this paper we further explore the influence of can­nibalism on the population dynamics of cyclopoids.

Method and model description

Modelling methodology Physiology and behaviour of copepods change drastic-ally during development. Therefore, a realistic model has to treat the various life stages separately. Building a multi-compartment model w i t h ordinary differential equations is an insufficient approach since Information on age structure wi th in each compartment is lost. The stage-structured population modelling methodology overcomes this problem (NISBET & G U R N E Y 1 9 8 6 , and references therein).

The model Here we give a short verbal description only. M o d e l equations w i l l be published elsewhere and are available on request.

Prey p o p u l a t i o n : The prey population grows logistic-ally in the absence of predators. Predation causes a cer­tain mortality rate.

Predator demography: Here we keep the environment constant and assume that there is no food shortage for the herbivorous stages. W e subdivide the cyclops pop­ulation into six stages: eggs, nauplii , copepodite I and II, copepodite III and I V , copepodite V , and the adults. The mathematical treatment of individuals in each stage can be visualized as particles moving on a conveyer belt (ex-cept the adults). W e discuss the copepodite I/II stage as an example. A n individual maturating out off the nauplii

stage, i.e. recruiting into the C I / I I stage, is placed o n the left hand side of the conveyer belt. The conveyer belt moves the individuals to the right. This movement re-presents aging. D u r i n g this aging individuals can die. Be-sides cannibalism as death factor, we assume a stage de-pendent but constant mortality rate. Individuals w h i c h are alive at the end of the conveyer belt fall onto the next conveyer belt, i.e. they mature out off the C I / I I stage. The length of the conveyer belt represents the stage duration.

Predation a n d c a n n i b a l i s m : Adults and copepodite V are predators and cannibalize nauplii and copepodites of stage I/II. Predation and cannibalism have H O L L I N G type II functional responses (multi-prey-type functional re-sponses, M U R D O C H & O A T E N 1975) .

P r e d a t o r reproduction: Depending on its biomass, each prey or conspecific individual eaten supplies the adult a certain amount of energy which is converted into off spring.

Calibration of the model The model was calibrated to describe Cyclops a b y s s o r u m , a highly predacious and cannibalistic species. Stage dura-tions correponding to 12 ° C where obtained f rom the l i -terature. Parameters of the functional responses, bio­mass of various stages and of prey items and the conver-sion efficiency of food eaten into offspring are calculated from laboratory measurements ( V A N D E N B O S C H & S A N T E R in prep.). D a p h n i a h y a l i n a has been used as a re-presentative prey species. Since death rates and carrying capacity of prey are u n k n o w n we performed runs with several combinations of values for these parameters.

Results and discussion

To study the consequences of cannibalism on pop­ulation dynamics we performed a series of runs for various degrees of cannibalistic activity. To this end we multiply the experimentally determined attack rates of the predators on conspecifics with a factor C which can take values between zero and one. Zero means no cannibalism, one means the cannibalistic activity as measured in the lab, other values represents a reduced degree of cannibalism.

0368-0770/91/0024-2848 $ 0.75 © 1991 E. Schweizerbart'sche Verlagsbuchhandlung, D-7000 Stuttgart 1

F. van den Bosch & W . Gabriel , Impact of cannibalism on population dynamics 2849

80

40

40

40

0

-Mi 1 h i i i i

h B

i i i c

-

i i i

\ 0

f i i i 0 2000 4000

time (days)

Fig. 1. T ime course of the prey and predator population densities for various degrees of cannibalistic activity of the predator. Continuous line: Prey. Dashed line: Pre­dator nauplii . Dotted line: Predator adults. A : no canni­balistic activity of the predator (C = 0). B: attack rates of the predator on conspecifics is 0.4 times the value meas­ured in the lab. (C = 0.4). C : attack rates 0.6 times the measured values (C = 0.6). D : attack rates equal to the measured ones (C = 1).

longer time compared to füll cannibalistic activity. (ii) The System shows cyclic fluctuations with a smaller amplitude than in the non-cannibalistic case.

Fig. 2 summarizes a large number of runs with the same parameter values as in Fig. 1. Leaving out the first parts of the runs where the populations are not yet at there "final behaviour", the maxi-mum and minimum population density of prey, nauplii and adults are plotted for each run depen-dent on the degree of cannibalism (C). The figure shows the gradual change from predator-prey os-cillations with large amplitudes to stable equilibria as the degree of cannibalism increases.

The model presented here is, as any model, an oversimplification of reality. It, however, enables

Fig. 1 shows a characteristic series of runs. With-bout cannibalism (C = 0) the model gives the well known predator-prey oscillations. The prey and all stages of the predator show stable cyclic changes with an approximate period of 500 days. The predator lags behind the prey by approx-imately one quarter of a period. When canniba­listic activity is put to the values measured in the laboratory (C = 1) the population rapidly con-verges to a stable equilibrium, i.e. no changes in density or composition of the population. For de­grees of cannibalism other than zero or one there can be two kinds of behaviour: (i) The System con-verges to a stable equilibrium, but this takes a

relative cannibalistic activity, C

Fig . 2. M a x i m u m and m i n i m u m population densities of prey (a), predator nauplii (b), and predator adults (c), (for the " f ina l behaviour") as a function of C (cannibalism at­tack rates in the Simulation = C times cannibalism at­tack rates measured in the lab.).

2850 X I I . Ecology of Aquatic Organisms. 3. Animals

us to study possible population dynamical con-sequences of cannibalism. In the laboratory or in the field, such investigations would be extremely difficult if not impossible. Further research on this is needed before we can generalize our findings. In the light of the present results we can pose the hypothesis at least in the case of Cyclops abys-sorum: Cannibalism is a stabilizing mechanism ca-pable of suppressing or even completely elim-inating predator-prey oscillations.

Acknowledgements

W . G . is grateful to the "Nederlandse Organisatie voor Wetenschappelijk Onderzoek" ( N . W . O.) and F. V D . B. to the Max-Planck-Gesellschaft for financial support.

References

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G A B R I E L , W . & L A M P E R T , W . , 1985: C a n cannibalism be

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Authors ' addresses:

F . v. D . B O S C H , Institute of Theoretical Biology, P . O . Box 9516, NL-2300 R A Leiden, The Nether­lands. W . G A B R I E L , Max-Planck-Institute for L imnology , Department of Physiological Ecology, P . O . Box 165, D - 2 3 2 0 P l ö n , F R G .