Translation Series No.1592

t(bRCHIVES

FISHERIES RESEARCH BOARD OF CANADA Translation Series No.1592

Progress in Shorygin's investigations on food habits and food relations in fiSh (from "Problems of commercial hydrobiology")

By M. V. Zheltenkova

Original title: Raboty A.A.'Shorygina po issledovaniyu pitaniya i pishchevykh otnoshenii ryb i razvitie etikh issledovanii ("Problemy Promyslovoi Gidrobiologii".)

From: Trudy Vsesoyuznogo Nauchno-Issledovatel'skogo instituta Morskogo Rybnogo Khozyaistva i Okeanografii (VNIRO) (Proceedings of the All-,Union Research Institute of Marine Fisheries and Oceanography). Publ. by Pishchevaya Promyshlennost, Moscow, Vol. 65, p. 26-40, 1969. Translated by the Translation Bureau( JP) Foreign Languages Division Department of the Secretary of State of Canada

Fisheries Research Board of Canada Biological Station, St. Andrews, N.B. Marine Ecology Laboratory,.Dartmouth, N.S. 1970

42 pages typescript OEPARTMENT OF THE SECRETARY OF STATE SECRÉTARIAT D'ÉTAT TRANSLATION BUREAU BUREAU DES TRADUCTIONS FOREIGN LANGUAGES DIVISION DES LANGUES DIVISION '77" ÉTRANGÈRES

.TRANSLATED FROM - TRADUCTION• DE INTO - EN

Russian English

AUTHOR - AUTEUR

Zheltenkova, M. V.

TITLE IN ENGLISH - TITRE ANGLAIS Progress in Shorygin's investigations on food habits and food relations in fish. Title in foreign language (transliterate fe-reign characters.) • Raboty A. A. Shorygina po issledovaniyu pitaniya i pishchevykh otnoshenii ryb i razvitie etikh issledovanii.

R5FRENCE IN FOREIGN I,ANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE FOREIGN CHAIRACTERS. REFERENCE EN LANGUE ETRANGÉRE . (NOM DU LIVRE OU PUBLICATION), AU COMPLET.TRANSCRIRE EN CARACTERES PHONETIQUES. Trudy Vsesoyuznogo nauchno-issledovatel'skogo instituta • morskogo rybnogo khozyaistva i okeanografii (VNIRO)

REFERENCE IN ENGLISH - RÉFRENCE EN ANGLAIS Proceedings of the A11/Union Research Institute of Marine Fisheries and Oceanography PUBL ISH ER - ÉDITEUR PAGE NUMBERS IN ORIGINAL DATE OF PUBLICATION NUMÉROS DES PAGES DANS DATE DE PUBLICATION L'ORIGINAL Pishchevaya Promyshlenost YEAR ISSUE NO. 26 - Affl VOLUME PLACE OF ANNEE NUMÉRO PUBLICATION NUMBER OF TYPED PAGES LIEU DE PUBLICATION NOMBRE DE PAGTS DACTYLOGRAPHIEES Moscow 1969 65 4'2

REQUE.STING DEPARTMENT Fisheries and Forestry TRANSLATION BUREAU NO. 2015 MIN ISTERE-CLIENT NOTRE DOSSIER NC) Fisheries Research Board BRANCH OR DIVISION TRANSLATOR (INITIALS) DIRECTION OU DIVISION 134olslgical Station TRADUCTEUR (INITIALES) J.P.

PERSON eEQUESTING DATE SOMPLETED DEMANDE PAR Dr. A. V. Tyler NOV 1 7 1970 ACHEVE 1. INED1TLD DRAl-T 1

YOUR NUMBER Only for information • 769-18-14 VOTRE DOSSIER N 0 TRADUCTION NON REVIS4 Information seulemere DAT E OF REQUEST DATE DE LA DEMANDE 15 July 1970

505-200.10.6 (R EV. 2/681 , feeg j2: V DiPARTMENT OF THE SECRETARY OF STATE SECRÉTARIAT D'ÉTAT TRANSLATION BUREAU • BUREAU DES TRADUCTIONS FOREIGN LANGUAGES DIVISION DIVISION DES LANGUES ÉTRANGÈRES. •

CANADA

CLIEN1"S NO. DEPARTMENT DIVISION/BRANCH CITY No DU CLIENT MINISTERE DIVISION/DI RECTION VILLE Fisheries Research Board 769-18-14 Fisheries and Forestry Biological Station St. Andrews, N.B

BUREAU NO. LANGUAGE TRANSLATOR (INITIALS) DATE No DU BUREAU LANGUE TRADUCTEUR (INITIALES) 'NOV 1 7 1970 2015 . Russian J.P.

Progress in Shorygin's investigation on food habits and food relations UNEDITED DRAFT TRANSLATION in fish. Only for heonneon TRADUCTION Zheltenkova, M. V. NON REVISÉE Information soulement For almost 10 years, beginning in 1935, A. A. Shorygin was

engaged in the study of the food habits and food relations of fish

and directed a group of coworkers which assisted in thèse efforts.

• The work was conducted at the laboratory of the food base and commercial

invertebrates VNIRO, which at that time went under the name of benthos

laboratory and later was called the laboratory of hydrobiology.

All investigations by A. A. Shorygin into the sphere of

food habits and food relations of fish were linked to the Caspian

Sea, mostly with fish feeding on benthos. The doctorate dissertation

and four special articles by A. A. Shorygin were devoted to these

investigations. Besides this, in his last article inmereW "0 he.ere4 biotsenozakh" (About biocoenoses),4a loattern for catching sea fish

according to their type of food habit.

The doctorate dissertation "Food habits and'food relations

of fish of the Caspian Sea" was defended by A. A. Shorygin in 1939.

The dissertation was prepared for print and published in 1952 after

the death of A. A. Shorygin; articles devoted to these problems were

publishèd during the lifetime of A. A. Shorygin in the

SOS-200-10-31 • period from 1939-1948. The article "0 biotse-

nozakh" (Of biocoenosese was published peieelumbué 1955. (Shorygin, 1939a, 1946, 1948, 1948a, 1952, 1955).

In his dèssertation A.A. sworyelnl made a" aarveY of all basic investigations'at tilome and abroad into te food

habits and food relations of fish; he .listed :bout 1500 titles (Shorygin, 1939). Shorygin examined' the basic methods and directions of these investigations, cCndacted an analysis of food habits of 19 species. of fish of the Caspian Sea, and after devising a method of quarititative analySià or food: relations ti$) of fish he investigated the dynamics'of food - comPetitlon of . fish of . the Caspian Sea and peculiarities- of utilizatiOn 'Of ivailable .food reserves. •

Shorygin . introduced . quantitative indioes of food Selecti-.; vity, food competition and food plasticity, feeding-activity and food potential of fish.

. While comparing the index values of food selectivity and the role (according to % Of weight) Of different organisms in the food of fish,Shorygin came to the conclusion that it is necessary to differentiate between categories-of food

organisms, of fish which should be based on the preference for

certain . .. food by the fish 'as well as on its cance as fish food. After inVestigating 5 categories of fish food, suggested by . Schiemehz (1905, 1924) ShorYgin - (1939, 1939a, 1952) introducéd'6'categories of.fifh food —' 3 according to preference (favourite, substitute, enforced)' • 3 . and the same number according to actuai importance (main food, secondary and incicbùfta1Y2. It was found that under natural conditions favourite organisms are often unavailable to the 'fish and its main food consists of substitute organisms. While investigating the comp&tition for food by fish iborygin (1939-1952) distinguished between 3 indices — volume, intensity and strength of competition. The strength of competition consists of the product of the volume of competitionby

the intensity of competition, so that its numerical value is more constant than that of either of its components. An analysis of the regularity which governs the change of these three values showed how the food competition softens, how species exit from food competition and how in some cases food competition'changes from one that can be observed into a potential form. According to A.A. Shorygin, the outcome of competition for food betweenitwo species of fish is subject to the magni- tude of their feeding activity ( ability to remain on prefe- rential food) and food plasticity (ability to change the food spectrum with changing external conditions). The food potential of fish is the product of feeding activity by the food plasticity.

Shorygin also confirmed from factual material under natural conditions by analyzing the food competition of fish of the easpian Sea Darwin's proposition that competition is fiercest betwein closely related forms. Tn the Caspian Sea,

as a rule, the more numerous fish belonging to the same or closely related genus have different types of feeding; while 'the basic food of one or the other species consists of a li- mitted number of organisms (2-3 organilims). The same was found

to be the case for fish with the same typelof feedihg-- carniuo--v rous, planktonfeeding and benthosfeeding fish of the Caspian Sea. This is caused by food competition which leads to

dispersion into different feeding niches of those forms which are . genetically or ecologically close to each other. The same phenomenon can be observed in fish of other seas, as shown by Shorygin (1955), which points to the limitation of food resources and to the competition for thee by the fish. It is also of significance that the main catch in . each separate Water

reservoir consists generallylof a limited number of species. Shorygin investigated 22 instances of citches in sea reservoirs and found thatrspecies of fish make up about 84% of the catch (the total number'of counted àpecies fluctuated from 10 to 118) e.g., 4% of species make up more than_4/5 of the catch of sea fish, but 96% of species of commercial fish pro— vide only 16% of the catch. (Shorygin, 1955).

Having provided a method of numerical evaluatioh of ' the feeding activity, feeding plasticity and the food potential of fish, Shorygin showed that the sturgeon and the seeryuga of the Caspian Sea are noted

for their high feeding activity and high food plasticity, the bream is noted for high feeding activity and low food plasticity, the Caspian roach on the other hand has loW activity and high food plasticity. On the basis of these observations Shorygin (1939, 1952)advanced the proposition that it is advisable to promote the breeding of the sturgeon

type of fish in the Caspian Sea, because they have high feeding activity and plasticity and as a result of a high food potential will be able to withstand successfully the competition with other species of fish as well as to stand against

the unfavourable reactions to the changing hydrological condi-

tions of tpdhe Caspian Sea. The works of Shorygin have a high theoretical signifi- -- canoe. In the case of the fish of the Caspian Sea there were developed, for the first time in the history of science,quantitative indices Suitable for the study of food compétition of living organisms under natural conditions.' These studies are also an important contribution to the fish industry, because they represent a pattern of investigations of the food habits and food relations of fish which could be carried out in water reservoirs of any type and which would have for its aim the discovery of ways in which a rational fish econimy could be built. The conclusions of Shorygin have also an immediate

practical value, because they establish the i'egularities which.' .

'underlie, the formation of the fish :Wealth of the Caspian Sea .and also show the direction of the most effective management of the natural resources of thie SPa for the fish industry.

The latest studies by Shorygin were made more thanr 20 years ago, and the fundamental propositions in the,area'of research:into the food habits and food relatidns of fish were formulated by smoi him more than 30 years agc. Naturally, the question arises w4ether'the propositions advanced by Shorygin ,have not lost their significance today and in what direction'these problems are nowbeingdeveloped.,r,

Shorygin's.conclusion that the most reliable charac-

teristic of fish food under natural conditions is obtained by the weight analysis of the contents of the alimentary canal of fishfollowed up by the formulation of indices and also enlisting the help of available experimeatil work continues

to remain important even at present. The weight method of investigating the feeding.of fish, worked out by Zenkevich

(1931) and BrotskaYa (1939) for benthoefeedingi fish and Bogo-

rovi (1934) for plankton feeding fish is recommended in the. instructions (Pirozhnikov, 1953) and manual for the research• into the feeding . of fish (1961) and Is UsedAn a great number of studies. The calculation of the yearly fish rations, which was accepted by Shorygin on the baits Of the experimental. work of Bokova (1939), .Karpevich C19401, grivebak (1942) is used, 'for examine by BirStalt..(19521, Zbeltele (1955, 1961). ShorYgles -evaslasionae-the advisability of intensified . breeding of the ettreeva .type of 'labia the 7.

Caspian Sea is accepted at present by rthose researebers ,who

on problems of reconstruction of the fish. industry of the Caspian Sea.(Ya4lonskaya, 1964; Kozhin, 1964). Due to the

• ) r develOpMent of acclimatized - c1s.epiorM(Nereis)ahel endesmia and the change of conditions in the . Northern Caspian bea this conclusion becoies even more- ..- •

important. . •

After development by ShOrygin•ofbquantitative indict«, of food relations in fish there app,..eated in the U.S.S.R.., large number of investigationsin which . these methodv were applied . to different species of fish.. In - most of these_stu- dies a.tally is make of the selective ability of fish and

the volume of their food competition or the degree of food similarity and only in a considerably Smaller nimber of these

investigations isthere . a numerical eviluation of tension and strength of food competition.(according‘tOStorygin's termi- •

nology) and the food plasticitl and food activity of fish. A very large number of investigations with.the appli-

cation 'of indices introduced by Shorygin xere devcitede.to' . fish of the northern part of the Caspinn Sea. In the works

of 1;ronokov (1 952), Krasnovaya (1952 ), 1$1.1.kine (1952), Gorbn- nova 4nd Kosovaya (1961), Epshtein(19‘1) there are.given indices of selectivity and the degree of food similarity of the of CasPian roach,. bream, "sazasi" - (of the carp . ..family). young

In the studies .by Saenkova(1947) and Zheitenkova (1951) long term changes of the degree of food - obelerity Of mature J. . • Caspian roach and bream are given. Estensive studies in this direction were carried . out in 1948-1949, when the food habits of fish of the Northern Caspian Sa were investigated in connection with their utilization of nereis. Sokoleva (1952) determined the selective ability of the sturgeon and sevryuga. Reinrikh (1950) determined the volume, t . intensityand strength of the competition of "lope a nd idEiveyed /29 11 bream and t) • Deirstein (1952) determined the- volume, intensity and strength of . competition for the carp type, the sturgeon and gobies and the total strength t. of competition of benthos feeding, fish of the Northern Caspian Sea. It was found that with the chaele of some fish to feeding on nereis, the forage reserve ,:ws utilized by them more evenly than in 1935. In the Azov Seakogvinovich n95I) was the firat to:determine the 1948 volume of competition of planktonfeediseeish, Later,Petipa (1955) and Bokeva (1959) determined the degree of similarity of food of young fish,. Zheltenkova investigated the annual changes of food relations of drfferent and also of the same species . of bread, sea roacl3,and.vimba , of the Taganrog Bay, which she (Ltd wtth the help of the analysis of the degree of food eimilerity.' Kanaeva (1957) obtained the indices of food selectivity for percarinaafter " she had determined the degree of food similarity of the food of percarina, comparing it with the rest of the - representatives of the,ichtiefiuna of the Azov Sea and 9.

the quantity of food required by the percarina and also showed the part the percarina plays as a competitor with commercial fish.

The food relations of the brill, flounder, and sturgeon type of the Black Sea were studied by Martino and Kapapetkova

(1957). Burnashevyi (1960) determined the selective ability, volume, tension and strength of competition of 13 species of fish inhabiting various parts of the Shaholat Estuary.

In the Baltic Sea (Zheltenkova, 1953) .l an evaluation of the peculiarities of food relations of fish permitted discussion of the question of reviewing the minimal scale of fishery of the river flounder. At presev.t, Kostrichkina

(196 )-i , 1968) is carrying out investigations into the food plasticity of the fish in Riga Bay. In Kursk Bay during the period 1950 - 1957, Kublitskas (1959) investigated the food selectivity and food similarity of the food of fully grown fish, and Vashkevichyuta (1958) that of young fish.

Zheltenkova (1960) calculated the degree of food similarities of bream and roach of Kursk Bay in 1949.

In the Barents Sea, Briskina (1939) determined the food selectivity of non-commercial fish. Petrova - Grinkevich (1944) the degree of food similarity of cod and haddock; Tseeb and Zhabreva

(1958) investigated the food peculiarities of cod and haddock. In the White Sea ( Onezhskii Bay ), ((ova (1953)studied the food relations of navaga and stickle—. 0 back. The indices of Sh rygin — the index of food selectivity and of food similarity — are applied also in the' investigations of the Pacific ocean. Kun (1949) made use of these indices for herring, Mikulich (1954) 'and Skalkin (1959) for the flounder. Andreevskaya (1957, 1965) showed 081 the basis other

' investigations of food and food relation of the

sockeye, and keta salmon in the sea, that,in! the• years when t

the pink salmon , is increasing in numbers the intensity of feeding and the food composition of all thee species is changed and their emmirth rate. declines. . The indices of food similarity and food selectivity are applied to many investigations of food and food relations of fish in freshwater reservoirs, in particular in wàier sto- , rage reservoirs. In the studies by Chvankina (1955), Bol— dia (1960), Yakov1eva(156) and .Koge (1962) ,the indices of selectivity and food similarity are applied to the investi— o f Pankratova gation › fish food of the Volga storage reservoirs; (1948) determined the degree of similarity of food composition of sterlet and bream of the Middle Volga. Pirozhnikov;(1955) provided an index of food similarity for fish'in the ilVer

Lena; Li shev (1950) for fish iri ,thePhme › • In the work of Basikalova and Vilisova (1959) on the food habits of benthos fëediiigl fish in the Maloe Seà —'one of the regions of the Baikal — the indices of food seleCtivity 11.

and food sinalarïfy of fish and the division of fiit:fsod ' /30 inte cateeries was carried out and—calculated is,preposed by Shorygin, according to the availabiIity and.preeerence of food. The work of Patakuev (1954) was .deircted• to the food and food relations'of planktonfeeding fish of the esikal. In the work of Yaroshenko and others (1960) the food simi1a- water reservoir is gives. rity, of fish in the Dubossarskii Tamanskaya (1957) and Rachinskii (1954) made use of the indi-

ces of food selectivity and food simllarity.in the investigation of young fish in the fish industry. COmpariscin Of,the iarities of feeding, the rate of growth and quantity of

representativeS of the species Rutilus rUtilus.(L.) in •

different' types of water reservoirs und combining these with the ;

results of investigation of the feeding of the teach in the Northern Caspian Sea (Zheltenkeva, 1939, 1939a) g.rovideethe

grounds for the propositiofl. thai the character of the roach populations in the individual water - reiervoirs is explained

by the peculiarities of its -feeding and competitive relations.

.A particularly good state of population of roaches is observed in water reservoirs* rich in mollusks (Schiemenx 1910, NeUhaus 1936; .Greze, 1953; Westphalen 1956; Kempé 1962; Nebol'sina,

1965). This can be.eXplained by the faCt that'according to * their nature the roaches tend to occupy the most free nook in the water reservoir, thus escaping from the pressure of food competition with other species of fish,. in particular .

the bream (Zheltenkova,.1949). with The aboVe-'cited Instances do not-exhaast by far all

the werk in • Which food relations of fish are investigated: and where the namerical indices of.Shotygin are applied. ' Numerical indices of food relations are attracting . tle attention of researchers and they enter more and More into the practical work of our lish economy. The investigations of Shorygià and the various works

continued in this direction concur with'Ahe investigation Of food relations of fish which were carried:out by Nikal l skil .and his students.. G.V. .NikOl'skii (1947, 1949, 1953) demon-

strated how the relationsof freshwatele fish are-aggeavated and hoW they subside.among fish of the same as well as diffe-

rent species. In a detailed analysis of food relations of fish of •

the river Ili, AmxDaeyo_ and Pechora,G ..V. Nikoliskii estab-

lished that:among fish belonging to the same fauna complex. '

the -food intensftyiS lower than . among fish of:,differeut fauna complexes . The former may use similar oeganisms which belong to secondary oijects of their food, while w4ith the latter similar organisms may prove to constitute the main components of their food. For fish of the same fauna complex the Interisity of food relations may be diminished:because of the differenée in time and areas of the use of similar objects. The conflict of representatives of different fauna complexes which are ecologically close to each other may result in displacement

of one species by another. •

7-14 ; •

13.

Accordiag - i o NikoPskii thè intendity of food relations . of fish of different latitudes differs.. In tropical seas the

•intensity of food relations is higher than'in moderate climates ' r which results in• the forcing of many sene•rically matind fïsti into

fresh water. • •

In discussing the food relations of fish Nikol'skii . . and those researchers who follow his course use different

indices. In several works, in ,partieular those* oft Lishev. (1950), the numerical indices of Shorygin are applied. A number of propositions of Shorygin recelynd further

deeelopment in the studies of Ivlev (1955). Iviev investigated under eXperimental conditions the order which governs the. /31 ' food relations of fish. .Aé experimental objects he used young • carp and aquarium fish: "amiurus' i:, blue perch' and goldfish. • "P.he • increase.or decrease of the food ration and the change of food composition when the fish were kept either separately or together were used as indications of the influence of fish on each other.

'A very interesting fact .from the aspect, of the problems: -

discussed in this article, and which was slrio.W.n thbr, Iiiev, is • • .s; D that different fish • have a food potential

of differe'nt capacity, .and they thereforeieact dïfferently to the , • influence of competitors. In the investigations of Ivlev the more activéspecietturned out to be "amiurusr after that—in . diminishing order(the "trophic poientlal".as Ivlev calls. this

index) follows ..the-blue perch., young carp, goldfish. [•.,â RentiWth'iander experimental Conditions of food .relations of the young of bream, roach, .:Aâprek: ind Ileak from the ponds of the Aksai fish industry . (.ineltenkova, '1965) showed Also that different species . of fish - have

different feeding activity. Young :::aap , .; i.15 distinguished ,by the highest feeding'activityl; the young of bream bas a. lower feeding activity than the young of roach. In' the presence , of young "asp' H the character of. 'feeding Of the young roath is changed; the presence of yOung reach mny

erode the conditions under which young- bi. eeM gainic;g

we1ght. The principle of analyzing the peculiarities of food relations of animals, worked out on fish and derived from the

discussion of ichtyocoeàoses, was( élsd applied:by, Shorygip , n ‘y“1

, . 1 1 to the analysis of bottaivUenoerkosee.y" . These principles are applied widely in the Sovl.et Union in the investigation of bottom and plankton communities (see the article of Vinogradova, published• in

this collection). Material available at present shows that food relations originating because of the demand for common food resources and food competition is attracting the attention of Soviet ichtiologists as well as hydrobiologists. The discussion le

Shorygin of the quantum method of investigation of food com-

petition of fish permitted the lid.entillicat.don axid refinement of the

principles governing ihese phenomena and brought about

! great: number of workS dedicated to this problem.. 15.

The works of Shorygin on the' 4uantitative'evaltiation 6e food relatiOnsof fisl presents the loglçal .continuation of' preceding . investigations Of food and . food relations of fish carried out, partly, 'by Forbes (1888), Stbiementz (1910, Rlegvad (1932), where a quality evatUation of these phenomena was made. ' To obtain a complete view of the state of this problem it is necessary therefore to nnalyze the àevelopment of investigations carried out abroad in the food relations of fish, i.e., the , formulatiOn of the problem and the methods • of solving it.

Some idea about this can be obtgined from a.,discussion of works which have appeared in foreign literature in the last 20-25 years, e:g., for the same period that was discussed for the Soviet investigations. Before entering into a discussion of specific investigations, it will be necessary to look in detail at two investigations by Elton (1946) and Larkin (1956) as well.as the article by Weatherley (1963). Elton (1946) on the basis of analyzing the composition of 55 animal and 27 plant groùnd surface associations has shown that the basic mass of genera in the association is represented by one species(; 86% of animal genera and 84% of' plant genera). On thé whole,1.3% genera of an!- mais are represented by 4 species (investigated were 2221 genera represented by 2666 species). This is explained by the

fact that the associations exist on limited food resources.

. . • 4.- 1 • •.• • •. . In highly organized terrestrieZ . associations — steppe, meadow, forest, — there are-many edible .specieil whiCh results in a wide ecological differentiation. Aatie, eeiocia- tions, according to Elton, provide - ..r possibility f6i. species differentiation.. . • in the same - , Two'species of the -Some genus, living association, have a different ecOlogiçad.aspect, different- peculiarities of behaviour and feeding. Generally,one of the species Qf a given pair is more numerous than the other..• • Elton points out that ecological investigations are dedicated mostly to the vertical. organizetion of inimelt — the transition of energy from one level to another. There ,' are few "horizontal" investigatiOnsi.but lt,, iWilève/itheiess neee- ssary to know how common - resources are otilized by different species. Larkin (1956) dedicated a special investigation to the analysis of interspecies competition as a factor which determines the state of population of freshwater fish. Larkin points out that considerably fewer investigations are dedicated to the interspecies relations of freshwater fish than to the interspecies relations of surface animais. This can be explained, in his opinion, (whicl is the accepted

view following Elton) that in fresh water there is little variety in biotypes as compared with iterrestrià1 higher e lej animal forms; which impedes changes mil/fish formation. eish have a wide ecological spectrum, the requirements of different species overlap, and the fish themselves easily change their habits. Larkin shows that in the literature of ichtiology there are two main trends: some researchers consider that the state of fish population is determined by abiotical conditions: temperature, salinity, wind conditions, etc.; others attribute the main significance to biotic factors:

Predation, • parasitism, compétition. However, in connec- , tion with this food competition is usually: regarded as being intraspecific. In the patterns of Rikker, although there are introduced indices of different factors which depend on the density of popitlations, - interspeciet- - competbt.ion is not

taken into account, beciufe the changes 4n-density of 011. 1y

one .%pecies is investigated.- Larkin points 'Out that actually a number of peculiarities of the population of fresh-,

water fish ts due to interspeciee cempetitions • Defining, food competition as "the deMand of. *Ore than one organism in one and the same.resource medium in a volume which exceeds thèir immediate supply,r Larkin - points onthat interspecies competition'of fish shoulebe cénsidered in the discussion Of the state Of populations and that igeoring this phenomenon harms the theoreticalinvestigations set- tical measures. In connection with this Larkin also notes that these investigations are complicated and that there are

no methods of quantity evaluation of interspecies competition of fish under natural conditions. The only patterns applied in the invéstig.ailons of competiti -ve: relations of organisas are the models of Yol'terr — Lotka. However, their applica- tion does not provide satisfactory results, according to Larkin, because these methods are unable to reflect all the complicated situations existing under natural conditions, Weatherley (1963) investigated the concept of the niche and of the competition among animals as it applies to freshwater fish. Some fish have a wide food spectrum and , easily change to different food, whereas others occupy More precisely defined niches. In the case of the latter the presence of other fish having similar food habits may result in lowering of the growth rate and change of pastures.

Due ' to the ability of fish to change their growth rate they easily survive periods of increased ePterekitYof, competition. When the density of population is increased the rate of growth of fish is decreased; when diminished — it increases; an increase in the rate of growth may occur also as a result of increase in the quantity of food organisms. It is difficult to observe the competition directly, usually it is noted by its results. The growih of fish increases with the lowering of density, naturally, only tô a certain degree, bet,M.%St

thei's is à physiological limit to the assimilation of food. by an organism. Investigations of problems connected with the selective . ability of fish and their food competition is contained in shindies dedicated to different species of fish inliwater reservoirs of different types. Brown and Cheng, (-1#46 1 . cOrXicit the food competition of cod and 'haddock "' on the ,

of Marmon and Ice1and.1Weillpanee*She composition of shores food in fish in one trial and reached a conelusiait *boat the selection of food by fish: cod feeds mainly on fish, haciclock on invertebrates, which is determined by anatomical peculiarities of cod and 'haddock." Hiatt (1947) imum,stigated fish of Hawaiian ponds in their biotic relations on the , basis of food composition and the structure of the alimentary canal.

According to Hiatt their exists among fish a fierce interspecies competition. He presents a diagram of food relations, beginning with the energy of the sun, nitrates and carbon di- oxide} and ending with fish and men and makes a concluilon about the neces.sity of the removal of undesirable fish from the ponds and the increase of the quantity of benthoii 'and benthos flora by the use of ,fertiliser. Hartley (1940 showed for the river Cam (England) that there are- no two species, that are absolutely identical in their food composition. Among

non4predatory fish there is food competition, By . increa-- sing the supply of one • food and decreasing the supply of other foods the competitive food relations will change. In this work 'food chains are given accordiig to separate tests.'

Hynes (1950), on the basis of food composition of two species of stickleback and roach reached the conclusion that fish are not indifferent toward food, but select definite food organisms. The stickleback and the roach do not compete foi 20,

food. becaUie—they require different organipiss. Bothspecies. of stickleback have a similar load coMposition; yet thereil no competition between them, because the fauna of the•stream is sufficiently rich to support a florinl concentration of

these species. the . number of speeleo or

creation of • large concentrations and schools of fist

may lead to temporary food. shortages. According to Kow (1950) the fish of the Singapore etraits have . a selectivi relation to food organisms. According to thecharacter of preference it is possible.to separate 6 groups - of fishwhich are dii- tinguished by the different structUre of gills and the other elements.of the alimentary system.

A very :large number 'of irivestiëatiOnè. have 'been 'Carried dtifi

on • the salmonids, in particular on 'troiit ai •eitefi:S1-1-, in connection with their acclimatization. Schmidt — Nielson

•(1939) points out that, although in some cases ChariandP'

trout use the same food, they have the characteristic . of, selective relations to food organisms, which tan be revealed by setting up corresponding exper. iments. According to SvOrd-

son (1949) , char, while feeding, hoil à• more agressive. behaviour than trout, which has to be taken into account when reared together, for intraspecies and interspeties competition'

influences the rate of growth of fish. This work by:. Sv8rdson.is related to a large cycle of his . inyest.igations dedicated to the.sympatristic formation .

of species. Svtrdson showed (1949a, 1953, 1957) 'ithot ,., *different: 21.

species of whitefish which originated in different river systems •

Sweden but are found in the same lakes are distinguished- by of

great lability in the rate of growth, onset of sexual maturity and longevity. In different water reservoirs the indices of representatives of one and the same species prove to be different. With the transfer of poorly growing whitefish into water reservoirs where

other species of whitefish are'absent the rate of growth of the transferred whitefish is increased because of the absence of

competitors. The differences in peculiarities of whitefish

related to their sympatric or allopatric habitation are viewed by

Sv8rdson as a proof of the absence of a sympatric formation of

species, because the manifested peculiarities have only a

phenotypical character. The only genotypical property is

the structure and number of gill rakers which determine the

size of food objects eaten by whitefish.

Nilsson (1958) investigated the food competition of

".pelyad" and "pyzhyan" (Coregonus peled and.Coregonus pid-

schian). His work started from propositions arising from

the research by Sv8rdson has shown that the cause for

the variance in the rate of growth, longevity, and onset

of sexual maturity in whitefish of different species are

their interspecies relations. As a result, the peculiarities

of whitefish are different in a sympatric habitation from those

in an allopatric habitation and the transfer of poorly growing whitefish into lakes where there are no,local whitefish.'

leads to an increase in their rate Of growth. • The growth of whitefish is linked to the volume of Consumed organisms which in its turn•is linked to the number of gill rakers. The best growth is obàerved in whitefish with a small number of gill rakers. and which consume large food organisms. "Pyzhyan"

(Coregonus pidschian). has 20 rakers, feede mainly on molluske, dhironomidae ("non-biting midges") and insect larvae; the "pelyad" .

has 45 rakers and its food consists basically (Coregonus peled) of Bosmina. In some cases .the food organisms of the peled and

are similar, but periods of their mairimum,requirements pidschian of one and the other species are different. The analysis of peculiarities of feeding at different age levels'of pidschiarr and peled has shown that to peleds of all groups of sizes it • is-more natural to feed on plankton than to the pidschian.

Nus son writes that his observations show that the peculiarities of the whitefish populations depend on their interspecies relations. Johannes and Larkin (1961) investigated the food competition of Richardsoniabaleatus and salmon (Salmo gairdneri) in two lakes of British Columbia, where R. baleatus were acclimatized. After R. baleatus appeared in the lakes the quantity of gammarids in the food of salmon sharply declined, because the Richardsonia baleatus, which had developed in great quantity, ate it away very actively. The appearance of R. baleatus had a negative effect on the feeding of young salmon especially, and their growth rate declined. The salmon of higher age groups improved their rate of growth, because

: they changed to consuming of R. baleatus, The authors reaCh the

conclusion that interspecies relations of fish may constantly change,

as a result of the change of the medium and behaviour of the

competitors. Therefore the niches of the competitors may not

be considered as constant. The feeding peculiarities are also

reflected in the loss of fish to predators. Young whitefish,

according to Lindstr8m (1962), are noted for high food plasticity.

Nevertheless, deterioration of nutrition leads to the lowering

of the rate of growth of the young and increases their losses

to predators.

For the purpose of clarifying the mechanism of food

competition in fish, a number of experimental works were carried

out. Thus, according to Newman (1956), for example, char

and trout were fed together. This produced a strong hierarchy

and the bigger fish drove out the smaller. Kolleberg (1958)

investigated the manifestation of agressiveness in trout

and salmon in their competition for territory and food. With

the increase in fish density each fish occupies a clearly

defined place and drives away other fish from its territory.

Those fish which'had received unfavourably situated

sectors fall behind in growth. In the water reservoir the

salmon stays farther away from shore, which Kolleberg explains

as due to the competition from trout.

The problem of utilizing the food relatiOn of fish

is investigated in an interesting way in Israel for the purpose of raising the productivity of ponds. Rom Moav (1960), while discusbing the theoreticalbases 6È cai-peWètics', itrites that it is:necessary to breed races which are able tu make . the best possible use of-erraronmental:dônditicins - Êcheïr l

growth. the free niches› : of carp ponds shoulibe stecked by "lish of secondary importance." The fact of changing the medium under the influence of secondary fish leads to the . necessity or raising the problem of breeding.races of carp or secondary fish which distinguish themselves by the best

symbiotic qualities. According , to Yashav and Chervinski (196112,

50- 40 - 30 - 20 - 10- :' 30125° o magoo. LIM 1 2 3 4 5 5 7 8 9 10 11 12.13 14 15161118192021

' Cocran alum! Coregonus peled (uauepxy) n C. pidschian (rainy):

A — Entomostraca; B — a01-1111ale 2K14130THble; B — nacexomble (JIn- gram! u napocabie); 1 — phi6a; 2 -- unpa; 3 Copepoda; 4 — Phyl- lopoda; 5 — Eurycercus; 6 — Gammarus; 7 Limnea; 8.— Pisidi- urn; 9 Oligochaeta; 10 — Hydrocarina; 11 — Triehoptera (larvae); 12 — Coleoptera (larvae); 13 — Chironomidae (larvae); 14 — Tipulidae; 15 — Spongiaria; 16 — Coleoptera (imago); 17 ---- Trichoptera (imago); 18 — Chironomidae (pupae); 19 — Chi- ronomidae (imago); 20 — uaaemunde . macexouhte; 21 — pacteana. [pucynou B3AT 113 pa6arbi Hambeana (Minoan, 1968)).

Composition o*ood of Coregonus „poled (top) and C. oidschiat (6-ilow)" A-Entomostraca; n-bottom animals; C-insects (larvae and adult) 1-fish; 2-spawn; 3-Copepeda; 4-Phyllopeda; 5-Eurycercus; 6-Gammarus; 7-Limnea; 9-01isechaeta; 10-Hydrocarina; 11-Trichoptera (larvae); 12-Coleoptera (larvae); 13-Chirono- midae (larvae) 14-Tipulidae; 15-Sponearia; 16-Coleoptera (imago); 17-Trichoptera (imago); 18.4411reaomidae (pupae); 19-Chironomidae (imago); 20-land insecte; 21-plants (Diagram taken from the work of Nils:3cm, 1958) 25;

the result of cohabitation of two species of fish depends on whether )

or not they are competing for food or use different food.

• The composition of food of' lltilapiya n (Tilapia nilotica),

a secondary fish for carp ponds, changes with its age. In

• different reservoirs the food of tilapia of the older age

groups is different and is composed of plants, plankton and

bottom organisms. There is evidence that tilapia eats the

excrement of other fish.. In carp ponds tilapia grows well, which

may be explained, according to Yashuv and Chervinsky, by the fact

that substances which tilapia is unable to assimilate are changed

by carp into substances it can assimilate.

'Thus, in forèign literature the food relations of fish,

and in particular inte cies competition, is viewed as one of

vital factors which determine the rate of growth, quantity and

behaviour (distribution) of commercial fish. Research carried

out in this field underlines the presence in fish parallel with ) 7 food plasticity,a selective relation to food and shows

that the food niches of fish are not quite as monotonous

as was held by Elton. At the saine time, none of these .'

studies gives quantity indices for food relations of fish,

nor for selective relations of fish to food organisms, not

to speak of competitive relations of fish. Only'Nilsson (1958)

gives some sort of graphic representation,of the degree of

food similarity of pidschian and peled, which bears some

analogy to the volume of competition representation according

.1;

to ShoryginhOWeVei less clearly Meanwhile, the importance of obtaining quantity indices or cempetitive rely- "ttions of fish . haS been pointed out by many foreign investi-

gators. The reason for.the absente of suCh . lndices . apparent -

'y is due to .the absence of a single common quantity method - Of food investigation of fish which would provide a clear - cut comparable result. Food relations in foreign investiga- - tions are judged on the composition of,lood. which is.expressed

in most diverse indices. In the evelvation of food composi - tion there are useà frequency of occurrence, 'number of : spe- cimens of food organisms for 1 fish or for 10 fish, Sfeit49P141 units, etc. The significance of organisas is expressed . either in absolute numbers or per cent. These Methods not only do not provide a possibility to approach the quantity evaluation of food competitiOn, but`theY.,also cover up the ■ selective relations, of fish toleard food organisas, e g., the fact of distribution of . different species of fish into diffe- Jofood renï\ • niches.The evaluation of the importance of food orga . nisms according to occurrence and number of samples, as is

repeatedly 'shown (Begorov, • 1 i 34; Shotygin, 1952; Zhelten- !ova, 1954), magnifies the role of secOndary and •dnimizes the role of the main food organises. :.The greatest possibili- ties in the sense, of investigation of food relations.oe:fish, as shown by Shorygin (1952) is given by weight evaluation of food followed by a calculation of indices, introduced by .

Zenkevitch and Bretskaya (1931) for «eenthda-feeding...... and Boge- i.ovym (1934) for plankton —feeding•iist.- .Çxtremely sigitieleent: • 27.

in this respect is the fact that more profound research into the

competitive relationships of fish for the purpose of collecting

material toward the solution of practical problems and questions

associated with such fundamental problems as the formation

of species are forcing researchers to use bulk procedures. This

has also occurred in the work of Nilsson (1958) and the work

of Johannes and Larkin (1961). The volume method, as pointed

out by Shorygin (1952), is next to the weight method in

potential solutions.

The necessity for deeper investigation into the

food relations of fish and deriving a quantitative evaluation

is expressed clearly enough in the work of investigators who

concern themselves with the dynamics of fish numbers. Biverton

and Holt (1957) point out that . for the construction of fish

quantity fluctuation patterns it is necessary to have data

on utilization of food by fish, and also data on variations

of food organisms as well as the data of intraspecific and

interspecific competition of fish. These authors point out

that there is little such data available because it is very

difficult to obtain.

The material presently available forces us to

review some classical propositions of ichtiology. Thus,

Bodenheimer (1958) shows that the proposition that the growth

of fish follows a logistic curve which was generally accepted 30

years ago, including by Bodenheimer himself, is incorrect. Neither

is there a constant correlation between the rate of fish growth

and the density of fish population. 28.

The life of a species is influenced by food, density of population, disease, enemies. „Bodenheimer points out that "in the first period of developing knowledge, enemies were considered as the main factor which regulates the animal population." The classical. object on which the influence of the density of population on the growth rate of individuals was demonstrated, i.e., intra-' specific competition, was plaice. Haempel (1958) showed that the position is much more complicated than it appeared to be earlier, because the rate of growth is also influenced by factors of the external medium such as the temperature of water and the amount of food. Therefore, the connection between rate of growth and density of population is frequently disturbed.

In order to be able to understand the structure of all these phenomena and to expose the influence of the individual factors it is necessary to have their quantitative characteristics.

In particular it is necessary to know the character of food relations of fish and the degree of the influence of this factor on the state ofAfish population.

The investigation of the food relationships of fish must be carried out oVer the entire complex of interrelated problems.

The investigation of selective ability of fish is related to the problem of the mutual link of predator and victim. Nevertheless the manifestation of selective relations of fish to food organisms

is the starting point for the analysis of interspecies and

intraspecies relations of fish because the 29. rise of competitive relations is possible only by the presence of similar meeds in: differént fish Food activity -_and food plasticity of fish determine the direction in which the relations .of fish will develop .when cessetftion: for food arises'. The determination of values of food actfvity, plasticity and food potential of fish in different stages of their develop ,- ment permits '.ustoistializ'e the' fate (Of ttlfisW population-under new hydrologieal conditions or à new biotic environment. Acknowledging the importance of investigations of food and food'relations of fish by ,our own and foreign researchers lives us reason to-think thet . thia wôik should be developed here under• a comprehenwilie plan and.the research be carried out in greater depth than is being done it present. We have available to us the . quantitati've. tiethoci, deVised be A.A..

Shorygin. This Method permits us :to nÔ ably -demotatratit the influence of food relations of fish . on, the state of their populations and derive conclusions from thls .phenomenon which

have . -. - immediate practiCal as , ..Well as theoretical aignificance, but also to approach the , qiiantitativei eiraluation of tte rolê -ofi) one of the Most complicated factors which determines the existence of populations of commercial fiSh and the fluctua.... tions of their strength under natural .-conditions. 30.

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