Behavioural and Functioning Interactions in the Schizothoracid Community in the River Mandakini: An Assessment Through Altering Sex Ratio Patterns

2004·3.4 MB·

by  N Singh

Journal of the Bombay Natural History Society, 101 (3), Sep-Dec 2004 374-380
BEHAVIOURAL AND FUNCTIONING INTERACTIONS
IN THE SCHIZOTHORACID COMMUNITY IN THE RIVER MANDARINE
AN ASSESSMENT THROUGH ALTERING SEX RATIO PATTERNS'
N. Singh2 3andK.C. Bhatt2
'Accepted November, 2001
'Zoology Department, P.0 Box 83, HNB Garhwal University, Srinagar Garhwal, Uttaranchal, India.
'Email: [email protected]
Theinterrelationshipsandfunctioningofthreecloselyrelatedspecies,SchizothoraxplagiostomusHeckel,Schizothorax
richardsonii Gray and Schizothoraichthys progastus McClelland (Teleostei, Family Cyprinidae, Subfamily
Schizothoracinae), comprising the snow trout or schizothoracid community, as reflected by the altering sex ratio
patterns, have been assessed quantitatively. Observations were made fortwo years, from January 1991 to December
1992,atfourlandingsites: Bheri(1,020m),Chandrapuri(827m),Agastyamuni(760m)andTilwara(724m),covering
the lowerstretch ofover30 km ofthe high altitudeglacier-fed River Mandakini intheGarhwal Himalaya. The water
characteristicsoftheriver(totalwaterdischarge,watervelocityandwatertemperature)weremeasuredatChandrapuri.
Thetotalfishcatchofthesespeciesfromallthesiteswasfirstpooledandarrangedaccordingtosex,percentage,breeding
and non-breeding seasons. The sex ratio was determined. These species breed twice ayear, from March to May and
AugusttoOctober, with well-defined non-breedingintervals. Thesespeciesindividuallyfollowedasimilarpatternof
responseto changes in the environment, as revealed by the altering sex ratio patterns i.e., highest values during first
breedingseasonof1991 and 1992(2.65:1,3.0:1,3.89:1 and2.56:1,3.86:1,4.75:1 respectively)whenwaterparameters
began rising from the lowest in the extreme winter. The lowest values ofsex ratio were observed during the second
breedingseasonsof1991 and 1992(2.03:1, 1.51:1, 1.58:1 and1.59:1, 1.82:1, 1.74:1 respectively)whenwatercharacteristics
valueswereatapeak,orjustbeganplummetingfromthepeaksofmonsoon.Thecorrespondingvaluesofsexratiointhe
entireschizothoracid communitywereobservedas 2.78:1, 2.83:1 and 1.91:1, 1.61:1 respectively, duringthefirstand
secondbreedingseasonsof1991, 1992. Sexratiobeginstoalteratthecommencementofjustrisingand/orpeak,orjust
plummetingperiods.Alteringsexratiopattern isoneoftheindicatorsofthebeginningofthebreedingprocess.Thatis
thefishtakethechangesin surroundingsasthecuetoinitiatebreedingprocess. Boththespeciesandthecommunityof
schizothoracinefishesaltertheirsexratio pattern in responseto changes intheirsurroundings. Thispattern can serve
asanindicatorofthefunctioningandinterrelationshipatindividual,population,speciesandcommunitylevels.Patterns
ofsexratiochangemustbeutilizedforassessingthebehaviouralandevolutionaryprocessesoveraperiodaswellasan
effective tool in the regulative management ofsnow trout community in the high altitude glacier-fed hillstreams of
Garhwal Himalaya.
Keywords: Schizothoracidcommunity,sexratio, RiverMandakini,functioninginteractions,behaviouralindicators,
evolutionary processes
INTRODUCTION herbivorous)andSchizothoraichthysprogastusMcClelland
(columndwellerand feeder,carni-omnivorous)areanalysed
Odum (1971) and Kendeigh (1980) described the asfurtherextensionofearlierworks(Bhatt 1993; Singh 1995,
conceptual framework of biotic communities. In fluvial 1997; Singh and Subbaraj 2000; Singh etal. 1996)focusing
systems, unidirectional flow and gradient determine the on the high altitude glacier-fed hill stream, Mandakini in
mobility of the subject. This offers entirely different GarhwalHimalaya.
challenges in the ways ofstudying the biotic communities Thesexratiooffishpopulation isaneffective indicator
therein. The biotic communities in the rapidly flowing offunctioning, behavioural strategiesand catch composition
hillstreams are heterogeneous assemblage of several plant (Nikolskii 1980;Engenwaji 1992). IntheIndiansubcontinent,
andanimaltaxaofdiversefeatureswithintricaterelationships. with immensescopeofdiversityand potentialsoffish fauna,
The upstream and downstream boundaries ofthe habitat(s) the assessmentoffunctioningand interrelationships through
and movement of the residents for diverse purposes are sexratioand/orsimilarindicesoffishesatpopulation,species
difficult to determine. In view of these restraints, the and community levelsremains unexplored, thus, eliminating
behavioural attributes in terms ofaltering sex ratio patterns their advantageous uses for determining the characteristics,
of schizothoracid or snowtrout community consisting of planning and management ofcultivable and non-cultivable
Schizothorax plagiostomus Heckel, Schizothorax fishes to any worthwhile level (Pantulu 1961; Bhatt 1993;
richardsonii Gray (both bottom dwellers and feeders, Nautiyal 1994).
INTERACTIONS IN THE SCHIZOTHORACIDCOMMUNITY IN RIVER MANDAKINI
The dominant status, economic potentials yet hitherto size, the percentage of males and females during the
little explored avenues ofschizothoracid community, in the corresponding period suitably conformed to the respective
entire Himalayan region, in general, and in Garhwal hills in structural representation in the community (Fig. 2). Further,
particular, offer enough incentives for assessing the the sample size did not cast its shadow on the overall
functioning interrelationships, their observable indices (sex response(s) patterns.
ratiochangebeingoneofthese),andresponse(s)tothemilieu Percentage ofmales and females: The analysis offish
of changing surroundings of glacier-fed hillstreams in the catchintennsofsexpercentageoftwoyearsofferedsimilarity
region likeRiverMandakini. of patterns which the three species exhibited respectively
(Table 1, Fig. 1). Forthe entire community, the corresponding
MATERIALAND METHODS valuesofpercentageofmaleswere 9.31, 13.12and 12.83, 14.39
respectively during the first and second breeding season of
The study is based on the analysis of the total fish 1991 and 1992. Forfemales the percentages were found to be
catch of Schizothorax plagiostomus, Schizothorax 3.35,6.87and4.53,8.93 respectivelyduringthecorresponding
richardsoniiand Schizothoraichthysprogastus in the lower breedingandnon-breedingseasonsof1991 and 1992(Fig.2).
stretch of over 30 km of glacier-fed high altitude River Sex ratio: It is an effective and definite indicator of
Mandakini, which finally meets with the still larger River response(s)and interactionswithinthecommunityaswell as
Alaknanda at Rudraprayag (JBNHS 94(2), 1997: Fig. I, to the changing surroundings. The analysis samples of
p.418).Therando—msamplingofadultspecimenswasmadeat Schizothorax plagiostomus, Schizothorax richardsonii and
four landingsites Bheri (1,020 m), Chandrapuri (827 in), Schizothoraichthys progastus revealed a consistent pattern
Agustmuni(760m),andTilwara(724m). Sinceallthesethree ofsexratioalterations(Table2,Fig. 1).Allthreespeciesshowed
species breed twice a year, from March-May and August- higher sex ratio (2.78:1, 2.83:1 respectively) during the first
October, the data were analysed and computed on the basis breeding season ofthe year but lower figures (1.91:1, 1.61:1
ofa pooled number as sample size, percentage ofmales and respectively)duringsecond breedingoftheyear(Fig. 2).
femalesinthetotalcatch,breedingandnon-breedingseasons WaterparametersoftheRiverMandakini(Figs 1,2):
with respect to individual species separately. The ratio of Thehabitatofthethreespeciesofschizothoracidcommunity
M:F(M-numberofmales,F-numberoffemales)duringthe in the River Mandakini, when analysed and quantified for
corresponding seasons gave the sex ratio ofeach species. total water discharge, water velocity and watertemperature,
—
The data ofwater parameters ofRiver Mandakini presented an overview conforming to the overall picture of
total water discharge (m—Vsec), water velocity (m/sec) and what had been stated so far. The mean monthly values of
water temperature (°C) during the corresponding study rivercharacteristicsbeganrisingfromMarch-May 1991, 1992
period have been obtained from the Uttar Pradesh Irrigation fromthe lowestfiguresduringextremewintersandremained
—
Department, Srinagar Garhwal as measured at Chandrapuri moderate totalwaterdischarge(36.96, 88.32mVsec),water
(JBNHS94(2), 1997: Fig. 1, p.418),andwereconverted into velocity(0.—745, 0.686 m/sec) and watertemperature (1 1.05,
mean monthly values ofrespective seasons. 1 1.61 °C) when males in the community comprised the
highest representation. Conversely, during the second
RESULTS breeding season in August- September, October 1991, 1992
these parameters were either at the peak or hadjust started
Sample size: The study is based on analysis ofa total coiningdown from thepeakvaluesofmonsoon; i.e., 155.34,
of5,587 adultspecimens. Examination ofthetotal fish catch 170.63 mVsec; 1.805, 1.919 m/sec and 15.05°, 15.8 °C
from all thefourlandingsiteswhenpooledtogetherrevealed respectively when the sex ratio touched the corresponding
evident variations. The highest representation of lowest values. Thus, the water parameters of the River
Schizothoraxplagiostomus[total4,585(82.07%),males3,120 Mandakiniperfectlysimulateand stimulatethepictureofthe
(81.95%),females 1,465 (82.30%)] placedthisspeciesonthe community response(s) as a whole when viewed along with
topstatusnotonly inthe schizothoracid community, butalso the corresponding data.
among all the fish species resident in River Mandakini.
Schizothorax richardsonii also had a good representation DISCUSSION
[total674(12.06%),males455(1 1.96%),females219(12.30%)|
but Schizothoraichthys progastus happened to be poorly (a) Majorstructural features such as dominant species
represented [total 328(5.87%), males 232(6.09%), females like forms or indicators, and (b) physical habitat of the
96(5.39%)](Fig. 1).Despitethisenormousvariationinsample community and functional attributes such as type of
1 Bombay Nat. Hist. Soc., 101 (3), Sep-Dec 2004 375
INTERACTIONS IN THE SCHIZOTHORACID COMMUNITY IN RIVER MANDAKINI
(°C)
temp
Water
velocity
(m/sec)
Water
water
/sec)
discharge3
Total (m
F)
:
(M
ratio
Sex
sample years
males
of
of two
%)
size
the
Total (inof
sample years
females
of
of two
size %)
the
Total (inof
sample
numbers) years
of
size two
(pooledof
Total
Fig 1 SexratioofSchizothoraxplagiostomus(SP), Schizothoraxrichardsonii(SR)
and Schizothoraichthysprogastus(SPRO)inrelationtosamplesize,percentageoffemalesandmales
andwaterparameters(totaldischarge, velocity&temp. duringbreedingandnonbreedingseasons
)
of1991-1992intheriverMandakim
376 J. Bombay Nat. Hist. Soc., 101 (3), Sep-Dec 2004
INTERACTIONS IN THE SCHIZOTHORACIDCOMMUNITY IN RIVER MANDAKINI
community,metabolismetc.areaconvenientbasisfornaming However,BhattandPathak(1992)haveexplainedafewspecies
and classifying the community (Odum 1971). Of these, atcommunity level.
functionalapproachesofferbetteralternativesforcomparison From quantitative and qualitative estimates ofpresent
ofallcommunitiesinwidelydifferenthabitats. Regardingthe study, the topmost status of schizothoracid community is
fish communities withinthe geographical regions, the major evidentamongvariousanimalcommunitiesinclusiveofthose
approachesmustinclude-(1)Zonalapproachforrecognizing, ofotherfishcommunitiesresidentinRiverMandakini. Based
classifying and listing in a sort ofcheck-list ofcommunity on dominance, various species ofschizothoracid community
type, (2) gradient analysis approach involving the may be arranged, from higher to lower ranks, as
arrangement ofpopulation along uni- or multi-dimensional (1) Schizothorax p/agiostomus, (2) Schizothorax
environmental gradient axis with community recognition richardsonii (3) Schizothoraichthysprogastus (Singh et al.
,
based on statistical comparison. Also, there are certain 1996) and so on. The variation in the quantitative values of
specifically interesting questions about fish communities - different functional attributes (including sex ratio, breeding
(i) To what extent can fish in similar habitat be predicted? seasons)atdifferentsites isduetothecontinuumofcomplex
(ii)Howarefishcommunitiesorganized?Doesthelastmember dynamics, altering interactions of individuals-individuals,
ofthe sensitive species result in the collapse or irreversible individual-population, population-population, population-
changes in the community? (iii) How is the state of species, species-species, species-community, community-
development or completeness measured, and hence community and also with surroundings in each case and at
assessment ofthe extent to which it has been degraded by each level apartfromworkingmodalities.
environmental change(s). Notable examples ofsuch studies The highest absolute numbers of specimens during
oftemperatefishcommunitiesofNorthAmericaincludethose breeding seasons, especially at Chandrapuri and Tilwara
by Harvey, 1975, 1978; Johnson et al. 1977; Tonn and (,JBNHS 94(2), 1997: Fig. 1, p. 418, where smaller rivulets
Magnuson 1983. debouch into river Mandakini), percentage of males and
Theanalyticalstudiesoffishcommunitiesinthe Indian femalesinthetotalcatchduringMarch,April,May 1991, 1992
context are not addressed to in right perspectives despite and then during August, September, October, 1991, 1992
the sizable scope of diversity, functional changes within respectively, are convincing proofofthese species breeding
shorter time and space (Shastri et al. 1982), potentials of twice a year (see Singh 1997). At the onset of breeding,
newerdistinctapproacheslikelytoemerge. InGarhwalregion, potential male and female brooders migrate from lower
Kumar(1991)analysedmicrozoobenthiccommunitiesofRiver stretches of larger glacier fed hill streams (like Ganga,
Alaknanda, and Rawat (1992) undertook the analysis Alaknandaetc.)totheupperreachesoftheirtributaries. Small
of community structure of plankton in high altitude Lake glacier/non-glacierfed streams orrivuletswith fasterwater
DeoriaTal. velocity, lesserturbidityetc.aremoreconduciveenvironsfor
The functional approach of community analysis of brooders,spawnandjuveniles. DestinationslikeChandrapuri
Indian fishes in diverse fluvial systems wherein the subject andTilwara(sitesofconfluence)aremorepreferredsitesfor
aswellasphysical habitathavehigh mobilityand, hence,the spawning and breeding purpose.
community functioning and interactions are at continuous Singh (1997) mentioned several intrinsicand extrinsic
—
change areratherobscureobviouslydueto lowfeasibility. factors interacting together and collectively responsible for
Table 1: Profile of pecentage of males and females ofthree species of schizothoracid community during breeding and non-breeding
seasons of 1991-1992 in the River Mandakini
Species Sex November-February March-May June-July August-October
(1st Non-breeding) (1st breeding) (2nd Non-breeding) (2nd breeding)
Jan-Feb Nov-Dec Jan-Feb Nov-Dec 1991 1992 1991 1992 1991 1992
1991 1991 1992 1992
Sp. 1 Male 5.03 9.68 3.01 12.72 19.07 3.09 5.26 19.10 22.18
Sp 2 Male 6.37 7.25 2.42 11.21 17.80 6.15 7.69 23.52 17.58
Sp 3 Male 7.76 5.60 3.45 31 89 16.38 6.03 1.72 12.93 14.22
Sp 1 Female 4.70 7.92 2.73 10.24 15.77 3.75 5.19 20.00 2969
Sp 2 Female 6.85 7.76 2.74 7.76 9.59 5.94 6.85 32.42 20 09
Sp 3 Female 10.42 9.38 4.16 19.79 8.33 6.25 2.08 19.79 19.79
Sp. 1 = Schizothorax plagiostomus, Sp. 2 = Schizothorax richardsonii. Sp 3 = Schizothoraichthys progastus
J. Bombay Nat. Hist. Soc., 101 (3), Sep-Dec 2004 377
INTERACTIONS IN THE SCHIZOTHORACIDCOMMUNITY IN RIVER MANDAKINI
(°C)
temp
Water
velocity
(m/sec)
Water
water
/sec)
discharge3
Total (m
F)
:
(M
ratio
Sex
years
sampleand
of males two
of
size %)
Total (infemales
numbers,
seperately)
(pooled
years
females
two
sample
of
of and
size males
Total
Fig. 2: SexratioofSchizothoracidcommunityinrelationtopoolednumbersaswellasmales
andfemalesseparately, %offemales&malesandwaterparameters(totaldischarge, velocity&temp. duringbreedingand
)
non-breedingseasonsof1991-1992intheRiverMandakini(ComparewithFig. 1)
378 J. Bombay Nat. Hist. Soc., 101 (3), Sep-Dec 2004
INTERACTIONS IN THE SCHIZOTHORACID COMMUNITY IN RIVER MANDAKINI
Table 2 Profile ofthe sex ratios ofthree species of schizothoracid community during breeding and non-breeding
seasons of 1991-1992 in the River Mandakini
Species November-February March-May June-July August-October
(1st Non-breeding) (1st breeding) (2nd Non-breeding) (2nd breeding)
Jan-Feb Nov-Dec Jan-Feb Nov-Dec 1991 1992 1991 1992 1991 1992
1991 1991 1992 1992
Sp 1 2.28:1 2.60:1 2.35:1 2.65:1 2.56:1 2.24:1 2.16:1 2.03:1 1.59:1
Sp 2 1.93:1 1.94:1 1.83:1 3.00:1 3.86:1 2.16:1 2.33:1 1.51:1 1.82:1
Sp 3 1.80:1 3.67:1 2.00:1 3.89:1 4.75:1 2.33:1 2.00:1 1.58:1 1.74:1
Schizothoracid 2.17:1 2.38:1 2.26:1 2.82:1 2.79:1 2.23:1 2.18:1 1.91:1 1.61:1
Community
Sp 1 = Schizothorax plagiostomus, Sp. 2 = Schizothorax richardsonii, Sp 3 = Schizothoraichthys progastus
higher male sex ratio during the first breeding season ofthe inhabitingsimilarhabitatandusingsimilarcuesforspawning,
year: (i)earlierdepartureofmalesand latearrival offemales, breedingand other vital processes? Here lie the possibilities
(ii)freshrecruitmentofnewbatchesofsubadultsintobrooders, of preponement and/or postponement of such changes in
(iii) difficulties encountered by female brooders during behavioural indicesand indicators(likesexratioalterations)
upstream migration because of their full-grown belly and by a few hours/days enough for such resource mobilization,
relatively lowerwaterdischargetocopewiththe largersized resource partitioning and minimizing the competition for
females.Theconditionsotherwiseareconduciveforspawning resources at successive levels within the community which
and breeding resulting from moderate conditions, and musthave been too intense. It isalso indicative ofintelligent
(iv) vulnerabilities offemale brooderstotheir predators and designing of behavioural strategies of schizothoracids in
othernaturalhazards.Also,environmentalconditionsduring natureformobilizationoftransitional butmoderateresources
the first breeding season favour the male, whereas females in terms oftimingand space for breeding.
are favoured during the second breeding period ofthe year. This analysis of altering sex ratio patterns in
Another possibility of sex ratio alterations may be sex Schizothorax plagiostomus Schizothorax richardsonii and
,
dependentmortalityandintersexes in population(anentirely Schizothoraichthysprogastus presents an overall picture in
newdimension). the River Mandakini in particular and other glacier-fed
Since the present assessment is based on the data of hillstreams of Garhwal region in general. This study of
threecloselyrelatedspeciesofschizothoracids, itindicatesa schizothoracid community, though raising several questions
similar picture of response(s) as evident from sex ratio tobeansweredfromvariouspointsofview,shouldbeutilized
variations in relation to changing river characteristics. This in two ways; first, in revealingthe processes ofsignallingof
similaritylendsfurthercredencetotheirclosegenetickinship individual-population-species-community responses,
astheyinhabitandsharecommonhabitat(theriverMandakini convergence-divergence at behavioural, physiological and
andlikesintheHimalayanregion)andalsoencountersimilar environmental levels, and second, in regulative management
challengesandopportunities, usesimilarcuesandstimulants. ofschizothoracidfisheryinglacier-fedhighaltitudehillstreams
Obviously, they must have evolved similar behavioural ofGarhwalregion.
repertoire, functioning strategies and response(s) at
individual,population,speciesandcommunitylevels.Varying ACKNOWLEDGEMENTS
sex ratio patterns, mobilization ofspawning grounds (Singh
1995) are among these. Such behavioural responses ofthe The author is grateful to Prof. AshaChandola Saklani,
community also include the interplay of intra- and inter- Head and Co-ordinator, UGC-SAP Department ofZoology,
specific convergence, divergence/diversity, which are at the HNBGarhwalUniversity, SrinagarGarhwalforherconsistent
helms ofevolutionary processes. Sex ratio alterations also support and for being available for critical suggestions at
reflect the pattern diversity of stratification (Pielou 1966), successive stages throughout the study tenure. Financial
zonation, activity, reproduction, social, co-action, assistance received from the Government ofIndia, Ministry
stochasticism etc. However, many significant questions ofEnvironment,ForestsandWildlife,NewDelhi(No. 35/20/
emanate out ofsuch a scenario, namely levels ofintra- and 90-RE) (presently monitored by GBPIHED, Kosi, Almora,
inter-specific convergence and divergence/diversity while Uttaranchal) is thankfully acknowledged.
J. Bombay Nat. Hist. Soc., 101 (3), Sep-Dec 2004 379
INTERACTIONS INTHE SCHIZOTHORACID COMMUNITY IN RIVER MANDAKINI
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