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EFFECTS OF WATER TEMPERATURE ON THE GROWTH ANDSURVIVAL OF CATFISH CLARIAS MACROCEPHALUS

GUNTHER) LARVAE

M . F. A. MOLLAH

School of Biological Sciences, University of Science, Penang, Malaysia.

A B S T R A C T

Five-day old Clarius macmcephalns larv ae of initial total length ( + S.D.)of 7.9 i 0.4 mm showed faster growth rate when raised at a wa ter-tem peratu reof 30C. In contrast, the survival rates of the larvae maintained at three differenttemperature regimes (e.g., 35C, 30C, and ambient: 27-30C) tested were not

significantly different throughout the 28-day study period. Thus, the recommendedtemperature for the culture of C. macrocephaliis larvae is 30C.

I N T R O D U C T I O N

The larval stage is the most 'sensitive' phase in the life history of thespecies and thus most susceptible to mortality. Larvae of different species havedifferent requirements for survival and growth. Water-temperature , dissolved-oxygen level, pH, salinity, type of food, type of pollutants and stocking densityare some of the many factors known to affect the larval culture of various fishspecies. Under controlled conditions, however, variations in temperature, foodtypes and stocking densities are often most critically examined. Of them water-temperature is an ubiquitous parameter that has been extensively investigatedfor reason of its direct influence on the activity and metabolic processes of fishas well as its indirect effect through dissolved oxygen level, and cost of maintenance. The larval stage in the life history of a species tends to be most sensitive to tem perature changes, although such temperature effects would havevarying responses in different fish species. While maximum and minimum lethaltemperatures for a particular species have to be avoided, it is equally importantto determine the optimum temperature for growth and survival. For most species,maximal growth rate tends to occur at a particular temperature range, this rangebeing described as the optimal temperature for the species. McCormick et al(1972) reported that the suitable range of temperature for growth and survivalof young brook trout Salvelinus fontinalis) is from 9.8 to 15.4, of which theoptimum lies between 12.4 and 15.4C. However, the optimal rearing tempera

ture for Mugil cephalus larvae is 22C (Kuo et al 197 3).

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WA1ER TEMPER ATURE A ND GROWTH OF CATFISH 6 9

Though the optimal temperature lies within the range of temperaturetolerance of a species, it tends to be at the warmer part of this tolerance limit.At warmer temperature, the metabolic activities of fish are faster and thus thefish , if given adequate food, would grow faster. The maximum size of meal thatthe fish would accept is depressed at both low and high tem perature (Brett &Higgs 1970). This could be due to changes in rate of gastric digestion, rate ofintestinal absorption, rate of return of appetite or the simultaneous interactionof all these three factors (Brett and Higgs 1970). The rate of secretion of digestive enzymes, which is temperature dependent (Smit 1967), undoubtedly affectsthe rate of digestion. Although the food evacuation time is inversely related withtemperature (Jobing et al 1977), gastric digestion is unlikely to be impairedwithin the optimal temperature range of a species (Smit 1967). In the formulation of a growth model for salmonids, Stauffer (197 3) assessed the variousfactors influencing growth, and subsequently concluded that any attempts atmodelling must include at least three factors - food ration, size of fish andtemperature - as the most important independent variables. Elliot (1975a, b),working on Salmo irutta, came to a similar conclusion.

MATERIAL AND METHODS

Source of larve

C. macrocephalus larvae used in the present study were obtained fromartificially fertilized eggs of fish ovulated with human chorionic gonadotropin(HCG) dose of 2IU|g body wt.

Experimental design

Nine glass aquaria of size 59 x 43 x 28 cm, each having 50 1 of water,were used for this experiment. The aquaria were divided into three groups, eachhaving three aquaria, and they were designated as Group I, II and III. Two

hundred 5-day-old larvae of an average total length + S.D.) of 7.9 0.4- mm were randomly selected for each of the aquaria. All three aquaria of GroupT were placed in an insulated room under a constant water temperature of 35.0 0.5C. The water temperature of the aquaria of Group II was maintained

at 30.0 0.5C in another insulated room, while the aquaria of Group III wereput under ambient temperature, which ranged between 27 and 30C duringthe period of experiment.

The larvae were fed three times (at 0800 hrs, 1500 hrs and 2300 hrs) aday with excess amount of live food Moina and|or chopped Tubifex worms) toensure that there was always food for the larvae. The water was aerated. Half ofthe water together with the fecal wastes from each aquarium was changed twicedaily, once in the morning and once in the evening before feeding. At these timesthe dead fish were removed and counted. The water used was maintained at the

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required temperature for at least 12 h before being used. Measurement of totallength of 40 fish from each aquarium was taken every 7 days. The experimentwas conducted for 28 days.

Data analysis

Data obtained on growth and survival rate for the effect of different watertemperature were compared using one way analysis of variance (ANOVA).Duncan's Multiple Range test at a = 0.05 was then employed for further analysisof the results (Vann 1972).

X RESULTS

With ample supply of live feed provided, it was observed that the larvaewere feeding till satiation at the various temperature regimes tested.

The mean increase in total length of larvae at different days during theexperimental period is shown in Figure 1. ANOVA test results indicated thatthere was a significant difference in mean growth rates among the 3 different

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. , 3a trnvl) 3 0 an wa i

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FIG. 1 Length-gain curves forC. macrocephalus larvae at different times of the experimentalperiod, when they were maintained at different water-temperatures. Each point representsthe mean i S.D. of 3 replicates.

FIG. 2. Survival rate of C. ma-crocephalus larvae at differenttimes of the experimental period,when they were maintained atdifferent water-temperatures.Each point represents the mean S.D. of 3 replicates.

groups of larvae maintained at water temperatures of 35, 30 and 27-30Crespectively (Table 1). Using Duncan's Multiple Range test, it was found that

the mean length-gain fish ' at day 7 in Group I (35C) and II (30C) was

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WATER TEM PERA TURE AND GROWTH OF CATFISH 71

significantly higher than that of Group III (ambient tem pera ture) . A similar

trend was observed at day 14. At day 2 1, the mean length-gain f ish in Grou pI was significantly higher than that of Group III but significantly lower thanthat in Group II . The mean length-gain fish in Group I and II was not signi

ficantly different at day 28. However, these two groups exhibited significantlyhigher length-gain when compared to Group III.

Figure 2 shows the survival rates of larvae under various temperatureregimes at different days during the experiment. Using Analysis of variance it wasfound that there was no significant difference in the mean survival rates amongthe different treatment groups.

TABLE 1. ANOVA table, for mean increase in total length {mm) of C. macro-cephalus Gunther) larvae at different times of the experimental periodwhen they were maintained at different water temperatures.

Day Sources of Degree of Sum of Mean square F value

variation freedom, squares7 Between groups 2 5.482 2.741 20.033**

Within groups 6 0.714 0.119

14 Between groups 2 22.615 11.307 29.5 99* *Within groups 6 2.294 0.382

21 Between groups 2 98.420 49.210 72.057 **Within groups 6 4.100 0.683

28 Between groups 2 81.236 40.618 28 .46 3* *Within groups 6 8.567 1.427

** Significant at p < 0.01

DISCUSSION

Water temperature plays an important role in the growth and survivalof fish in young stages. Results of the present study showed that the rate of

growth in terms of length-gain fish in Group III (27-3 0C ) was significantlylower than those in Group I (35C) and Group II (30C) throughout the wholeexperimental period.

Rate of digestion ajppears to be the main limiting factor to consumptionand hence retards the growth at low temperature. In sockeye salmon Oncor-hynchus nerka) fingerling the rate of digestion drops significantly as the temperature is decreased from 15C, a temperature optimum for its growth. The digestion rate approaches zero at about 0C (Brett and Higgs 1970). Digestion has

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been reported to proceed faster with the rising temperature in Fundulus hetero-clitus (Nicholls 1931), Mkropterus salmoides (Molnar and Tolg 1962 ) , Percafluviatilis, Silurus glanis (Molnar e t a l 1967) , Ictalurus nebulosus (Smit 1967)and Ictalurus punctatus (Shrable et al 19 69 ), reaching a maximum rate as thegeneral limit of temperature tolerance is approached. With increasing tempera

ture the food evacua tion time has been shown to be progressively reduce d(Edw ards 197 1, Jobling and Davies 19 79) . Any factor which reduces the t imea meal remains in the gastrointestinal tract could reduce assimilation efficiency(Jobling et al 1977) but not the rate of gastric digestion within the normal temperature range of a species since gastric acid and enzyme secretion vary directlywith the meal size and temperature (Gregory 1965, Smit 1967).

Increase in length, as observed in the present study, is related to theassimilated energy availab le for grow th. A ssimilation efficiency reflects totalavailable energy uptakes, digestion rate merely reflects breakdown of food intake;not necessarily all food digested is assimilated. Thus although the requirementsfor food intake are increased as temperature increases beyond the optimumrange (Winberg 1956) the energy available for growth is not identical with the

digestion rate. Therefore, the sustained capacity to consume and digest does notnecessarily imply an availability of more energy for growth when the fish aremaintained at a temperature above the optimal for the species concerned. SinceC. macrocephalus larvae maintained at 35C failed to show significantly highergrowth rate when compared with those maintained at 30C it cannot be saidwith certainty from the present study whether this temperature (35C) is abovethe optimum level for culturing the larvae of this species.

Although the survival rates in all three groups were not significantlydifferent throughout the study period, the growth rate of larvae maintained at30C was significantly faster than those maintained at 35C at day 21 and 28.This indicates that a water temp eratu re of 30C is the most suitable for theculture of C. macrocephalus larvae.

R E F E R E N C E S

BRETT, J. R. AND D . A. HIGGS. 1970. Effect of temperature on the rate of gastric digestion in fingerling sockeye salmon, Oncorhychus nerka. J. Fish, Res. Bd. Cana da, 27:1767-1779.

EDWARDS, D . J. 1971. Effects of temperature on the rate of passage of food throughthe alimentary canal of the plaice Pleuronectes platessa L.). J. Fish Biol., 3: 433-439.

ELLIOT, J. M. 1975a. The growth rate of brown trout, Salmo trutta L. fed on maximumrations. /. Anim. Ecol., 44 : 805-821.

ELLIOT, J. M. 1975b. The growth rate of brown trout Salmo trutta L.) fed on reducedrations. J. Anim. Ecol., 44: 823-842.

GREGORY, R. A. 1965. Secretory mechanisms of the digestive trac t. Ann. Rev. Physiol,,

27: 395-414.

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WATER TEMPERATURE AND GROWTH OF CATFISH 73

JoBLiNG, M. AND P. S. DAVIES. 1979. Gastric evacuation in plaice, Pleuronectes platessaL.: effects of temperature and meal size. ] Fish. Biol., 14: 539-546.

JoBLiNG, M., D. GWYTHER AND D. J. GROVE. 1977. Some effects of temperature, mealsize and body weight on gastric evacuation time in the dab. Limanda limanda L.).y. Fish Biol. 10: 291-298.

Kuo, C. M., Z. H. SHEHADEH AND C. E. NASH. 1973. Indueced spawning of captive greymullet Mugil cephalus L.) females by injection of human chorionic gonadotropin.Aqiiacultiire. 1: 429-432.

MCCORMICK, J. H., K. E. F. HOKANSON AND B. R. JONES. 1972. Effects of young brooktrout, Salvelinus fontinalis. J Fish Res Bd Canada, 29: 1107-1112.

MoLNAR, G., E. TAMASSY AND I. TOLG. 1967. The gastric digestion of living, predatoryfish. / ' The Biological Basis of Freshwater Fish production, 135-149, S. D. Gerking(Ed . ) , Blackwell Scientific Publications, Oxford.

MoLNAR, G. AND I. TOLG. 1962. Relation between water temperature and gastric digestion of largemciuth bass, Macropterus salmoides. J Fish. Res Bd Canada, 19: 1005-1015.

NiCHOLLS, J. V. V. 1931. The influence of temperature on digestion in Fundalus hetero-clitiis. Contr. Can Biol. Fish., 7: 45-55.

SHRABLE, J. B., O. W TIEMEIER AND C. W. DEYOE. 1969. Effects of temperature on rateof digestion by channel catfish. Prog. Fish.Cult., 31: 131-138.

SMIT, H. 1967. Influence of temperature on the rate of gastric juice secretion in thebrown bullhead Ictalurus nebulosus). Comp, Biochem. Physiol., 21: 125-132.

STAUFFER, G . D . 1973 A growth model for salmonids reared in hatchery environments.Ph.D. Thesis, University of Washingron, Seatle.

VANN, E. 1972. Fundamentals of Biostatistics. D. C. Heath and Company, Lexington,Massachusetts, Toronto, London, pp. 184.

WiNBERO, G. G. 1956. Rate of metabolism and food requirements of fishes. Transl. fromRussian by: Fish. Res Bd Canada Transl. Ser No. 194 (1960).