Pertanika 13(3), 367 - 370 (1990)

COMMUNICATION III

The Use of Live, Frozen and Pottasium PermanganateTreated Moina micrura for Catfish (Clarias macrocephalus) Larvae

ABSTRAK

Moina mi crura yang hidup, yang dibekukan da'[t yang diolahkan dengan kalium permanganat (KMn0,J telahdiberikan kepada lava ikan keli (Clarias macrocephalus) selama 20 hari. Pengolahan dengan KMn0

4sebelum

dimakan bertujuan untuk mengurangkan paras mikroorganisma yang terdapat di dalam kultur M. micrura.Kadar pertumbuhan dan nisbah penukaran makanan untuk M. micrura hidup dan yang diolah denganKlVln04 tidak mempunyai perbezaan bererti. M.micrura yangdibekukan mempunyai kadarpertumbuhan yangrendah dan nisbah penukaran pemakanan yang tinggi. Nilai-nilai ini mempunyaiperbezaan yang bererti apabiladibandingkan dengan yang diperolehi untuk M. micrura yang tidak diolah. Keputusan ini mencadangkanbahawa M. micrura masih mempunyai kualiti pemakanan walaupun selepas olahan dengan 111M KMn0

4dan

ia sesuai sebagai makanan lava ikan.

ABSTRACT

Live, frozen and pottasium permanganate (KMnO,J treated Moina micrura were fed to catfish (Clariasmacrocephalus) larvae for 20 days. The aim ofKMnO4 treatment prior to feeding was to minimise the level ofmicroorganismspresent in theM. micrura culture. The growth rates andfeed conversion ratiosfor the live untreatedand KMn04 treated M. micrura were not significantly different. Frozen M. micrura had a significantly lowergrowth rate and significantly higherfeed conversion compared with the live, untreated M. micrura. The results onrelativegrowth andfeed conversion offry fed the treated and untreated suggest that M. micrura retained its nutritivequalities even when treated with 1 11M Ki\1n04 and is suitable as a larval feed.

INTRODUCTION

The recen t in tensification of catfish Clariasmacrocephalus culture in Malaysia has resulted inincreased demand for its fry. However, a majorconstraint faced by fish farmers presently is lowrates of larval survival and growth, often due tofungal and bacterial infection present in thenatural food provided (Lau & PIumb 1981, Viveenet al. 1986) or unsuitable artificial larval feeds.

Natural food organisms such as Daphnia pulex(Hecht 1981) and rotifers (Lubzens et al. 1987)have been widely used as first feeds for larvae.However, live feeds have several disadvantagessuch as seasonal availability and the introductionof pathogens and parasites into the hatcherysince they cannot be sterilised (Dys and Hecht1985). To overcome the availability problem,frozen or freeze-dried natural food can be usedbut these have been found to be unsuitable (Brett1971; Fluchter 1980).

Locally, Moina micrura is used to feed newlyhatched catfish larvae for the first four weeks oflife. However, we have experienced inconsistentlarval survival when M. micrura was used and lowlarval survival was often due to fungal and bacterialinfection such as from F. columnans. The infectedfish were treated with pottassium permanganate(KMnO4) because of its therapeutic propertiesagainst external bacterial and protozoaninfections (Lau and Plumb 1981 and Duncan1987). Since the fish are stress-sensitive at thelarval stage, KMnO4 treatment was often too lateand resulted in high mortalities.

In this study, the effectiveness offreezing andKMnO4 treatment on M. micrurato obtain optimalgrowth and survival of larvae as compared tountreated M. micrura was tested. M. micrura wastreated with KMn40 prior to feeding the larvaewith the aim of reducing the level ofmicroorganisms present in the M. micruracultureand consequently reducing the risks of larval

R. HASHIM AND A. ALI

infection. Preliminary studies ofKMn04

treatedand untreated [VI. mirrurrt cultures to determinethe presence of microorganisms has shown theformer to contain a lower colony count. SinceKi\1.nO.1 is a strong oxidant, toxicity problemswhich frequently arise during KMn0

4treatment

were avoided by using a concen tration ofoxidantthat was high enough to eliminate themicroorganisms but low enough in toxicity toensure survival of the Moina and subsequentlythe larvae.

MATERIALS AND METHODS

Moina rnicrumwas obtained from a nearby moinacultivation farm. Diet 1 was untreated M. micrum,Diet 2, M. micrum treated with 1uM KMn0

4and

Diet 3, M. micrum frozen at -400C. KMn04

treated M. micrum (Diet 2) was rinsed thoroughlywith water and the frozen M. micrum (Diet 3) wasthawed at room temperature prior to feeding.The nutrient content of all the three diets wasfound to be very similar (Table 1).

TABLE 1Proximate analysis of Moina 1Ilicrura

(% dry weight)

I Measured as Kjeldahl-N x 6.252 Extracted in Chloroform-Methanol:\ Untreated Moinfl1llicTum

Clanas macrocephalus larvae were obtained byinduced spawning using human chorionicgonadotropin (Mollah & Tan 1983). The larvaewere transferred from the breeding tanks to theexperimental aquariums on the final day of yolkabsorption and before exogeneous feedingstarted. The nine experimental aquariums werefilled with 30 liters of fresh water, aerated andstocked with 100 larvae. Water exchange rate was5 lhr- I and the temperature was maintained at29°C throughout the feeding trial. All experimentswere carried out with three replicates pertreatment.

The larvae were fed to satiation twice daily.Before feeding, fecal matter and excess feedswere siphoned out and half the volume of waterdrained. The feeding trial was terminated on the20th day and all the fish in the tanks were coun tedand weighed. The relative growth rate and thefeed conversion ratio (FCR), defined as the totalfeed taken per unit of fish weight gain, wascalculated. The results obtained were analysedusingANOVAat5% level ofsignificance followedby Duncan's new multiple-range test forcomparison ofthe means obtained (Steel & Torrie1960).

RESULTS AND DISCUSSION

Survival time of M. rnicrum treated with l/-1MKMn04 was not significantly different fromun treated ones. The results at the end of the 20­day feeding trial are summarised in Table 2.

Table 2Average weight gain, feed conversion and

survival rate for Clanas rnaCTocejJhalus larvae feddiets containing different types of

M. micrum.

Means in the same row with the same superscript arenot significantly different (P<O.05).

Both Diets 1 and 2 which consisted oflive M.rnicrum were preferred by the larvae comparedwith a tentative and delayed acceptance of thefrozenM. micrum.DabrowskiandBargeda (1984)observed that coregonid larvae accepted live foodmore readily than artifical diets. The food intakeoflarvae is dependen t on such factors as mobility(Braum 1978), chemical attractan ts (Applebaum1979) and physical characteristics such as particlesize and texture (Dabrowski & Bargeda 1984) ofthe feeds. Thus it is possible that the mobile liveand KMn04 treated M. micrum (Diets 1 and 2)were chemically and physically more attractive.

368 PERTANlKA VOL. 13, NO.3, 1990

CSE OF LIVE, FROZE:-.I AND POITASIUM PERMANGANATE TREATED ill!. MICRURA FOR CATFISH LARVAE

The relative growth and survival rates oflarvae and the feed conversion ratios for theexperimental diets are presented in Table 2.Larvae fed on live untreated (Diet 1) and KMn0

4treated (Diet 2) M. rnic11lra had similar growthrates whereas larvae fed on frozen lVI. rnicrura hadthe lowest growth rate. Fish fed Diet 1 showed asignificantly higher growth rate than that fedDiet3. However, no significant difference betweenDiets 2 and 3 was observed. Several observationshave been reported regarding the use of frozenzooplankton as an experimental food for fishlarvae. Fruchter (1980) reported that Arterniaremained completely effective as larval food afterbeing slowly frozen, although a gradual loss in anessential growth substance was observed. Theyfound that whitefish larvae completedmetamorphosis equallywell when fed with Artemiathat had been shock frozen in liquid nitrogen (­196° C) up to at least 2 hours after thawing or withlive A1·temia. Biochemical analysis of frozen andfreeze-dried zooplankton showed that proteasesand enzymes of intermediary metabolism werenot diminished by freezing, freeze-drying or bystorage at-18°C (Grabner et al. 1981). However,upon thawing, these freeze damaged cellimmediately release as much as 70-75% ofproteases and much more ofamino acids into thewaterwithin 10 minutes. Thus frozen zooplanktonis not suitable as a larval diet due to leaching ofnutrients once they are thawed.

The feed conversion ratio was lowest for Diet1 but this was not significantly lower than that ofDiet 2. Diet3 had a significantly higher conversionratio compared with Diet 1. This is consistentwiththe fact that the nu tri tive value offrozen M. rnicrurais lower than that oflive ofKMn°4 treated sampIes.

The survival rates of the larvae for all thetreatments were high and not significantlydifferent. This suggests that KMn04 treatmentand slow freezing can eliminate or lower the levelof pathogens present in the M. micrura culture.However, the high survival of larvae fed onuntreated M. micrura during the experimentsuggest that the batch of lVI. micruraused as controlwas either not highly contaminated or that thefish larvae were physiologically healthy enoughto withstand infection. Previous experience usinguntreated M. micrura had often resulted ininconsistencies in larval survival; low larval survivalwas found to be due to fungal and bacterial

infections.The lack of significant difference in the

relative growth rates and feed conversion ratiosoflarvae fed with untreated and KMn0

4treated

M. miClura indicated that the nutritive quality ofthe treated M. micrura is comparable to theuntreated samples. Hence, instead of treatingthe larvae with KMn0

4only when they are

infected, which is often too late, M. miClUra itselfshould also be treated with KMn0

4prior to

feeding to avoid microbial infections. Presently,studies are being carried out to determine thelowest level of KMn04 required to effectivelyeliminate these microorganisms with minimaltoxicity to the M. miClUra and larvae.

CONCLUSION

The use of KMnO of to treat lVI. micrum prior tofeeding ensures a high survival rate of Clariasmacrocephaluslarvae. It is therefore recommendedthat Moina micruraobtained from farms be treatedroutinelywith KMn04 to minimise larval infectioncaused by microorganisms present in this naturalfood.

ACKNOW1EDGEMENTS

This studyis funded by the Malaysian GovernmentResearch & Development Grant 1-07-06-01-08.

R. HASHIMA. ALI

School ofBiological SciencesUniversiti Sains Malaysia11800, Pulau Pinang, Malaysia

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PERTANlKA VOL. 13, NO.3, 1990 369

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(Received 22 janumy, 1990)

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