,•

SPONSORS

Hydrobiologists from East, Central and West Africa with substantial support from otherAfrican countries, Fishery Scientists in the United States, Canada, U. K., Europe, SovietUnion and Israel.

EDITOR

Dr. 1. Okedi, Director, E.A.F.F.R.O., Jinja, Uganda.

EDITORIAL BOARD

AN INSTANCE OF

SOUTHERN OFFSH

G. E. B. KITAKA

Mr. M. Abolarin, Co-Manager, Kainji LakeProject, Lagos, Nigeria.Mr. J. Kambona, Chief Fisheries Officer,Dar es Salaam, Tanzania.Mr. J. Mubanga, Director, Fisheries Division,Chilanga, Zambia.Dr. L. Obeng, Director, Institute of AquaticBiology, Achimota, Ghana.Mr. N. Odero, Director of Fisheries, Nairobi,Kenya.Mr. S.N. Semakula, Chief Fisheries, Officer,Entebbe, Uganda.

PROGRAMME

Professor W.B. Banage, Makelere Univer­sity, Kampala, Uganda.Mr. R.E. Morris, Director, E.A.M.F.R.O.,Zanzibar.Dr. T. Petr, Senior Lecturer in Hydrobiology,Makerere University, Kampala, Uganda.PlOfessor Mohamed Hyder, University ofNairobi, Kenya.Professor, A. F. De Bont, Universite deKinshasa, Kinshasa XI, Republique Demo­cratique du Zaire

E~

W~

m;thmiVile(

G.Jil

The African Journal of Tropical Hydrobiology and Fisheries will only accept original andwell suppOIted ideas on techniques, methodology and research findings from scientists, fishery

fficers, fishery economists and sociologists.The Journal will therefore strengthen the African lesearch scientist by making researchmaterial available and also increasil1g the awareness and utility of aquatic resources.[ts quality will conform to International standards, and will be published in English andFrench.

MANUSCRIPT ADDRESSManuscripts should be addressed to E.A.F.F.R.O.,EastAfrican freshwater Fisheries, ResearchOrganisation, East African Community, Box 343, Jinja, Uganda.

REPRINTSAuthors will receive 60 reprints free of charge. Extra reprints may be procured on cost.

PUBLISHEREast African Literature Bureau, P.O. Box 30022, Nairobi, Kenya.

ISSUESThe Journal consists of one volume n year, consisting of two issues with approximatelyeighty pages each.

SUBSCRIPTIONAnnual subscription within East Africa Sh. 35. Outside East Africa, East African Sh. 70,

$ 10.00

Upwelling of deep watsurface is of great biolcespecially in stratified lakespreviously locked up inwater are brought up into I

zone; but the process mayphic mortalities of animfish, if this water shoulecontain appreciable amausuch as hydrogen sulphiddioxide (WOR THHGRAHAM 1929; FISH UTER 1963, 1968; AeRIE1966).

Upwelling is normally ilcurrents moving away frby a downward leewardmocline in response to thepilimnetic water, and ofcurrents associated with tlthe thermocline during ,movement after cessatior

A

..,

SPONSORS

Hydrobiologist from East, Central and West Africa with substantial support from otherAfrican countries, Fishery Scientists in the United States, Canada, U. K., Europe, SovietUnion and Israel.

EDITOR

Dr. J. Okedi, Director, E.A.F.F.R.O., Jinja, Uganda.

DITORIAL BOARD

Mr. M. Abolarin, Co-Manager, Kainji LakeProject, Lag s, Nigeria.Mr. J. Kambona, Chief Fisheries Officer,Dar e Salaam, Tanzania.Mr. J. Mubanga, Director, Fi heries Division,Chilanga, Zambia.Dr. L. Obeng, Director, Institute of AquaticBiology, Achimota, Ghana.Mr.. Odero, Director of Fisheries, Nairobi,Kenya.Mr. S.N. Semakula, Chief Fisheries, Officer,Entebbe, Uganda.

PROGRAMME

Professor W.B. Banage, Makelere Univer­sity, Kampala, Uganda.Mr. R.E. Morris, Director, E.A.M.F.R.O.,Zanzibar.Dr. T. Petr, Senior Lecturer in Hydrobiology,Makerere University, Kampala, Uganda.PlOfessor Mohamed Hyder, Univer ity ofNairobi, Kenya.Professor, A. F. De Bont, Universite deKinshasa, Kinshasa XI, Republique Demo­cratique du Zaire

The African Journal of Tropical Hydrobiology and Fisheries will only accept original andwell support d ideas 011 techniques, methodology and research findings from scientists, fisheryofficers, fishery economists and sociologists.Th Journal will therefore strengthen the African lesearch scientist by making researchmaterial available and also increasing the awareness and utility of aquatic resources.It quality ill conform to International standards, and will be pubh h d ill English andFren h.

MANUSCRIPT ADDRESSManuscripts should be addressed to E.A. F.F. R.O., East African Freshwater Fi, heries, ResearchOrgal isation, East African Community, Box 343, Jinja, Uganda.

REPRiNTSAuthors will receive 60 reprints free of charge. Extra reprints may be procureJ on cos1.

PUBLISHEREast African Literature Bureau, P.O. Box 30022, Nairobi, Kenya.

ISSUESThe Journal consists or one volum [l year, consisting of two issues with approximatelyeighty pages each.

SUBSCRIPTIONAnnual subscriptIon within ast Africa Sh. 35. Outside East Aflica, East African Sh. 70,

S $ 10.00

t..

THE TOXICITY OF FOUR INSECTICIDES AND A HERBICIDE

UNDER TROPICAL CONDITIONS

R. L. WELCOMME

The toxicitie, of fOUf insecticides and a llerbicide to Till/pia I/lUcruchir weretested in the laboratory. The 24 hour LC.,,'s were estimated as follows:Endrin 20o/c , 0.008 ppm; Lindane 5% granules, 4.6 ppm; Synexa 50 (HCH50%),5.6 ppm; Synex8 25 (HCH 25%), 14.8 ppm; TOK herbicide (Nitrofen),100% survival for 24 hours at 100 ppm. These estimates agree with resultsob\aiued by othe-r workers elsewhere in the world. The laboratory determi­nation of toxicity is important in e'stima,ting the direct effects of poisonoussubstauces on fish, but other indirect effects may r~sllJL from their use. Theseshould be investigated in the field.

R. L. We/can/me, UI/iled Naliul/s Develupmel/I P"uyramme (UND?),CuIOI/OU. Dahomey.

Present address:Ii/fui/d Fishery Resollrces Bral/ch. Fishery Rnvllrces Divi.\ivi/. DepaJ'll'ilel/1

of Fisheries, F,lO, Rume.

The estimation of the toxicity of the manysubstances that tind their way into the world'swaterways has become increasingly imporl­ant. In Africa the problem of contaminationby industrial wastes is generally less severethan in some parts of the globe where a com­plete degradalion of the aquatic environmentoccurs. The need for maximum productionof food. however. may precipitate a conflictbetween the demands of agriculture and thoseof fisheries, for among other things the habi­tual use of insecticides and other toxic pro­ducts to improve the agricultural yield canhave a disastrous effect on the quality andyield of the associated waterways. This prob­lem is especially acute in those regions whererice culture is practised and a particularlyclose relationship exists between the cerealcrop and the water. Such a situation was typi-

fled in Dahomey (West Africa) when theauthor wa$ serving there as a Food and Agri­culture Organization /Technica.l Assistance(FAO / T A) Inland Fishery Biologist. AUNDP/FAO/Special Fund/Pilot Project forthe development of the Oueme VaHey wasestablishing rice culture of the Oueme Riverfloodplain that also supports a rich and high­ly developed fishery. The project personnelwere concerned that the various biocides tha twere thought necessary for the achievementof maximum rice yields might prove dele­terious to the fishery. Little published infor­mation exists on the effects of biociJes in thetropical African environment. most studieshaving been carried out in temperate Europeand North America. The author was there­fore requested to assess under local conditionsthe toxicities and other possible harmEul

THE TOXiCITY OF FOUR INSECTICiDES AND A HERBICIDE

UNDER TROPICAL CONDITIONS

R. L. WELCOMtvJE

The toxicitie, ot four insecticides and a herbicide to Ti!opia IIweru<;hir weretested In rhe laboratory. The 24 hour LC.,,'s were estimated as follows:Endrin 20%, 0.008 ppm; Lindane 5% granules, 4.6 ppm; Synexa 50 (HCH50%),5.6 ppm; Sy'nexa 25 (HCH 25%), 14.8 ppm; TOK hCTbicide (Nirrofen),100% survival for 24 hours at 100 ppm. These estimates agree with resultsoblaiued by other workers elsewhere in the world. The labora tory determi­na.tion of toxicity is important in estima,ring the direct effects of poisonoussubstances on fish, but other indirect effects may result from their use. Theseshould be investigated in the field.

R. L. WelcOl/1me, UI/ired Nariulls Deve!UjJmellr P1'()JjrCI/1II1'/(' (UNDPj,CUrO/lo/./. Dahomey.

Present address:II/Iulld Fishery Resu/lrces Brol/ch. Fisher)' R"SOI.II"U'.I' Divi.\iol/. Deporrmel/r0/ Fisheries, FdO, Rume.

The estimation of the toxicity of the manysubstances that tind their way into the world'swaterways has become increasingly import­ant. In Africa the problem of contaminationby industrial wastes is generally Jess severethan in some parts of the globe where a com­plete degradation oj' the aquatic environmentoccurs, The need for maximum productionof food, however, may precipitate a conflictbetween the demands of agriculture and thoseof fisheries, for among other things the habi­tual use of insecticides and other toxic pro­ducts to improve the agricultural yield canhave a disastrous effect on the quality andyield of the associated waterways, This prob­lem is especially acute in those regions whererice culture is practised and a particularlyclose relationship exists between the cerealcrop and the water. Such a situation was typi-

fled in Dahomey (West Africa) when the.author wa~ serving there as a Food and Agri­culture Organization jTechnical Assistance(FAO / T A) Inland hshery Biologist. AUNDPj -AO/Special Fund/Pilot Project forthe development of the Oueme Valley wasestablishing rice culture of the Oueme Riverfloodplain that also supports a rich and high·ly developed fishery. The project personnelwere concerned that the various biocides thatwere thought necessary for the achievementof maximum rice yields might prove dele­terious to the fishery. Little published infor­mation exists on the effects of biociJes in thetropical African environment. most studieshaving been carried out in temperate Europeand North America. The author was there­fore requested to assess under local conditionsthe toxicities and other possible harmful

108 R. L. WELCOMME

effects of the various products available tothe project. The following paper presents theresults of the laboratory tests undertaken andalso discusses some of the sublethal effectsthat may arise from the use of such biocides.

METHODS

Young pond-reared Tilapia macrochir(Boulenger) of 40 to 80 mm standard lengthwere' acclimatized to laboratory conditionsfor several weeks. Tests were carried out in4-litre aquaria at temperatures of between25° and 27° C. Batches of three fish were ex­posed to different concentrations of the sub­stance under study and the individual survivaltimes were recorded and ll;sed to calculatemedian survival time for each concentration.The tests ended after 2LJ. hours. The solutionsin the aquaria were 110t changed, thereforethe tests were carried out under static condi­tions which correspond to the single flush oftoxic material that may result on spraying acrop, rather than to the continuous dischargerepresented by the methodology developedby ALABASTER and ABRAM (1965). Thefact that the tests were static implies thatthere was a loss of toxic material throughoutthe test due to uptake by the fish and possiblydue to volatilisation and breakdown. Forthis reason the estimated survival times wereprobably inclined to be longer than theywould be in the situation whe,re the solutionis maintained at its original concentration.

RESULTS

Endrin

The preparation presented for test contain­ed 20% of the active ingredient, a chlorinatedhydrocarbon, in the form of a liquid freelymiscible with water. The results obtained arepresented in Fig. 1. The extrapolated concen­tration of the formulation which would pro­duce the death of 50% of the fish with·in 24hours (24 hour LCso) was 0.008 ppm. This

estimate compares well with estimates byother workers (McKEE and WOLF 1963).

The extreme toxicity of Endrin, togetherwith its persistence in the: aquatic environ­ment (IYATOMI et al. 1958) makes the useof this substance extremely inadvisable in anyarea where there is any possibility of it pene­trating waters containing fish.

Lindane 5%The preparation presented for test was in

the form of insoluble granules containing 5%of the active ingredient, a chlorinated hydro­carbon. Test concentrations, based on theamount of active ingredient, were preparedfrom three stock solutions each producedafter a different period of contact betweenone gram of granules and one litre of water(4, 12, and 24 hours). The toxicity of thesolutions was greater the longer the period ofcontact (Fig. 2). All the active ingredient wasassumed to have entered into solution after24 hours. The 24 hour LCso was 4.6 ppmestimated from those concentrations made upafter 24 hours o{ contact between granulesand water.

Even taking into account the low percent.age of active-ingredient in this formulation,its toxicity is considerably less than wouldhave been expected from much of the pre­vious work (McKEE and WOLF 1963),However, in many of these experiments theLindane was dissolved in acetone prior tomaking up the solutions and thus was morereadily available to the fish. In other te.stswhere this practice was presumably notadopted, the estimated toxicity was muchcloser to the above values (DEPT. OF SCIAND INDUST. RES. 1958).

In rice culture. Lindane is usually scatter­ed on the ground some time before the flood­ing of the rice paddies. It is therefore possiblethat some degradation of the product willoccur before it reaches the water. To testthis, one gram of Lindane granules was mix­ed with damp soil and kept for 57 days. Three

1000

-tilcE-Ql

Ei='iii 100>'>..~

t/)

c.~1JQl

~

10

Fig. 1. SUrviViall fi~h were

~

h'.

/

108 R. L. WELCOMME

effects of the various products available tothe project. The following paper presents theresults of the laboratory tests undertaken andalso discusses some of the sublethal effectsthat may arise from the use of such biocides.

METHODS

Young pond-reared Tilapia macrochir(Boulenger) of 40 to 80 mm standard lengthwere acclimatized to laboratory conditionsfor several weeks. Tests were carried out in4-litre aquaria at temperatures of between25° and 2r C. Batches of three fish were ex­posed to different concentrations of the sub­stance under study and the individual survivaltimes were recorded and ~sed to calculatemedian survival time for each concentration.The tests ended after 2L; hours. The solutionsin the aquaria were llot changed, thereforethe tests were carried out under static condi­tions which correspond to the single flush oftoxic material that may result on spraying acrop, rather than to the continuous dischargerepresented by the methodology developedby ALABASTER and ABRAM (1965). Thefact that the tests were static implies thatthere was a loss of toxic material throughoutthe test due to uptake by the fish and possiblydue to volatilisation and breakdown. Forthis reason the estimated survival times wereprobably inclined to be longer than theywould be in the situation wheTe the solutionis maintained at its original concentration.

RESULTS

Endrin

The preparation presented for test contain­ed 20% of the active ingredient, a chlorinatedhydrocarbon, in the form of a liquid freelymiscible with water. The results obtained arepresented in Fig. 1. The extrapolated concen­tration of the formulation which would pro­duce the death of 50% of the fish with·in 24hours (24 hour LCso) was 0.008 ppm. This

estimate compares well with estimates byother workers (McKEE and WOLF 1963).

The extreme toxicity of Endrin, togetherwith its persistence in the aquatic environ­ment (IYATOMI et al. 1958) makes the useof this substance extremely inadvisable in anyarea where there is any possibility of it pene­trating waters containing fish.

Lindane 5%The preparation presented for test was in

the form o-f insoluble granules containing 5%of the active ingredient, a chlorinated hydro­carbon. Test concentrations, based on theamount of active ingredient, were preparedfrom three stock solutions each producedafter a different period of contact betweenone gram of granules and one litre of water(4, 12, and 24 hours). The toxicity of thesolutions was greater the longer the period ofcontact (Fig. 2). All the active ingredient wasassumed to have entered into solution after24 hours. The 24 hour LCso was 4.6 ppmestimated from those concentrations made upafter 24 hours of contact between granulesand water.

Even taking into account the low percent­age of active-ingredient in this formulation,its toxicity is considerably less than wouldhave been expected from much o,f the pre­vious work (McKEE and WOLF 1963),However, in many of these experiments theLindane was dissolved in acetone prior tomaking up the solutions and thus was morereadily available to the fish. In other testswhere this practice was presumably notadopted, the estimated toxicity was muchcloser to the above values (DEPT. OF SCIAND INDUST. RES. 1958).

In rice culture. Lindane is usually scatter­ed on the ground some time before the flood­ing of the rice paddies. It is therefore possiblethat some degradation of the product willoccur before it reaches the water. To testthis, one gram of Lindane granules was mix­ed with damp soil and kept for 57 days. Three

,..

TOXICITY OF FOUR INSECTICIDES AND A HERBICIDE 109

Fig. 1. Survival of Tilapia macrochir in Endrin 20%. Vertical bars represent lime between when

all fish were observed alive (bottom of bar) and when all fish were observed dead (top' of bar).

•

•

•

Concenttat ion (ppm)

1000

CilEi='iii 100>'S;..:lIJ)

~VIc:E-

ted for test was in~ les containing 5%chlorinated hydro­

'ns, based on thet, were prepared

ilS each produced

~ contact betweenone litre of water

he toxicity of the

mger the period oftive ingredient wasInto solution after

,Coo was 4.6 ppm:nlrations made up

between granules

/lith estimates by

nd WOLF 1963).: Endrin, together~ aquatic environ­

58) makes the useinadvisable in any

ssibility of it pene­sh.

.t the low percent.this formulation,

( less than wouldmuch of the pre.d WOLF 1963),e experiments the

acetone prior toldthus was more)h. In other tests

presumably not'xicity was much(DEPT. OF SCI

58).is usually scatter­

: before the flood­therefore possiblethe product wille water. To test

~anules was mix­'or 57 day.. Three

TOXICITY OF FOUR INSECTICIDES AND A HERBICIDE 109

1000

~IIIc:E-~

Ei='iii 100>';;..::l

IJ)

c:III

:s~

~

•

1o·-L----.----,----,---.....--r----r--3T.l--1ro-~3~1-~,~O=-O~

Concenttat ion (ppm)

Fig. 1. Survival of Tilapia macrochir in Endrin 20%. Vertical bars represent time between when

aJl fish were observed alive (bottom of bar) and when all fish were observe<! dead (top of bar).

I J 0 R. 1.. WFLCOMME

Fig. 2. Survival of Tilopia moel'oeilil' in Lindane 5%. Solution prepared with 1 gm of product leftiu contact with 1 litre of water for 4 hou['s (x ... xi, 12 hours (0 - - - 0), and 24 hours (e--e).

!'\

Synexa 50 and,

These product:of very limiteddient (Hexachlored hyd rocarbon)tion of 50% (Sj25). Test solutiorfrom a stock preduct left in canfor 24 hours.

The results anextrapolated 24Synexa 50 and ]<

values are entirelof other workers

Synexa was itfloods at a cancelfor Synexa 50 ;Synexa 25. Wh<depth of static wppm Synexa 50 (result after treatl

25J610

The recommer5% granules isOueme flood plaimetres of water,ppm may be pr<undated to a dtwater. This can,estimated 24 hOI

Table J. Toxicity,Rnd after 57 days

Coneentratioll (ppn

lest solutions weigranules which \1

one litre of wat<of this tesl Crabthe survival timea loss in toxicjt~

this product in I

o

)<.

100

"o

..

63

"

40

x

251610

,\,

\\\\\\\\, )<.\,,,,,,,,,,

? '. ,o '\

"\ 0,,,,,,,,, , , , ,

o " .... ,"

0','"

"," ...........

Concentration (ppm)

6'3

1

4'0

1000

100

"If)cE..-

QI

E~

iii>>~

::Il/)

CC\l

-0QI

~ 10

)

•,

I J0 R. 1.. WFLCOMME

o

x

""

o

..

""

"

x

"

x

I\III\\,

\\\\\\\\\

\\\

\\ ,

? "o " ,

"\ 0,,,,,,,,, , , , ,

o ' ........."

C>',..............

..........." "

1 J.I

1000

100

"<J1c:E

QI

Et=r\l>>~

:::lVl

c:n:l

"0QI

:E 10

4'0 10 16 25 40I

63I

100

Concentration (ppm)

Fig. 2. Survival of Ii/apia macrochir in Lindane 5%. Solution prepared with 1 gm of product leflin contact with 1 litre of water for 4 hours (x ... x), 12 hours (0 - - - 0), and 24 hours (e--e).

110 R. L. WELCOMMF

Fig. 2. Survival of Tilapia maclachi, in Lindane 5%. Solution pl'epared with I gm of product leffin contact with 1 jitre oE water for 4 hours (x ... x), 12 hours (0 - - - 0), and 24 hours (e--e).

II I 1 I I I I ' '--

4'0 6'3 10 16 25 40 63 100

Synexa 50 and 5These produds

of very limited sdient (Hexachlorced hydrocarbon)tion of 50% (Syr25). Test solution:from a stock pre[:duct left in contifor 24 hours.

The results areex tra poJa ted 24 1Synexa 50 and ]4values are entjreJ~

of otheT workersSynexa was in

floods at a concerfor Synexa 50 aSynexa 25. Whedepth of static Wi

ppm Synexa 50 aresult after treatn

25]610

The recommen5 % granules isOueme flood plairme tres of wa ter,ppm may be proundated to a dewater. This conoestimated 24 hou

Table I. Toxicity (a nd a Eter 57 days I

COl/cel/fralion (ppm

test solutions wegranules which 'i'

one litre of watfof this test (Tabthe survival timea. loss in toxicinthis product in 1

x

o

--," "

o

"

x

x

\\\

\\\

\\

\

? "o " \

'\.0\

\ ,,\

\ ,\

\ , , ,o "

' ............0"_---

'.

'.

Concentration (ppm)

6,,\\\

11000

100~

(J)

c:

E-<11

Et=~>>...::l:f)

c:~

"0ell

~ 10

", '. /

110 R. L. WELCOMMF

1000

'00'""'

Cflc:::

E

C1I

Ei=~

>>....::l

(/)

c:::o:l

"0C1I

::!: '0

1 61\\1\

'.

x'.

\ '.\\

\

" X\\

\

? "o " \

\,0,,,,,,,,,, , , ,

0 .. o

..

"

o

-'---------4'·0---6'·3---.'0----,1~---2'15---4Tb--'61'3--1·C;O-

Concentration (ppm)

Fig. 2. Survival of Tilapia macrochir in Lindane 5%. Solution pl'epared with I gm of product leffin c:ontacl wilh 1 litre of water for 4 hours (x". x), 12 hours (0 - - - 0), and 24 hours (e--e).

I JO R. L. WELCOMMF

Fig. 2. Survival of Tilapia macrochir in Lindane 5'70. Solution prepared with 1 gm of product Jeflill contacl with 1 litre of: water for 4 hours (x ... x), 12. hours (0 - - - 0), and 24 hours (e--e).

Concentration (ppm)

Synexa 50 and 5These products

of very limited sdienl (Hexachlorccd hydrocarbon)lion of 50% (Syr25). Test solution:from a stock prer:duct left in cant;for 24 hours

The results areextrapolated 24 1Svnexa 50 and 14values are entjrel~

of other workersSynexa was in

floods at a concerfor Synexa 50 aSynexa 25. Whedepth of static w;ppm Synexa 50 aresult after treat]1

25J610

The recommen5 % granules isOueme flood plairmetres of water,ppm may be proundated to a dewater. This conoestimated 24 hou

Table / Toxicity (and after 57 U:lYs ,

COl/cel/tra/ion (ppm

test solutions wegranules which \l

one litre of watfof th is test (Tabthe survival timea loss in toxicit~

this product in j

o

J<

1100

~

o

613

'.

140

x

125

11610

x

\,,,,,,,,? "

o " ," 0,,,,

"" ,, ,-, ,

o " --­'­0..........."

'-,'"

"-

6'3

6,,\\\

4'0

11000

100"""'enc:

E-~

Ei=~>>....::::l

tJ)

c:~

"0~

~ 10

)

•l "

1J0 R. L. WELCOM.MF

o

xo

,o " ...........

"0' ......

.................................

°0

\\

\\

" J(\\

\

? \o \

\\ \ 0

\

"\ " .." ..

\ ,\ , ,

6,,\\\

1000

100~

<J'lC

E

QJ

Et=r\l>>...:l'J)

Cr\l

"0QJ

:!: 10

I16

I25

I40

I100

Concentration (ppm)

Fig. 2. Survival of Tilapia macrochir in Lindane 5%. Solution prepared with 1 gm of product Jetlin contact with 1 litre of: water for 4 hours (x. , . x), 12 hours (0 - - - 0), and 24 hours (e--e).

,", 4

TOXICITY OF HJUR l.NSECT1C[I)],S AND A HERBICIDE I I I

Tobie 1. Toxicity of Lindane 5 % granules beforeand a.fter 57 d<tys contact with mOlst soil.

test solutions were then prepared using thesegranules which were then left in contact witllone litre of water for 24 hours. The resultsof this test Crable 1) showed an increase inthe survival time of the fish which indicateda loss in toxicity due to the degradation ofthis product in the soil.

",

COl/centl'alion (ppm)

25J610

M edirm snl'vival tilne (mil/)

Dny 0 Day 57J 5 11831 337

280 508

greater than these concentrations for bothsubstances and they may be safe for use at thedosages proposed subject to satisfactory sup­plementary observations jn the field.

[OK Herhicide (Nirrofen B.S.l.)

TOK herbicide (2, 4 DichloroA Nitro Di­phenyl Ether) was in the form of granules oflimited solubiJity. One gram was left in con­tact with one litre of water for 24 hours be­fore making up the test solutions. The resultsobtained are summarised in Table 2.

Tobie 2. Tox.icity ot TOK herbicide.

TOK herbicide was intended for useagainst the'dense masses of floating vegeta­tion which constantly invade and choke thevarious irrigation ditches and channels. Therelatively high concentration tolerated by fishsuggests thal the compound is safe for thispurpose from the standpoint of its toxicity,

DISCUSSION

Tn the Hght of present-day knowledge ofthe pollutic~n of the aquatic environment. itis axiomatic that the use of biocides in oraround waters that either support valuablefisheries, or that drain into such, is an ex­tremely dangerous practice. However, theneed to maximise food production oftenseems to require the employment of theseagents. We are, therefore, frequently present­ed with situations which necessitate a choicebelween the sacrifice of a fishery in the inter­est of an increase in agricu Jtura] yield, or acompromise, where bOlh agricultural andfishery interests are to some extent safeguard­ed. In lhe latter case a less effective but lesstoxic product may be favoured over one thatis more effective but lethal to fish or fishfoods. Here a knowledge of the toxicities of

"'.

ox

" "..................

"o

gm of product leftL hours .--.

The recommended treatment with Lindane5 % granules is 16 kg per hectare. As theOueme floodplain is submerged under 1 to 2metres of water, concentrations of up to 1.6ppm may be produced when the land is in­undated to a depth of 1 metre with staticwater. This concentration is lower than theestimated 24 hour LCjo of 4.6 ppm.

Synexa 50 and Synexa 25

These products were in the form of powdersof very limited solubility. The active ingre­dient (Hexachloro cyclo Hexane, a chlorinat­ed hydrocarbon) was present in the propor­tion of 50 % (Synexa 50) and 25 % (Synexa25). Test solutions were in each case made upfrom a stock prepared from one gram of pro­duct left in contact with one litre of waterfor 24 hours.

The results are presented in Fig. 3 and theextrapolaled 24 hour LCoo was 5.6 ppm fOfSynexa 50 and 14.8 ppm for Synexa 25. Thesevalues are entirely consistent with the findingsof other workers (McKEE and WOLF 1963).

Synexa was intended for use during thefloods at a concentration of 2.5 kg per hectarefor Synexa 50 and 20 kg per hectare forSynexa 25. When inundated to one metredepth of static water, a concentration of 0.25ppm Synexa 50 or 2.0 ppm Synexa 25 wouldresult after treatment; the 24 hOUf LC~n 's a.re

COI/l;elllmfioll (ppm)1000310100

Median survival time (mill)330720

100% survival for 24 hours

TOXIClTY OF H)UR lNSECTlCfD]oS AN)) A HERBICIDE III

Table J. Toxicity of Lindane 5 % granules beforeand after 57 days conlact with moist soil.

test solutions were then prepared using thesegranules which were then left in contact withone Ii tre of wa ter for 24 hours. The resultsof this test Crable 1) showed an increase inthe survival time of the fish which indicateda loss in toxicity due to the degradation ofthis product in the soil.

COl/eenttolion (ppm)

25J610

Median survival tir/"le (117il/)

Doy 0 Day 5715 11831 337

280 508

greater than these concentrations for bothsubstances and they may be safe for use at thedosages proposed subject to satisfactory sup­plementary observations in the field.

TO K Her hicide (Nitrofen B.S.l.)

TOK herbicide (2, 4 Dichloro-4 Nitro Di·phenyl Ether) was in the form of granules oflimited solubility. One gram was left in con·tact with one litre of water for 24 hours be­fore making up the test solutions. The resultsobtained are summarised in Table 2.

Tobie 2. Tox.icity of TOK herbicide

TOK herbicide was intended for useagainst the dense masses of floating vegeta­tion which constantly invade and choke thevarious irrigation ditches and channels. Therelatively high concentration tolerated by fishsuggests that the compound is safe for thispurpose from the standpoint of its toxicity,

DISCUSSION

Tn the light of present-day knowledge ofthe pollution of the aquatic environment. itis axiomatic that the use of biocides in oraround waters that either support valuablefisheries, or that drain into such, is an ex­tremely dangerous practice. However. theneed to maximise food production oftenseems to require the employment of theseagents. We are, therefore, frequently present­ed with situations which necessitate a choicebetween the sacrifice of a fishery in the inter­est of an increase in agricultural yield. or acompromise, where both agricultural andfishery interests are to some extent safeguard­ed. In the latter case a less effective but lesstox.ic product may be favoured over one thatis more effective but lethal to fish or fishfoods. Here a knowledge of the toxi ities of

The recommended treatment with Lindane5 % granules is 16 kg per hectare. As theOueme flood plain is su bmerged under 1 to 2metres of water, concentrations of up to 1.6ppm may be produced when the land is in­undated to a depth of 1 metre with staticwater. This concentration is lower than theestimated 24 hour LCjo of 4.6 ppm.

Synexa 50 and Synexa 25These products were in the form of powders

of very limited solubility. The active ingre­dient (Hexachloro cyc\o Hexane, a chlorinat­ed hydrocarbon) was present in the propor­tion of 50 % (Synexa 50) and 25 % (Synexa25). Test solutions were in each case made upfrom a stock prepared from one gram of pro­duct left in contact with one litre of waterfor 24 hours.

The resu lts are presented in Fig. 3 and theextrapolated 24 hour Le:;o was 5.6 ppm forSynexa 50 and 14.8 ppm for Synexa 25. Thesevalues are entirely consistent with the findingsof other workers (McKEE and WOLF 1963).

Synexa was intended for use during thefloods at a concentration of 2.5 kg per hectarefor Synexa 50 and 20 kg per hectare forSynexa 25. When inundated to one metredepth of static water, a concentration of 0.25ppm Synexa 50 or 2.0 ppm Synexa 25 wouldresult after treatment; the 24 hour L ~,,'s are

COIICel1lmliol/ (ppm)1000

310100

M ediall sl/rvival lime (mill)330720

fOO%surviva[ for 24 hours

112 R. L. WELCOMME

10 I I I I T

Fig. 3. Survival of Tilapia macrochi,. in Synexa 50 (.--.) and Synexa 25 (0 - - - 0).

the various biocidthis context it is 01

of toxicity of theabove were consisted by other workeOn this slender e'be concluded thatvironment behave itemperate zone cwork is required, hsality of this conel

The measuremeIratory serves as a gJ

effects of the prod,field, and is particling such highly tcwhose use was abathe basis of the alcompounds tested,judged to be ani)Synexa 50 and SynTOK appears to lworking dosages.

In interpreting tlborne in mind thaipresence of toxic subwell belOW those thathe use of insecticideculture, may discouinto the treated area.tats, such as the rietto the breeding of 1

grate into them inand any hindrance t(hibit successful rep!eggs and fry may dilviduals in both thtpoison and their attimed applications (seriously reduce one

Less direct effeotssuch as the Ouemeof the species are in:peated use of insecti,tions below those ttthe fish, could elirnin

1000100

Concentration (ppm)

10

II

100%' 66~ 33%

! ! \ J,II,,

IIIIIII\\\

\0\\\\\\

\\

\\

\\ ,,,

\ ,\ ,

'(),\

\ ,,,....0' ..

""0

100% 66%

1

1000

"":'tJlc:E-GI

Ei=lU>'>...:::l

II) 100c:lU:cGI

:IE

>

•1 '.

/

112 R. L. WELCOMME

1000

~VIr::E-Q)

Et=eu>>...~

CJ) 100r::eu

:osQl

:IE

100% 66%

1,\

100%' 66~ 33%

! b\ 2"0,\,

\,\\,,

\\\\\\

" 0\\\\\\

\\\,,,,,,,,,,

'(),,,,,,,,0',

''0

10---.l-,...----------r---------r--------r-"-----10 100

Concentration (ppm)

1000

Fi8. 3. Survival of Tilapia macrochil' in Synexa 50 (e--e) and Synexa 25 (0 - - - 0).

,..

TOXICITY OF FOUR JNSECTlClDES AND A HERBIClDE 113

-r1000

(0---0).

the various biocides available is essential. Inthis context it is of interest that the estimatesof toxicity of the four insecticides examinedabove were consistent with the results obtain­ed by other workers elsewhere in the world.On this slender evidence it may tentativelybe concluded that fishes in the tropical en­vironment behave in a similar manner to theirtemperate zone counterparts. Much morework is required, however, before the univer­sality of this conclusion can be established.

The measurement of toxicity in the labo­ratory serves as a guide to the probable directeffects of the product when it is used in thefield, and is particularly valuable in indicat­ing such highly toxic products as Endrin,whose use was abandoned in the Oueme onthe basis of the above work. Of the othercompounds tested, however, Lindane 5 % isjudged to be only marginally acceptable.Synexa 50 and Synexa 25 may be safe andTOK appears to be safe at the proposedworking dosages.

In interpreting these results, it must beborne in mind that fish may react to thepresence of toxic substances at concentrationswell below those that are lethal. For instance,the use of insecticides, particularly in wet riceculture, may discourage fish from movinginto the treated area. Vegetation grown habi­tats, such as the rice paddies, are importantto the breeding of many species which mi­grate into them in order to lay their eggs,and any hindrance to this movement may in­hibit successful reproduction. Furthermore,eggs and fry may differ from the larger indi­vid uals in both their susceptibility to thepoison and their ability to avoid it. Badlytimed applications of toxicant may therebyseriously reduce one year's recruitment.

Less direct effeots are also likely. In areassuch as the Oueme floodplain the majorityof the species are insectivorous. Here the re­peated use of insecticides, even in concentra­tions below those that would directly affectthe fish, could eliminate most of the potential

food and in this way diminish the fish crop.Alternatively some persistent insecticides maybuild up in the food chain, being stored inthe tissues of the various organisms, andthereby present a hazard to health of humanswho may use these fish for food. The use ofherbicides, too, may remove vegetation thatis valuable as a source of food and which mayalso be important for spawning, shelter andshade. In this way a product that is not initself toxic to fish can rapidly destroy anecosystem, and with it the species that werehitherto found there.

From the above it may be concluded thatthe actual killing of fish by a biocide is onlythe most extreme of a variety of effects., all ofwhich can lead to the degradation of a fishery.Therefore, before any product can be con­sidered safe for use on the scale demandedby modem, agriculture, a more completeunderstanding of its ecological effects mustbe obtained from field ~tudies as well as fromthe simple determination of its toxicity in thelaboratory.

SUMMARY

1. The toxicities of four insecticides and aherbicide to Tilapia macrochir have beentested in the laboratory. The estimatesobtained for the four insecticides agreewith the results obtained by other work­ers elsewhere in the world.

2. These results, expressed as 24 hourLCijo's, were as follows:Endrin 20% 0.008 ppmLindane 5% granules 4.6 ppmSynexa 50 (HCH 50%) 5.6 ppmSynexa 25 (HCH 25%) 14.8 ppmTOK herbicide 100% survival

(Nitrofen) at 24 hours in100 ppm

TOXICITY OF FOUR lNSECTlCIDES AND A HERBICIDE 113

the various biocides available is essential. Inthis context it is of interest that the estimatesof toxicity of the four insecticides examinedabove were consistent with the results obtain­ed by other workers elsewhere in the world.On this slender evidence it may tentativelybe concluded that fishes in the tropical en­vironment behave in a similar manner to theirtemperate zone counterparts. Much morework is required, however, before the univer­sality of this conclusion can be established.

The measurement of toxicity in the labo­ratory serves as a guide to the probable directeffects of the product when it is used in thefield, and is particularly valuable in indicat­ing such highly toxic products as Endrin,whose use was abandoned in the Oueme onthe basis of the above work. Of the othercompounds tested, however, Lindane 5% isjudged to be only marginally acceptable.Synexa 50 and Synexa 25 may be safe andTOK appears to be safe at the proposedworking dosages.

In interpreting these results, it must beborne in mind that fish may react to thepresence of toxic substances at concentrationswell below those that are lethal. For instance,the use of insecticides, particularly in wet riceculture, may discourage fish from movinginto the treated area. Vegetation grown habi­tats, such as the rice paddies, are importantto the breeding of many species which mi­grate into them in order to lay their eggs,and any hindrance to this movement may in­hibit successful reproduction. Furthermore,eggs and fry may differ from the larger indi­viduals in both their susceptibility to thepoison and their ability to avoid it. Badlytimed applications of toxicant may therebyseriously reduce one year's recruitment.

Less direct effeots are also likely. In areassuch as the Oueme floodplain the majorityof the species are insectivorous. Here the re­peated use of insecticides, even in concentra­tions below those that would directly affectthe fish, could eliminate most of the potential

food and in this way diminish the fish crop.Alternatively some persistent insecticides maybuild up in the food chain, being stored inthe tissues of the various organisms, andthereby present a hazard to health of humanswho may use these fish for food. The use ofherbicides, too, may remove vegetation thatis valuable as a source of food and which mayalso be important for spawning, shelter andshade. In this way a product that is not initself toxic to fish can rapidly destroy anecosystem, and with it the species that werehitherto found there.

From the above it may be concluded thatthe actual killing of fish by a biocide is onlythe most extreme of a variety of effects., all ofwhich can lead to the degradation of a fishery.Therefore, before any product can be con­sidered safe for use on the scale demandedby modem, agriculture, a more completeunderstanding of its ecological effects mustbe obtained from field studies as well as fromthe simple determination of its toxicity in thelaboratory.

SUMMARY

1. The toxicities of four insecticides and aherbicide to Tilapia macrochir have beentested in the laboratory. The estimatesobtained for the four insecticides agreewith the results obtained by other work­ers elsewhere in the world.

2. These results, expressed as 24 hourLCijo's, were as follows:Endrin 20% 0.008 ppmLindane 5% granules 4.6 ppmSynexa 50 (HCH 50%) 5.6 ppmSynexa 25 (HCH 25%) 14.8 ppmTOK herbicide 100% survival

(Nitrofen) at 24 hours in100 ppm

114 R. L. WFLCOMME

REFERENCES

RESUME

]. Les toxicites de quatre insecticides et unherbicide ~l Tilapia rrzacrochir ont eteevaluecs en Jaboratoire.

2. Les estimations obtenues pour les quatreinsecticides s'accordent bien avec lesresultats obtenus par d'autres travaiI­leurs aiJJeurs dans Ie monde. Ces resuI­tats, cxprimes en 24 hemes LC;,o sontles suivants:

ndrin 20% 0.008 ppmLindane 5% granules 4.6 ppm

Alabaster. J. S. and F. S. H. Abram (1965). Deve­lopment and LIse of a direct method of evalual­ing toxicity to fish. Proc. 2nd 1111. Waf. Po/!.Res. COII(. 1964: 41-59.

Deparlment of Scientific and lndustrial Research(1951'). Waste waters Jnd fish. NOles on W"lerPollillioll. 2: 1-4.

fyalomi, K., T. Tamura, Y. Hazawa, r. Hanyu, andS. Sugiura (19S~). Toxicity of Endrin to fish.PIO!:refsil'(' Fish ('"Itllrist 20. 155-162.

The traditionTanganyika sannothrissa miodlnicae) is to spr'allowing a fewdried fish are tJpacked, along wbags and transjducts thus drielin quality and I

but very little chas been made.

This studychemical campition. appearancl

KO WATANABE

CHEMICAL,

EXAMINAT

PRESENTL)

En vue des toxicites et des epandagesprevus il est conclu que L'Endrin esttres dangereux et que rutilisation de ceproduit doit etre defendu aupres de reau.Le Lindane est moins dangereux maisson utilisation n'est pas it conseiller.Le Synexa 25 et Ie Synexa 50 presententmoins de danger et peuvent etre utilisessous controle stricte.Le TOK herbicide semble ne presenteraucun danger direct.

Synexa (HCR 50%) 5.6 ppmSynexa (HCH 25%) 14.8 ppmTOK herbicide 100 %de survie

(Nitrofen) apres 24 heuresit 100 ppm

This paper is published by permission of IheFood and Agriculture Organization of the UnitedNaliolls. The views expressed are Iho"e ,of Ihealflhor (/nd do 1101 lIecessarily coincide witil Ihoseof Ihe Org{/nizalio/l.

McKee,.l E. and H. W. Wolf, eds. (1963). Walerquality r:rituia. "\'<tler Quality Conlrol Board.Sacramento, California. 548 p.

ACKNOWLEDGEMENTS. The author wishesto thank the Direotor of the Dahomeen FisheriesService, Dr. E. K. Azandegbc. for his C()-opera-tionin providing lhe facilities for carrying out theserests.

4. L'evaluation de la toxicite est valablecomme indication des eftcts portant di­rectement sur les poissons, mais doitetre supplemente par d'autres observa­tions sur Ie terrain afin de determinerdes efIets qui peuvent porter moins di­rectemcnt sur les populations piscicoles.

3.

The estimation of toxicity in the labora­tory is an important indication of thedirect effects on the fish. but should besupplemented by field observations todetermine any indirect effects on fishpopulations.

The recommendations for use based onthe toxicities and on the proposed dos­ages are as follows:Endrin: Use extremely in­

advisable, should beforbidden near water

Lindane: Only marginally ac­ceptable

Synexa 25 and 50: May be safe understrict control

TOK herbicide: May be safe

3.

4.

•l

114 R. L. WFLCOMME

RESUME

]. Les toxicites de quatre insecticides et unherbicide ~l Ti/apia macrochir ont eteevaillecs en laboratoire.

2. Les estimations obtenues pour les quatreinsecticides s'accordent bien avec lesresultats obtenus par d'autres travail·leurs ailleurs dans Ie monde. Ce.s resul­tats, exprimes en 24 heures LCbo sontles suivants:

ndrin 20% 0.008 ppmLindane 5% granules 4.6 ppm

ACKNOWLEDGEMENTS. The author wishes[0 thank the Direotor of the Dahomeen FisheriesService, Dr. E. K. Azandegbc. for his co-operationin providing the facilitie" for carrying out theserests.

4. L'evaluation de la toxicite est valablecomme indication des elfets portant di­rectement sur les poissons, mais doitetre suppJemente par d'autres observa­tions sur Ie terrain afin de determinerdes effets qui peuvent porter moins di­rectement sur les populations piscicoles.

En vue des toxicites et des epandagesprevus il est conclu que L'Endrin esttres dangereux et que l'utilisation de ceproduit doit etre defendu aupres de l'eau,Le Lindane est mains dangereux maisson utilisation n'est pas a conseiller.Le Synexa 25 et le Synexa 50 presententmoins de danger et peuvent erre utilisessous contrale stricte.Le TOK herbicide semble ne presenteraucun danger direct.

Synexa (HCR 50%) 5.6 ppmSynexa (HCH 25%) 14.8 ppmTOK herbicide 100% de survie

(Nitrofen) apres 24 heuresa 100 ppm

3.

The recommendations for use based onthe toxicities and on the proposed dos­ages are as follows:Endrin: Use extremely Ill­

advisable, should beforbidden near water

Lindane: Only marginally ac­ceptable

Synexa 25 and 50: May be safe understrict control

TOK herbicide: May be safe

The estimation of toxicity in the labora­tory is an important indication of thedirect effects on the fish, but should besupplemented by field observations todetermine any indirect effects on fishpopulations.

4.

3.

REFERE C ··S

Alabaster, J. S. and F. S. H. Abram (1965). Deve­lopment and lise of a direct melhod of evaluat­ing toxicity to fish. Proc. 2nd /111. Wal. Po/l.Res. COIlf. /964: 4{-59.

Deparlnlent of Scientific and Industrial Resear'ch(195~). Waste waters and fish. NOles on WalerPollulioll, 2: 1-4.

ry~lorni, K" T. Tamura, Y. Itazawa, l. Hanyu, andS. Sugiura (I ,)5~). Toxicity of Endrin to fish.Pm!:rff.l'il'e Fish Cuilurisl 20. 155-J62.

McKee,.1 E. and H. W. Wolf, eds. (1963). Wow''1ualily r:rilcrio. Waler Qualily Conlr'ol Board.Sacramento, California. 548 p.

Tlris paper is publi,filed hy permission of IheFood and Agriculture Orgallizatioll of Ihe UlliledNalioas. Tire views expressed are lilo.~e ,Of lire{{lIlfror and do 1101 necessorily coincide w/lil Ihoseof Ihe OrgOllizalion.