Onchocerciasis control programme in West Africa

C h e m o s p h e r e , V o I . 1 7 , No.2, P r i n t e d in G r e a t B r i t a i n

pp 4 2 1 - 4 4 0 ,

1988

0 0 4 5 - 6 5 3 5 / 8 8 $3.00 + .OO P e r q a m o n J o u r n a l s Ltd.

ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA:

IEN YEARSMONITORINGOF FISH POPULATIONS

C. Leveque l, C.P. Fairhurst 2, K. Abban 5, D. Paugy I, M.S. Curtis 2, K. Traore 4

1.

ORSTOM, 213 rue LB Fayette, 75480 Paris Cedex i0, France.

2.

University of Sslford, Department of Biological Sciences, Salford M5 4W7, U.K.

3.

Institute of Aquatic Biology, P.O. Box 38, Achimota, Ghana.

4.

Institul d' Ecologie tropicale, 08 BP 109, Abidjan 08, Cote d' Ivoire.

ABSTRACT

Commencing have

been

in 1975, under the auspices of W.H.O., weekly applications of insecticides

employed

to

control the blackfly which transmits human river blindness in West

Africa.

The results provided in this paper do not show, as a whole, any clear impact of

OCP-applied

pesticides on fish populations.

The total catch, tile number of species caught

in

each sample and coefficient of condition, appeared to fluctuate around a mean value, and

no

long-term

generally

drop

clear.

was

observed

over

the period investigated.

Tile seasonal pattern is

In some cases longer term declines occur, generally being followed by a

rise correlating with changing hydrological conditions.

421

422

INIRODUCIION

Human Sudanian The

Onchocerciasis

is

a

dermal

filaria

damnosum

Onchocerca

complex

volvulus

particularly

serious in Guinean and

(Philippon,

is transmitted to man by female blackfly of the Simulium

1977).

in fast-flowing parts of rivers. In the

filariasis

African savannas where it causes irreversible blindness among exposed populations.

The larvae of these flies are aquatic and occur only

Thus the disease is most prevalent near water courses.

the absence of any effective cure suitable for large-scale use, vector controi ~as

most

effective

difficult,

way

chemical

to

prevent

treatment

of

the

spread

of

this disease.

larval

stages

in

the

Adult control being

rivers ~as considered the only

feasible method (Anon., 1985). The auspices

Onehocereiasis

first

Programme

(OCP)

commenced

in

December 1974 under the

of the World Health Organisation (WHO) and was planned for a t~enty year intensive

implementation Burkina

Control

(Davies

et

al.,

1978).

The initial control area of 764,000 km 2 included

Faso and parts of Ivory Coast, Ghana, Togo, Benin, Niger and Mall (Figure i). routine

insecticide

The

treatments were in February 1975 in the central part of the OCP

area, and have been progressively extended.

Up to 18,000 km of rivers have been monitored,

and treated when necessary in the weekly spraying programme. Prolonged and

and extensive use of insecticides could have important environmental risks,

therefore

it

was

necessary

to

evaluate

the possible short-, medium- and long-term

effects of insecticides on the non-target fauna (Leveque et al., 1979). The

aquatic

monitoring programme is performed by national teams of scientists in the

countries in the OCP area, aided by outside specialists. little information on the aquatic fauna was available, concerned

with

importance, An

two

and

important

major

categories of organisms:

This support was essential because the surveillance has been primarily

the fish, by virtue of their economic

the benthic invertebrates, which may more quickly respond to insecticides.

consideration for OCP is the demonstration to the local human population that

care is being taken in reducing the risks of pollution. An every by

independent Ecological Group, consisting of experts of international repute, meets

year and is in charge of the evaluation of the collected data which has been analysed

outside specialists (Cummins, 1985).

The group advises OCP on safe insecticide use and

new monitoring procedures.

AlMS AND PROTOCOL All to

prove

insecticides used by OCP have to follow an intensive screening procedure in order their

high

toxicity

non-target fauna (Leveque, any

direct

impact

on

1987).

fish

nor

against the S. damnosum larvae, and their low toxicity for The criteria are that the pesticides should have neither any

effect

on

their

life cycles.

Among hundreds of

insecticide formulations tested by OCP, few are selected after operational field trials. The fish monitoring programme was based on t~o fundamental ideas:-

423

")'~1"~

< Senegal

~[ssau

-h .10°

\

I

Mali

I -I d-,LJ--~'J/

WESTERN "~"~

I I Ik

j'

-~.--,~

~.~=~..~.-~=~^

>

FIGURE i

10°

C y oast

~

!

5°

..

~

i

0o

- Hap oF OCP a r e a .

~ t

I,; 2f FIGURE 2 -

"-h

G!ull_J,a'~iJi'_i;;~:;;~-"i',Ghana " ' ~ ~

s ~ ~ ° "

15°

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

/ ~

,ot 4~ ~ ¢

..

2 f

Location of Major Fish Monitoring Stations in Ivory Coast and Ghana.

1. 3. 5. 7. 9. 11. i3.

Leraba - Pont Frontiere Bandama - Niakaramandougou Nzi - bridge of Dabakala Road White Volta - Daboya Oti - 5abari Sassandra - Semien Wawa - Dodo Papasse

2. 4. 6. 8. 10. 12.

Comoe - Ganse Bandama - Harabadiassa Black Volta - Bamboi Bagoe - Kouto Maraoue - Mankono Pru - Asubende

424

a)

repealed long-term treatments could change the reproductive cycle of fishes, either by

affecting changes would

the

physiology or by direct effect on eggs or juveniles.

If so, there could be

in fish recruitment and, on a long-term basis, a decrease in fish abundance. apply

This

to the fish community as a whole, or to particular species which could be more

sensiLive to insecticides. b)

Insecticides could affect the food chain leading to a serious reduction in diet.

It

should

laboratory

be

noted

because

of

that

the

such

number

investigations

and

diversity

of

could fish

hardly species

be

conducted in the

involved,

and

the

difficulties of maintaining most of the species in rearing conditions to complete their life cycle. The

monitoring

seasons,

stations

suitability

(Figure 2) were chosen on the basis of accessibility at all

for sampling, availability of hydrological data and abundance of fish

stocks. In

establishing

the

monitoring

programme,

the

terms

of

reference

included the

introduction of simple standardized sampling techniques for use by different teams and under various

environmental conditions

carried

out

using

sets

(Leveque et al., 1979). Experimental fishing is therefore

of gill nets 25 metres long and two metres deep with various mesh

sizes (15,20,25,30 and 40 mm). Usually

each

collection

is

the

result

of

two

sets

of gill nets fishing on two

consecutive nights, but some protocol variations have taken place, particularly in the early years

of the programme.

Data sheets for each sample record the number and total weight of

individual species caught in the different mesh sizes. results

For comparison and standardization,

are expressed as catch per unit effort (CPUE) which is the number or weight of fish

caught in lO0 m 2 of net per night.

Most of the monitoring stations were investigated every

three months, but again there were some protocol variations during the ten years~ mainly due to the accessibility of stations and availability of teams.

From

the

results obtained in sampling the different stations, it was therefore possible to

follow long-term changes in:-

a)

total catch for the set of g i l l

nets w i t h different mesh s i z e s

or combinations of mesh

sizes.

b) c) d)

the number o f species caught, the q u a n t i t y o f each species caught. the s t r u c t u r e

o f the f i s h catch i . e .

relative

abundance o f species i n each mesh s i z e .

Coefficient of condition, is a standard expression of the health of fishes which provides an assessment weighed, lO 5

/l3.

of to

feeding estimate

and

ecological

conditions.

Fish were individually measured and

the coefficient of condition (K) derived from the formula:-

where W is the weight in grammes and L is the standard length in mm.

K = W x

425

Before ecology the

the

of

results

since

monitoring

programme

West African fishes,

there

were very few detailed studies on ~he biology and

it was soon apparent that additional research was essential if

of the monitoring programme were to be correctly interpreted.

provided a better knowledge of the biology of the main species:

nurse,

B.

imberi,

Petrocephalus

B.

bovei

macrolepidotus,

(Merona,

1980),

B. ]ongipinnis

(Paugy,

Various studies have

Alestes baremoze,

1978, 1980a,

1980b,

Brycinus

1982a,

1982b),

Schilbe mystus and Eutro_pius mentalis (Leveque & IHerbinet,

1980, 1982). A

study of the Bandama basin (Merona,

species and confirmed the representative been

carried

198]) provided information on the ecology of the fish

nature of monitoring stations.

Electro-fishing

has also

out in the rapids of some rivers to give a better understanding of fish populations

of these habitats which cannot be sampled by gill nets, and of their changes over time. to

help

the

different

teams

(Leveque & Paugy, 1984).

in

identification

In order

of species, a catalogue of fishes was produced

All this information wilZ be developed further in other publications.

INSECIICIDE TREATMENTS Temephos 1980.

( " A b a t e " ) i s an organophosphorus l a r v i c i d e

season, and at 0.1 mgl - I In

December

S. damnosum forest

temephos

(Guillet

resistance

eL

a].,

developed

]980;

thuringiensis

areas

of

in

larvae

of

some c y t o s p e c i e s o f the

Kurtak, 1986) and spread rapidly to the southern

zone and part of the humid savanna zone.

This situation led to a large-scale application

HI4 ("feknar") during the dry season (dose rate 1.2 mgl -] per 10 mn) in

resistance,

together with "Chlorphoxim",

season (0.025 mgl -I per i0 mn). in

However,

another organophosphate,

acceleration appeared

of

to

per

screening

be promising,

during the wet

a resistance to ChIarphoxim was discovered

the forest species already resistant to temephos (Kurtak et al., 1982).

mgl -I

from 2975 t o

per ]0 mn in dry seasons.

1979

complex

of Bacillus these

which was used e x c l u s i v e l y

A 20% emulsion c o n c e n t r a t e was a p p l i e d a t a dosage o f 0.05 mg] -1 per 10 mn d u rin g the wet

of other alternative insecticides,

in July 1981

fhis necessitated an

and "Permethrin" and "Carbosulfan"

fhese had only been used in the field during the rainy season (0.015

I0 mn) where resistance to organophosphates

was observed.

No direct effect on fishes

was apparent. By still

the

used

end in

populations; was used alternate

where

regions

discharge

larvicides a

result,

regime

of

the south-west,

river

other As

treatment

those in

1986).

of 1985 the treatment situation could be summarised as follows,

for

the

lemephos was

the OCP area where no resistance had developed among Simulium where strains resistant to this larvicide had appeared, feknar 3-I was below 75 m s Above this level, the strategy was to

such

as temephos,

Chlorphoxim and, when necessary,

insecticide treatment varied between rivers.

PermethrJn

(WHO,

Figure 3 illustrates the

main fish monitoring stations since the start of observations.

More

details of insecticides and treatment strategies will be found in Anon (1985). It Coast. water

must be remembered that other insecticides may also affect the rivers in Ghana and Ivory Large amounts of agricultural

courses.

methyIparathion been

replaced

According

to

pesticides,

Calamari

which are difficult to evaluate, may reach the

(]985),

300

t of DDI, 600 t of Lindane,

and 30 t of other compounds were used in 1976 in Ivory Coast. by

organophosphates,

carbamates

and pyrethroids.

tO0 t of

Since 1979 DDf has

Similar values are given for

Ivory Coast by Balk and Koeman (1984) and are expected to increase two to three fold by the end of the century.

426

siis

1975

1976 I 1977 I 1978 I 1979 I 1980 t 19811 1982 I 1983 I 1984 I 1985 ] [~0

IEE]O001

[

|IIIIlilII|IHHHNI~IlHIflll HIIII m HBIIil~||lt~llllll~ ~

I~

f

I0 I - - l O I

~

3

4

II

5

O0

1

I I

I I

1 8 ~ ~

II

m~

[--] ~ F & ~ m

F//////~ ~

~

m

6 7

O000~EIOr--] OI

0

LI

0]08~0

I[--3t

11

OOBOI

[~

Abate

FIGURE 3 -

~

IE B O

Bt

II] [--1

IO00

OI

11

I 0 0 0 0 [] O O D E O

I

~

Chlorpl...... ~

O0

L

i EOE

0 O[] [] O E

0 O0

~l~]i~

Carbosulfan

~

H

P...... hrine

Insecticide Treatment at Lhe Major AquaLic NoniLoring SLations

The areas surrounding some Nest African rivers are also trealed with insecticides t o control tsetse

Flies.

The side effects of helicopl.er applications of dieJdrin, endosulfan, permethrJn

and azameLhiphos fish

were

morLaiity

moniLored

(EverLs

et al., 1983a, 1983b:

Takken eL al., 1978).

endosulfan spraying (Koeraan eL al., 1978) as we]] as in ivory £oasL (EverLs AnoLher rivers.

No acuLe

was observed, exeepL in Nigeria where a mass morLaiiLy of Fish occurred Following

source The

of

po]iuLion

is

Lhe

sugar

eL al., ]983b).

and FruiL FacLorJes ofLen siLuaLed along Lhe

residues from Lhis organic polluLion could cause Fish morLaliLies,

such as Lhose

reporLed From Lhe Sassandra upsLream of Lhe Semien moniLoring sLaLion in 3985-]986.

RIVER HYDROLOGY AND BIOLOGICAL SIGNIFICANCE The OCP area covers major river systems in West AFrica, such as the Volta basin, part of the Niger basin, the northern parts of the Sassandra, Bandama, Comoe, Mono and Oueme basins. these

rivers

November, Ivory

with

Coast,

are a

Most of

savanna type, with a water regime characterised by a Flood period from JuJy to peak

in

hydrological

September and a lengthy low water period From January to June. and

physicochemical

summarised in [iris and Leveque (1982).

characteristics

For

For the main waLer courses are

For the Volta basJr,, Moniod et al (1977) gave a synthesis

of hydrological data. Many

of

completely. course in

Flow

is

Lhe For

rivers permanent

in

the rivers

central part of the OCP area are intermittent and may dry up discharge

is very low during the dry season, and the upper

sometimes reduced to a series of pools.

[here are therefore several seasonal changes

which result in major ecological changes For Lhe Fish species.

However,

the importance

of the flood period is also directly related to the abundance of seasonal rains and as a resulL of climatic (Figure

fluctuations, 4).

There

the

water

discharge

of rivers exhibits large changes from year to year

may be differences between basins, but it is clear that a poor hydrological

situation prevailed in the whole OCP area From ]982 to 1984.

427

In

tropical

behaviour.

rivers

Fish

(Welcomme,

Fish biologists

reproduction

1985).

recognise

that hydrology plays a major role in fish

lends to be highly seasonal and correlated primarily with flow

This is the case For many West African species which spawn during the earlier

part of the

Flood: Alestes baremoze, Bryeinus nurse, Petrocephalus

M. ussheri,

Labeo

1982;

Leveque

&

It

the

year:

bovei, Marcusenius

L. coubie, 5chilbe myslus, Eutropius mandibu]aris

Herbinet, 1980, 1982; Paugy, 1978, 1980).

breed throughout Hemichromis

senegalensis,

B. imberi, B. mgcroiepidotu A

furcidens,

etc. (Albaret,

However, some species are known to

14ydrocynus forska]ji, ~i]apia zillii,

fascialus (Albaret, 1982; Paugy, [980 , ]982 ).

is

also

assumed

that

breeding

success

and survival of fry of many species could be

related to the duration and water level of the flood period (for review see Welcomme, 1979, 1985). In

years when there is insufficient water, the young fish have fewer refuges, are more vulnerable

to

predators

and have fewer sources of Food. Dansoko el a] (]976) have shown that the reduction

in commercial

catches of Hydrocynus brevis and H. ForskaJii in ]972 and J973 was a consequence of

inadequate

levels

during

the

flood

periods,

and resulted in a poor condition Factor, limited

growth and weak recruitment to the fish stocks.

discharge (m3/s) 500-

100

i

I0001

~

t

~

/

i

i

i

I

i

Bandama

i

i

t

~

i

i

Oti

50C

1974

FIGURE 4 -

'

1975

'

1976

'

1977

'

1978

'

1979

1980

'

1981

'

1982

'

1983

~

1984

1

Discharge (m 3 s -1) per month For Some Monitoring Stations in the OCP area.

428

In (1983)

a

detailed

were

between

also

study of fish populations From the Logone flood plain, Benech and Quensiere

able

to

demonstrate

over

ten years the existence of a positive correlation

fish production and flood volume, as well as changes in species composition and community

structure

related

to drought periods.

beginning

of

flood

fry.

the

Many fish species migrate long disLances upstream at the

in order to spawn and find good conditions favouring the development of

this Js the case in Lhe rivers considered here for A. baremose, B. ]euciscus, Mormyrus

rume, Mormyro_~

deJiciosus,

seneqalensis,

eLc.

schemes

such

as

greatly

by

the

Distichodus

rosLratus,

Eutropius niioLicus, E. mandibu]aris, Labeo

these migration patterns could be modified as a result of water management dams

and impoundments, whose numbers and surface area are expected Lo increase

end of the century (Clay, 1984).

These dams could act as barriers interrupting

upstream migrations, but could also favour species which develop in the lakes where they find good ecological

conditions

and migrate upstream during ftood (See Bernaczek, 1984, for review).

Such

examptes

are the Volta and Kainji lakes (Kapetsky & PeLf, 1984) as well as the Kossou lake on the

Bandama.

Since the beginning of the monitoring programme other dams have been built, such as the

Taabo

the

on

Bandama,

Buyo

on the Sassandra and numerous smaller irrigation reservoirs on the

upper reaches of the rivers. As

a

Other projects are planned for the Future in Ivory Coast and Ghana.

result of Lhis management, changes in fish community structures are expected in many rivers

both upstream and downstream of the dams (Bernaczek, 1984). In

conclusion,

seasonal

changes

Fluctuations;

as e)

the a

composition result

of

experimental

of migrations;

b)

fish

catches

could be subjecL to:

a)

year to year changes as a resulL of climatic

long-term changes following effects of impoundmenLs;

d)

possible larvicide

impacts.

ECOTOXICOLOGICAL STUDIES

The

effects of organophosphates (temephos and Chlorphoxim) in laboratory experiments showed

that Fish were able to accumulate temephos (Miles el al., 1976;

Matthiessen & Johnson, 1978), but

this accumulation seems to be limited and does not increase indefinitely, as was observed with DDT for instance. mg ]-]

As an example, Sarotherodon mossambieus exposed weekly to operationa] doses (0.05

For tO minutes) accumulated 3-4 mg kg -1 by direct absorption.

residues

by

eating

contaminated

food.

An

They cou]d also accumulate

affinity of temephos for fatty tissues has been

observed, but in contrast to organochlorides there is no accumulation in the liver. According during 14.3

to

results

obtained

mg

I -I

according

to

contaminated

five

fietd conditions (Que]ennec el ai, 1977) fish captured

species) one day after treatment.

lower (between ] and 7 mg l-l).

lower;

in

the dry season just below the spraying point exhibited traces of temephos (between 1.3 and Six days later contamination was

At a distance of t km below the spraying point, fish were weakly

(between 0 and 0.23 mg 1-1).

In the rainy season, accumulation of temephos is much

0-0.4 mg i -I five hours after spraying, just below the spraying point, and 0-0.03 mg 1-I days later.

It should be mentioned that DDI residues were also found (0.01-0.35 mg 1-1) in

the fish studied, probably as a result of the use of this pesticide in agriculture.

429

lhe

i n h i b i t i o n of a c e t y ] c h o l i n e s l e r a s e a c t i v i t y

laboratory

and

f i e l d conditions.

due to organophospbates was also studied in

In tile ] a b o r a t o r y (Gras c t a ] . ,

1982;

P e l i s s i e r et a l . ,

1982,

]983), where o p e r a t i o n a l doses were tested (0.05 mg 1-1 For lO minutes) i n h i b i t i o n by' temephos was about

25%

For

exposures. much higher; Fish

Tilapia ~uineensis,

no

but

Fish

intoxication was noted after repeated weekly

When Fish were exposed to the operational

did

dose For 24 hours, the inhibitory effect is

38% after one exposure ad 69% after three weekly exposures.

not

survive.

The inhibition of aeetylcholinesterase

In the latter case the

activity appears more important

with Chlorphoxim. In

Field conditions,

significantly Scheringa a

20%

different

et al, 1981).

reduction

in

the aceLycholJoesterase

in

rivers

treated

activity in the fish brain does not seem to he

~ith

temcphos

When £hlorphoxim is used,

enzymatic

or

untreated

(Ailtwi, t983, 1984;

Fish captured below spraying points exhibited

activity, but this inhibition was shown to be reversib]e

(Ant~i,

1983, 1985).

80o

LERABA

WHITE VOLTA

600

300

600

400

2O0

4OO

200

100

200

2500 i ?ooo

COMOE

1500

5oo 600

50O 0

SASSANDRA

800

~

2000

o

. . . .

Site 3

~

400

_

MARAOUE

:~

OTI

2000 I,O0

o ~--~

~

I000 BLACK VOLTA

800

Is00

300

600

10oo

200

400

500

100

200

0

0

5000 BANDAMA Site 4

4ooo 3000

BAGOE

800 600

2000

• oo

PRU

~00 300

!1

200

N

1000

,oo

0

2

3 4 5 6 7 8 9 10 11 12

1

2

3

4

5

6

7

8

9 10 11 12

1

FIGURE 5 - Total Numbers of the Most Common Fish Caught in G i l l Major Aquatic Monitoring S t a t i o n s .

i. 3. 5. 7. 9. li.

Petrocephalus bovei Alestes baremoze Brycinus imberi Brycinus leuciscus Schilbe mystus Eutropius mandibularis

2. 4. 6. 8. lO. 12.

2

3

4

5

6

7

B

9

10 11 12

Nets per Unit E f f o r t

Hydrocynus rorskalii Brycinus macrolepidotus Brycinus nurse Labeo seneqaJensis Eutropius nilotieus Chrysichthys veliFer

at the

430

RESULIS OF ECOLOGICAl MONITORING

I.

Species Composition ]he

the

monitoring

water course,

relative

abundance

south-flowing

basin)

are situated in different river basins and at differeI~[ levels off

between species (Figure 5).

Ivory

co-dominant.

stations

It is therefore not surprising to observe differences between stations in the

The

Coast

rivers

Sassandra

except

in

demonstrates

Alestes baremoze is the dominant species in the the

Leraba-Oomoe

and Volta exhibit a somewhat different fish fauna:

and Chrysichthys

auratus

instead

of

basin

where Schilbe mzstus is

a spectrum similar to the Naraoue.

Brycinus

JmberJ,

AJestes

[euciscus,

The Bagoe (Niger Eutropius niloticus

EutropJus mar,dibutaris

and Cbrysichthys

velifec respectively.

2.

Number o f F i s h Species The number o f Fish s p e c i e s caught at s e l e c t e d s t a t i o n s

with are

a

species fish

maximum at low w a t e r .

different

This r e p r e s e n t s the g r e a t e s t e f f i c i e n c y

l o n g - t e r m t r e n d s i n each r i v e r ,

richness

o v e r the ten year p e r i o d .

but o v e r a l l

The replaced,

total

a s e a s o n a l change

o f the g i l l

to the poor r i v e r

ttowever,

o f s p e c i e s c o u l d mask changes i n s p e c i e s c o m p o s i t i o n , the r e s u l t s

There

discharges during that

The r e c o v e r y observed i n ]985 Follows a season o f p a r t i c u l a r l y number

nets.

t h e r e i s no evi dence o f a r e d u c t i o n i n

For I v o r y Coast, t h e r e i s a decrease i n the number o f

s p e c i e s between 198l and ]984 which c o u l d be r e l a t e d

period (Figure 4).

( F i g u r e 6) e x h i b i t s

heavy r a i n .

some s p e c i e s bei ng

d i d not show e v i d e n c e o f d i s a p p e a r a n c e o f Fish s p e c i e s i n the

experimental catches.

i~

7~

1,

~8

79

eo

e,

~2

FIGURE 6 - Changes i n Number o f Fish expectation of 2 sets of Gills

eJ

e.

~s

,7

,e

7~

.o

e,

Species per Sample n e t s on 2 c o n s e c u t i v e

~2

es

84

a5

ea

at Various Stations nights.

Based on

431

c.p.u.e

50. 50J 40. 30. 20. Io

;5

~e

5°I

17

.

;e

~9

eo

el

A

e2

e3

A

el

ss

c .....

7s

77

78

79

80

el

B2

83

84

85

:0

PFu

FIGURE 7 - Changes in Mean C.P.U.E. NeLs in Various Stations

3.

for the Nhole Set of Gill

Chanqes in Iota1 Experimental Catches When considering

standardized catches Flood more

(Catch per ]OOm 2 per night)

at

set

(August

gill

end to

efficient

appear to

of

the

changes

the

Fish

catches,

expressed

as

the

mean CPUE for the

nets (Figure 7), a seasonal p a t t e r n i s g e n e r a l l y observed, with higher

o f the high water period (November to January) and lower catches during the

September).

in

in

Again t h i s paLtern is p a r t l y the r e s u l t of the Fishing gear being

low water conditions.

The high CPUE values observed in the Sassandra in 1980

be due to an increase in Alestes/Brycinus species (Alestes baremoze, Brycinus nurse, B.

imberi).

A similar phenomenon was observed in ]980-]98] in the Leraba due to incFeased catches

of Aiestes

baremoze,

Eut£opius

mandibular]s,

Schilbe mystus and Lares nitoticus.

Over the ten

year period no long-term reductions in mean catch can be discerned. When efficient

considering For

hydrology. 1976-1977 more

At and

favourable

(Figure 8b).

different

juveniles, Niaka

there

mesh is

a

sizes more

(Figure obvious

8),

and

particularly

correlation

the smat]er ones

with year-to-year changes in

on the Bandama, for instance, catches in the ]5 mm mesh size are lo~er in

1982-1984 which correspond to a poor flood (Figure 4). hydrology

between

t979

and

1981.

]he catch was better with

A similar situation occurred on the Leraba

432

15 m m kg

70-

......

20mm

. . . .

40ram

Station

1

60-

5 0-

',; il / il

40-

i;l ',1 ..-,

30-

I,",i tr ',', f 'J~ I 1 ,"" 1 \~ I ,i

..,.

,"/

/!'~I

~,!

20-

10-

olll 75

76

77

78

79

80

81

82

83

84

kg

Station 3

70

I~

6.o

;'

:~1"

50 A /I 11

4 /lll 3oJ I

" Ili!ll v:fll

2.o ,4~

h I1 I I

I

I

~ ,

Ill', i/li

\

I

;

I

;, ~,~ ~'"

I.i ,. . .

I

,,

'/x"

~

75

'

76

{

77

]

78

\ "~

I

FIGURE B - Changes in Catch (C.P.U.E.) (Leraba and Bandama) 4.

r

li

~,', i ,

\I

~

79

I

,' / ' :i

vyy \"i 80

[

81

i

for Different

82

[',

' , : ,

'\,

,

~

83

&

', I ', ,

i

84

i

85

I

Mesh 5izes at l~o Monitoring

Stations

Chanqes in the Structure of the Fish catches It

is

difficult to compare many graphs of species abundance against time and overlay these

with abiotic factors. the

/A

,, ,s1 \ . . , N ( - , \

' |

85

factorial

elsewhere

Therefore multivariate analyses are appropriate and the method used here is

analysis

(Benzecci,

of

correspondence,

1973:

the

Lebard & Fenelon,

salient

1973:

points

Hilt,

of

1974).

which are amply described This method is particularly

informative as it permits simultaneous graphical representation of species and samples. ]wo

examples

treatment Mo

has

are

given

being applied. received

here,

the

first

being

the river Oti at Sabari with only Abate

Although treatments have been less frequent in recent years, the river

heavy insecticide applications.

This tributary joins the Oti before the Volta

Lake so all migratory fish would be exposed to Abate at some time. In

the ordination presented in Figure 9a. the first axis separates the samples into low and

high water species, high

periods. as

water

Comparison common

samples with

after

period. monitoring

Dry period collections are eharacterised by Alestes, Labeo and Chrysichthys

well as Synodontis in

the

filamentosus and Schilbe mystus,

middle,

with

lhe second axis has a group of

rising and falling water periods being more diffuse.

Figure I0 gives some reasons for this pattern, as the Petrocephalus spp. are not

1979,

while

Eutropius

nilotieus continues to be abundant throughout the sampling

Apparent reductions in abundance can also be correlated with a reduction in frequency of from

under-represented

monthly

to

quarterly.

Therefore

species

such

as

as the main migration period is more likely to be missed.

E.

niloticus

may be

433

a

2 Ps

I

j'J

•

[

/ / ~

BiX

x

&

X

x x

Bn

Ca Cn x A x x

x x x Bm.X

~x x

\~

Lc x z~ \Ls \

sf

\

/

Sg

>/ , ' / \\

•

~

\\

0

x \\\

L/*, I •

x

"\

x

~ -~=

~.

Ss •

FIGURE 9 -

High

X

Low

Z~

Falling

•

Rising

I II

//

\~

0

I l

• 0

So

Sss

/ 1/ 0

Hf

I

En

0

x

/

Correspondence Analysis of experimental catches (in Fish numbers) at: a) b) Pb Ps Se So Sss Sg Ss Sf Sb Em En llf

Oti at Sabari Bandama at Niakaramandougou Petrocephalus bovei Petrocephalus simus Synodontis eupterus Synodontis ocellifer Synodontis sorex Synodontis qambiensis Synodontis schall Synodontis filamentosus Synodontis bastiani Eutropius mandibularis Eutropius niloticus Hydrocynus forskalii

Bm Bn B1 Bi Ab Cv Ls Lc Sm Ln Tg Mb

~1982~1984 ]

b

x

x

Cv

I 0

•

Hf x Sb

x

/I

Schilbe mystus Lates nileticus

Tilapia galilea Harcusenius bruyerei

I1

x ~ ~. Em Ss O~ \ x

I t ""

Bm O

I

/ /

/

I

Mb

Ab x

I

x

•

I

x 1

/

/I / /I

A O

O

Bn

Z~

i /

x

I I

/ •

0

0

tf

Z~

/

I I

/

z~

x

Brycinus nurse Brycinus l e u c i s c u s Brycinus i m b e r i A l e s t e s baremoze Chrysichthys v e l i r e r I_abeo senegatensis Labeo coubie

2 O

~

Brycinus macrolepidotus

T

x Sm z~

/

LC x rz

/

!

O

/

X

High t OW

/

Falling

/ !

Ls

•

Rming

434

In than

conclusion,

year-to-year

major

p a t t e r n s o f community change r e f l e c t

differences.

partial

explanation

and

simus

P.

the

in

appear

Changes

in

abundance

r e d u c t i o n o f sampling f r e q u e n c y , to

become

rarer,

seasonal influences

rather

or J ~ i d i v i d u a l s p e c i e s o v e r time have a but s p e c i e s such as P e t r o c e p h a l u s b o v e i

a t r e n d which i s more d i f f i c u l t

t o e x p l a i n i n terms o f

hydrology. The Kossou of

second

example

is

the

river

Bandama at Niakaramandougou.

D a m , and e a r l y t r e a t m e n t s were w i t h Abate, o t h e r i n s e c t i c i d e s

1980.

closer

The

ordination

examination

becoming

more

galilaea~

The

of

proportJon

mandibularis sampling

off

the

has

period.

filling

a

distinct

another

of

which

the

community

change C. v e l i f e r

at the end o f 1976, w i t h

A. nurse

and Hydrocynus f o r s k a l i i

increasing

second a x i s i s dominated by Labeo s e n e g a l e n s i s , S e h i l b e mystus and T i ~ a p i a

indicative

smaller

Feeds i n t o

( F i g u r e 9b) appears to s e p a r a t e Abate t r e a t m e n t s fJ:om the rest~ but

reveals

r a r e and s p e c i e s such as A. i m b e r i ,

i n abundance.

1he r i v e r

bei ng employed From the end

change

catch

at

the

b e g i n n i n g o f 1982 when t hese s p e c i e s became a

( F i g u r e 16).

maintained

In the c e n t r e o f the o r d i n a t i o n

a relatively

constant proportion

The reason f o r the changes c o u l d l i e

lies

Eutropius

o f the c a t c h t h r o u g h o u t the

in a combination of a lag ef f ect

the Kossou Lake and the wet years of 1979 and 1980.

o f the

Therefore, effects of treatment

are again not obvious, and this conclusion is reached For other sampling stations.

5.

Coefficient of Condition Long-term

changes

in

the

mean

coefficient

abundant species at the different monitoring sites. species

of

condition

(K) were studied For the most

Selected examples are given in Figure 10 For

whose food is primarily based on aquatic invertebrates.

The values of the coefficient of

condition are relatively random, fluctuating around a mean which does not seem appreciably altered over

the

ten

irreversible

year

period

modification

of in

treatment. K.

decreases were observed For a few species. extent

for

occurred

Eutropius

for

decreases, every

Brycinus

which

site,

restricted

nurse

apparently

seem to

mandibularis in

There

is no evidence of a long-term decrease or

Nevertheless, when examined in detail, significant short-term

in the

This is the case For Alestes baremoze and to a lesser the

Bandama

river in 1976-1977.

A similar phenomenon

Sassandra and Leraba rivers between 1981 and 1983.

Such

do not affect all species in the same river, or the same species at

difficult to explain.

However, the drop in K for A. baremoze in 1976-1977 was

the course of the Bandama between the Kossou and Ferkessedougou dams (Paugy, 1978)

and coincided with a period of poor Floods (Figure 4). fhe fall ir, va]ue of K For A. nurse between 1981-t983 coincided with severe drought in the Sassandra and Leraba. there

should

be

a

relationship

between

relate to the life cycle and the seasons (Paugy, 1978, 1980 ; also

observed

that

For some species, therefore,

K and changes in hydrology.

Minor Fluctuations in K

Leveque & Herb]net,

1980).

It was

for the same species there could be differences in K for the different river

basins. The normally start

relative

stability

in treated rivers.

of

coefficient

of conditiorl indicates that fish are able to feed

In fact, stomach content analysis carried out in 1975, just after the

of treatment (Vidy, 1978), and in 1976-1977, did not reveal significant changes in the diet

of fish species feeding entirely (Petrocephalus bore]) or partially nurse,

E.

treatment it

does

mentalis)

on

the

aquatic

invertebrate

fauna.

(A. baremoze, B. imberi, B.

It has been observed that temephos

resulted in a temporary reduction of aquatic insects by only 30-40% (Dejoux, not seem that treatment could lower Food stocks to a critical threshold.

adaptability

198]), and

Moreover,

the

of many freshwater Fishes to various types of Food has been demonstrated a number of

435

_ _ .......

Leraba Comoe Maraoue

_____

Chrysiehthys maurus

24 22

.... .', ,:'

204

-=~'~---"-

....... ~

~

-'~

,,'~7-

1 87 75 76 - Leraba --'--'-~-----/C°nmd°ea

Kt

77

78

79

80

81

82

83

84

85

Eutropi . . . . .

diUui....

14 13 t2

/

.

t,

.i, ~

,

I,"

\

09

..-".

.

"/~/

\l, /

0,8.

07-~

75 _ - ......... .... ----

76 Leraba Comoe Baridama Sassandra

77

78

79

80

81

82

83

84

85 Alestes baremoze

15

I 1 4t3-

t211-

.

10-

.

.

"\j

09 t OB 75 .........

29-

.

_ _ _____

m 76 Bandama Leraba Sassandra

.

,

,

i,,7\j

V 77

78

79

80

81

82

83

I

84

85

Brycinus nurse

2827, 26. 25 24 23

.'! ..... '~

i ~, ,:"4,,'; :,! : t.-':~ !',

,, '~..-" ".-'" ~

v

\,, \'~'

+

'-...

/ ,:t.1 . ,' ' tL

"'-

22] 212019-

",.2 75

FIGURE 10 -

76

77

Changes i n

78

79

coefficient

80

81

or conditions

82

83

84

f o r s e l e c t e d species

85

436

times diet

(Lauzanne, of

some

Mastaeembelus

1976;

fish,

Welcomme,

1985).

particularly

Nevertheless,

Mormyridae.

Corbet (1956) observed a change in the

Some species with a specialized diet, such as

victoriae apparently suffered from malnutrition or migrated.

CONCLUSIONS Experimental weekly

with

fish sampiing has been carried out for ten years in West African rivers treated

insecticides

by

OCP

using

the

standard

protocol.

The

monitoring stations

investigated differed in many ways, with:-

a) b)

their location on different river basins the

relative

abundance

of

fish

species,

despite many species being common to different

basins e)

the

insecticides

used,

some

stations

always

being

treated

temephos up to 1980 and later with an alternation of insecticides

with temephos, others with (Figure 3).

For the inLerpretation of data collected, we were faced with different sources of bias:-

a)

the

human

factor, in that data were collected by different teams and there were changes in

the personnel responsible

for fish monitoring in Ivory Coast and Ghana.

some

on

differences

which

This could lead to

occasion could be recognised by detailed statistical analysis.

This source of bias did not appear to change the overall picture.

b)

lack

of

knowledge

concerning

the

changes in natural environmental which

could

changes

factors.

in

fish community structure as the result of

This is the case for instance for river discharge,

vary greatly between years, and is known to affect the reproductive success of

fishes.

c)

lack of knowledge concerning the uses and abuses of insecticides other than those applied by OCP.

It is known (Calamari,

1985; Balk & Koeman, i784) that large amounts of agricultural

pesticides are used in the OCP area, but the questions are: what reaches the river beds, and what

is

the

insecticides

impact are

on

the

sometimes

aquatic fauna?

A few direct, observations

used as poison when fishing in rivers.

also showed that

However,

the extent of

this influence is not known.

ACKNOWI_EDGEMIZNIS the

independent

presentation. identification Antwi,

R.

The

Ecological Group of O.C.P. is recognised as the general instigator of this authors would like to acknowledge the work of many people in the collection,

and data analysis phases. Particular mention should be made of J.J. Albaret, I.A.K.

Bigorne,

H.R. Dankwa and B.de Merona.

OCP in general, and especially L. Yamengo,

Henderickx and P. Pangalet of the Vector Control Unit, have given considerable assistance.

3.

437

REFERENCES Albaret, J.J. Rev. Hydrobiol.

Anon.

"fen

years

of

Trop. 1982, 15, 547-571.

Onchocerciasis Control in West Africa".

Report OCP/GVA/85.1B, WHO.

1985, 115 pp.

Antwi,

L.A.K.

"The effect of Abate and chlorphoxim on the brain activity of fish from some

treated rivers in the Volta Basin area".

Antwi,

L.A.K.

treated

Report to OCP. 1983, 25 pp. mimeo.

"The effect of Abate on the brain acetylcholinesterase activity of fish from

rivers

in

the

Upper

Volta;

rivers

White

Volta

and

Black Volta".

Report

OCP/VCU/HYBIO/84.15. 1984. Antwi, L.A.K. zilli".

Balk,

"Effects of chlorphoxim on the brain acetylcholinesterase activity of lilapia

Report to OCP. 1985, 5 pp.

l.F.

&

Koeman, J.H.

"Future hazards from pesticide use, with

West Africa and Southeast Asia".

Commission of Ecology Papers No.6.

special reference to IUCN, Gland. 1984, 100

PP.

Benech,V. & Quensiere, J. Rev. Hydrobiol. frop. 1983, 16, 287-316.

Benzecri,

J.P.

"L'analyse

correspondances".

des

Dunod, P a r i s .

donnees.

I.

La

taxonomie:

II.

L'analyse

des

1973, 619 & 631 pp.

Bernaczek, G. CIFA Technical Paper 11. 1984, 98 pp. C a l a m a r i , D. " S i t u a t i o n du C e n t r e " .

Clay,

C.H.

de l a p o l l u t i o n

dans l e s eaux i n t e r i e u r e s

de l ' A f r i q u e

de l ' O u e s t e t

Document o c c a s i o n a l du CPCA No.12. 1983, FAO. Rome.

"New

Reservoirs in Africa,

1980-2000".

CIFA Occasional Paper No.11. 1984, 23

pp., FAO, Rome.

Corbet,

P.S.

insectivorous Brazzaville.

"Some

effects

fishes". 1956.

Second

Symposium

on

African Hydrobiology and Inland Fisheries,

CCTA 1956, 81.

Cummins, K.W. World Health.

October 1985. 14-15.

Dansoko, D., Brehman, N. & Daget,

Davies,

of 5imulium control by insecticide on the feeding habits of

J. Cah. ORSTOM. set. Hydrobiol. 1976, 10, 71-76.

J.B., Le Berre, R., Walsh, J.F. & Cliff, B.

Mosquito News, 1978, 38~ 466-472.

438

Dejoux, C. Rev. Hydrobio]. Trop. 1983, 16, 165-179.

Everts,

J.W.,

van Frankenhuyzen, K., Roman, B., Cullen, J., Copplestone, J. & Koeman, J.14.

Trop. Pest. Manaq.

Everts,

J.W.,

Toxicol.

1983a,2_99, 177-182.

van

Frankenhuyzen,

K.,

Roman,

B.

&

Koemao, J.H. Arch. Environ. Contam.

1983b, 12, 91-97.

Gras, G., Pelissier, C. & Leung Tack, D. Toxicol. Europ. Res.

Guillet,

P.,

Escaffre,

H.,

1982. 4, 301-308.

Ouedraogo, M. & Quillevere, D. Cah. ORS]OM. set. Ent. med. eL

Parasitol. 1980, 291-299.

Hill, M.O.

App. 5tat. 1974, 2, 340-354.

lltis, A. & Leveque, C. Rev. Hydrobiol. Tro E. 1982, 15, 115-130.

Kapetsky,

J.M.

& Petr, T. "Status of African Reservoir Fishes.

"CIFA Technical Paper I0".

1984, 326 pp.

Koeman,

J.H.,

Den

Boer,

W.M.J., Feith, A.F., de Jongh, H.H. & Spleithoff, P.C. Environ.

Pollut. 1978, 15, 31-59.

Kurtak, D. Parasitoloqy Today. 1986, 2, 19-20.

Kurtak,

D.,

appearance larvae

Ouedraogo, in

already

Ivory

M.,

Coast

resistant

Ocran,

M., Barro, f. & Guillet, P.

note on the "Pr ellmlnary '

of resistance to chlorphoxim in Simulium soubrense/sanctipauli to

temephos (Abate R.)".

Unpublished document WHO/VCB/82. 850.

1982. Lauzanne, L. Cah. ORSTOM. set. Hydrobiol.

Lebard,

L.

&

Fenelon,

J.P.

1976, l0, 267-310.

"Statistique eL informatique appliquees".

(2eme edition).

Dunod. Paris. 1973, 457 pp.

leveque,

C.

"The

use

of

insecticides

aquatic monitoring in West Africa".

Leveque,

C., Odei, M. & Pugh Thomas, M.

Perring & K. Nellanby.

in the Onchoeereiasis Control Programme and the

(to be published in a SCOPE volume). 1987.

In: "Ecological Effects of Pesticides".

Linnean Society Symposium Series No.5. 1979, 133-143.

Leveque, C. & Herbinet, P. Cah. ORSfOM set. Hydrobio]. 1980, ]3, ]61-170.

Eds. F.H.

439

Leveque, C. & Herb]net, P. Rev. Zool. A f r . Leveque, contre

C.

&

Paugy,

l'Onchocercose

ORSfOM, P a r i s .

1982, 96, 366-392.

D. "Guide des poissons d'eau douce de l a zone de programme de l u t t e en

Afrique

de

l'Ouest".

Rapport

de convention ORSTOM - OMS.

1984, 393 pp.

Matthiessen, P. & Johnston, 3 . S . J .

Fish Biolo

1978, 1~, 575-586.

Merona, B. de., Cah. ORSfOM ser. H y d r o b i o l . 1980, 13, 117-127. Merona, B. de., Revo Hydrobiol f r o p . 198], 1~, 63-75. M i l e s , J.W., Dales, W.E. & C h u r c h i l l , Moniod,

Fo,

Peuyaud,

Hydrologiques No.5.

B.

&

ORSTOM.

F.C. Arch. Env. Cont. f o x ] c o l .

Sechet,

P.

"Le

bassin

du

fleuve

1976, 5, 29-41. Volta".

Monographies

Paris. 1977, 513 pp.

Paugy, D. Cah. ORSTOM. ser. H y d r o b i o l . 1978, 12, 245-275. Paugy, D. Cah. ORSIOM. s e t . H y d r o b i o l . 1980a, 1~, ]29-141. Paugy, D. Cah. ORSTOM. s e t . H y d r o b i o l . 198gb, l Z , 143-159. Paugy, D. Rev. Zool. A f r .

1982a, 96, 286-328.

Paugy, D. Cybium. 1982b, 6, 75-90. Pe]tisier,

C., Leung l a c k , D. & Gras, G. T o x i c o l . Europ. Res. 1982, 4, 309-319.

Pellisier,

C., Leung Tack, D. & Gras, g. T o x i c o l . Europ. Res. 1983, ~, 63-69.

Philippon,

B. "Etude de l a t r a n s m i s s i o n d' Onchocerca v o l v u l u s (Leuckart, 1983) (Nematoda :

Onchocercidae)

par

Simulium

damnosum (Theobald,

1903)".

Travaux et documents ORSIOM.

No.63, 1977, 308 pp. Quelennec, in

mud,

G.,

M i l e s , J.W., Dejoux, C. & Merona, B. de.

oysters

and

V o l t a River Basin a r e a " . Scheringa, activity

E.J.F.,

"Chemical m o n i t o r i n g for temephos

Fish from a r i v e r w i t h i n the Onchocerciasis Control Programme in the WHO/VCB/77.683.

Strik,

3.3.I.W.A.

1977, 6 pp. &

Ant~i,

L.A.K.

"Fish brain acetylcholinesterase

after Abate applications against SimulJum damnosum in the Volta river basin area".

Unpublished report to OCP. 1981, 27 ppo

440

lakken, W., Balk, F.,Jansen, R.C. & Koeman, J.H. Vidy, de

G.

"Etude du regime a]imentaire de quelques poissons inseetivores dans ]es rivieres

Cote d'Ivoire.

cadre

Paris. 1978, 24, 455-466.

de

Recherche de I'inf]uence des traitements insecticides effectues dans ]e

la lutte contre i'Onchocercose".

Rapport du centre ORSTOM de Bouake No.2. 1976,

36 pp. mimeo.

Welcomme, R.L. "Fisheries ecology of floodptain rivers".

Welcomme, R.L.

WHO. of

"River Fisheries".

FAO. Fisheries ]echnica]

"Onchocereiasis Control Programme in West Africa". the

Seventh

Session.

Bamako.

16-20 June 1986.

mimeo. (Received

in G e r m a n y

6 April

Longman, London.

1987)

Paper No.262,

1979, 317 pp.

1985, 530 pp.

Expert Advisory Committee - Report

JPC7.5.

(OCP/EAC/86.1).

1986, 35 pp.