CJASR-12-11-86

Caspian Journal of Applied Sciences Research, 1(11), pp. 58-64, 2012

Available online at http://www.cjasr.com

ISSN: 2251-9114, ©2012 CJASR

58

Feed Intensity of Characidae Fish in the Jebel Aulia Reservoir in Sudan

Fathi Mirghani Yousif1, Asma Abdel Rahman Ahmed

2

1Ministry of animal resources and fisheries, administration of General fisheries and aquatic resources, Natural fisheries

department, Khartoum, Sudan 2-

Faculty of science, University of Al-Neelain, Khartoum, Sudan

*Corresponding Author: Email: [email protected]

This study was conducted from November 2007 to October 2008 into the two main fishing sites in Jebel Aulia

Reservoir; this was Jebel Aulia site (45kms) south Khartoum city) and Kosti site about 355 km southward

Khartoum city. The study focuses in family Characidae that has two geniuses Hydrocynus (H. forskalii, H.

lineatus and H. brevis) and Alestes (A. baremose, A.dentix and A. nurse). Water characteristics investigated

including temperature, concentration of dissolved oxygen, electrical conductivity, transparency, pH,

compositions and abundance of Phytoplankton. However, there is an un-normal decline of phytoplankton and

zooplankton production at the vicinity of the dam indicating a prospected hazard. The study covered the

biological parameter of characid fishs feeding and maturity. In two sites Jebel Aulia and Kosti Sites fishs showed

maximal of incidence of full stomachs at the end of the rainy season exactly in August 2008 and the other peak

was recorded during the high abundance of planktonic organism in March 2008.

Key words: food, feeding characid.

1. INTRODUCTION

Three factors play an important role in plankton

distribution, light, temperature and movement of

water-masses (Prows and Talling, 1958). These in

turn affect the food chain beside the other

biological processes.

Water temperature is an important factor, which

affects growth, reproduction, maturity of fish and

the food chain. Therefore, every individual fish

species shows the best physiological performance

at an optimum temperature. Furthermore, the

temperature effects on the amount of dissolved

oxygen and consequently the rate of respiration of

fish Bishai (1962). Reported that the normal

temperature to which a fish is adapted in temperate

regions is between 0-30˚C. Value above 30˚C

occurs in shallow water in summer FAO (1989).

Minimum temperatures prevail during in autumn

and winter. Oxygen concentrations and

transparency are the major factors limiting

phytoplankton abundance and distribution in water

Ahmed (1989).

It was reported that the water transparency at

Al-Kalakla and Um Shabasha showed maximum

records during Dec and Feb, but it decreased in a

horizontal gradient towards the dam due to the

distribution of the suspended materials such as

planktons and detritus and seasonally during flood

season (9-13 cm) due to the sediment and

accumulation of the water hyacinth. Recording that

turbidity was higher in December and September,

and was lower in Mar and June (Manteifel1961).

The dissolved oxygen concentration for most

fresh water fish is above 7.0 p.p.m at any time

FAO (1982).It is fetal at high temperature.

Dissolved Oxygen concentration at Jebel Aulia

reservoir was above saturation all the year round.

The highest concentration was recorded in

December and lowest in August. The mean oxygen

concentration in the Jebel Aulia reservoir is

beyond the demand of fish and other aquatic

organisms.

Water with pH value ranging about 6.5 to 9 at

day break this is most suitable for fish production.

In Jebel Aulia reservoir range of pH was 7.4 to 8.6.

The high values were recorded during flood

season. The importance of pH it is roles in ionizing

chemical compound to produce free ions for the

readily use of phytoplankton.

Composition and seasonal fluctuation of

phytoplankton and zooplankton exhibited the

maximum levels in March during the season of low

water discharge Bashier (2007). The average

zooplankton biomass throughout the whole

reservoir was 0.192 g/m2 in April with greater

value found near the dam ((Russian Research

Expedition, (1964) and Adam (1977). reported two

annual peaks of plankton growth and a decline in

Jebel Aulia reservoir. One of beak growth occurs

just before flood season and the second occurs

during winter (Nov. – January).

The food supply is thus governed by the

condition for obtaining and utilizing the food

Manteifel (1961) its also dependent on a biotic

condition during the feeding period such as

temperature, illumination, wind, fluctuation in

Yousif and Ahmed


59

water level, and changes in size of feeding area.

The supply is also influenced considerably the

protection from predators during the feeding

period.

The purpose of conducting this study, were to

determine fish food and feeding intensity of

Characids fish in Jebel Aulia Reservoir Dam.

2. MATERIALS AND METHODS

Samples of water were collected at monthly from

November 2007 to October 2008 using fishing nets

and collecting fishing from the landing sites,

interval from the open water at the Jebel Aulia site

and at the season intervals at Kosti site. At the

same time measurement of dissolved oxygen, ionic

conductivity, pH and degrees of water temperature

were recorded from the field. Dissolved oxygen

(ppm) was measured by Winkler’s method.

Temperature recorded by a thermometer, the pH

meter and ionic conductivity meter was measured

by Hanna′s instrument. Water transparency was

measured with standard Secchi-disc.

Phyto and zooplankton were collected by

standard plankton nets that were hauled for a

minute. volume of water hauled was estimated

from the hauling distance and the dimension of the

net (net ring diameter and the height of the net

cone).The plankton collected was rinsed in

sampling bottles and preserved in 4.0% formalin.

Planktonic organisms were examined under a light

microscope (x 40 or x 100) and the number of

organism per ml of the collected sample was

counted and the number of organism per liter of

water was computed using the volume of the water

sieved during the haul of the plankton net.

Family Characidae classification was done by

the following the keys: Abu Gideri (1984),

Boluenger (1907) and Latif (1973), the genus

Hydrocynus (Cuv1817) include predator fish

belonging to three species H. forskalii. (Cuv1817),

H. lineatus (Blkr), H. brevis (Gthr).The genus

Alestes (M. and T, 1844) whose members are non

pisciviorous comprised three species, A. baremose

(Joann), A. dentex (L), A. nurse (Riip) of these

species A. baremose. Of these species A. baremose

was the most common.

Rate of digestion had been measured by the rate

of disappearance of gut content i.e. the

transparency of the gut fullness methods.

3. RESULTS AND DISCUSSION

3.1. Results

3.1.1. A biotic result:

Degrees of water temperatures recorded during the

study duration the reservoir of Jebel Aulia dam and

Kosti were as follows:

In Jebel Aulia dam, the highest degree

temperature was 31˚C recorded by the end of

flooding season in October 2008, while the lowest

degree was 21˚C during winter in February 2008.

In Kosti, the highest temperature was 29 ˚C in

summer season in May 2008, while the lowest one

was 23 ˚C recorded in winter season in March

2008.

In Jebel Aulia dam, high transparency values

(67.3) were recorded in March 2008, while the

lowest value (11.4cm) was recorded during the

flooding season in July. A high transparency value

was recorded during the end of winter season in

March 2008. Low one was recorded during

commence of flooding season in May 2008.

In Jebel Aulia dam, with a minimum value of

electric conductivity during the flooding season in

July2008 (185 µmho); whereas, the highest one

(308µmho) was observed during months of

summer in May 2008. In Kosti, with minimum

value at commence of March (165µmho). The

highest was also observed during commence of

summer season in March (243µmho).

In Jebel Aulia Site, high value was recoded in

November 2007(8.5) but low reading was recorded

in September 2008(6.22).In Kosti Site, high value

(8.3) was recorded in mid-autumn in October

2008, while in mid-winter in March 2008 reading

had the lowest value (6.5).

Jebel Aulia Site dissolved oxygen recorded in

April 2008 water highly saturated with dissolved

oxygen, while in May 2008 had been lowest

dissolved oxygen concentration. In Kosti, water the

highest saturation with dissolved oxygen was

recorded in October 2008, where, as March 2008

showed the lowest value of dissolved oxygen in

water.

In Jebel Aulia dam, the annual maximum

abundance of phytoplankton and zooplankton were

recoded during the end of the autumn in March

2008, while the lowest levels were during the

flooding season in July 2008. In Kosti, the annual

maxima were recoded during the start of the

summer season in March 2008, while; the lowest

level were recoded during the start of flooding

season in July 2008.


60

Table 1: The average of water characteristic in Jebel Aulia Dam during 2007/2008

Month

Water characteristic

Nov.

2007

Dec.

2007

Jan.

2008

Feb.

2008

Mar.

2008

April

2008

May

2008

June

2008

July

2008

Aug.

2008

Sept.

2008

Oct.

2008

Transparency (cm)

Temperature (°C)

Conductivity (µmho)

Dissolved oxygen(ppm)

pH

Phytoplankton

abundance (No. /ml))

Zooplankton abundance

(No./ ml )

18.8

26

201

6.07

8.7

2.15

1.54

32.2

24

240

6.9

8.1

2.96

1.98

35.8

23

252

6.3

6.7

3.45

2.44

22.4

21

234

6.97

7.7

2.53

2.01

67.3

26

265

7.13

8.5

6.61

3.7

47.9

24

296

7.93

7.8

4.29

3.22

14.8

27

308

6.13

8.5

1.88

1.37

13.3

28

221

7.6

6.5

1.36

0.96

11.4

30

185

7.7

6.26

1.07

0.8

12.5

29

221

7.6

7.6

1.36

0.86

13.2

29

197

7.9

6.22

1.42

0.89

17.9

31

199

7.3

6.51

1.95

1.01

Table 2: The average of water characteristic in Kosti area during 2007 / 2008

3.1.2. Fish food and feeding intensity

The fish food in the stomach of family Characids

was determined at both sites Jebel Aulia dam and

Kosti, fishes showed full stomachs at the different

times through out the study period. The maximal

index of stomach fullness was at the end of the

rainy season exactly in August 2008. The other

peak of incidence of the full stomach was recorded

during the high abundance of planktonic organism

in May 2008.Results of both sides indicate the

seasonality of availability of food. Rainy season

coincides with the breeding season of most Nile

fishes when there is a plenty of fry and fingerlings,

the main food for genus Hydrocynus and the

aquatic insect larva and grains of aquatic weed for

genus Alestes coincide of the full stomach were

higher for Alestes′s species in almost all the

seasons specially summer, fish with empty

stomach were high for Hydrocynus′s species. Full

stomachs were in summer then winter and least in

autumn. Explanation of high incidence of the full

stomach in May, it may be explained by the low

water level and more possibilities of successfully

praying for both fish and other aquatic organelle.

season

Water characteristic Winter Summer Autumn

Transparency(cm)

Temperature (°C)

Conductivity (µmho/cm)

Dissolved oxygen(p.p.m)

pH

Phytoplankton abundance (No.ml))

Zooplankton abundance (No./ ml )

71.2

23

243

6.5

8.3

6.99

4.01

17.4

29

199

6.83

7.5

5.13

2.74

26.1

27

166

8.2

7.5

3.98

2.35

Yousif and Ahmed


61

Table 3: Fish food and feeding intensity of Characidae fish in Jebel Aulia Dam from (2007/2008)

Characid

Seasons

H. forskalii H. lineatus H. brevis A. baremose A. dentex A. nurse

F 1/2F E F 1/2F E F 1/2F E F 1/2F E F 1/2F E F 1/2F E

Autumn 2008 19.9 35.5 45.6 17.1 28.6 54.3 29.5 32.3 38.2 52.4 34.3 13.3 69.8 19.4 10.8 76.5 12.9 10.6

Summer 2008 22.9 21 56.1 8 10 82 26.5 26.5 47 37 23.6 39.3 21.3 26.7 48 59.2 15.5 25.3

Winter 2008 6.6 22.7 70.7 8.7 22.3 69 38.6 5.8 55.6 36.5 30.1 25.4 20 20 40 45.9 27 27

Keys: F= Full stomach content, 1/2 F = Half stomach content, E=Empty stomach content.

Table 4: Fish food and feeding intensity of Characidae fish in Kosti during 2007/2008

Characid

Seasons

H. forskalii H. lineatus H. brevis A. baremose A. dentex A. nurse

F 1/2F E F 1/2F E F 1/2F E F 1/2F E F 1/2F E F 1/2F E

Autumn 2008 28.5 14.3 57.1 9 0 90 27.3 0 72.7 57.9 21.1 10.5 77.8 18.5 3.7 70 26.7 3.3

Summer 2008 22.2 22.2 55.6 36.8 15.8 47.4 58.3 0 41.7 81.4 11.6 7 83.8 16.2 0 94.1 2 3.9

Winter 2008 32.5 7.5 60 37.5 4.2 38.3 32.1 0 67.9 70.7 17.1 12.2 66.6 16.7 16.7 64.3 33.7 0

Keys: F= Full stomach content, 1/2 F = Half stomach content, E=Empty stomach content.


62

Fig. 1: Fish food and feeding intensity of Characidae fish in Jebel Aulia Reservoir Dam from (2007/2008)

Fig. 2: Fish food and feeding intensity of Characidae fish in Kosti from (2007/2008)

3.2. Discussion

Temperature degrees during winter were low and

similar at all study stations; where water

transparency was relatively not high and ranged

between 17.4 cm and 67.3cm (Table 1). Decline of

fish in winter were probably correlated with low

temperatures and high transparency, presence of

fish into deep waters and low fishing.

The results of water temperatures and transparency

during all the year of present study are in

corresponding with those of Sinada (1972); Saeed

(1976) and Ahmed (1989).

Yousif and Ahmed


63

The dissolved oxygen content of the water is the

second factor to temperature as the biological

significant factor in aquatic resources .Absence or

two low level of water oxygen limit to distribution

of plant and animal. The water of Jebel Aulia dam

was normally over saturated with oxygen (6.07 to

7.93 p.p.m).The concentration of aquatic oxygen

was observed to decrease during the flood season.

However, no oxygen attention was recorded. These

results are in harmony with findings of other

researchers (Hamaza, 1981; Kawai, 1994).

In Jebel Aulia dam reservoir the pH of water

ranged between 6.22 to 8.7.The high values were

probably a result of carbon oxide release that

accompanied the annual outbreak of plankton

production Abu Gideri (1962) and Prows AND

Talling (1958).

The observed seasonal fluctuations electric

conductivity (winter: 240 ±12 µmho;during

flood:200.5 ± 14.5 µmho and summer:269.7 ±

24.7 µmho cmˉ1) were most likely due to leaching

of salt by flood water that over flow the river banks

and wash from rain stream into the river.

Plankton flourished and densely reproduced during

the time of slow water flow in period from March

to May 2008 and November to December

2008.These observations are in agreement with

these of Hamaza (1981) and Ahmed

(1989).Production was minimal due to flood and

high water discharge (Rzoska and Brook, 1954) in

addition to the effects of the biotic and a biotic

factor.

Although the previous result Adam (1977), record

higher flourish of planktons (primary and

secondary) at the vicinity of the dam in comparison

to be downstream, the present recorded the reverse

i.e. lowest densities. This indicates change in the

habitat at the vicinity the dam is more likely to

place either due to change in the regime of the dam

operation or due to electro – generating power

plants instead to the dam.

Feeding intensity governed by food availability

which in related to environmental habitat

parameter and other factors that were effective,

cloud formation, decreased water discharge and

hence high water levels. Fluctuations in the

environmental conditions of this habitat clearly

suggested that fish responded to environmental

variables in the same general way as the rest of

vertebrates and that their maturation and breeding

activities are still primarily governed by light

cycles. The percentage of full stomach was decline

in the piscivorous fish i.e. Hydrocynus .The role of

the vision in feeding has tested experimentally by

previous studies Petts (1988) and FAO(1982) who

recorded threshold of light intensity is required for

searching power for prey and the daily feeding

period vary considerably with season.

So high siltation and low transparency can be

considered within the main factor .This can be

considered within the main factor. This can be

further influenced by the high water current that

prevailed during this season with accompanied by

the flood of White Nile. However, the ability to

search for preys depend on the distance depends on

the movement of the prey, its orientation and

abundance in the specific area.

4. CONCLUSION

Further studies in food and feeding intensity of

Characidae fish in the Jebel Aulia Reservoir.

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CJASR-12-11-86