This survey was conducted from November 2007 to October 2008 into the two chief fishing sites in Jebel Aulia Reservoir ; these were Jebel Aulia site ( 45 kilometer south Khartoum metropolis ) and Kosti site about 355 kilometers southbound Khartoum metropolis.
The survey focuses in household Characidae that has two genera Hydrocynus ( H. forskalii, H. lineatus and H. brevis ) and Alestes ( A. baremose, A.dentix and A. nurse ) .
Water features investigated including temperature, concentration of dissolved O, conduction, transparence, pH, composings and copiousness of Phytoplankton. However, there is un-normal diminution of phytoplankton and zooplankton production at the locality of the dike bespeaking prospected jeopardy.
The survey covered the biological parametric quantity of characin fishes feeding and adulthood. In two sites Jebel Aulia and Kosti Sites fishes showed maximal of incidence of full tummy at the terminal of the rainy season precisely in August 2008 and the other extremum was recorded during the high copiousness of planktonic being in March 2008.
Keywords: nutrient, feeding characins.
Three factors play of import function in plankton distribution. These are light incursion, incursion, temperature and motion of water-masses Prows and Talling ( 1958 ) . These in bend affect the nutrient concatenation beside the other biological procedures.
Water temperature is an of import factor, which affects growing, reproduction, adulthood of fish and the nutrient concatenation. Therefore, every single fish species shows the best physiological public presentation at an optimal temperature. Furthermore, the temperature affects on the sum of dissolved O and accordingly the rate of respiration of fish Bishai ( 1962 ) . Reported that the normal temperature to which a fish is adapted in temperate parts is between 0-30EsC. Value above 30EsC occurs in shallow H2O in summer FAO ( 1989 ) . Minimal temperatures prevail during in fall and winter. Oxygen concentrations and transparence are the major factors restricting phytoplankton copiousness and distribution in H2O Ahmed ( 1989 ) .
Many research workers have studied transparence of the White Nile. Of them, Hamaza ( 1981 ) . reported that the H2O transparence at Al-Kalakla and Um Shabasha showed maximal records during Dec. and Feb. , but it decreased in a horizontal gradient towards the dike due to the distribution of the suspended stuffs such as planktons and debris and seasonally during inundation season ( 9-13 centimeter ) due to the deposit and accretion of the H2O jacinth. Recorded that turbidness was higher in Dec. and Sep. and lower in Mar. and June Manteifel, ( 1961 ) .
The dissolved O concentration for most fresh H2O fish is above 7.0 p.p.m at any clip FAO ( 1982 ) ( . It is foetal at high temperature. Dissolved Oxygen concentration at Jebel Aulia reservoir was above impregnation all the twelvemonth unit of ammunition Ahmed ( 1985 ) .The highest concentration was recorded at December and lowest at August. The average O concentration in the Jebel Aulia reservoir is beyond the demand of fish and other aquatic beings Ahmed ( 1985 ) .
Water with pH value runing approximately 6.5 to 9 at twenty-four hours interrupt.This is most suited for fish production Ahmed ( 1989 ) , In Jebel Aulia reservoir scope of pH was 7.4 to 8.6. The high values were recorded during inundation season. The importance of pH it is functions in ionising chemical compound to bring forth free ions for the readily usage of phytoplankton Ahmed ( 1985 ) .
Composition and seasonal fluctuation of phytoplankton and zooplankton exhibited maximal degree in March during the season of low H2O discharge Bashier, ( 2007 ) . The mean zooplankton biomass throughout the whole reservoir was 0.192 g/m2 in April with greater value found near the dike ( Russian Research Expedition, ( 1964 ) and Adam ( 1977 ) ) . reported two one-year extremums of plankton growing and a diminution in Jebel Aulia reservoir. One of beak growing occurs merely earlier flood season and the 2nd occurs during winter ( November – January ) .
The nutrient supply is therefore governed by the status for obtaining and using the nutrient Manteifel, ( 1961 ) .and it is besides dependent on a biotic status during the feeding period such as temperature, light, air current, fluctuation in H2O degree, and alterations in size of feeding country. The supply is besides influenced well the protection from marauders during the feeding period.
The intent of carry oning this survey, were to find fish nutrient and feeding strength of Characids fish in Jebel Aulia Reservoir Dam.
2. MATERIALS AND METHODS
Samples of H2O were collected at monthly from November 2007 to October 2008 utilizing angling cyberspaces and roll uping fishing from the landing sites, interval from the unfastened H2O at the Jebel Aulia site and at season interval at Kosti site. At the same clip measuring of dissolved O, ionic conduction, pH and grade of H2O temperature were recorded from the field. Dissolved O ( ppm ) was measured by Winkler ‘s method. Temperature recorded by thermometer, the pH metre and ionic conduction metre was measured by Hanna instrument. Water transparence was measured with standard Secchi-disc.
Phyto-and zooplankton were collected by standard plankton cyberspaces that were hauled for a minute, the volume of H2O hauled was estimated from the haling distance and the dimension of the net ( net ring diameter and the tallness of the net cone ) . The plankton collected was rinsed in trying bottles and preserved in 4.0 % formol. Planktonic beings were examined under a light microscope ( ten 40 or x 100 ) and the figure of being per milliliter of the gathered sample was counted and the figure of being per litre of H2O was computed utilizing the volume of the H2O sieved during the draw of the plankton cyberspace.
Family Characidae categorization was done by the following the keys: ( 8,20 and13 ) , 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 member are not 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 have been measured by the rate of disappearing of intestine content i.e. the transparence of the intestine comprehensiveness methods.
3. RESULTS AND DISCUSSION
Degrees of H2O temperatures recorded during the survey continuance at reservoir of Jebel Aulia dike and Kosti were as follows:
In Jebel Aulia dike, the highest degree temperature was 31EsC recorded by the terminal of deluging season in October 2008, while the lowest grade was 21EsC during winter in February 2008. In Kosti, the highest temperature was 29 EsC in summer season in May 2008, while the lowest 1 was 23 EsC recorded in winter season in March 2008.
In Jebel Aulia dike, high transparence values ( 67.3 ) were recorded in March 2008, while the lowest value ( 11.4cm ) was recorded during the implosion therapy season in July. A high transparence value was recorded during the terminal of winter season in March 2008. Low one was recorded during commence of deluging season in May 2008.
In Jebel Aulia dike, with lower limit of electric conduction value during the implosion therapy season in July ( 185 Aµmho ) ; whereas, the highest 1 ( 308Aµmho ) was observed during months of summer in May 2008. In Kosti, with minimal value at commence of March ( 165Aµmho ) . The highest was besides observed during commence of summer season in March ( 243Aµmho ) .
In Jebel Aulia Site, high value was recoded in November 2007 ( 8.5 ) but low reading were 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 ) .
pH in Jebel Aulia dike, collected recorded in April 2008 H2O extremely saturated with dissolved O, while in May 2008 had lowest dissolved O concentration. In Kosti, H2O the highest impregnation with dissolved O was recorded in October 2008, where, as March 2008 showed lowest value of dissolved O in H2O.
In Jebel Aulia dike, the one-year upper limits copiousness of phytoplankton and zooplankton were recoded during the terminal of the fall in March 2008, while the lowest degrees were during the implosion therapy season in July 2008. In Kosti, the one-year upper limit were recoded during the start of the summer season in March 2008, while ; the lowest degree was recoded during the start of deluging season in July 2008.
Table ( 1 ) : The norm of H2O feature in Jebel Aulia Dam during 2007/2008
Transparency ( centimeter )
Temperature ( A°C )
Conductivity ( Aµmho )
Dissolved O ( ppm )
Phytoplankton copiousness ( No. /ml ) )
Zooplankton copiousness ( No./ milliliter )
Table ( 2 ) : The norm of H2O feature in Kosti country during 2007 / 2008
Transparency ( centimeter )
Temperature ( A°C )
Conductivity ( Aµmho/cm )
Dissolved O ( p.p.m )
Phytoplankton copiousness ( No.ml ) )
Zooplankton copiousness ( No./ milliliter )
Fish nutrient and eating strength
The fish nutrient in tummy of household Characids was determined at both Jebel Aulia dike and Kosti, fishes showed full tummy at the different times through out the survey period. The maximum index of tummy comprehensiveness was at the terminal of the rainy season precisely in August 2008. The other extremum of incidence of full tummy was recorded during the high copiousness of planktonic being in May 2008. Consequences of both sides indicate the seasonality of handiness of nutrient. Rainy season coincides with the genteelness season of most Nile fishes when there is a plentifulness of Fry and fingerlings, the chief nutrient for genus Hydrocynus and the aquatic insect larva and grains of aquatic weed for genus Alestes coincide of full tummy were higher for Alestes species in about all the seasons specially summer, fish with empty tummy were high for Hydrocynus species. Full tummy were in summer so winter and least in fall. . Explanation of high incidence of full tummy in May, it may be explained by the low H2O degree and more possibility of successfully feeding for both fish and other aquatic cell organs.
Table ( 3 ) : Fish nutrient and feeding strength of Characidae fish in Jebel Aulia Dam from ( 2007/2008 )
Table ( 4 ) : Fish nutrient and feeding strength of Characidae fish in Kosti during 2007/2008
Fig ( 1 ) : Fish nutrient and feeding strength of Characidae fish in Jebel Aulia Reservoir Dam from ( 2007/2008 )
Fig ( 2 ) : Fish nutrient and feeding strength of Characidae fish in Kosti from ( 2007/2008 )
Temperature grades during winter were low and similar at all survey Stationss ; where H2O transparence was comparatively non high and ranged between 17.4 centimeters and 67.3cm ( Table 1 ) . Decline of fish in winter were likely correlated with low temperatures and high transparence, presence of fishes into deep Waterss and low fishing.
The consequences of H2O temperatures and transparence during all the twelvemonth of present survey are in matching with those of Sinada, ( 1972 ) , Saeed ( 1976 ) . and Ahmed ( 1989 ) and with those of Muso, ( 2002 ) . ( whose trying site was 700 km South of Jebel Aulia dike.
The dissolved O content of the H2O is 2nd factor to temperature as the biological important factor in aquatic resources.Absence or two low degree of H2O O bound to distribution of works and animate being. The H2O of Jebel Aulia dike was usually over saturated with O ( 6.07 p.p.m to 7.93 p.p.m ) . The concentration of aquatic O was observed to diminish during the inundation season. However no O attending was recorded. These consequences are in harmoniousness with findings of Hamaza, ( 1981 ) and Kawai, ( 1994 ) .
In Jebel Aulia dike reservoir the pH of H2O ranged “ between 6.22 to 8.7 ” . The high values were likely a consequence of C oxide release that accompanied the one-year out interruption of plankton production ( Abu Gideri, ( 1962 ) and Prows & A ; Talling, ( 1958 ) ) .
The ascertained seasonal fluctuations electric conduction ( winter:240A±12 Aµmho ; during inundation: 200.5 A±14.5 Aµmho and summer:269.7 A±24.7 Aµmho cmE‰1 ) were most likely due to leaching of salt by inundation H2O that over flow the river Bankss and wash from rain watercourse into the river.
Plankton flourished and dumbly reproduced during the clip of slow H2O flow in period from March to May and November to December.These observation are in understanding with these of ( Hamaza, ( 1981 ) and Ahmed.,1989 ) . Production was minimum due to deluge and high H2O discharge ( Rzoska and Brook, 1954 ) in add-on to the effects of the biotic and a biotic factor.
Although the old consequence Adam, ( 1977 ) , record higher flourish of planktons ( primary and secondary ) at the locality of dike in comparing to toss off watercourse, the present recorded the contrary i.e. lowest densenesss. This indicates alteration in the home ground at the locality the dike is more likely to put either due to alter in the government of the dike operation or due to electro – bring forthing power workss alternatively to the dike.
Feeding strength governed by nutrient handiness which in related to environmental habitat parametric quantity. Other factors that were effectual, cloud formation, reduced H2O discharge and therefore high H2O degrees. Fluctuations in the environmental conditions of this home ground clearly suggested that fish responded to environmental variables in the same general manner as the remainder of craniates and that their ripening and genteelness activities are still chiefly governed by light rhythms.
The per centum of full tummy was diminution in the piscivorous fish i.e. Hydrocynus.The function of the vision in eating has tested by experimentation by old surveies Petts, ( 1988 ) and FAO ( 1982 ) who recorded threshold of light strength is required for seeking power for quarry and the day-to-day eating period vary well with season.
So high siltation and low transparence can be considered within the chief factor.This can be considered within the chief factor. This can be farther influenced by the high H2O current that prevail during this season with accompanied by the inundation of white Nile.However, the ability to seek for prey depend on the distance depend on the motion of the quarry, its orientation and copiousness in the specific country.
Further surveies in type of nutrient and eating of Characidae fish in White Nile.