JURNAL B.INGGRIS

CONTRADICTIONS

Abstrack 1

The breeding season, fecundity, length-weight relationship and condition factor of Oreochromis niloticus from Lake Tana, Ethiopia, were studied from monthly samples collected using a bottom trawl between March, 1992 and March, 1993. In Lake Tana Oreochromis niloticus spawns throughout the year, with a high activity between April and August peaking in June and July. The peak spawning coincided with the onset of the rainy season. There was a curvilinear relationship between fecundity and total length (TL) (logF — -0.01 - 2.O1LogTL, r—0.86, pX0.001) and a linear relationship between fecundity and body weight (W) (F —- 234.65#-1.51Tw, r—0.84, pX0.001) and gonad weight (GW) (F — 394.55 429.1GW, r-0.67, px0.001). The length-weight relation- ship was less than a cube, Logrw — -1.373-42.742LogTL, n-680, r—0.97, p 0.001 indicating allometric growth of the fish. The length-weight regression coefficients for both males (2.748) and females (2.747) were almost the same. A significant seasonal fluctuation (ANOVA, pX0.001) was observed in the condition of the fish. The relatively low values during April to August may be due to the high energy cost of spawning.

Abstrack 2

Reproductive biology of Oreochromis niloticus in Beseka was studied. Samples of O. niloticus were collected monthly during September 2010 to August 2011 using different centimeter mesh sizes of gillnets. The relationship between total length and total weight was curvilinear and sex ratio was different throughout the sampling periods. The 50% sexual maturity length (L₅₀) was estimated at 14 cm TL for females and 17 cm TL for males. Estimated fecundity was linearly related with total length and total weight of the fish. Absolute fecundity was estimated in number and range from 125 to 251 with a mean of 161 ± 2.5. The frequency of ripe gonads suggested that O. niloticus in Lake Beseka breeds throughout the year and intensive breeding coincided with the rainy seasons.

Material and Menthods 1

Monthly samples from two sites were collected between March 1992 and March 1993 with a bottom trawl of a code end mesh size of 40 mm. Trawling was done for about 30 minutes during each sampling occasion. All fish collected were mixed and a random sub-sample of 30 to 60 fish were taken for analysis. Total length (TL) and total weight (Tw) of each fish were measured to the nearest 0.1 cm and 0.1 g, respectively. Sex of each fish was determined by examination of gonads and the weight of gonads was recorded to the nearest O.1g. Gonado-somatic index (GsI), gonad weight as a percentage of total body weight, was calculated for each fish. Maturity of the gonads was determined according to Siddigui (1977) and Babiker and Ibrahim (1979). Fecundity was determined by counting all ripe eggs in ovaries that were preserved in Gilson's fluid (Synder, 1983). Length-weight relationship was constructed using. least sguares regression fitted to log transformed length and weight data, i.e., Logrw - loga # blogTL, where a and b are constants fitted by least sguares regression.

Material and Menthods 2

Samples of O. niloticus were collected using gill nets monthly between September 2010 and August 2011 from different sites. The gear were set parallel to the shoreline in the afternoon (5:00 pm) and lifted in the following morning (7.00 am). Immediately after capture, total length (TL) and total weight (TW) of each specimen were measured to the nearest 0.1 cm and 0.1 g, respectively. The ripe ovaries were split longitudinally and turned inside out, to ensure the penetration of the preservative before they were stored in labeled jars. Finally, ripe ovaries were preserved in Gilson’s fluid to estimate fecundity (Bagenal and Tesch, 1978). Preserved samples were then transported for further laboratory analysis. The number of female and male O. niloticus caught was recorded for each sampling occasion. Sex-ratio (female : male) was then calculated for each month and total sample.

Introduction 1

Tilapia (Cichlidae) are widely distributed in tropical and sub-tropical waters of Africa, South America and Asia (Fryer and Iles, 1972). The tilapia, Oreoch- Tomis niloticus, occurs in almost all the lakes and streams of Ethiopia (Shibru “Tedla, 1973), and accounts for about 604 of the annual commercial fishery (LrDp, 1995). 32 Zenebe Tadesse. Reproductive biology of O. niloticus from Ethiopian Rift Valley Lakes was studied by Zenebe Tadesse (1988) and Demeke Admassu (1994: 1997). Food and feeding habits were studied by Getachew Teferra (1987), Getachew Teferra and Fernando (1989), Eyualem Abebe and Getachew Teferra (1992), Getachew Teferra (1993) and Zenebe Tadesse and Getachew Teferra (1997) and age and growth was studied by Demeke Admassu (1989) and Yosef Tekle-Giorgis (1990).

Introduction 2

A cheap source of protein is urgently required to support an ever increasing human population. Fishery resources definitely can offer one of the solutions to the problem of food shortage in a country like Ethiopia. Moreover, the Nile tilapia (Oreochromis niloticus) is the most preferred fish species in Ethiopia for human consumption and the demand has increased rapidly over the last few years.

Result 1

A total of 680 O. niloticus individuals were examined in 13 sampling occasions. Males were more numerous than females (chi-sguare, p « 0.05) in the total catch as well as in samples from April, May and June (Table 1). There was also a preponderance of males in length-groups that were larger than 27.0 cm TL (Table 2). SINET: Ethiop. J. Sci., 2061), 1997 35. The number of males, females and sex-ratio in monthly samples of O. niloticus caught from Lake Tana. The last column shows chi-sguare values. “, Significant (p €0.05). Month Males Females Sex ratio Chi-sguare (male: female)

Result 2

The length-weight relationship of O. niloticus in Lake. Beseka was curvilinear and statistically highly significant (P<0.05) (Figure 1). The equations separated by sex were as follows:

Males:  TW = 0.0124 x TL^2.61, R² = 0.631, n = 273

Females: TW = 0.0141 x TL^2.73, R² = 0.709, n = 793

Discussion 1

This study demonstrates that males predominated in the catch that was taken during the peak spawning period of the fish and this could be one of the reasons why males were more numerous than females in the total catch as well as in size groups above 27 cm TL (Tables 1 and 2, Figs Ib and 1c). The prepon- derance of males over females in the catch taken during the peak breeding season may be explained by the interactive effects of the reproductive behaviour of the fish and the sampling gear. During the spawning season, male tilapia build their spawning nests at the bottom and guard them against intruders 40 Zenebe Tadesse

Discussion 2

The largest fish caught in the present study was 25 cm (TL) which was smaller than Lake Babogaya (28 cm) (Lemma, 2012). There were a curvilinear relationship between total length and total weight of the fish in the lake (Figure 1). The value of b (2.69) was close to the theoretical value (b = 3), indicating isometric growth. These finding are in agreement with the principle of fish growth (Bagenel and Tesch, 1978).

Equation

First journal and second journal same at the place in the Euthopia and discus about Oreochromis niloticus.