The authors have declared that no competing interests exist.
In order to contribute to the improvement of aquaculture production, reproductive parameters of three populations of
Human societies are facing a huge challenge of food supply enough rich in protein and that of providing livelihoods to an estimated population of over nine billion by mid-21st century
Cameroon is drained by four watersheds namely the Sanaga, Congo, Niger and Chad. The Nile Tilapia is naturally widespread in the watersheds of the Benue (Niger) and Lake Chad
The study took place from 20 March to 05 May 2019 at the IRAD’s farm of Foumban, more precisely at the fish station of Koupa-Matapit (LN: 5º 21' to 5 ° 58 'and LE: 10º 17' to 11º 02 '). The average altitude is 1145 m. The climate is Sudano-Guinean and includes one rainy season (March - October) and one dry season (November - February). The annual average temperature and rainfall are 22ºC and 1800mm respectively.
Eighty-one (81) spawners including 54 females (average weight 124 ± 6g) and 27 males (average weight 144 ± 5g) have been used. Thus 18 females and 9 males of each Hydrogeographic origin were randomly distributed in three concrete tanks (length 1.5 m, width 0.7 m, height 0.8 m)equipped with a system to bring and overflow and fully drainable by gravity. The completely randomized design with 3 treatments ("Sanaga" = fish population of Sanaga, "Niger" = population of Niger, and "Koupa" = population of IRAD station of Foumban) and 3 repetitions was used. Thus, 54 females and 27 males were divided into triplicate randomly into 3 lots and within 9 tanks.
The implementation of the trial began 07 May 2019 by cleaning the tanks and putting them in Assec (let dry on the sun) for seven days. After this period, the impoundment (put in water) has been made in order to obtain a water depth of 60 cm. Three days later, the fish were randomly distributed at a density of 9 individuals / m² and a sex ratio of 1 male for 2 females. When putting the fishes into tanks, a sample of 10% of the total fishes was weighed and measured individually, using respectively an electronic balance (reference: BF-400, accuracy 0.1g) and an ichtyometer (1 mm accuracy).
During the test, all treatments received 20% protein feed twice per day, consisting in fishmeal, soybean meal, yellow corn meal, blood meal, palm oil and vitamin premix prepared at the IRAD station as described by
Forty-five days after the implementation of the test, the tanks were drained, adults and juveniles collected and counted. In order to evaluate the gonado-somatic and the gonado-metric parameters at the end of reproduction, all spawners were weighed and eviscerated. The gonads were removed and weighed, as well as the eviscerated fishes.
At the end of this test some characteristics were determined or calculated. The total or absolute productivity is the average number of offspring (fry, alevins and eggs) produced per female. The relative productivity is the number of offspring produced per g of females stored. The productivity of the system is the average daily production of offspring per m² of the operated area. Absolute fecundity is determined by counting the total number of newly recovered egg of the oral cavity of the female. Gonado-Somatic Ratio (GSR) and gonado-Somatic Index (GSI) correspond respectively to the gonad weight (GW) in percentage of the body weight (BW) (GSR = GW / BW * 100) and the eviscerated fish weight (EW) (GSI = GW / EW * 100). The formula used to calculate the Gonado-metric Ratio (GMR) and gonado-metric Index (GMI) was respectively GMR = GW / TL * 100 and GMI = GW / SL * 100. Where GW = gonad weight (g); BW = body weight; EW = eviscerated fish weight (g); TL = fish's total length (cm) and SL = fish's standard length (cm).
The data were submitted to the one-way analysis of variance (ANOVA 1). When the effect of the waterway of origin was significant, the Duncan test was used to separate the means clustering at 5% threshold. The F test was used to determine the significance of the effect of sex and means clustering were compared pairwise using the t test of Student. All analyzes were performed using the SPSS software version 21. 0.
The gonado-somatic ratio, the gonado-somatic index, the gonado-metric ratio and the gonado-metric index of the fish population of the Koupa research station are significantly lower (P ≤ 0.05) than those of the Niger and Sanaga watersheds and whose values were comparable (P ≥ 0.05) between these two populations. Considering the sex and regardless of the characteristic considered, the males presented the lowest significant values (P ≤ 0.05). (
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x̄ |
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x̄ |
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Sanaga | 0.05 ± 0,01 |
Sanaga | 0.06 ± 0,02 |
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Koupa | 0.04 ± 0,02 |
Koupa | 0.05 ± 0,03 |
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Niger | 0.06 ± 0.01 |
Niger | 0.07 ± 0.01 |
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Female | 0.06 ± 0,02 |
Female | 0.07 ± 0,02 |
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Male | 0.04 ± 0,01 |
male | 0.04 ± 0,01 |
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Sanaga | 0.37 ± 0.15 |
Sanaga | 0.43 ± 0,19 |
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Koupa | 0.29 ± 0,08 |
Koupa | 0,34 ± 0,07 |
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Niger | 0.40 ± 0,06 |
Niger | 0.49 ± 0,09 |
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Female | 0.36 ± 0,14 |
Female | 0.45 ± 0,10 |
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Male | 0.23 ± 0,08 |
male | 0.29 ± 0,09 |
ab and c: mean affected with the same letter for the same characteristic indicate that there is no significant difference between populations or sex (P ≥ 0.05). SD= standard deviation and x̄ =mean
From
Characteristics |
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x̄ |
x̄ |
x̄ |
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391.50 ± 28,99 |
352.00 ± 9,89 |
504.50 ± 13,43a |
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3,09 ± 0,10 |
2.71 ± 0,01 |
3.91 ± 0,32 |
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844.00 ± 45,25 |
823.50 ± 44,55 |
1005.00 ± 25,46 |
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1,62 ± 0,04 |
1.60 ± 0.12 |
1,96 ± 0,08 |
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18.75± 0,50b | 18,30± 0,49b | 22.33± 0,28a |
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211.00 ± 11,31b | 205.87 ± 11,14b | 251.25 ± 6,36a |
ab and c: mean affected with the same letter on the same line were no significant differences between populations (P> 0.05). F = fertility, P = productivity, S= standard deviation. x̄ = mean
It appears in
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1 | |||||||
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0.832 * | 1 | ||||||
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0.848 * | 0.942 ** | 1 | |||||
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0.832 * | 0.998 ** | 0.942 ** | 1 | ||||
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0.977 ** | 0.787 | 0.871 * | 0.787 | 1 | |||
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-0.131 | 0,056 | -0.281 | 0,056 | -0.331 | 1 | ||
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0.078 | 0,181 | -0.127 | 0,181 | -0.133 | 0.918 ** | 1 | |
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0.832 * | 0.999 ** | 0.942 ** | 0.998 ** | 0.787 | 0,056 | 0,181 | 1 |
*, **= bearing securities are significant at (p ≤ 0.05) and (p≤0,01) F = Absolute fecundity, P = productivity
The gonado-somatic and gonado-metric characteristics are generally higher in females than in males. This corroborates the results obtained by
In our experience the absolute fecundity and relative fecundity varied significantly between different populations. This is contrary to the results obtained by
Our values for the absolute fertility (452 ± 39.90 to 43.43 ± 604 eggs per female) are low compared to those reported by
Comparison of reproductive performances of
The productivity of the system is 22.33 larvae / m² / day is less than 32 larvae / m² / d obtained by
At the end of our study on the evaluation of gonadal-somatic characteristics gonado-metric and reproductive performances of three populations of