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Reproductive Strategy of Chrysichthys nigrodigitatus (Lacepede, 1803) in a Natural Environment in the Nkam River, Littoral Cameroon

Reproductive Strategy of Chrysichthys nigrodigitatus (Lacepede, 1803) in a Natural Environment in... Hindawi International Journal of Zoology Volume 2020, Article ID 1378086, 8 pages https://doi.org/10.1155/2020/1378086 Research Article Reproductive Strategy of Chrysichthys nigrodigitatus (Lacepede, 1803) in a Natural Environment in the Nkam River, Littoral Cameroon 1 2 3 Claudine Tekounegning Tiogue´ , Boddis Tsiguia Zebaze, Paul Zango, and Minette Eyango Tomedi-Tabi Laboratory of Applied Ichthyology and Hydrobiology (LAIH), School of Wood, Water and Natural Resources (SWWNR), Faculty of Agronomy and Agricultural Sciences (FAAS), !e University of Dschang, P.O. Box 786, Ebolowa Antenna, Dschang, Cameroon Laboratory of Applied Ichthyology and Hydrobiology (LAIH), Department of Animal Productions, Faculty of Agronomy and Agricultural Sciences (FAAS), !e University of Dschang, P.O. Box 222, Dschang, Cameroon Laboratory for Aquaculture and Demography of Fisheries Resources (LADFR), Departement of Aquaculture, Institute of Fisheries and Aquatic Sciences of Yabassi (IFAS), !e University of Douala, P.O. Box 2701, Douala, Cameroon Correspondence should be addressed to Claudine Tekounegning Tiogue´; claudine.tiogue@univ-dschang.org Received 30 July 2019; Accepted 20 December 2019; Published 15 February 2020 Academic Editor: Cucco Copyright © 2020 Claudine Tekounegning Tiogue et al. (is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A study on the reproductive strategy of Chrysichthys nigrodigitatus was conducted from October 2015 to August 2016, in the Nkam River in Yabassi, Littoral Region of Cameroon. For this purpose, 154 specimens of C. nigrodigitatus with total mean weight of 829.96± 829.58 g and total mean length of 367± 156 mm collected from artisanal fishermen were used. Twenty-nine (29) females at stage V of sexual maturity were selected for the evaluation of the fecundity. It appears that the oogenesis in C. nigrodigitatus is of an asynchronous type with multiple laying spread over a long period. (e gonadosomatic index (GSI) peaks in June (17.9± 7.1 for females and 1.06± 0.27 for males). Hepatosomatic index (HSI) was higher in females than in males throughout the year. (e mean condition factor K was 1.07 ± 0.09%. (e breeding season occurred from April to October during the rainy season. Gonadosomatic and hepatosomatic indices were positively correlated with rainfall, contrary to the K factor, which has been strongly and negatively correlated with this physical parameter. (e sex ratio of 1M: 1.5F was in favour of females, thus reflecting an “r” type reproductive strategy. Absolute fecundity was estimated at 1374± 1022 oocytes for individuals of 107.3± 111.9 g mean weight. Mean relative fecundity was 14± 3 oocytes/g of body weight. It was recommended that future work focuses on the captivity of this species. In Africa, and particularly in Cameroon, as reported by 1. Introduction Cacot [3], fish farming has remained focusing on three Fish is an extremely nutritious food, a vital source of protein species of fish: Clarias gariepinus, Oreochromis niloticus, and and essential nutrients, especially for many low-income Cyprinus carpio. At the present state of knowledge, very few people around the world [1]. According to FAO [2], world of these farmed species have reached a large-scale devel- fish supply reached a record of 20 kg per capita, in favour of opment potential. (is situation would certainly be at the strong growth in aquaculture, which now provides half of origin of the intensification of research towards new species the fish for human consumption. (is growth is correlated better adapted to the constraints of African aquaculture. (is with the progressive enhancement of native species in is particularly the case for studies on some African carp and certain regions of the world [2]. African catfish: Labeo senegalensis by Montchowi et al. [4], 2 International Journal of Zoology Labeo parvus by Montchowui et al. [5] and Montchowui et 2.3. Assay Conduct and Data Collection. (e collected fish al. [6] and Chrysichthys auratus [7, 8] in Benin and Egypt, were kept alive in 20-liter buckets and transported to the ´ Laboratory for Aquaculture and Demography of Fisheries Labeo coubie in Nigeria by Ikpi and Okey, and Labeobarbus batesii and Clarias jaensis in the Mboˆ Floodplain in West Resources (LADFR) of the Institute of Fisheries and Aquatic Cameroon by Tiogue´ et al. [10], Tiogue´ [11], Tiogue [12], Sciences of Yabassi (IFAS), where they were identified Tomedi et al. [13], Zango et al. [14]. according to the identification key of Stiassny et al. [20]. Each (e ichthyological fauna of Cameroon’s freshwater is of individual was then recorded and sexed with the naked eye. exceptional interest. Nearly 60 species of fish have recently (e total and standard lengths (tL and sL, respectively) were been identified by Ajonina and Tomedi [15] in the Nkam measured with a 1 mm ichthyometer. (e total weight (tW) River, amongst which the most abundant and much ap- and the weight after evisceration (evW) were obtained using a preciated species was Chrysichthys nigrodigitatus, locally Sartorius Competence electronic scale at the 10th of g. After ` ` called “mayepe.” (is fish species is the subject of many dissection of each fish using the scissors of a dissection kit, the traditional recipes in households and restaurants, according gonads (Figure 2(a)) and the liver were removed with a razor blade, drained, and weighed at 0.01 g on a sensitive electronic to Ajonina and Tomedi [15], the consequence of which is the decrease of wild stocks. (erefore, studies on the biology of scale brand TATINA model 1479V (Figure 3(a)). Based on this species is essential to better develop its breeding cap- the sexual maturity scale of the ovaries of C. nigrodigitatus tivated. Aspects of the biology of C. nigrodigitatus have established by Ote´me´ [21], only the ovaries of 29 females at already been the subject of several studies in West Africa, stage V of sexual maturity were selected for the estimation of more particularly in Ivory Coast, where captive breeding the fecundity: three samples of 1 g of ovary were collected in trials have been successfully tested by Djehi ´ [16]. In the rostral, middle, and caudal regions (Figure 2(b)) and Cameroon, there is very little information on its repro- weighed. One gram of ovary was put in Gilson’s liquid (pure ductive cycle. Hence, the general objective of this study was ethanol 98 C (60 ml) + water (920 ml) + acetic acid (9 ml) + to evaluate some elements of the reproductive cycle of C. mercury chloride (20 g)) to dissociate the oocytes and thus nigrodigitatus in view of its domestication, and more spe- facilitate counting (Figure 3). (e oocytes of each sample were cifically, it was to determine in this species the breeding counted under a stereoscopic binocular magnifying glass period, sex ratio, and fecundity of this species depending on (magnification ×10). the endogenous and exogenous factors of the Nkam River. 2.4. Collection of Physical Parameters of Water. One station 2. Materials and Methods representing the fishing location was selected in the up- stream part of the Nkam River. Due to a lack of chemical 2.1.StudyZone. (e study was conducted from October 2015 parameter collection equipment, only the following physical to August 2016, in the Nkam River in Yabassi Township, parameters were determined: the transparency, the depth, District of Yabassi, Department of Nkam and Littoral Region of ° ° the temperature, and the rainfall were measured monthly, Cameroon (Figure 1). It is located between 9 50′ and 10 10′ of ° ° respectively, using a Secchi disk to within 1 cm, a gallows LN and between 4 20′ and 4 40 LE, with mean altitude of 15 to graduated to the nearest mm, a mercury thermometer, and a 20 m [17]. (e climate is subequatorial with a tropical tendency rain gauge. of two seasons: a dry season that runs from November to March and a rainy season that runs from April to the end of October. (e hottest month is January and the coldest is August. (e mean annual rainfall is 2927 mm; the maximum 2.5. Studied Parameters rainfall is between July and August. Monthly temperatures ° ° range from 25 C to 35 C and are favourable for aquaculture 2.5.1. Breeding Period. (e breeding period was determined by calculating the following indices as used by Saadia ˆ [22]: [18]. (e Nkam River results from the merger of two rivers: the “Small Nkam” (Department of Haut-Nkam) and the “Ngoung” (i) Gonadosomatic index (GSI): GSI (%) � (gW/evW) (Department of Menoua). It flows from from Nkongsoung × 100, where gW � gonads weight and evW � (Moungo Department), passing through Yabassi, into the eviscerated weight of fish Wouri River at Akwa North (Wouri Department) [19]. (ii) Hepatosomatic index (HSI): HSI (%) � (lW/evW) × 100, where lW � liver weight and evW � eviscerated weight of fish 2.2. Animal Material. A total of 154 specimens of Chrys- ichthys nigrodigitatus of mean total weight of 829.96± (iii) K factor has been calculated using the formula of 829.58 g and mean total length of 367± 156 mm were col- Ricker [23]: K � (tW/tL ) × 100, where tW and tL lected from the local fishermen of Nkam River. Sampling are, respectively, the total weight and the total was done monthly and fish samples were hand-harvested length of the fish using 3- and 4-finger gillnets. After the first 6 months of collection, noting that this capture technique was selective, it was replaced by “bamboo China” structures installed in the 2.5.2. Sex Ratio (S/R). (e sex ratio according to Ragheb [8] various points of the selected station, to have a wide range of is translated by the following relation: S/R � number of the size of the individuals. males/number of females. International Journal of Zoology 3 889294 924572 960050 995428 030808 9 9 9 9 10 Township Yabassi and Bodiman Cameroon 9°10 9°50 10° 10°10 10°20 10°20 10°40 5°10 Nkam division 5° Legend Study Zone 4°50 Villages 4°40 Roads 4°30 Streams 4°20 Nkam River 4°10 00,512 34 Sampling area Killometers 4° 9°10 9°50 10° 10°10 10°20 10°20 10°40 889294 924672 960050 995428 030806 9 9 9 9 10 Figure 1: Geographical location of Yabassi. (a) Cameroon, (b) Nkam Department, and (c) Yabassi District (source: adapted from [19]). Rostral region Middle region Caudal region (a) (b) Figure 2: (a) Ovaries of C. nigrodigitatus, (b) testes of C. nigrodigitatus. 2.5.3. Fecundity. Fecundity was evaluated according to 2.6. Statistical Analysis. Descriptive statistics, the χ2 com- Ragheb [8]: parison test, the Pearson correlation test, and the one-way ANOVA test were used to process the data for the pa- (i) Absolute fecundity (aF) was determined on a sample rameters studied at 5% level of probability. (is was done of 29 females at stage V of sexual maturity. It is using the SPSS16.0 statistical software. defined by the formula: af � total weight of oocytes × number of oocytes in 1 g of ovary 3. Results (ii) Relative fecundity (rF) was calculated from the aF. It is translated by: rF � total number of oocytes/weight 3.1. Monthly Evolution of Gonadosomatic Index. Figure 4 of the female (Kg) shows the monthly evolution of the gonadosomatic index 353158 383332 418226 450320 483014 4 4 4 4 4 4 International Journal of Zoology (a) (b) Figure 3: (a) Electronic scale, (b) oocyte counting device. 30 1.8 1.6 1.4 Female 20 1.2 Male 0.8 10 0.6 0.4 0.2 0 0 ON D J F M A M J J A ON D J F M A M J J A Period (month) Period (month) (a) (b) Figure 4: Monthly evolution of GSI by sex of C. nigrodigitatus between October 2015 and August 2016 in the Nkam River: (a) female, (b) male. (GSI) in C. nigrodigitatus by sex. It seems that regardless of 3.4. Correlation between Reproduction and Physical the sex considered, the GSI has evolved in the same way with Parameters. Correlations between reproduction parameters values significantly (P< 0.05) high from April, and the peak (GSI, his, and condition factor K) and environmental pa- is observed in June. rameters as presented in Table 1 and Figure 7 revealed a positive and significant correlation between rainfall and gonadosomatic index (r � 0.74, P< 0.01) on the one hand 3.2. Monthly Evolution of the Hepatosomatic Index. and a negative and significant correlation between this same Figure 5 portrays the monthly evolution of the hep- parameter and the condition factor K (r � − 0.73, P< 0.05) on atosomatic index (HSI) in C. nigrodigitatus by sex. In fe- the other hand. Negative but insignificant correlations were males, three (3) increasing peaks were successively observed: observed between GSI, transparency, and temperature. Only November (1.05± 0.21), March (1.24± 0.49), and June the precipitation correlated positively with HSI, but not (1.78± 0.56), while in males two (2) decreasing peaks were significantly (P> 0.05). observed in November (1.41± 0.33) and in April (1.01± 0.27). (e minimum values of HSI were reached in 3.5. Monthly Variation of Sex Ratio. (e monthly variation December (0.84± 0.32) and in February (0.88± 0.15) in of sex ratio in C. nigrodigitatus (Table 2) indicates that the females and in March (0.64± 0.15) and May (0.48± 0.20) in mean sex ratio during the study was in favour of females (1 : males. In females, the maximum HSI registration period 1.5). (is sex ratio value was statistically not significantly coincided with that of the IGS (June). (P< 0.05) different from the theoretical sex ratio (1 :1). Sex ratio in favour of males was observed only in June. (e standard sex ratio (1 :1) was recorded only in May and 3.3. Monthly Evolution of Condition Factor K. Figure 6 il- December. However, except for November, a sex ratio (1 : 4) lustrates the monthly variation of condition factor K in C. significantly (P< 0.05) different from the theoretical sex nigrodigitatus by sex in the Nkam River. It shows that the ratio (1: 1) was recorded. mean K factor ofC.nigrodigitatus recorded between October 2015 and August 2016 in the Nkam River was 1.09± 0.07%. Except for the month of December, there was no significant 3.6. Fecundity. (e absolute fecundity was 1374 ± 1022 difference between the sexes and the months (P> 0.05). oocytes for females with a mean weight of 107.3± 111.9 g However, between May and July, the K factor remained and a mean total length of 211± 52.8 mm and the relative slightly below 1 (0.97± 0.01) in females. fecundity of 14± 3 oocytes/kg for females. GSI (%) GSI (%) International Journal of Zoology 5 2.5 2.5 Female Male 2 2 1.5 1.5 1 1 0.5 0.5 0 0 ON D J F M A M J J A O N D J F MAM J J A Period (month) Period (month) (a) (b) Figure 5: Monthly evolution of HSI by sex of C. nigrodigitatus between October 2015 and August 2016 in the Nkam River. 500 20 2.5 450 18 400 16 350 14 300 12 250 10 1.5 200 8 150 6 1 100 4 50 2 0 0 0.5 ON D J F M A M J J A Period (month) 0 Rainfall ON D J F M A M J J A GSI Period (month) Figure 7: Correlation between the gonadosomatic index of C. nigrodigitatus and rainfall in the Nkam River. Female Male Figure 6: Monthly variation of K factor by sex of C. nigrodigitatus Table 2: Monthly variation of sex ratio in C. nigrodigitatus between between October 2015 and August 2016 in the Nkam River. October 2015 and August 2016 in the Nkam River. Sex ratio Number Month Male (N) Female (N) M : F Table 1: Correlation between reproduction parameters of C. October 1 2 1 : 2 nigrodigitatus and physical parameters of the environment in the November 3 12 1 : 4 Nkam River. December 3 3 1 :1 Physical parameters of the environment January 4 9 1 : 2.3 Reproductive February 6 8 1 :1.3 parameters Depth Transparency Temperature Rainfall March 2 4 1 : 2 Gonadosomatic ∗∗ 0.18 − 0.53 − 0.59 0.74 April 9 12 1 :1.3 index May 12 14 1 :1.2 Hepatosomatic − 0.01 − 0.41 − 0.29 0.57 June 8 6 1 : 0.8 index July 8 13 1 :1.6 K condition factor − 0.39 0.59 0.54 − 0.73 August 6 9 1 :1.5 ∗ ∗∗ Significantly (P< 0.05) correlated, significantly (P< 0.01) correlated. Total 62 92 1 : 1.5 N � number, M: F � male: female, significantly (P< 0.05) different from the theoretical sex ratio 1 � : 1. Figure 8 shows the relationship between absolute fe- cundity and total weight and between this same parameter and the total length ofC.nigrodigitatus females. It shows that 4. Discussion a very strong and significantly positive correlation exists between absolute fecundity and total weight on the one hand 4.1.BreedingPeriod. (e breeding season of C. nigrodigitatus (r � 0.97, P< 0.01) (Figure 8(a)) and between this same coincides with the continuous rainy season, which lasts ap- parameter and the total length (r � 0.98, P< 0.01) on the proximately six months and is characterized by a single other hand (Figure 8(b)). spawning season in June as reported elsewhere [11, 12, 24, 25]. K-factor (%) HSI (%) HSI (%) Rainfall (mm) GSI (%) 6 International Journal of Zoology 6000 6000 aF = 8.7134tW + 419.98 aF = 18.687tL – 2588.6 5000 R = 0.9441 5000 R = 0.9717 4000 4000 3000 3000 2000 2000 1000 1000 0 0 0 100 200 300 400 500 600 700 0 100 200 300 400 500 Total weight (g) Total length (mm) AF = absolute fecundity (a) (b) Figure 8: Relationship between absolute fecundity and total weight (a) and the total length (b) in C. nigrodigitatus females in the Nkam River. nigrodigitatus. However, the slight drop in K-factor values (e reproduction of C. nigrodigitatus is of the asynchronous type as reported elsewhere [11, 12], thus making this species a (0.94± 0.06) noted between May and August may be related partial or heterochronous breeder, or fish with multiple to female oviposition weight loss. Indeed, according to spawning or split-spawning. (e peak breeding period ob- Kra¨ıem [35], the fall in values of the relative condition served between April and June is similar to that recorded by coefficient (Kr< 1) indicates the postspawning period Ekamen [26] and Offem et al. [27] in the Cross River in Nigeria qualified by energy expenditure and weight loss. in the same species and by Dia [28] and Dossou [7], re- spectively, in Ivory Coast and in Benin. (ese results, however, 4.2. Sex Ratio. (e sex ratio of 1M: 1.5F observed in this are different from those obtained by Ote´me´ [29] and Dje´hi study is statistically close to the theoretical sex ratio (1 :1). [16], who under breeding conditions observed maximum However, it is biologically in favour of females, thus giving laying in September and October; and those reported by this species a reproductive strategy of “r” type, thus a po- Ragheb [8] which show that the spawning season ofC.auratus lygamous matrimonial regime. (ese results are similar to extends from October to June. According to Dia [28], laying the observations made on C. auratus (1M: 2F) and on C. occurred between May and July and lasted until November nigrodigitauts (1M: 4F) by Imerbore and Bakare [36] and on ° ° when temperatures had varied between 25 C and 27 C. Hem C. auratus (1M: 1.18F) by Ragheb [23] in Damietta branch of [30] and Albaret [31] also observed C. nigrodigitatus spawning the River Nile in Egypt. (ese observations are contrary to during the rainy season, adding that temperature is a major those reported in Lake Asejire by Taiwo and Aransiola [37] factor in this phenomenon, associated with salinity and floods. and Dossou [7] in C. auratus (1M: 0.96F) and C. nigrodi- (e geographical position, the duration of the rainy season, gitatus (1M: 0.93F), respectively. In addition to the spatial and the specific characteristics of the water courses may vary and temporal difference, the sex ratio diversification could the extent and the period of reproduction in C. nigrodigitatus also be due to the fishing techniques practiced: Indeed, as recorded by Otte´me´ [29]. A positive correlation has been during this study, between May and August, fishermen have recorded between the gonadosomatic and the hepatosomatic replaced the usual gill nets with bamboo from China placed indices, whereas logically these two weight indices vary in about 3 m on the banks. (is fishing gear allows the capture opposite directions. Indeed, the fish would draw the reserves of of C. nigrodigitatus by couple (sex ratio of 1M: 1F). Dossou the liver (in particular, the vitellogenin in the females) to [7] also reported the use of this technique in Benin. manufacture the sexual products as discussed elsewhere However, the sex ratio obtained during the breeding season [11, 12, 32]. It should probably be due to the fact that some is close to the theoretical sex ratio (1: 1) just like that ob- females emit their eggs in a split way; and the partially emptied served elsewhere [7, 21, 27]. (us, it seems that the natural ovaries do not return to complete rest but continue the vi- approximation of males and females is in relation with the tellogenesis of oocytes that will be emitted later. (ese results reproduction period. are similar to those of Bouaziz et al. [33] in the Merlu, Merluccius rnerlucc´ıu Linnaeus, 1758. 4.3.Fecundity. (e absolute fecundity recorded in this study (e K condition factor of C. nigrodigitatus obtained in this study was higher compared to that obtained by Ezenwa is very low compared to the 24000 oocytes observed in et al. [34] and Dossou [7], respectively, recorded in the Imo Kousson on Bandama in Ivoiry Coast by Kouassi [38]. It is River in Nigeria (0.78) and small water body of the Ouem ´ e´ also lower than that of 4878 to 87724 oocytes recorded by basin in Benin (0.64), showing that the samples of the Nkam Oteme´ [21] in Ebrie´ Lagoon in individuals weighing from River were of good overweight. (ese results are close to 500 g to 6000 g with an average of 20000 oocytes. However, it 0.96, 0.97, and 0.99, respectively, reported in the Bandagry is close to 7596 oocytes reported in the South Benin Lagoon ` ` Lagoon in Nigeria by Ezenwa et al. [34] and the river cross in Complex by Laleye et al. [39]. In the Cross River in Nigeria, Nigeria by Ekamen [26] and Offem et al. [27] in the same Ekamen [26] and Offem et al. [27], respectively, reported a fecundity of 12063 and 25905 oocytes. More recently, in the species. As a result, the Nkam River may have very favourable natural conditions for the development of C. small water plans of the Ouem ´ e´ basin in Benin, Dossou [7] AF (oocytes number) AF (oocytes number) International Journal of Zoology 7 recorded fecundity from 3474 to 28778 with an average of Conflicts of Interest 10783 oocytes in individuals weighing 557.3 g to 2270.1 g. (e authors declare that they have no conflicts of interest. However, these results are nevertheless comparable to those of Fagade and Adebisi ´ [40], which counted 2884 oocytes in Lac Asejire populations. In addition to the fact that fecundity Acknowledgments varies from one region to another and from one watercourse to another, it would certainly be linked to environmental (e authors thank all the fishermen of the Nkam River for factors. It could be strongly related to the weight and length their contribution in the collection of fish samples. of individuals. According to Otem ´ e´ [29], the length of C. nigrodigitatus allows a better estimate of its fecundity. Offem References et al. [27] added that this fecundity increases with the length and weight of C. nigrodigitauts. [1] FAO, La situation mondiale des pˆeches et de l’aquaculture, Unlike absolute fecundity, relative fecundity varies very vol. 255, FAO, Rome, Italy. little from one region to another. (e absolute fecundity [2] FAO, La situation mondiale des pˆeches et de l’aquaculture obtained in this study is comparable to that reported by 2016. Contribuer a` la s´ecurit´e alimentaire et a` la nutrition de other authors elsewhere: Dossou [7] reported 15± 6 oocytes/ tous, vol. 224, FAO, Rome, Italy, 2016. [3] P. Cacot, “Contribution a` l’amelioration ´ de la production g, Otem ´ e´ [29] 15 oocytes/g, Ekamen [26] 13 oocytes/g, d’alevins au Cameroun: essais de reproduction et d’´elevage de Offem et al. [27] 13 oocytes/g, and Hem [30] 14 oocytes/g in nurserie avec Clarias gariepinus et deux autres especes,” ` the same species. However, the slight spatial and seasonal Compte rendu de mission du projet ATP-CIROP. CIRAD, variations in the fecundity of C. nigrodigitatus are not to be vol. 64, 2006. neglected. According to Offem et al. [27], this could be [4] E. Montchowui, P. Laley ` e, ` P. Poncin, and J.-C. Philippart, related to the availability of the food. Gorenka et al. [41] add “Reproductive strategy of Labeo senegalensis valenciennes the duration of the spawning season and accumulated re- 1842 (Teleostei: Cyprinidae) in the Ouem´ ´ e basin, Benin,” serves. According to Offem et al. [27], an overweight fish is African Journal of Aquatic Science, vol. 35, no. 1, pp. 81–85, more likely to produce large numbers of oocytes compared to one with poor conditions. [5] E. Montchowui, M. Ovidio, P. Laleye, C. J. Philippart, and P. Poncin, “Strategies ´ de reproduction et structure des pop- ulations chez Labeo parvus Boulenger, 1902 (Cypriniformes: 5. Conclusion Cyprinidae) dans le bassin du fleuve Ouem ´ e´ au Benin,” Annales desSciencesAgronomiques, vol. 15, no. 2, pp. 153–171, C. nigrodigitatus breeds between April and October in the middle of the rainy season. Reproduction in C. nigrodigitatus [6] E. Montchowui, P. Laleye, J. C. Philippart, and P. Poncin, is of the multiple-spike asynchronous type. Gonadosomatic “Reproductive behaviour in captive African carp, Labeo index (GSI) is higher in females throughout the year, and the parvus boulenger, 1902 (Pisces: Cyprinidae),” Journal of peak is observed in June in both sexes. (e hepatosomatic Fisheries International, vol. 6, no. 1, pp. 6–12, 2011. index (HSI) was higher in females than in males throughout [7] S. D. H. Dossou, ““Exploitation et biologie compar´ee de deux the year. It correlated positively with GSI in females during especes ` de Chrysichthys (Poissons, Siluriformes) dans les spawning. Condition factor K was˃1 indicating that the Nkam petits plans d’eaux du bassin de l’Ouem ´ e: ´ cas du village de Kessounou, ´ commune de Dangbo, Benin,” ´ Diplome ˆ d’Etude River is a favourable environment for the good development Approfondie. Facult´e des Sciences Agronomique,” Universit´e of C. nigrodigitatus. Condition factor K correlated negatively d’Abomey-Calavi, vol. 49, 2011. with the increase in GSI during the reproduction period of C. [8] E. Ragheb, “Reproductive biology of catfish Chrysichthys nigrodigitatus. (e gonadosomatic and hepatosomatic indices auratus, Geoffroy Saint-Hilaire, 1809, (Family: bagridae) from were positively correlated with precipitation, in contrast to Damietta branch of the river Nile, Egypt,” !e Egyptian the K factor, which was strongly and negatively correlated Journal of Aquatic Research, vol. 42, no. 3, pp. 349–356, 2016. with this physical parameter of the environment. [9] U. Ikpi and B. I. Okey, “Estimation of dietary composition and (e sex ratio was in favour of females for most of the year fecundity of African carp, Labeo coubie, cross river, Nigeria,” and is close to the theoretical sex ratio in December, May, Journal of Applied Sciences and Environmental Management, and June, reflecting an “r” type reproductive strategy. vol. 14, no. 4, pp. 19–24, 2011. Absolute and relative fecundity increases with weight [10] C. T. Tiogue, ´ M. T. E. Tomedi, D. Nguenga, and J. Tchoumboue, ´ “Caracteristiques ´ de morphologie gen ´ erale ´ et and length of C. nigrodigitatus, but these parameters seem to de croissance du Cyprinidae Africain Labeobarbus batesii be directly influenced by certain environmental factors dans la plaine inondable des Mbo, ˆ Cameroun,” International (food, temperature, salinity, etc.). Journal of Biological Sciences, vol. 4, no. 6, pp. 1988–2000, In view of these results, C. nigrodigitatus is a potential candidate for aquaculture in Cameroon. [11] T. C. Tiogue, ´ “Regime ´ alimentaire, caracteristiques ´ de croissance et de reproduction de Labeobarbus batesii, Bou- Data Availability lenger, 1903 (Teleostei: Cyprinidae) en milieu naturel dans la plaine inondable des Mboˆ au Cameroun,” Universit´e de All raw and analyzed data of this work are available from the Dschang, Dschang, Cameroun, ( ese ` de Doctorat Ph/D, corresponding author (claudine.tiogue@univ-dschang.org/ Faculte´ d’Agronomie et des Sciences Agricoles Universite´ de Claudinetekou@gmail.com) upon request. Dschang, Dschang, Cameroun, 2012. 8 International Journal of Zoology [12] C. T. Tiogue´, M. T. E. Tomedi, and J. Tchoumboue´, “Repro- [28] K. A. 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Zabi, Eds., pp. 239–279, Editions de p. 533, 2016. l’ORSTOM, Paris, France, 1994. [15] N. G. Ajonina and M. E. Tomedi, “Aquaforests and aqua- [32] R. Fehri-Bedoui, H. Gharbi, and A. EL Abed, “Periode ´ de forestry: Africa,” in Encyclopedia of Natural Resources: Land, reproduction et maturite´ sexuelle de Liza aurata des cotes ˆ Est pp. 16–38, Taylor & Francis, New York, NY, USA, 2014. et Sud de la Tunisie,” Bulletin Institutionnel Natl Science [16] B. Y. Djehi, ´ “Contribution a` l’etude ´ des effets de l’age ˆ sur les Technique Mer Salamm-Boˆ, vol. 29, pp. 11–15, 2002. performances de reproduction du machoiron ˆ (Chrysichthys [33] A. Bouaziz, A. Bennoui, F. Djabali, and C. Maurin, “Repro- nigrodigitatus) elev ´ e´ a` la station experimentale ´ d’aquaculture duction du merlu Merluccius merluccius (Linnaeus, 1758) de Layo en Cote ˆ d’Ivoire,” ( ese ` de Doctorat, Dakar, Senegal, dans la region de Bou-lsmaıl,” CIHEAM-Options p. 72, 2008. M´editerran´eennes, vol. 35, pp. 109–117, 1998. ´ ´ ´ [17] MINEPAT, Rapport trimestriel d’activite. Delegation Provin- [34] L. B. Ezenwa, L. Ikusemiju, and O. I. C. Olaniyan, “Com- ciale/MINEPAT, vol. 69, MINEPAT, Yabassi, Cameroun, parative studies of the Catfish, Chrysichthys nigrodigitatus (Lacepede) in three isolated geographical areas in Nigeria for [18] MINADER, Rapport trimestriel d’activit´e. D´el´egation pro- breeding purposes,” in Aquacult. Res. In the African Region, vinciale/MINADER, vol. 66, MINADER, Yabassi, Cameroun, E. A. Huisman, Ed., Wageningen Academic Publishers, Wageningen, Gelderland, (e Netherlands, 1986. [19] INC, Carte du littoral dans le Cameroun, carte de Yabassi dans [35] M. M. Kra¨ıem, “Systematique, ´ biogeographie et bio-ecologie ´ le Nkam au 1/50000, Institut National de Cartographie, de Barbus callensis Valenciennes, 1842 (poisson, Cyprinid´es) Yabassi, Cameroon, 2010. de Tunisie,” ( eese ` de doctorat, p. 227, University of Tunis, [20] M. L. J. Stiassny, G. G. Teugels, and D. C. Hopkins, “(e Fresh Tunis, Tunisie, 1994. and brackish water fishes of lower Guinea, West-Central [36] A. M. A. Imevbore and O. Bakare, “(e food and feeding Africa,” in Faune et Flore Tropicales, vol. 2, p. 805, Tervureen, habits of non-cichlid fishes of the River Niger in the Kainji MRAC, Paris, France, 2007. reservoir area,” in Kainji: a Nigerian man-made lake. Kainji ´ ´ ´ ´ ˆ [21] Z. J. Oteme, “Reproduction et fecondite du machoiron Lake studies, S. A. Visser, Ed., vol. 1. Ecology, pp. 49–64, Chrysichthys nigrodigitatus en elevage,” ´ Journal Ivoire Nigerian Institute of Social and Economic, Research, Ibadan, Oc´eanologie Limnologie Abidjan, vol. 2, no. 1, pp. 53–59, 1993. Nigeria, 1970. [22] B. Saadia, ˆ “Bio-Ecologie de Barbus callensis (Valencienne [37] O. I. Taiwo and M. O. 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Poncin, “Biologie de la Eds., vol. 176–199, Croom Helm, London, UK, 1983. reproduction de deux especes ` de Chrysichthys (Siluriformes ; [25] J. Nuñez-Rodriguez, Z. Otem ´ e, ´ and S. Hem, “Comparative Bagridae) au lac Nokoue´ et a` la lagune de Porto-Novo au study of vitellogenesis of two African catfish species Chrys- Benin,” ´ Journal Africain de Zoologie, vol. 109, no. 3, ichthys nigrodigitatus (Claroteidae) and Heterobranchus pp. 213–224, 1995. longifilis (Clariidae),” Aquatic Living Resources, vol. 8, no. 4, [40] O. S. Fagade and A. A. Adebisi, “On the fecundity of pp. 291–296, 1995. Chrysichthys nigrodigitatus (Lacepede) of Asedjire dam, Oyo [26] B. S. Ekanem, “Some reproductive aspects of Chrysichthys state Nigeria,” Nigerian Journal of Science, vol. 1, pp. 127–131, nigrodigitatus (Lacepede) from cross river Nigeria,” Naga, ICLARM, vol. 2, no. 2, 2000. [41] S. Gorenka, K. C. Vanja, and Z. Barbara, “Population [27] O. B. Offem, Y. S. Akegbejo, and T. I. Omoniyi, “Diet, size and structure, size at maturity and condition of sardine, Sardina reproductive biology of the silver catfish, Chrysichthys pilchardus (Walb, 1792), in the nursery ground of the eastern nigrodigitatus (Siluriformes; Bagridae) in the cross river, Adriatic sea (Krka river Estuary, Crotia) Estuarine,” Coastal Nigeria,” Review Biology in Tropics, vol. 56, no. 4, pp. 1785– and Shelf Sciences, vol. 76, pp. 739–744, 2008. 1799, 2008. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Journal of Zoology Hindawi Publishing Corporation

Reproductive Strategy of Chrysichthys nigrodigitatus (Lacepede, 1803) in a Natural Environment in the Nkam River, Littoral Cameroon

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Hindawi International Journal of Zoology Volume 2020, Article ID 1378086, 8 pages https://doi.org/10.1155/2020/1378086 Research Article Reproductive Strategy of Chrysichthys nigrodigitatus (Lacepede, 1803) in a Natural Environment in the Nkam River, Littoral Cameroon 1 2 3 Claudine Tekounegning Tiogue´ , Boddis Tsiguia Zebaze, Paul Zango, and Minette Eyango Tomedi-Tabi Laboratory of Applied Ichthyology and Hydrobiology (LAIH), School of Wood, Water and Natural Resources (SWWNR), Faculty of Agronomy and Agricultural Sciences (FAAS), !e University of Dschang, P.O. Box 786, Ebolowa Antenna, Dschang, Cameroon Laboratory of Applied Ichthyology and Hydrobiology (LAIH), Department of Animal Productions, Faculty of Agronomy and Agricultural Sciences (FAAS), !e University of Dschang, P.O. Box 222, Dschang, Cameroon Laboratory for Aquaculture and Demography of Fisheries Resources (LADFR), Departement of Aquaculture, Institute of Fisheries and Aquatic Sciences of Yabassi (IFAS), !e University of Douala, P.O. Box 2701, Douala, Cameroon Correspondence should be addressed to Claudine Tekounegning Tiogue´; claudine.tiogue@univ-dschang.org Received 30 July 2019; Accepted 20 December 2019; Published 15 February 2020 Academic Editor: Cucco Copyright © 2020 Claudine Tekounegning Tiogue et al. (is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A study on the reproductive strategy of Chrysichthys nigrodigitatus was conducted from October 2015 to August 2016, in the Nkam River in Yabassi, Littoral Region of Cameroon. For this purpose, 154 specimens of C. nigrodigitatus with total mean weight of 829.96± 829.58 g and total mean length of 367± 156 mm collected from artisanal fishermen were used. Twenty-nine (29) females at stage V of sexual maturity were selected for the evaluation of the fecundity. It appears that the oogenesis in C. nigrodigitatus is of an asynchronous type with multiple laying spread over a long period. (e gonadosomatic index (GSI) peaks in June (17.9± 7.1 for females and 1.06± 0.27 for males). Hepatosomatic index (HSI) was higher in females than in males throughout the year. (e mean condition factor K was 1.07 ± 0.09%. (e breeding season occurred from April to October during the rainy season. Gonadosomatic and hepatosomatic indices were positively correlated with rainfall, contrary to the K factor, which has been strongly and negatively correlated with this physical parameter. (e sex ratio of 1M: 1.5F was in favour of females, thus reflecting an “r” type reproductive strategy. Absolute fecundity was estimated at 1374± 1022 oocytes for individuals of 107.3± 111.9 g mean weight. Mean relative fecundity was 14± 3 oocytes/g of body weight. It was recommended that future work focuses on the captivity of this species. In Africa, and particularly in Cameroon, as reported by 1. Introduction Cacot [3], fish farming has remained focusing on three Fish is an extremely nutritious food, a vital source of protein species of fish: Clarias gariepinus, Oreochromis niloticus, and and essential nutrients, especially for many low-income Cyprinus carpio. At the present state of knowledge, very few people around the world [1]. According to FAO [2], world of these farmed species have reached a large-scale devel- fish supply reached a record of 20 kg per capita, in favour of opment potential. (is situation would certainly be at the strong growth in aquaculture, which now provides half of origin of the intensification of research towards new species the fish for human consumption. (is growth is correlated better adapted to the constraints of African aquaculture. (is with the progressive enhancement of native species in is particularly the case for studies on some African carp and certain regions of the world [2]. African catfish: Labeo senegalensis by Montchowi et al. [4], 2 International Journal of Zoology Labeo parvus by Montchowui et al. [5] and Montchowui et 2.3. Assay Conduct and Data Collection. (e collected fish al. [6] and Chrysichthys auratus [7, 8] in Benin and Egypt, were kept alive in 20-liter buckets and transported to the ´ Laboratory for Aquaculture and Demography of Fisheries Labeo coubie in Nigeria by Ikpi and Okey, and Labeobarbus batesii and Clarias jaensis in the Mboˆ Floodplain in West Resources (LADFR) of the Institute of Fisheries and Aquatic Cameroon by Tiogue´ et al. [10], Tiogue´ [11], Tiogue [12], Sciences of Yabassi (IFAS), where they were identified Tomedi et al. [13], Zango et al. [14]. according to the identification key of Stiassny et al. [20]. Each (e ichthyological fauna of Cameroon’s freshwater is of individual was then recorded and sexed with the naked eye. exceptional interest. Nearly 60 species of fish have recently (e total and standard lengths (tL and sL, respectively) were been identified by Ajonina and Tomedi [15] in the Nkam measured with a 1 mm ichthyometer. (e total weight (tW) River, amongst which the most abundant and much ap- and the weight after evisceration (evW) were obtained using a preciated species was Chrysichthys nigrodigitatus, locally Sartorius Competence electronic scale at the 10th of g. After ` ` called “mayepe.” (is fish species is the subject of many dissection of each fish using the scissors of a dissection kit, the traditional recipes in households and restaurants, according gonads (Figure 2(a)) and the liver were removed with a razor blade, drained, and weighed at 0.01 g on a sensitive electronic to Ajonina and Tomedi [15], the consequence of which is the decrease of wild stocks. (erefore, studies on the biology of scale brand TATINA model 1479V (Figure 3(a)). Based on this species is essential to better develop its breeding cap- the sexual maturity scale of the ovaries of C. nigrodigitatus tivated. Aspects of the biology of C. nigrodigitatus have established by Ote´me´ [21], only the ovaries of 29 females at already been the subject of several studies in West Africa, stage V of sexual maturity were selected for the estimation of more particularly in Ivory Coast, where captive breeding the fecundity: three samples of 1 g of ovary were collected in trials have been successfully tested by Djehi ´ [16]. In the rostral, middle, and caudal regions (Figure 2(b)) and Cameroon, there is very little information on its repro- weighed. One gram of ovary was put in Gilson’s liquid (pure ductive cycle. Hence, the general objective of this study was ethanol 98 C (60 ml) + water (920 ml) + acetic acid (9 ml) + to evaluate some elements of the reproductive cycle of C. mercury chloride (20 g)) to dissociate the oocytes and thus nigrodigitatus in view of its domestication, and more spe- facilitate counting (Figure 3). (e oocytes of each sample were cifically, it was to determine in this species the breeding counted under a stereoscopic binocular magnifying glass period, sex ratio, and fecundity of this species depending on (magnification ×10). the endogenous and exogenous factors of the Nkam River. 2.4. Collection of Physical Parameters of Water. One station 2. Materials and Methods representing the fishing location was selected in the up- stream part of the Nkam River. Due to a lack of chemical 2.1.StudyZone. (e study was conducted from October 2015 parameter collection equipment, only the following physical to August 2016, in the Nkam River in Yabassi Township, parameters were determined: the transparency, the depth, District of Yabassi, Department of Nkam and Littoral Region of ° ° the temperature, and the rainfall were measured monthly, Cameroon (Figure 1). It is located between 9 50′ and 10 10′ of ° ° respectively, using a Secchi disk to within 1 cm, a gallows LN and between 4 20′ and 4 40 LE, with mean altitude of 15 to graduated to the nearest mm, a mercury thermometer, and a 20 m [17]. (e climate is subequatorial with a tropical tendency rain gauge. of two seasons: a dry season that runs from November to March and a rainy season that runs from April to the end of October. (e hottest month is January and the coldest is August. (e mean annual rainfall is 2927 mm; the maximum 2.5. Studied Parameters rainfall is between July and August. Monthly temperatures ° ° range from 25 C to 35 C and are favourable for aquaculture 2.5.1. Breeding Period. (e breeding period was determined by calculating the following indices as used by Saadia ˆ [22]: [18]. (e Nkam River results from the merger of two rivers: the “Small Nkam” (Department of Haut-Nkam) and the “Ngoung” (i) Gonadosomatic index (GSI): GSI (%) � (gW/evW) (Department of Menoua). It flows from from Nkongsoung × 100, where gW � gonads weight and evW � (Moungo Department), passing through Yabassi, into the eviscerated weight of fish Wouri River at Akwa North (Wouri Department) [19]. (ii) Hepatosomatic index (HSI): HSI (%) � (lW/evW) × 100, where lW � liver weight and evW � eviscerated weight of fish 2.2. Animal Material. A total of 154 specimens of Chrys- ichthys nigrodigitatus of mean total weight of 829.96± (iii) K factor has been calculated using the formula of 829.58 g and mean total length of 367± 156 mm were col- Ricker [23]: K � (tW/tL ) × 100, where tW and tL lected from the local fishermen of Nkam River. Sampling are, respectively, the total weight and the total was done monthly and fish samples were hand-harvested length of the fish using 3- and 4-finger gillnets. After the first 6 months of collection, noting that this capture technique was selective, it was replaced by “bamboo China” structures installed in the 2.5.2. Sex Ratio (S/R). (e sex ratio according to Ragheb [8] various points of the selected station, to have a wide range of is translated by the following relation: S/R � number of the size of the individuals. males/number of females. International Journal of Zoology 3 889294 924572 960050 995428 030808 9 9 9 9 10 Township Yabassi and Bodiman Cameroon 9°10 9°50 10° 10°10 10°20 10°20 10°40 5°10 Nkam division 5° Legend Study Zone 4°50 Villages 4°40 Roads 4°30 Streams 4°20 Nkam River 4°10 00,512 34 Sampling area Killometers 4° 9°10 9°50 10° 10°10 10°20 10°20 10°40 889294 924672 960050 995428 030806 9 9 9 9 10 Figure 1: Geographical location of Yabassi. (a) Cameroon, (b) Nkam Department, and (c) Yabassi District (source: adapted from [19]). Rostral region Middle region Caudal region (a) (b) Figure 2: (a) Ovaries of C. nigrodigitatus, (b) testes of C. nigrodigitatus. 2.5.3. Fecundity. Fecundity was evaluated according to 2.6. Statistical Analysis. Descriptive statistics, the χ2 com- Ragheb [8]: parison test, the Pearson correlation test, and the one-way ANOVA test were used to process the data for the pa- (i) Absolute fecundity (aF) was determined on a sample rameters studied at 5% level of probability. (is was done of 29 females at stage V of sexual maturity. It is using the SPSS16.0 statistical software. defined by the formula: af � total weight of oocytes × number of oocytes in 1 g of ovary 3. Results (ii) Relative fecundity (rF) was calculated from the aF. It is translated by: rF � total number of oocytes/weight 3.1. Monthly Evolution of Gonadosomatic Index. Figure 4 of the female (Kg) shows the monthly evolution of the gonadosomatic index 353158 383332 418226 450320 483014 4 4 4 4 4 4 International Journal of Zoology (a) (b) Figure 3: (a) Electronic scale, (b) oocyte counting device. 30 1.8 1.6 1.4 Female 20 1.2 Male 0.8 10 0.6 0.4 0.2 0 0 ON D J F M A M J J A ON D J F M A M J J A Period (month) Period (month) (a) (b) Figure 4: Monthly evolution of GSI by sex of C. nigrodigitatus between October 2015 and August 2016 in the Nkam River: (a) female, (b) male. (GSI) in C. nigrodigitatus by sex. It seems that regardless of 3.4. Correlation between Reproduction and Physical the sex considered, the GSI has evolved in the same way with Parameters. Correlations between reproduction parameters values significantly (P< 0.05) high from April, and the peak (GSI, his, and condition factor K) and environmental pa- is observed in June. rameters as presented in Table 1 and Figure 7 revealed a positive and significant correlation between rainfall and gonadosomatic index (r � 0.74, P< 0.01) on the one hand 3.2. Monthly Evolution of the Hepatosomatic Index. and a negative and significant correlation between this same Figure 5 portrays the monthly evolution of the hep- parameter and the condition factor K (r � − 0.73, P< 0.05) on atosomatic index (HSI) in C. nigrodigitatus by sex. In fe- the other hand. Negative but insignificant correlations were males, three (3) increasing peaks were successively observed: observed between GSI, transparency, and temperature. Only November (1.05± 0.21), March (1.24± 0.49), and June the precipitation correlated positively with HSI, but not (1.78± 0.56), while in males two (2) decreasing peaks were significantly (P> 0.05). observed in November (1.41± 0.33) and in April (1.01± 0.27). (e minimum values of HSI were reached in 3.5. Monthly Variation of Sex Ratio. (e monthly variation December (0.84± 0.32) and in February (0.88± 0.15) in of sex ratio in C. nigrodigitatus (Table 2) indicates that the females and in March (0.64± 0.15) and May (0.48± 0.20) in mean sex ratio during the study was in favour of females (1 : males. In females, the maximum HSI registration period 1.5). (is sex ratio value was statistically not significantly coincided with that of the IGS (June). (P< 0.05) different from the theoretical sex ratio (1 :1). Sex ratio in favour of males was observed only in June. (e standard sex ratio (1 :1) was recorded only in May and 3.3. Monthly Evolution of Condition Factor K. Figure 6 il- December. However, except for November, a sex ratio (1 : 4) lustrates the monthly variation of condition factor K in C. significantly (P< 0.05) different from the theoretical sex nigrodigitatus by sex in the Nkam River. It shows that the ratio (1: 1) was recorded. mean K factor ofC.nigrodigitatus recorded between October 2015 and August 2016 in the Nkam River was 1.09± 0.07%. Except for the month of December, there was no significant 3.6. Fecundity. (e absolute fecundity was 1374 ± 1022 difference between the sexes and the months (P> 0.05). oocytes for females with a mean weight of 107.3± 111.9 g However, between May and July, the K factor remained and a mean total length of 211± 52.8 mm and the relative slightly below 1 (0.97± 0.01) in females. fecundity of 14± 3 oocytes/kg for females. GSI (%) GSI (%) International Journal of Zoology 5 2.5 2.5 Female Male 2 2 1.5 1.5 1 1 0.5 0.5 0 0 ON D J F M A M J J A O N D J F MAM J J A Period (month) Period (month) (a) (b) Figure 5: Monthly evolution of HSI by sex of C. nigrodigitatus between October 2015 and August 2016 in the Nkam River. 500 20 2.5 450 18 400 16 350 14 300 12 250 10 1.5 200 8 150 6 1 100 4 50 2 0 0 0.5 ON D J F M A M J J A Period (month) 0 Rainfall ON D J F M A M J J A GSI Period (month) Figure 7: Correlation between the gonadosomatic index of C. nigrodigitatus and rainfall in the Nkam River. Female Male Figure 6: Monthly variation of K factor by sex of C. nigrodigitatus Table 2: Monthly variation of sex ratio in C. nigrodigitatus between between October 2015 and August 2016 in the Nkam River. October 2015 and August 2016 in the Nkam River. Sex ratio Number Month Male (N) Female (N) M : F Table 1: Correlation between reproduction parameters of C. October 1 2 1 : 2 nigrodigitatus and physical parameters of the environment in the November 3 12 1 : 4 Nkam River. December 3 3 1 :1 Physical parameters of the environment January 4 9 1 : 2.3 Reproductive February 6 8 1 :1.3 parameters Depth Transparency Temperature Rainfall March 2 4 1 : 2 Gonadosomatic ∗∗ 0.18 − 0.53 − 0.59 0.74 April 9 12 1 :1.3 index May 12 14 1 :1.2 Hepatosomatic − 0.01 − 0.41 − 0.29 0.57 June 8 6 1 : 0.8 index July 8 13 1 :1.6 K condition factor − 0.39 0.59 0.54 − 0.73 August 6 9 1 :1.5 ∗ ∗∗ Significantly (P< 0.05) correlated, significantly (P< 0.01) correlated. Total 62 92 1 : 1.5 N � number, M: F � male: female, significantly (P< 0.05) different from the theoretical sex ratio 1 � : 1. Figure 8 shows the relationship between absolute fe- cundity and total weight and between this same parameter and the total length ofC.nigrodigitatus females. It shows that 4. Discussion a very strong and significantly positive correlation exists between absolute fecundity and total weight on the one hand 4.1.BreedingPeriod. (e breeding season of C. nigrodigitatus (r � 0.97, P< 0.01) (Figure 8(a)) and between this same coincides with the continuous rainy season, which lasts ap- parameter and the total length (r � 0.98, P< 0.01) on the proximately six months and is characterized by a single other hand (Figure 8(b)). spawning season in June as reported elsewhere [11, 12, 24, 25]. K-factor (%) HSI (%) HSI (%) Rainfall (mm) GSI (%) 6 International Journal of Zoology 6000 6000 aF = 8.7134tW + 419.98 aF = 18.687tL – 2588.6 5000 R = 0.9441 5000 R = 0.9717 4000 4000 3000 3000 2000 2000 1000 1000 0 0 0 100 200 300 400 500 600 700 0 100 200 300 400 500 Total weight (g) Total length (mm) AF = absolute fecundity (a) (b) Figure 8: Relationship between absolute fecundity and total weight (a) and the total length (b) in C. nigrodigitatus females in the Nkam River. nigrodigitatus. However, the slight drop in K-factor values (e reproduction of C. nigrodigitatus is of the asynchronous type as reported elsewhere [11, 12], thus making this species a (0.94± 0.06) noted between May and August may be related partial or heterochronous breeder, or fish with multiple to female oviposition weight loss. Indeed, according to spawning or split-spawning. (e peak breeding period ob- Kra¨ıem [35], the fall in values of the relative condition served between April and June is similar to that recorded by coefficient (Kr< 1) indicates the postspawning period Ekamen [26] and Offem et al. [27] in the Cross River in Nigeria qualified by energy expenditure and weight loss. in the same species and by Dia [28] and Dossou [7], re- spectively, in Ivory Coast and in Benin. (ese results, however, 4.2. Sex Ratio. (e sex ratio of 1M: 1.5F observed in this are different from those obtained by Ote´me´ [29] and Dje´hi study is statistically close to the theoretical sex ratio (1 :1). [16], who under breeding conditions observed maximum However, it is biologically in favour of females, thus giving laying in September and October; and those reported by this species a reproductive strategy of “r” type, thus a po- Ragheb [8] which show that the spawning season ofC.auratus lygamous matrimonial regime. (ese results are similar to extends from October to June. According to Dia [28], laying the observations made on C. auratus (1M: 2F) and on C. occurred between May and July and lasted until November nigrodigitauts (1M: 4F) by Imerbore and Bakare [36] and on ° ° when temperatures had varied between 25 C and 27 C. Hem C. auratus (1M: 1.18F) by Ragheb [23] in Damietta branch of [30] and Albaret [31] also observed C. nigrodigitatus spawning the River Nile in Egypt. (ese observations are contrary to during the rainy season, adding that temperature is a major those reported in Lake Asejire by Taiwo and Aransiola [37] factor in this phenomenon, associated with salinity and floods. and Dossou [7] in C. auratus (1M: 0.96F) and C. nigrodi- (e geographical position, the duration of the rainy season, gitatus (1M: 0.93F), respectively. In addition to the spatial and the specific characteristics of the water courses may vary and temporal difference, the sex ratio diversification could the extent and the period of reproduction in C. nigrodigitatus also be due to the fishing techniques practiced: Indeed, as recorded by Otte´me´ [29]. A positive correlation has been during this study, between May and August, fishermen have recorded between the gonadosomatic and the hepatosomatic replaced the usual gill nets with bamboo from China placed indices, whereas logically these two weight indices vary in about 3 m on the banks. (is fishing gear allows the capture opposite directions. Indeed, the fish would draw the reserves of of C. nigrodigitatus by couple (sex ratio of 1M: 1F). Dossou the liver (in particular, the vitellogenin in the females) to [7] also reported the use of this technique in Benin. manufacture the sexual products as discussed elsewhere However, the sex ratio obtained during the breeding season [11, 12, 32]. It should probably be due to the fact that some is close to the theoretical sex ratio (1: 1) just like that ob- females emit their eggs in a split way; and the partially emptied served elsewhere [7, 21, 27]. (us, it seems that the natural ovaries do not return to complete rest but continue the vi- approximation of males and females is in relation with the tellogenesis of oocytes that will be emitted later. (ese results reproduction period. are similar to those of Bouaziz et al. [33] in the Merlu, Merluccius rnerlucc´ıu Linnaeus, 1758. 4.3.Fecundity. (e absolute fecundity recorded in this study (e K condition factor of C. nigrodigitatus obtained in this study was higher compared to that obtained by Ezenwa is very low compared to the 24000 oocytes observed in et al. [34] and Dossou [7], respectively, recorded in the Imo Kousson on Bandama in Ivoiry Coast by Kouassi [38]. It is River in Nigeria (0.78) and small water body of the Ouem ´ e´ also lower than that of 4878 to 87724 oocytes recorded by basin in Benin (0.64), showing that the samples of the Nkam Oteme´ [21] in Ebrie´ Lagoon in individuals weighing from River were of good overweight. (ese results are close to 500 g to 6000 g with an average of 20000 oocytes. However, it 0.96, 0.97, and 0.99, respectively, reported in the Bandagry is close to 7596 oocytes reported in the South Benin Lagoon ` ` Lagoon in Nigeria by Ezenwa et al. [34] and the river cross in Complex by Laleye et al. [39]. In the Cross River in Nigeria, Nigeria by Ekamen [26] and Offem et al. [27] in the same Ekamen [26] and Offem et al. [27], respectively, reported a fecundity of 12063 and 25905 oocytes. More recently, in the species. As a result, the Nkam River may have very favourable natural conditions for the development of C. small water plans of the Ouem ´ e´ basin in Benin, Dossou [7] AF (oocytes number) AF (oocytes number) International Journal of Zoology 7 recorded fecundity from 3474 to 28778 with an average of Conflicts of Interest 10783 oocytes in individuals weighing 557.3 g to 2270.1 g. (e authors declare that they have no conflicts of interest. However, these results are nevertheless comparable to those of Fagade and Adebisi ´ [40], which counted 2884 oocytes in Lac Asejire populations. In addition to the fact that fecundity Acknowledgments varies from one region to another and from one watercourse to another, it would certainly be linked to environmental (e authors thank all the fishermen of the Nkam River for factors. It could be strongly related to the weight and length their contribution in the collection of fish samples. of individuals. According to Otem ´ e´ [29], the length of C. nigrodigitatus allows a better estimate of its fecundity. Offem References et al. [27] added that this fecundity increases with the length and weight of C. nigrodigitauts. [1] FAO, La situation mondiale des pˆeches et de l’aquaculture, Unlike absolute fecundity, relative fecundity varies very vol. 255, FAO, Rome, Italy. little from one region to another. (e absolute fecundity [2] FAO, La situation mondiale des pˆeches et de l’aquaculture obtained in this study is comparable to that reported by 2016. Contribuer a` la s´ecurit´e alimentaire et a` la nutrition de other authors elsewhere: Dossou [7] reported 15± 6 oocytes/ tous, vol. 224, FAO, Rome, Italy, 2016. [3] P. Cacot, “Contribution a` l’amelioration ´ de la production g, Otem ´ e´ [29] 15 oocytes/g, Ekamen [26] 13 oocytes/g, d’alevins au Cameroun: essais de reproduction et d’´elevage de Offem et al. 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International Journal of ZoologyHindawi Publishing Corporation

Published: Feb 15, 2020

References