Napata Scientific Journal, Vol.1 (1) 2022 pp. 45-57
Relationships in 1 populations of two Nile Cichlids in the Sudan
O.M. Omer1, A.H Abdalla2, E A. Hagar3; Z.N. Mahmoud4*
1 Department of Fisheries, Ministry of Agriculture, Khartoum State, Sudan
2 Department of Agronomy, Faculty of Agriculture, University of Khartoum, Sudan
3 Department of Fisheries, College of Natural Resources and Environmental Studies, University of Bahri
4 Department of Zoology, Faculty of Sciences, University of Khartoum, Sudan
The objective of this work is to quantify the body weight, body depth and standard length relationship of Oreochromis niloticus, Sarotherodon galilaeus from the Nile and its tributaries to find out the population of best traits.
Methods: Fish body weight was recorded to 0.1gm using an electronic field balance. The standard length and body depth were measured using a measuring tape to the nearest cm.
Results: The standard length-body weight relationship of O. niloticus and S. galilaeus 15 populations, was significant (p<0.05 top<0.001), except for S. galilaeus populations from Wad Medani and Shendi (p>0.05). The growth mode of the different populations of O. niloticus and S. galilaeus ranged from negative allometric, isometric to positive allometric.The standard length-body depth relationship of O. niloticus and S. galilaeus was mostly significant (p<0.05 top<0.001
The study concluded that there is a relatively high level of polymorphism and genetic diversity within and between O. niloticus and S. galilaeus and a comparatively high overall interspecies pair wise divergence. The population of O. niloticus from Al Kalakla is quite different from other populations, and thus can be recommended for improvement of other tilapias varieties.
Keywords:Body relations, Oreochromis niloticus, Sarotherodon galilaeus.
In fishery biology the correlated length-weight relationship is very important for proper exploitation and management of wild and aquaculture populations of fish species [1, 2, 3] in addition to determining the impact of stress of water pollution on the fish’s body condition . Regression analysis of these parameters yields an equation with an intercept (a), slope (b) and correlation (r) values. A significantly correlated determined from regression coefficient (r) or coefficient of determination (R2) can be used with high accuracy to estimate the body weight of a fish species at a given length . This relationship enables assessing the well-being of individuals and differences between separate populations of the same species  and compare their growth .
According to [4, 7] the b values in length-weight relationships tells the growth pattern of fish species. The value of b indicates an isometric growth when equal or close to 3 (fish becomes more full-bodied with increasing length). When b is far less or greater than 3, growth in the fish is allometric (the fish becomes thinner with increase in length).
Body shape in fish can evolve in response to a variety of evolutionary trait such as genetic makeup  predation, competition and environmental factors acting on populations  linking morphology to species interaction . The body depth in fishes determines their susceptibility to predator, attraction of mate, swimming performance, habitat specialization and phenotypic traits .
The objective of this work is to quantify the body weight, body depth and standard length relationship of Oreochromis niloticus, Sarotherodon galilaeus from the Nile and its tributaries.
Material and Methods
Source of fish.
Fifteen populations of O. niloticus and S. galilaeus were collected from different site (Table 1). Collection was made by purchasing highly fresh specimen from commercial fishers operating in the area. Fish were kept chilled fish in an ice parked plastic container.
The body weight (BW) was recorded to the nearest 0.1g using an electronic field balance. The standard length (SL): distance from tip of snout to the caudal fin base at articulation, and the body depth (BD): maximum vertical depth of the body depth situated in between anterior base of dorsal fin and origin of pelvic fin. Measured were recorded to the nearest cm using a measuring tape.
Correlation analysis between the measured parameters was done by Microsoft Excel sheet programme.
Table 1. Sample sites O. niloticus and S. galilaeus populations and abbreviations.
|Site||Locations||Coordinates||Number of specimens|
|N||E||O. niloticus||S. galilaeus|
The standard length-body weight relationship of O. niloticus and S. galilaeus 15 populations, was observed to be significant (p<0.05 top<0.001, Table 2 and Figs. 1 to 6), except for S. galilaeus populations from Wad Medani and Shendi (p>0.05, Table 2). The correlation coefficient ranged from r=0.764 to 0.978 (Table 2). This indicates that in 8 populations of O. niloticus and 5 populations of S. galilaeus the body weight of the fish species could be estimated with a high degree of accuracy from known standard lengths. The growth pattern of the different populations of O. niloticus and S. galilaeus ranged from negative allometric, isometric to positive allometric, but mostly negatively allometric (Table 2).
Table 2. Standard length body weight relationships in 15 populations of O. niloticus and S. galilaeus
|Ad Damazin||O. niloticus||Y=0.1218X2.4761||0.876||p<0.001||-ve allometric|
|Sinnar||O. niloticus||Y=0.0209X3.1167||0.898||p<0.001||≈ isometric|
|S. galilaeus||Y=0.0384X2.7786||0.978||p<0.001||-ve allometric|
|Wad Madani||O. niloticus||Y=0122X2.5969||0.774||p<0.05||-ve allometric|
|S. galilaeus||Y=0.0005X4.5584||0.737||p>0.05||+ve allometric|
|Getina||O. niloticus||Y=0.4553X2.8508||0.932||p<0.001||≈ isometric|
|S. galilaeus||Y=0.0678X2.9694||0.764||p<0.001||≈ isometric|
|Jebl Aulia||O. niloticus||Y=0.1764X2.3696||0.912||p<0.01||-ve allometric|
|S. galilaeus||Y=0.1771X2.4795||0.755||p<0.001||-ve allometric|
|Alkalakla||O. niloticus||Y=0.0563X2.7768||0.926||p<0.01||-ve allometric|
|S. galilaeus||Y=0.2617X2.2311||0.852||p<0.001||-ve allometric|
|Al Morada||O. niloticus||Y=1.7348X1.3935||0.824||p<0.01||-ve allometric|
|Shendi||O. niloticus||Y=0.1446X1.3767||0.885||p<0.01||-ve allometric|
|S. galilaeus||Y=0.2428X2.1502||0.864||p>0.05||-ve allometric|
|Fig 1. Standard length body weigh relationship of O. niloticus from Blue Nile
|Fig 2. Standard length body weigh relationship of O. niloticus from White Nile.|
|Fig 3. Standard length body weigh relationship of O. niloticus from the Nile||Fig 4. Standard length body weigh relationship ofS. galilaeus from Blue Nile.|
|Fig 5. Standard length body weigh relationship of S. galilaeus from the White Nile.||Fig 6. Standard length body weight of S. galilaeus from the Nile.|
|Fig 7. Standard length body depth relationship of O. niloticus from the Blue Nile.||Fig 8. Standard length and body depth relationship of O. niloticus from the White Nile.|
|Fig. 9. Standard length body depth relationship of O. niloticus from the Nile.||Fig. 10. Standard length body depth relationship of S. galilaeusBlue Nile.|
|Fig. 11. Standard length body depth relationship of S. galilaeusWhite Nile.|
The standard length-body depth relationship of O. niloticus and S. galilaeus 15 populations, was observed to be significant (p<0.05 to p<0.001, Table 3 and Figs.7 to 11), except for S. galilaeus population from Jebel Aulia (p>0.05, Table 3). The correlation coefficient ranged from r=0.760 to 0.931 (Table 3).
Table 3. Standard length body depth relationships in 15 populations of O. niloticus and S. galilaeus
|Ad Damazin||O. niloticus||Y=4.8109X1.6268||0.877||p<0.001|
|Wad Madani||O. niloticus||Y=1.1105X2.5745||0.854||p<0.01|
|Jebl Aulia||O. niloticus||Y=1.4041X2.3616||0.828||p<0.001|
|S. galilaeus||Y= 27.089X0.7381||0.333||p>0.05|
|Alkalakla||O. niloticus||Y=0.515X 2.942||0.760||p<0.001|
|Al Morada||O. niloticus||Y=0.855X2.6884||0.894||p<0.001|
The standard length-body weight relationship of the 15 populations O. niloticus and S. galilaeus, was significant (p<0.05 to p<0.001, except for S. galilaeus populations from Wad Medani and Shendi (p>0.05). The correlation coefficient ranged from r=0.764 to 0.978. Shalloof and El- Far  reported highly correlated growth equations in O. niloticus (r=0.979); Orechromis aureus (r=0.983), Tilapia zillii (r= 0.986) and S. galilaeus (r= 0.978) in Abu- Zaabal Lakes, Egypt. Basohan et al.  derived a highly correlated (r=0.850) standard length-body weight equation for O. niloticus from Ibiekuma stream. Kara  worked on the same species in Roseris Dam reservoir and recorded r2 = 0.996 and 0.996 for males and females O. niloticus respectively. Nigeria. Atama et al.  studied this relationship in O. niloticus, Hemichromis bimaculatus, T. zilli, Hemichromis fasciatus and Tilapia mariae from Anambra River, Nigeria and reported highly correlated relations (r= 0.771-0.966). Adite et al.  studied the linear regression between total length and body weight of O. niloticus and S. galilaeu fishes at LakeToho, South Benin in its fresh water and the ecotonal coastal zone. They reported r=0.990 and 0.990 for O. niloticus, and r=0.980 and 0.990 for S. galilaeus, respectively. From Lower Benue River, Nigeria, Azua  found a strong relationship between log of body weight and standard length with r value of 0.932 in O. niloticus while a weak relationship was obtained in Tilapia zilli with r value of 0.298. Famoofoand Abdul  found highly correlated (r=0.518-0.953) length-weight relationship for S. arotherodon galilaeus, H. fasciatus, T. zilli and S. melanotheron fromLekki Lagoon,Nigeria. It is apparent that the standard length-body weight relationship in the same species differs in different water bodies.
In the present study the growth of O. niloticus and S. galilaeus was isometric in Getina site and mostly negatively allometric in other sites. In Alkalakla, Almorada and Sheni the populations of both species was negatively allometric. Positive allometry with b>3 (S. galilaeus from Wad Medani) implies asymmetrical growth or increases in length more than in weight. Idris and Mamoud  reported similar observations in labeo niloticus. Shalloof and El-Far  reported negative allometric growth in O. niloticus (b=2.403), O. aureus (b=2.108), T. zillii (b=3.147) and S.galilaeus (b=2.758) in Abu-ZaabalLakes.
Laghari et al.  investigated the length-weight relationship from 500 specimen of O. niloticus maintained in a concrete pond and found positive allometry as b=4.55. Ibrahim et al.  from Kontagora Reservoir in Niger state recorded b-value of 2.8 for Barilius niloticus Cyprinids. Atama et al.  reported positive allometric growth for H. bimaculatus and T. zilli (b =3.828 and 3.210, respectively, while H. fasciatus, Tilapia mariae and O. niloticus exhibited negative allometric growth with b =2.667, 2.272 and 2.792, respectively. Ngodhe and Owaor-JB  reported that O. niloticus showed positive allometric growth of 3.16 an3.09 in cage culture and open waters in WinamGulf in L. Victoria. Famoofoand Abdul  found that S. galilaeus and H. fasciatus exhibited negative allometric growth with b=2.27 and 2.42, respectively; while T. zilli and S. melanotheron exhibited positive allometric growth with b=3.312 and 3.411, respectively. Silva et al.  reared 3,000 juvenile O. niloticus in three circular cages and reported isometric growth b=3.0604.
The water characteristic and/or culture media may play role in growth mode. Alex et al.  found negative allometric growth in fresh water and positive allometric growth in full strength sea water for T. zilli. Adite et al.  reported b-values of 2.977 and 3.007 for O. niloticus and 2.976 and 2.831 for S. galilaeu fishes in fresh water and ecotonal coastal, respectively. From Lekki Lagoon,Nigeria,and Oreochromis urolepis.
Little attention was given to standard length-body depth relationship. In the present study O. niloticus and S. galilaeus 14 populations, showed significant (p<0.05 to p<0.001) in the standard length-body depth relationship of O. niloticus and S. galilaeus, except for S. galilaeus population from Jebel Aulia (p>0.05). The correlation coefficient of both lengths ranged from r=0.760 to 0.931. Fernando et al.  reported that in Centrarcids, the standard length body depth relationship were generally good, with coefficient of determination R2=0.764-0.998.The body depth morphology in fishes was tackled by many authors from different behavioural aspects and habitat specialization .
The study concluded that there is a relatively high level of polymorphism and genetic diversity within and between O. niloticus and S. galilaeus and a comparatively high overall interspecies pair wise divergence. The population of O. niloticus from Al Kalakla is quite different from other populations, and thus can be recommended it for improvement of other tilapias varieties.
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Conflict of Interest
The authors declare no conflict of interest, financial or otherwise.
The Ministry of Agriculture and Animal Wealth and Irrigation, KhartoumState financed this work. Thanks are due to the fisheries administrations in the different states of Sudan for facilities.
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