Characterization of Oreochromis Niloticus Strains of Lake Kariba Culture Fisheries Using Morphological and Meristic Methods

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American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/

Characterization of Oreochromis niloticus Strains of Lake Kariba Culture Fisheries using Morphological and Meristic Methods

Mauris Chinyama Makechea*, Walter Muleyab, Tamuka Nhiwatiwac

a,cDepartment of Biological Sciences, Faculty of Science, University of Zimbabwe, P. O. Box MP 67, Harare, Zimbabwe a,cUniversity of Zimbabwe Lake Kariba Research Station, P.O. Box 7, Kariba, Zimbabwe bDepartment of Biomedical Sciences, School of Veterinary Medicine, University of Zambia, P. O. Box 32379 aEmail: [email protected] cEmail: [email protected]

Abstract

Oreochromis niloticus fish collected from Yalelo Fishery, Fwanyanga Fishery and Choombwe Fishery of Lake Kariba were investigated by multivariate analysis of 23 morphometric measurements and 7 meristic counts. Dendrograms were used to delineate the sampled specimens using PC-ORDTM Software and the differences among strains were tested using One-way ANOVA in Statistix 9 Software (P = 0.05). Meristic analysis did not show a high divergence among the strains while morphometric analysis showed that the sampled fish could be characterized into three different strains. These results showed that the tested fish samples could be grouped into 3 types based on morphometric characters. The morphometric differences among the sampled O. niloticus strains may have appeared due to genetic differences among the collected specimens.

Keywords: Dendrogram; Yalelo Fishery; Fwanyanga Fishery; Choombwe fishery.

------* Corresponding author.

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

1. Introduction

The Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758), is a widespread species used in tropical Aquaculture. Natural populations of these fish occur in Africa and the species O. niloticus has been introduced to almost every tropical country in the world for Aquaculture purposes [1]. The Fisheries sub-sector in Zambia contributes approximately 3.2% to the National Gross Domestic Product (GDP). The Aquaculture sub-sector currently contributes 27% of the total fish produced in Zambia. The sector has experienced some increase in production from 12, 998 metric tonnes in 2012 to 32, 888 metric tonnes in 2017. Aquaculture production is expected to increase by 1, 148 metric tonnes by December, 2020 due to the various interventions by the Zambian Government [2]. The increase in fish production is attributed to the commercialization of the Fisheries sub- sector which has witnessed an increase in the number of people venturing into fish farming. Besides the economic returns from Tilapia Aquaculture, tilapiines have also been adopted for use as control-agents for aquatic vegetation and elimination of unwanted aquatic fauna such as snails and mosquitoes [3]. Oreochromis niloticus is the most widely cultured bream in Zambia and its success in Lake Kariba Culture Fisheries is because it is extremely hardy, it has a wide range of trophic and ecological adaptations, and it possesses adaptive life history characteristics such as fast growth, high fecundity, big egg sizes that have few predators, high dietary overlap across size, class, habitat and season [4,5,6]. „Characterization‟ refers to the description of a character or quality of an individual or entity [7]. The word „characterize‟ is synonymous to the word „distinguish‟, that is, to mark as separate or different, to individualize, to differentiate, or to separate into kinds, classes or categories. This identification may in broad terms refer to any difference in the appearance or make- up of an accession. The term „characterization‟ refers to the description of characters that are usually highly heritable, easily seen by the eye and equally expressed in all environments [8]. Morphometric and the meristic methods remains the simplest and most direct way among methods of species identification. From previous studies [9,10,11,12] it is understood that the analysis of phenotypic variation in morphometric measurements or meristic counts is the method most commonly used to delineate stocks of fish. Despite the advent of techniques which directly examines biochemical or molecular genetic variation, these conventional methods continue to have an important role in stock identification even to date [3]. The general objective of the study was to characterize Oreochromis niloticus strains of Lake Kariba Culture Fisheries using morphological and meristic methods. The study used simple and cheap methods to establish whether or not the O. niloticus fish species being reared by fish farmers of Lake Kariba are the same or not. It is important to characterize the cultured fish species in order to re-strategize management practices. It is hoped that the results of this study will form the basis of taxonomic description of O. niloticus strains of Lake Kariba Culture Fisheries. The research was limited to Lake Kariba because it houses Zambia‟s largest Commercial Fishery called Yalelo Fishery Limited, and it is the largest man-made Lake in Zambia that has diverse ecological habitats that are rich in fish biodiversity.

2. Materials and Methods

The study was conducted from Lake Kariba (Figure 1) which lies between latitude 16º28'S and 18º06' S, and longitude 26°40'E to 29º03' E. Lake Kariba has a catchment area of 663,000km2 with a maximum length and maximum width of 280km and 40km. Lake Kariba has a total surface area of 5,580km2. Lake Kariba has a water storage capacity of 185 km3, making it the largest man-made lake in Southern Africa [13]. Fish samples

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

were collected from cage Aquaculture fish farms of Lake Kariba. Fish samples were collected in April and May, 2020 from Yalelo Fishery Limited, Fwanyanga Fishery and Choombwe Fishery. Yalelo Fishery Limited is a commercial Fishery which is located in Kamimbi bay along longitude 28.63° E and latitude -16.47° S. 66 fish samples were collected from Yalelo Fishery Limited. Fwanyanga Fishery is a subsistence Fishery located in Kabyobyo bay along longitude 28.68° E and latitude -16.52° S. 81 fish samples were collected from Fwanyanga Fishery. Choombwe Fishery is a subsistence Fishery that lies along longitude 28.02° E and latitude -16.00° S. 64 fish samples were collected from Choombwe Fishery.

Figure 1: Location of the study sites within Lake Kariba

The sampled data was combined because the fingerlings from all the sampled Fisheries were from the same brood stock housed at Chirundu Breams. A total of 30 morphological characters were used which included 23 morphometric measurements and 7 meristic counts. Meristic counts included number of dorsal fin spines (DFS), number of dorsal fin rays (DFR), number of anal fin spines (AFS), number of anal fin rays (AFR), number of lateral line scales (LLS), number of scales from the lateral line to the dorsal fin (LLD) and number of scales

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

from the lateral line to the ventral fin (LLV). Morphometric measurements were measured to the nearest 0.1cm except for body weight (BW) which was measured to the nearest 0.1g using an SF-400A electronic compact scale. Other morphometric measurements included (Figure 2) total length (TL), standard length (SL), head depth (HD), body height (BH), head length (HL), pre-dorsal distance (PDD), pre-anal distance (PAD), pre- pectoral distance (PPD), pre-ventral distance (PVD), pectoral fin length (PFL), ventral fin length (VFL), dorsal fin base length (DFBL), anal fin length (AFL), inter-orbital distance (IOD), eye diameter (ED), snout length (SNL), caudal peduncle length (CPL), Caudal peduncle depth (CPD), greatest dorsal spine length (GDSL), third anal spine length (TASL), longest anal ray length (LARL) and post-orbital length (POL).

Figure 2: Diagram of morphometric measurements (Adopted from [14]).

Since meristic characters are independent of size of the fish and do not change during growth [11,15] the raw meristic data were used in the analysis. However, to avoid possible biases produced by size effects on the morphometric variables, all morphometric characters were standardized in PC-CORDTM Software version 5.10 [16] before constructing dendrograms. Meristic and morphometric dendrograms were constructed in order to identify the number of O. niloticus strains among the sampled fish at 50% similarity index in PC-CORDTM Software version 5.10. Meristic data was used to construct the dorsal formula and anal formula of the sampled fish. Analysis was carried out separately for morphometric and meristic characters. This is because the two types of variables are different with respect to statistical (morphometric are continuous and meristic are discrete) and biological data (morphometric characters can be susceptible to environmental factors while most meristic characters are fixed early during the development) [11]. Statistix Software version 9.0 [17] was used to determine significant differences (P = 0.05), if any, among the meristic and morphometric variates of

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

Oreochromis niloticus strains.

IBM Statistics Software version 21.0 [18] was used to determine the number of principal components in multivariate analysis among the determined O. niloticus strains of Lake Kariba Culture Fisheries.

3. Results 3.1. Meristic results

The dendrogram that was constructed to characterize the collected Oreochromis fish samples of Lake Kariba Culture Fisheries based on meristic counts is given in Figure 3.

Dendrogram for lake kariba meristics 1 Distance (Objective Function) 0 9.6E-02 1.9E-01 2.9E-01 3.8E-01 Information Remaining (%) 100 75 50 25 0

nilo1 nilo28 nilo23 nilo136 nilo19 nilo125 nilo190 nilo20 nilo64 nilo74 nilo114 nilo154 nilo169 nilo6 nilo38 nilo191 nilo14 nilo76 nilo130 nilo61 nilo166 nilo172 nilo97 nilo179 nilo18 nilo99 nilo153 nilo32 nilo62 nilo65 nilo83 nilo127 nilo129 nilo139 nilo193 nilo199 nilo43 nilo75 nilo53 nilo118 nilo122 nilo171 nilo3 nilo11 nilo30 nilo113 nilo119 nilo17 nilo180 nilo194 nilo178 nilo13 nilo41 nilo162 nilo200 nilo24 nilo58 nilo72 nilo80 nilo86 nilo96 nilo144 nilo66 nilo124 nilo160 nilo210 nilo89 nilo173 nilo7 nilo8 nilo16 nilo73 nilo81 nilo148 nilo187 nilo161 nilo33 nilo47 nilo63 nilo70 nilo112 nilo128 nilo138 nilo149 nilo211 nilo56 nilo164 nilo207 nilo195 nilo123 nilo201 nilo37 nilo79 nilo107 nilo126 nilo132 nilo170 nilo59 nilo95 nilo131 nilo189 nilo71 nilo93 nilo105 nilo117 nilo49 nilo174 nilo50 nilo88 nilo185 nilo87 nilo106 nilo151 nilo156 nilo202 nilo134 nilo82 nilo103 nilo108 nilo143 nilo203 nilo104 nilo182 nilo197 nilo184 nilo60 nilo69 nilo100 nilo183 nilo90 nilo135 nilo109 nilo205 nilo133 nilo198 nilo2 nilo22 nilo39 nilo137 nilo175 nilo44 nilo157 nilo165 nilo176 nilo51 nilo52 nilo25 nilo91 nilo208 nilo140 nilo111 nilo142 nilo27 nilo159 nilo68 nilo101 nilo67 nilo155 nilo181 nilo206 nilo26 nilo84 nilo98 nilo121 nilo204 nilo168 nilo35 nilo48 nilo77 nilo147 nilo36 nilo57 nilo29 nilo55 nilo46 nilo34 nilo115 nilo167 nilo4 nilo42 nilo152 nilo163 nilo192 nilo158 nilo10 nilo186 nilo5 nilo145 nilo45 nilo116 nilo146 nilo9 nilo92 nilo120 nilo141 nilo188 nilo31 nilo209 nilo21 nilo54 nilo12 nilo110 nilo102 nilo150 nilo40 nilo177 nilo94 nilo78 nilo85 nilo196 nilo15

Figure 3: Dendrogram of meristic counts of sampled fish from Lake Kariba Culture Fisheries.

The dendrogram showed that the sampled fish specimens of Lake Kariba Culture Fisheries can be characterized into two strains (types) at 50% similarity index, namely strain 1 and strain 2. Strain 1 contained Oreochromis niloticus number 18 while strain 2 contained all the other Oreochromis niloticus samples of Lake Kariba. The identified strains were discriminated on 3 principal components. The eigen values ranged from a low of 1.003 for principal component 3 to a high of 1.254 for principal component 1. Principal component 2 had an eigen value of 1.141. The extracted principal component accounted for a cumulative percent variance of 48.534%. The contribution of each meristic variate to the observed variation in each of the 3 principal components is given in Table 1.

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

Table 1: Principal component loadings for meristic counts of Lake Kariba Culture Fisheries

Component 1 2 3 DFS .462 .037 .483 DFR -.662 .255 .185 AFS -.187 .217 .696 AFR -.180 -.414 .397 LLS .550 .399 .231 LLD .454 -.473 .015 LLV .165 .688 -.199

The most influential meristic counts in principal component 1 which caused the largest variation and were important in strain identification were LLS, DFS, LLD and LLV. From the raw meristic counts, it was determined that the dorsal formula of Oreochromis niloticus strains of Lake Kariba Culture Fisheries can be expressed as: D XVI-XVIII, 11-13 while the anal formula of Oreochromis niloticus strains of Lake Kariba Culture Fisheries can be expressed as: A III-IV, 9-11.

3.2. Morphometric results

Dendrogram for lake kariba Distance (Objective Function) 6.2E-06 1.5E-01 2.9E-01 4.4E-01 5.8E-01 Information Remaining (%) 100 75 50 25 0

nilo 1 nilo 96 nilo 104 nilo 126 nilo 98 nilo 103 nilo 128 nilo 71 nilo 84 nilo 115 nilo 130 nilo 88 nilo 121 nilo 89 nilo 113 nilo 106 nilo 144 nilo 57 nilo 90 nilo 75 nilo 200 nilo 156 nilo 85 nilo 179 nilo 180 nilo 164 nilo 163 nilo 199 nilo 186 nilo 184 nilo 171 nilo 205 nilo 181 nilo 109 nilo 178 nilo 166 nilo 135 nilo 174 nilo 193 nilo 137 nilo 208 nilo 158 nilo 142 nilo 202 nilo 185 nilo 72 nilo 170 nilo 136 nilo 145 nilo 204 nilo 151 nilo 105 nilo 165 nilo 182 nilo 154 nilo 155 nilo 183 nilo 198 nilo 97 nilo 141 nilo 189 nilo 190 nilo 114 nilo 118 nilo 148 nilo 169 nilo 143 nilo 161 nilo 206 nilo 211 nilo 188 nilo 134 nilo 139 nilo 160 nilo 173 nilo 192 nilo 153 nilo 201 nilo 131 nilo 159 nilo 195 nilo 196 nilo 147 nilo 210 nilo 2 nilo 34 nilo 120 nilo 175 nilo 197 nilo 138 nilo 203 nilo 32 nilo 53 nilo 176 nilo 87 nilo 177 nilo 168 nilo 74 nilo 94 nilo 127 nilo 81 nilo 146 nilo 99 nilo 112 nilo 140 nilo 191 nilo 209 nilo 78 nilo 162 nilo 172 nilo 167 nilo 207 nilo 77 nilo 92 nilo 110 nilo 93 nilo 100 nilo 119 nilo 3 nilo 41 nilo 22 nilo 16 nilo 11 nilo 23 nilo 30 nilo 123 nilo 129 nilo 21 nilo 31 nilo 24 nilo 27 nilo 45 nilo 102 nilo 6 nilo 17 nilo 111 nilo 13 nilo 133 nilo 4 nilo 149 nilo 64 nilo 79 nilo 107 nilo 122 nilo 124 nilo 132 nilo 194 nilo 5 nilo 7 nilo 12 nilo 8 nilo 66 nilo 28 nilo 62 nilo 59 nilo 60 nilo 61 nilo 63 nilo 36 nilo 125 nilo 152 nilo 91 nilo 150 nilo 187 nilo 58 nilo 101 nilo 83 nilo 9 nilo 10 nilo 55 nilo 15 nilo 26 nilo 50 nilo 29 nilo 14 nilo 18 nilo 19 nilo 157 nilo 20 nilo 37 nilo 25 nilo 47 nilo 35 nilo 65 nilo 49 nilo 46 nilo 33 nilo 52 nilo 43 nilo 38 nilo 42 nilo 44 nilo 39 nilo 40 nilo 48 nilo 86 nilo 51 nilo 54 nilo 56 nilo 116 nilo 108 nilo 69 nilo 80 nilo 82 nilo 76 nilo 70 nilo 95 nilo 73 nilo 117 nilo 67 nilo 68

Figure 4: Dendrogram of morphometric measurements of sampled fish from Lake Kariba Culture Fisheries

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

The dendrogram that was constructed to characterize the collected Oreochromis fish samples of Lake Kariba Culture Fisheries based on morphometric measurements is given in Figure 4.

The dendrogram showed that the sampled fish specimens of Lake Kariba Culture Fisheries can be characterized into three strains (types) at 50% similarity index. One-way Analysis of Variance conducted in Statistix Software version 9.0 [17] on the morphometric variates of the identified strains in order to determine significant differences (P = 0.05), if any, showed that there was a significant difference (P = 0.0000) among the morphometric variates of Lake Kariba Culture Fisheries. The Least Significant Difference (LSD) All-Pairwise Comparison Test was then used to determine which means were statistically different (P = 0.05) from the other. The results of the LSD test conducted in Statistix Software version 9.0 [17] are given in Table 2.

Table 2: LSD All-Pairwise Comparison Test results of morphometric variates of Lake Kariba Culture Fisheries

Variable Mean Homogenous groups Strain 1 96.850 A Strain 2 69.676 B Strain 3 56.72 C

The results of the LSD All-Pairwise Comparison Test showed that there were three different types of Oreochromis niloticus strains at Lake Kariba. The three different types of Oreochromis niloticus strains were assigned to three different homogenous groups namely A, B and C with different mean morphometric variates. The identified strains were discriminated on 4 principal components. The smallest principal component was observed in principal component 4 which had an eigen value of 1.317 and the largest eigen value was observed in principal component 1 with an eigen value of 10.623. Principal components 2 and 3 had the eigen values 2.148 and 1.731. the extracted principal components accounted for a cumulative percent variance of 68.778%. The most influential morphometric measurement in principal component 1 which caused the largest variation and were important in strain identification were TL, BW, SL, BH, HL, PAD and PVD. The communalities test that was performed in IBM Statistics Software version 21.0 [18] to determine the most important morphometric variable in the description of the identified O. niloticus strains of Lake Kariba Culture Fisheries showed that total length with an extraction coefficient of 0.948 was the most important variable while pre-dorsal distance with an extraction coefficient of 0.264 was the least important.

4. Discussion

The general sentiment shared by Fisheries managers regarding Lake Kariba Culture Fisheries is that there are many different strains of Oreochromis niloticus being farmed by Aquaculture farmers [19]. Morphometric results of this study showed that there are 3 strains of Oreochromis niloticus being farmed within Lake Kariba. These morphometric results are in agreement with other studies by [12] who morphometrically identified two species of Oreochromis niloticus at Lake Barigo. [10,14] also identified two species of Oreochromis niloticus using morphometric analyses. [11] also delineated Tilapia samples from Reservoirs in Sri Lanka into four groups using morphological methods. The results of the study agree with [20] hypothesis that most fish farmers

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

keep more than one Tilapia strain and there is a possibility of the presence of inter-strain hybrids within a Culture Fishery. Morphometrically, the characters measured in all principal components except 1 had mixed coefficients indicative of shape variations rather than variation in size. This observation is in harmony with findings by [12,15] who observed that, any component having all coefficients of the same sign was indicative of size variation whereas any component having both positive and negative coefficients was indicative of shape variation. This observation implies that Oreochromis niloticus strains being farmed by Aquaculture farmers of Lake Kariba differ in shape. This, too, is a popular opinion shared by Fisheries managers in Zambia [19]. Meristic results of this study showed that there are 2 strains of Oreochromis niloticus being farmed by Aquaculture farmers of Lake Kariba. Meristic and morphometric results thus complemented each other. The dorsal formula of Oreochromis niloticus strains of Lake Kariba Culture Fisheries was found to be D XVI-XVIII, 11-13 and the anal formula of Oreochromis niloticus strains of Lake Kariba Culture Fisheries was A III-IV, 9- 11. These results are within the range of results that were found from previous studies by [9,12,21]. Previous studies on Oreochromis fish species indicated that the number of anal spines always ranges between III to IV while the number of dorsal spines varies between XV to XVIII [9,12,21]. This study could not phenotypically delineate Oreochromis niloticus strains at high similarity index (95%) to sub-species level because of overlapping meristic counts from the sampled specimens. This finding is agreeable with the hypothesis by [11,12,21] which stated that meristic counts do not show sufficient divergence among Tilapia populations. All Oreochromis niloticus strains show overlapping narrow-ranged meristic counts and any divergence of characters from a standard range could be fatal to the individual because it can be indicative of a mutation [14]. This could be the reason why closely-related species or sub-species have a narrow variable range of meristic counts. The high similarity among meristic traits signifies a possibility of hybridization among O. niloticus strains of Lake Kariba Culture Fisheries. All the sampled Fisheries on Lake Kariba had fish samples with the same dorsal formula and anal formula because the brood stock is purchased from Thailand by Chirundu Breams in Chirundu, Zambia where all fish farmers from Lake Kariba buy fingerlings from. Any variation in the number of strains at each Fishery can be attributed to differences in levels of hybridization at each Fishery. The presence of three strains of Oreochromis niloticus within Lake Kariba Culture Fisheries may suggest that fish farmers of Lake Kariba are possibly farming the three commonly cultured Oreochromis niloticus strains, namely: Genetically Improved Farmed Tilapia (GIFT), Oreochromis niloticus Chitralada and Oreochromis niloticus niloticus [20,22].

5. Conclusion

This study used morphometric and meristic methods to establish the existence of more than one type of Oreochromis niloticus fish species among Lake Kariba Culture Fisheries. This study provided Aquaculture farmers, researchers and Fisheries workers a useful tool for the identification and assessment of stock status of O. niloticus strains. Since the identification of fish populations and their connectivity with each other is a major point for management, breeding and conservation of species, the use of morphometric and meristic traits in delineating fish species is very effective.

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2020) Volume 74, No 1, pp 31-40

6. Recommendations

Phenotypically, this study delineated Oreochromis niloticus fish species of Lake Kariba Culture Fisheries using meristic counts and morphometric measurements. Similar studies should be conducted in other Aquaculture Fisheries to ascertain the number of O. niloticus strains being reared in Zambia. Application of molecular genetic markers such as microsatellites, cytochrome c oxidase subunit 1 (CO 1) gene and the displacement loop (D-loop) region would be effective methods of examining the discreteness of O. niloticus strains of Lake Kariba Culture Fisheries and facilitate the development of species-specific management strategies.

Acknowledgements

This study was part of the Ph. D study of the ﬁrst author, funded by the African Development Bank through the Zambia Aquaculture Enterprise Development Project and the Ministry of Fisheries and Livestock of Zambia. I would like to thank my supervisors Prof. Tamuka Nhiwatiwa (University of Zimbabwe) and Dr. Walter Muleya (University of Zambia) for guiding my thoughts in writing this article. I also thank Mr. Walubita Nasilele (Fisheries Aquaculture Officer, Siavonga, Zambia) for accompanying me in the field during data collection.

7. Copyright declaration

We, the authors, do hereby declare that this Journal article represents our own work and that it has not previously been submitted for publication to this or another Journal.

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