EYO, Joseph Effiong and INYANG, Nicholas Mathias39Table 1 continuesCoefficient <strong>of</strong> difference between two speciesMorphometric CharactersC. albopunctatusvs.C. gariepinusC. albopunctatusvs.C. anguillarisC. gariepinusvs.C. anguillaris1 Standard length [STL] 1.28 1.37 0.412 Total length [TOL] 1.40 1.42 0.413 Predorsal length [PDL] 1.58 1.59 0.444 Prepectoral length [PPL] 1.40 1.68 0.505 Prepelvic length [PPeL] 1.47 1.66 0.476 Preanal length [PAL] 1.54 1.55 0.427 Preorbital length [POL] 1.21 1.59 0.598 Caudal peduncle length [CPL] 0.75 1.04 0.639 Head length [HEL] 1.90 1.77 0.4110 Maximum head depth [MHD] 1.11 1.32 0.4411 Maximum body depth [MBD] 0.93 0.78 0.3712 Maximum caudal peduncle depth [MCPD] 2.20 2.01 0.4013 Maximum head width [MHW] 1.51 1.39 0.4114 Pelvic fin height [PeFH] 1.73 1.65 0.4315 Pelvic fin base length [PeFBL] 1.03 1.34 0.5116 Pectoral spine height [PSH] 1.14 1.21 0.2017 Pectoral fin base length [PFBL] 1.26 1.38 0.3418 Anal fin base length [AFBL] 0.88 1.12 0.4119 Anal fin height [AFH] 2.30 1.79 0.1320 Dorsal fin base length [DFBL] 1.12 1.22 0.4421 Dorsal fin height [DFH] 1.81 1.80 0.0322 Inner mandibular barbel length [IMBL] 0.46 0.46 0.1323 Outer mandibular barbel length [OMBL] 0.77 0.64 0.0124 Nasal barbel length [NBL] 0.44 0.28 0.2125 Maxillary barbel length [MBL] 0.85 0.51 0.1326 Inner mandibular barbel space [IMBS] 0.88 1.42 0.5827 Outer mandibular barbel space [OMBS] 1.28 1.60 0.4928 Nasal barbel space [NBS] 1.31 1.74 0.6529 Maxillary barbel space [MBS] 1.47 1.76 0.5130 Premaxillary teeth band width [PrTBW] 1.81 2.18 0.8031 Premaxillary teeth band depth [PrTBD] 0.83 1.25 0.6032 Vomerine teeth band width [VTBW] 1.89 1.81 0.6333 Vomerine teeth band depth [VTBD] 1.13 0.10 0.5934 Mouth width [MOW] 1.85 2.18 0.4635 Eye diameter [EDIA] 2.41 1.76 0.1836 Prefrontal fontennelle length [PFFL] 1.45 1.66 0.5237 Frontal fontennelle length [FFL] 2.46 2.37 0.2538 Frontal fontennelle width [FFW] 1.50 1.22 0.2539 Preoccipital fontennelle length [POFL] 1.83 1.75 0.4940 Occipital fontennelle length [OFL] 1.37 0.37 0.7841 Occipital fontennelle width [OFW] 0.87 0.01 0.6842 Frontal fontennelle - Occipital fontennellespace[FOS] 0.90 1.13 0.3643 Internasal space [INS] 1.38 1.83 0.6144 Interorbital space [IOS] 1.53 1.61 0.4545 Maximum body width [MBW] 1.52 1.34 0.3746 Caudal fin length [CFL] 2.04 1.71 0.3347 Pectoral - Pelvic fin space [PPeS] 1.45 1.56 0.3648 Pelvic - Anal fin space [PeAS] 1.35 1.17 0.1049 Occipital - Dorsal fin space [ODS] 0.55 1.21 0.6150 Prenasal length [PNL] 0.85 1.26 0.5651 Prenasal barbel length [PNBL] 1.36 1.55 0.6552 Nasal - Nasal barbel space [NNBS] 1.01 1.12 0.4453 Nasal barbel - Orbital space [NBOS] 1.65 1.72 0.4754 Nasal - Orbital space [NOS] 1.62 1.59 0.42Significantly different coefficients <strong>of</strong> difference are underlined.
Mayr’s coefficient <strong>of</strong> difference among Clarias species40maxillary barbel space, premaxillary teeth banddepth, vomerine teeth band width, mouthwidth, eye diameter, prefrontal fontennellelength, frontal fontennelle length, preoccipital,fontennelle length, and frontal fontennelleoccipitalfontennelle space. Furthermore otherdifferentiating characters were internasal space,inter orbital space, maximum body width,caudal fin length, pectoral-pelvic fin space,pelvic-anal space, occipital-dorsal fin space,prenasal barbel length, nasal barbel-orbitalspace and nasal orbital space. Furthermore,considering the discriminating charactersbetween C. albopunctatus and C. gariepinus, 90% <strong>of</strong> C. albopunctatus differed <strong>from</strong> 90 % <strong>of</strong> C.gariepinus in 32 characters. The characterswere standard length, total length, predorsallength, prepectoral length, prepelvic length,preanal length, head length, maximum caudalpeduncle depth, maximum head width, pelvic finbase length, anal fin height, dorsal fin height,nasal barbel space, maxillary barbel space,premaxillary teeth band width, vomerine teethband width, mouth width, eye diameter,prefrontal fontennelle length, frontal fontennellelength, frontal fontennelle width, preoccipitalfontennelle length, occipital fontennelle length,internasal space, interorbital space, maximumbody width, caudal fin length, pectoral-pelvic finspace, pelvic-anal fin space, prenasal barbellength, nasal barbel-orbital space and nasalorbitalspace.Thirty five characters discriminated 90% <strong>of</strong> C. albopunctatus <strong>from</strong> 90 % <strong>of</strong> C.anguillaris. The characters were standardlength, total length, predorsal length,prepectoral length, prepelvic length, preorbitallength, caudal peduncle length, head length,maximum body depth, maximum caudalpeduncle depth, maximum caudal peduncledepth, maximum head width, pelvic fin height,pelvic fin height, inner mandibular barbel space,outer mandibular barbel space, nasal barbelspace, maxillary barbel space, premaxillaryteeth band width, vomerine teeth band width,mouth width, eye diameter, prefrontalfontennelle length, frontal fontennelle length,preoccipital fontennelle length, internasal space,inter orbital space, maximum body width,caudal fin length, pectoral-pelvic fin space,prenasal barbel length, nasal barbel-orbitalspace and nasal-orbital space. Discriminating C.gariepinus <strong>from</strong> C. anguillaris based on thecoefficient <strong>of</strong> difference was impossible for allthe 54 characters assessed. The coefficient <strong>of</strong>differences among all clariids studies was almostidentical in 10 characters namely: maximumbody depth, pectoral spine height, anal fin baselength, inner mandibular barbel length, outermandibular barbel length, maxillary barbellength, premaxillary teeth band depth, vomerineteeth band depth, prenasal length and nasalnasalbarbel space.DISCUSSIONConsidering Mayr’s coefficient <strong>of</strong> differencebetween two species, it was evidently clear thatno differences existed between C. ebriensis andC. albopunctatus considering the 54morphometric characters. This result is contraryto an earlier report, employing F-LSD, <strong>of</strong> 2 rawdata, 9 ratio data and 6 not easily identifieddifferences in morphometric characters amongthe clariids <strong>of</strong> <strong>Anambra</strong> river, Nigeria (Eyo,2002a). The observed corresponding increasednumber <strong>of</strong> sex differentiating characters withClarias definitive size may not be unconnectedwith variations in their respective growth rates(Eyo 2002 b). Furthermore, discriminating 90% <strong>of</strong> C . ebriensis <strong>from</strong> C. gariepinus; C.ebriensis <strong>from</strong> C. anguillaris; C . albopunctatus<strong>from</strong> C. gariepinus and C. albopunctatus <strong>from</strong> C.anguillaris were possible utilizing the standardlength, total length, prepelvic length, preanallength, head length, maximum caudal peduncledepth, maximum head width, pelvic fin height,anal fin height, dorsal fin height, maxillarybarbel space, premaxillary teeth band width,vomerine teeth band width mouth width,prefrontal fontennelle length, frontal fontennellespace, maximum body width, caudal fin length,pectoral-pelvic fin space, prenasal barbel length,nasal barbel-orbital space and nasal-orbitalspace. None <strong>of</strong> these characters exhibited anydifference among the clariids when F-SLD <strong>of</strong>raw, ratio and residual data was employed,except for the ratio data <strong>of</strong> dorsal fin height andresidual <strong>of</strong> standard length (Eyo, 2002a). In fishtaxonomy, the analytical tool employed, maypose biased elements that affect properdifferentiation <strong>of</strong> species. Thus statistical toolwith explicit taxonomic objective may become amajor problem <strong>of</strong> the fish taxonomist andresearcher, as different statistical tools <strong>of</strong>ferdifferent discriminating characters even whenutilizing the same data. Previous workers onClarias taxonomy did not pay attention to Mayr’scoefficient <strong>of</strong> difference between species(Sydenham 1978, 1980, Sydenham andOlawoye1981; Teugels 1980, 1982 a, b, c;Ezenwaji 1986, 1989 and Teugels and Roberts
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