By Nwafili, SA; Akpoilih, BU (2023).

Greener Journal of Biological Sciences Vol. 13(1), pp. 1-7, 2023 ISSN: 2276-7762 Copyright ©2023, the copyright of this article is retained by the author(s) DOI: https://doi.org/10.5281/zenodo.7736700 https://gjournals.org/gjbs

Some Aspects of the Biometry of the Silver Catfish, Chrysichthys nigrodigitatus from Freshwater and Brackish water Environment in Nigeria.

Nwafili, SA;Akpoilih, BU

Department of Fisheries, Universirty of Port Harcourt, P.M.B 5323, Choba, Rivers State, Nigeria.

ARTICLE INFO	ABSTRACT
Article No.: 121122102 Type: Research Full Text: PDF, HTML, PHP, EPUB DOI: 10.5281/zenodo.7736700	The study was carried out to investigate the differences in morphometric traits of Chrysichthys nigrodigitatus inhabiting a purely lacustrine freshwater and lotic brackishwater environments in Nigeria. The specimens were obtained from the New Calabar River (Brackish) and Oguta Lake (Freshwater) during fields trips in during 2018. A total of 80 individuals comprising of 40 from each water body were analysed for 16 morphometric traits. The head length and head width were not significantly different (p>0.05) in the species between the two locations. The ratio (%) of predorsal fin length to standard length, preanal fin length to standard length, prepectoral fin length to standard length, body depth to standard length, gut length to standard length were also not significantly different (p>0.05) for the two locations. However, other parameters such as snout length, the dorsal fin Length, dorsal fin depth, anal fin length and pectoral fin length and ratio of head length to standard length, snout length to head length, and pectoral fin length to standard length differed significantly (p<0.05). The Relative Gut Length of 1.15 and 1.12, respectively for NCR and OGL indicate omnivory. Traits in which differences were not detected or minimal could be used for the species identification. Racial and population genetic studies encompassing  the different ecological zones in the species will be in the right direction.
Accepted: 12/12/2022 Published: 15/03/2023
*Corresponding Author Dr. Nwafili Sylvanus E-mail: sylvanus.nwafili@ uniport.edu.ng
Keywords: Silver catfish, Oguta Lake, New Calabar river, Chrysichthys nigrodigitatus, Claroteidae.

INTRODUCTION

The silver catfish, Chrysichthys nigrodigitatus, which belongs to the family Claroitidae (Mo 1990) is a euryhaline species. It is widely distributed in fresh and brackish waters of West Africa (FAO 1969; Holden and Reed 1991), where it constitutes an important component of artisanal fisheries. The flesh is considered superior and highly relished and its growth relatively good to warrant its aquaculture. However, the aquaculture potentials of the animal in Nigeria is yet to be harnessed. For instance, fingerlings of the species are captured from the wild with attendant seasonal in availability, limited growth, and collection of mixture of different strains which may be difficult to separate (Agokei and Ansa 2010).

Fish improvement and fisheries management depends on some basic studies, which includes biometric data. Length and weight relationship (LWR) is a good method of growth assessment in fish (Arshad et al. 2012) while condition factor is effective in determining the physiological condition of fish and as well the status of the aquatic ecosystem in which fish live (Oni et al. 1983; Anyanwu and Ugwumba 2003; Anene 2005). The differences in morphometric characters are also assets used in separation of population of widely distributed species (Diaz et al. 2000; Lawson 2010). Anyanwu and Ugwumba (2002) and Adedeji and Araoye (2006) have shown that morphometric variations in species from different localities can have environmental or genetic underpinnings. According to Diaz et al. (2000) and Lawson (2010) morphometric differences help separation of population of widely distributed species.

Several studies which compared populations of C. nigrodigittus in Nigeria are scanty. However, Kusemiju (1975) and Ezenwa et al. (1986) compared three isolated geographical populations of C. nigrodigitatus in Nigeria to identy the best population for breeding purposes. knowledge on the identity of the species chosen for culture is an impelling necessity to eliminate mixing of species (Mariappan and Balasundaram 1999).

We collected some C. nigrodigitatus from the New Calabar River and Oguta Lake during a visit. The aim of this paper was to examine the aspects of the biometry of the animal from the two water bodies, a lacustrine freshwater lake and lentic brackish-freshwater environment.

2. MATERIALS AND METHODS

2.1 Study Area

The New Calabar River (NCR) and Oguta Lake (OGL) are located in the south-eastern part of Nigeria (Figure 1). The NCR empties into a coastal lagoon and the creeks bordering the Atlantic Ocean. It co-ordinates are latitude: 44^o 25ʹ0ʺ N and longitude: 7^o 16ʹ0ʺ E (NDES, 2003). Several ecological studies show that NCR is a fresh water system at some points but euryhaline (brackish water) at the Choba axis where university of Port Harcourt is situated (Gideon and Chidiebere 2008).

Oguta Lake is the largest natural lake in Imo State of Nigeria located within the equatorial rainforest. The lake is fed mainly by the Njaba and Obana River and empties itself into the River Niger drainage system through river Orashi respectively. It is purely fresh water and lacustrine.

Collection of fish samples

The fish samples used for the study were collected from 2 stations along the New Calabar River and OGL during November, 2018. Specimen were transported in ice to the Fisheries Laboratory, Faculty of Agriculture, University of Port Harcourt.

Measurement of Morphometric Traits

Specimen were measured immediately in the Laboratory, dissected and their guts removed. Measurement were taken on each individual of C. nigrodigitatus for the following morphometric characters (Table 1).

Table 1: List of Morphometric data taken on C. nigodigitatus from two water bodies in Nigeria.

S/N	Trait	Description
1	Standard length (SL)	Distance from the tip of the snout to end of the caudal peduncle
2	Head length (HdL)	Distance from the tip of the snout to the tip of the occipital process. It is expressed as percentage of the standard length
3	Head width (HdW)	Distance across the widest point of the head but discounting any lateral projection of the branchiostegal membranes
4	Snout length (SnL)	from the tip of the snout to the middle of the vertical line connecting anterior eye border
5	Nasal barbal length (NBL)	Distance from its base to the tip
6	Predorsal length (PrDL)	Distance from the tip of the snout to the origin of the dorsal fin
7	Preanal length (PrAnL)	measured from the tip of the snout to the origin of the anal fin (in mm)
8	Prepelvic length (PPeL)	from the tip of the snout to the origin of the pelvic fin (in mm)
9	Prepectoral length (PPecL)	distance between the tip of the snout to the origin of the pectoral fin was measured (in mm); and expressed as % SL
10	Pectoral fin length (PFL)	measured from the pectoral fin base to tip of the pectoral fin; expressed as % Sl
11	Dorsal-Caudal length (DCL)	measured the distance between the dorsal and caudal fins; expressed as % SL
12	Caudal peduncle depth (CPD)	measured the distance from the dorsal surface to the ventral surface of the caudal peduncle; expressed as % SL
13	Body depth at anus (BD)	the vertical distance between the dorsal and ventral surfaces (at the anus) was measured and expressed as % SL
14	Dorsal fin depth (DFD): expressed as % SL
15	Anal length: expressed as % SL
16	Relative Gut length (RGL).	Ratio of the length of intestine to the SL expressed as %

Data analyses

The morphometric traits were calculated as percentage of the standard length. The t-test statistic was used to determine if differences exist between specimen from the lentic OGL and New Calabar River. Specimen from NCR were segregated into two groups because the river has both the freshwater and brackish water portions, that is, Choba and Ogbogoro, respectively. Since the species can migrate between brackishwater and freshwater, the assumption is, however, that the individuals from both axes are the same. The ratios of HdW, NBL and SnL to HdL were calculated (expressed as percentage). The ratios of other morphometric traits to the SL were also calculated and expressed as percentage.

The relative length of the gut (RLG) was also calculated as a possible indicator of the major diet components using the equation RLG = GL/SL (Yamagishi et al. 2005), where GL = gut length (cm), and SL = standard length (cm).

All the statistical analysis were implemented using EXCEL, PAST3 and JASP softwares. All statistical analyses were considered significant at 5% (p<0.05).

RESULTS

A total of 80 individuals comprising 40 from each of the locations were analyzed. For the NCR, two stations were sampled: the brackish water (Ogbogoro = 20 individuals) and fresh water (Choba = 20 individuals) axes. The test for difference between individuals from caught from the freshwater and brackish water axes of NCR showed no significant difference in all parameters (p>0.05). Therefore, the samples were pooled as NCR for further analysis. The SL of C. nigrodigitatus from 12.0cm to 24 cm ( =17.85cm) and 10.9 to 18.5 cm ( =14.32cm) in NCR and OGL, respectively. The HdL ranged from 4-6.1cm and 2-7.0cm for OGL and NCR, representing 35.61% and 27.51% of the SL for OGL and NCR, respectively. There was significant statistical difference in SL between the two water bodies. However, the HdL and HdW displayed a non-significant difference between NCR and OGL (P > 0.05). All other parameters including SnL, NBL, PrDL, PrAnL, PPeL and PPecL were significantly different (p<0.05) between C. nigrodigitatus from the two water bodies.

The mean values of morphometric characters of C. nigrodigitatus expressed as percentage of SL are presented in Table 2. The HdL represented about 27.04% in NCRand 35.65% in OGL of the SL The predorsal length was 40.53 ±1.36% and 40.38±0.597% of the SL from NCR and OGL, respectively. Similarly, the gut length was approximately 115.07±4.17% and 112.06±4.29% of the SL (p>0.05), respectively for NCR and OGL. In otherwords, the RGL were 1.15 and 1.12 for NCR and OGL, respectively. The differences in the SnL, NBL, PrDL, PrAnL, PPeL and PPeCL of C. nigrodigitatus were significant (P<0.05). Also, the DFL, DFD, AFL and PFL were all significantly different (P < 0.05).

Table 2: Mean values of morphometric characters of C. nigrodigitatus from New Calabar River and Oguta Lake, Nigeria

Character	New Calabar River	Oguta Lae	Significance (P-value
	Mean (in % HdL)	Mean (% HdL)
Head width	66.43±6.32	66.45±1.42	NS
Snout length	33.18±3.34	32.72±0.62	NS
Nasal barbell length	9.84±3.13	10.24±0.51	NS
	Mean (in % SL)	Mean (% SL)
Head width	13.04±1.16	17.63±0.002	**
Head length	27.04±1.16	35.65±0.002	**
Predorsal length	40.53±1.36	40.38±0.597	NS
Preanal length	74.13±2.45	76.76±1.55	**
Prepelvic length	54.67±1.45	58.37±1.15	**
Prepectoral length	26.86±1.50	26.13±0.52	**
Dorsal fin depth	29.88±1.41	27.31±0.85	**
Dorsal fin length	13.40±0.70	11.06±0.30	**
Anal fin length	18.16±0.63	15.11±0.52	**
Pectoral fin length	16.56±0.52	16.01±0.50	**
Caudal peduncle length	42.56±2.06	34.40±0.88	**
Caudal peduncle depth	12.61±0.44	11.16±0.30	**
Gut length	115.07±4.17	112.06±4.29	NS
Body depth	26.99±0.82	26.54±0.15	**

** and NS implies that the means were significantly different and Non Significant, respectively.

The range of ratios of morphometric traits expressed as percentage of SL or HdL as shown in Table 3.

Table 3: Comparison of ratios of morphometric variables between Chrysichthys nigrodigitatus of New Calabar River and Oguta Lake, Nigeria.

Trait Ratio	New Calabar River		Oguta Lake		P-value
	Range (%)	Mean ± SD	Range (%)	Mean ±SD
HdL vs SL	8.64-14.68	11.65±1.4	7.50-41.5	27.04±7.0	*
NBLvs HdL	9.09-11.87	29.67±19.0	6.78-18.96	13.23±3.0	*
SnL vs HL	15.38-51.20	41.93±17.26	26.32-42.22	32.72±3.93	**
PrDL Vs SL	10.00-75.25	40.53±8.6	30.27-50	40.38±3.8	NS
PreAnL Vs SL	8.30-112.5	75.11±1.6	52.59-105.5	80.51±0.96	NS
PPecL Vs SL	5.67-62.26	26.86±9.5	20.5-35.00	26.13±3.30	NS
AFL vs SL	4.00-29.70	18.16±3.95	8.00-21.10	15.11±3.27	*
PFL vs SL	4.50-25.00	16.56±3.28	8.00-21.00	16.00±3.14	*
BD vs SL	6.67-35.26	26.995±5.18	21.47-36.69	26.539±3.84	NS
CPD vs SL	2.67-18.00	12.61±2.81	7.03-16.51	11.16±1.88	**
DCL vs SL	8.16-82.50	42.62±12.99	25.84-47.71	34.40±5.57	**
DFL vs SL	8.17-5.00	29.88±8.93	18.18-41.53	27.31±5.35	NS
GL vs SL	25.5-105.20	71.90±15.69	33.09-106.78	65.13±18.00	NS

NS = p>0.05; *= p <0.05 and **= p<0.01.

DISCUSSION

Some studies have showed that environmental variations could lead to morphological heterogeneity (Begg et al. 1999; Tzeng and Yeh 1999; Collins et al. 2007; Torres et al. 2014). Morphometric variation between stock can provide a basis for stock structure, applicable for studying a short-term, environmentally induced variation (e.g. in fisheries management) (Begg et al. 1999). The mean values for PPeL , PPecL, DFD, DFL, AFL and PFL fall within the range reported by Erondu (1997) for C. nigrodigitatus in the NCR, the PrDL and PrAnL were slightly higher in the present study. Our results are also in concordance with the studies of Oyebamiji and Yisa (2018) for C. nigrodigitatus fished from two different ecological zones in Nigeria. The mean BD of about 27% of the SL for both water bodies obrained in this study was above the figures reported by Atobatele (2013) for the s species in Epe Lagoon.

The differences in morphometric characters in C. nigrodigitatus between the two water bodies may be accounted by the fact the species has a distribution across a broad tange of ecological conditions. According to Collyer et al. (2005) with the type of distribution ascribed to C. nigrodigitatus is usually accompanied by diverse morphological variations to enable the species adapt to the environmental conditions. For eample, salinity could possibly affect body shape (Collyer et al. 2005 and Collyer et al. 2007). Price et al. (2003) observed the existence of strong relationship between speciation events and colonization of new environments, a situation that may possibly induce changes in organism’s morphology. Schluter and McPhail (1993) found evidence of morphological diversification in the three spined sticklebacks in which two sympatric forms evolved because of ecological divergence. Oyemibaji and Yisa (2018) attributed the differences between two freshwater populations of C. nigrodigitatus in lentic environments to ecological factors.

With respect to the GUT length, the non-significant difference between the species in the two water demonstrates that they exploit the same food niche typical of omnivores. Our result agrees with Gbaguidi et al (2017) who reported GL/SL of 1.10±0.27 for C. nigrodigitatus introduced in an man-made pond. Nwadiaro and Okorie (1987) reported a RGL of 1.9 for a closely related Claroteid, Chrysichthys filamentoses in Oguta Lake. Similar results were obtained for other claroteids including Chrysichthys auratus (1.98) and Auchenoglanis occidentalis (1.98). These results firmly placed these members of the claroteids as omnivores. Various dietary analysis have conformed that C. nigrodigitatus is an opportunistic feeder (Gbaguidi et al. 2017). Oluwale (2019) estimated RGI of 1.25 for juveniles of C. nigrodigitaus in Epe Lagoon, a morphological indication that the species is omnivorous or opportunistic feeders (Nwadiaro and Okorie, 1987)

CONCLUSION AND RECOMMENDATION

A broad scale morphometric and population genetic studies of the species across salinity gradients and ecological zones to ascertain the effect of ecological factors on the species distribution in Nigeria

Conflict of interest

There is no conflict of interest,

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Cite this Article: Nwafili, SA; Akpoilih, BU (2023). Some Aspects of the Biometry of the Silver Catfish, Chrysichthys nigrodigitatus from Freshwater and Brackish water Environment in Nigeria. Greener Journal of Biological Sciences, 13(1): 1-7, https://doi.org/10.5281/zenodo.7736700.