Greener Journal of Biological Sciences Vol. 12(1), pp. 01-10, 2022 ISSN: 2276-7762 Copyright ©2022, the copyright of this article is retained by the author(s) http://gjournals.org/GJBS

Morphometric Characterization of Four Commercially Important Fish Species of the New Calabar River, Rivers State, Nigeria.

Nwafili Sylvanus Anene

Department of Fisheries, Faculty of Agriculture, University of Port Harcourt, P.M.B 5323, Choba, Rivers State, Nigeria.

ARTICLE INFO	ABSTRACT
Article No.: 122821158 Type: Research Full text: HTML, PDF, EPUB, PHP	Morphometric analyses have been very useful in separating species, populations and races, and it also helps in identification of species. The objective of this study was to characterize four common species encountered in artisanal catches of the New Calabar River obtained during July to October 2018 market survey. A total of 84 individuals comprising Oreochromis niloticus (22), Tilapia guineensis (22), Mugil cephalus (20) and Liza falcipinnis (20) were measured for weight (Wt) (0.01gm), total length (TL), head length (HL), body depth (BdP), dorsal fin length (DFL), eye diameter (ED), pectoral fin length (PFL), pelvic fin length (PeFL) and gut length (GL) (0.01cm). The results showed negative allometric growths pattern for the length-weight and length-gut length relationship. The ratios of DFL/HL, DFL/TL and PFL/HL were significantly different between the two tilapinne species (p < 0.05) while HL/TL, BdP/HL, PFL/HL, ED/HL and ED/HL were significantly different between the mugilids (P<0.05). The Relative Gut Length of the four species showed that tilapiine species were herbiores (6.23±0.28 – 6.86±0.14) and mugilids omnivores (2.67±17 – 2.78±0.11).The study contributes to our comparative knowledge of morphometric characteristics of cichlids and mugilids in the New Calabar River.
Accepted: 29/12/2021 Published: 20/01/2022
*Corresponding Author Nwafili Sylvanus Anene E-mail: sylvanus.nwafili@ uniport.edu.ng
Keywords: Mugil cephalus; Oreochromis niloticus; New Calabar River; Gut-length; Relative gut length.

INTRODUCTION

The New Calabar River, NCR is a very important system because of the numerous economic activities centered on it. The communities living within the catchment area of the river rely on it for livelihood including artisanal capture fisheries (Ibim et al., 2016), agricultural, recreational, lumbering and sometimes, domestic water supplies (Abu and Egenonu, 2008). Various aspects of the ecology and biology of the fish of the NCR have been documented (Uzukwu et al., 2013; Agbugui and Deekae, 2014; Nwineewii and Unochukwu, 2018; Dienye and Woke, 2015; Onojake et al., 2017; Dienye and Olopade, 2018; Dienye et al., 2019; Chukwu, 2019). Nwadiaro and Ayodele (1992) harvested fish of the families Cichlidae, Mugilidae, Clupeidae, Sciaenidae, Bagridae and Haemulidae in the Choba axis while Olori (1995) cited in Ibim et al. (2016) reported 14 fish species including Chrysichthys nigrodigitatus, Chrysicthys auratus, Tilapia Malanorium, Chromidotilapia guentheri, Hemichromis elongatus, Tilapia mariae, Pellonala afzeliusi, Psettias sebae, Alestes nurse, Alestes longipenus, Eliotris diaganensis, Channa obscura, Hepsetus odoe and Brienomyias niger. Dickson et al. (1999) reported that species belonging to the families of Bagridae and Cichlidae were more abundant in the NCR. In a more recent study, Ibim et al. (2016) reported 61 species belonging to 54 genera and 41 families in the lower and upper reaches of the river.

Anthropogenic inputs into the NCR is huge, putting fish populations at risk; thus, necessitating proper documentation of fish species that could lead to good management practices and culture. Biometric data have important applications in the identifications of species and design of improvement programmes. Knowledge of biometric variations is necessary for the description of species and Umaru et al. (2015) noted that understanding of the differences in morphometric and meristic characters of fish stocks give vital clues about their phylogenetics and provide information that could be useful for genetic improvement. Morphological parameters and biometrical characteristics have remained the simplest and most direct among methods of species identification (Turan et al., 2004).

The objective of this study is to morphologically characterize and determine the gut length of four commercial fish species of the New Calabar River obtained during a fish market survey from July to October, 2018. The Choba fish market is a small market which receives supply of fresh fish from artisanal fishers of the NCR. The fish mongers rotate their activities on alternate days. Characterization of the gut length is fundamental to understanding dietary preferences and feeding habits of different fish species. The gut length, in particular, provides important information on species’ feeding habits (Kramer and Bryant 1995) and it can be used as a reference point for interspecific comparisons (e.g., Al-Hussaini 1947). Differences in gut length of closely related species is used as good predictor of dietary habits. Thus, the relationship between gut length and total length are especially important for ecomorphological studies (Motta, 1988).

MATERIALS AND METHODS

Sample Collection

Samples of predominant fishes comprising 22 individuals each of Tilapia guineensis and Oreochromis niloticus and 20 individuals each of Mugil cephalus and Liza falcipinnis were obtained during market survey of common fishes among fish mongers at the Choba fresh fish market. While O. niloticus and T. guineensis are tialapinne cichclids, M. cephalus and L. falcipinnis belong to the mugilids. Choba market is one of the landing sites on the bank of the New Calabar River. Monthly purchasing of the specimen was taken for four months (July to October 2018).The fish specimen were transported in plastic containers containing ice block to keep the fish fresh.

After the identification, the total weight (Wt) of individual species was measured (nearest 0.01gm) using a digital balance. The following morphometric characters were measured to the nearest 0.1cm in individuals of each species: total length (TL), head length (HL), head width (HW), eye diameter (ED), pectoral fin length (PFL), pelvic fin length (PeFL) and dorsal fin length (DFL).

To obtain the Relative Gut Length, RGL, each individual was split open with the aid of scissors to expose the viscera. The gut was detached, uncoiled and after carefully removing mesenteric connective tissues, it was measured as Gut Length (GL) with a measuring tape to the nearest 0.01cm. The GL was determined following Hyslop (1980), Ribble and Smith (1983), Kramer and Bryant (1995).

Data analysis

The data were analyzed using the SPSS v-20 (Statistical Packages for Social Sciences), Medcalc and PAST32b computer software. The estimation of species Length-weight relationship will be done using the formula W=aL^b, which was transformed into natural logarithmic form In W=Log a+b Log L, where W=body weight (g), L=Total length (cm), ‘a’ is a constant; ‘b’ is exponent: allometric coefficient. The parabolic equation according to Ribble and Smith (1983), Y= a.X^b, or GL = aTL^b (Hyslop, 1980, Kramer and Bryant, 1995) was used to express the relationship between the gut length (Y=axis) and total body length X-axis). Gut length, total length, and relative gut length measurements were log transformed to meet the assumption of normal distribution of data. The means of the morphometric traits were compared between the two similar species using the t-test.

Figure 1

RESULTS AND DISCUSSIONS

The range and means ± standard deviation values of morphometric characters for the species are presented in Tables 1-4. The total length and weight of T. guineensis, O. niloticus, M. cephalus and L. falcipinnis were 9-18.1cm ( and 11-104 g ( = 57.88±29.26g), 11-16.5cm ( = 13.35±1.51cm) and 23.0-66.0g ( 39.2±12.74g), 14-23cm and 26-90g ( and 14.5-21cm and 28-94g (, respectively. Kurton and Adeniyi (2014) reported standard length of 13-15cm for T. guineensis of the Lagos Lagoon and Badagry Lagoon. Similarly, Azua et al. (2017) obtained the means of 15.51 g and 10.76 cm, respectively for body weight and total length in O. niloticus. Kolawole-Daniels et al. (2017) reported from the Lagos Lagoon that the total length (TL) of M. cephalus ranged between 12.5 to 28.7cm (16.9±0.14cm), weight ranged between 20.5 to 196.4g ( 49.9±1.53g) and that of L. falcipinnis ranged in total length from 12.5 to 21.5cm (17.06±0.13 cm) and weight ranged from 20.1g to 180g ( 81.76±2.9g).

The HL in this study were 2.5-4.6, 2.6-4.5, 3.0-4.5 and 3.1-4.5 for T. guineesis, O. niloticus, M. cephalus and L. falcipinnis, respectively. There was no difference (P = 1.00) between the HL of M. cephalus and L. falcipinnis. Likewise there was no difference (P = 0.95) between the HL of the two tilapiine species. The HW significantly differed between the L. falcipinnis and M. cephalus (P = 0.0004) but not between O. niloticus and T. guineensis (P = 0.53). The range of HL in our study is within the range of 4.2-4.5cm reported by Kurton and Adeniyi (2014) and Olufeagba et al. (2015) for T. guineensis in the Badagry Creek and Lagos Lagoon and Cichlids of Kainji Lake, respectively. Azua et al. (2017) obtained mean HL of 3.68 cm for O. niloticus while Raj et al. (2016) obtained mean HL of 6.68cm for O. niloticus in lentic habitats of Kerala. The differences observed in this study and those under reference may be due to various factors such as food availability, environmental conditions, stage of maturity and seasonal changes, mortality rate or recruitment or fishing pressure all of which ultimately accumulating in racial differences.

The DFL showed significant difference between the tilapinnes (P = 0.0095) and non-significant in the mugilids (P = 0.57). other paramenters including PeFL and PFL were not also signicantly different from each other between the tilapias (P = 0.06 and 0.10, respectively). Similarly, DFL, PeFL and PFL showed no difference between the two mugilids (P = 0.57, 0.058 and 0.056, respectively). For the tilapinnes, the BdP (P =0.029) also differed.

The eye diameter, ED in this study were in the range of 0.6-1.2cm, 0.7-1.5cm, 0.5-1.2cm and 1.0 -2.1cm for O. niloticus, M. cephalus, T. guineensis and L. falcipinnis, respectively. Statistically, t-test showed there was no difference in ED between the two tilapiine species (P = 0.53); however, the parameter showed significant difference between the mugilids (P = 0.003). Khayyami et al. (2015) reported ED of 1.11 and 1.10 for two populations of M. cephalus in the Persian Gulf. In the Badagry Creek and Lagos Lagoon, ED in T. guineensis ranged between 1.2-1.3cm (Kurton and Adeniyi, 2014). Similar ED (1.30-1.54 cm) was measured for invasive Oreochromis aureus in inland waters of Iran (Valikhani et al., 2016). This result is also in agreement with Olufeagba et al. (2015). However, For L. falcipinnis of Badagry Creek according to Lawson et al. (2010), ED varied between 6 and 12mm (0.6-1.2cm). Bhatt and Mankodi (2020) also reported ED of 2.1cm for M. cephalus in Sabarmati Rivers in India. The ED of a fish may be influenced by level of water pollution and turbidity.

The gut length and mean gut length are given in Table 1-4. The gut length (GL) ranged from 72 – 110 cm in O. niloticus, 60-135cm in T. guineensis, 35-70cm in M. cephalus and 25-70cm in L. falcipinnis. The gut lengths were 6.67 – 7.46, 6.55 – 6.67, 2.5-3.04 and 1.72 – 3.33 times the TL for T. guineensis, O. niloticus, M. cephalus and L falcipinis, respectively. The highest mean RGL of 6.86 ± 0.14 and 6.23 ±0.28 were found for O. niloticus and T. guineensis, respectively. There was no significant difference between the two (P>0.5). Similarly, mean RGL for the mugilids were 2.26±0.17 and 2.78±0.11 for L. falcipinnis and M. cephalus, respectively. Relative gut lengths in vertebrates have long been studied and compared within and among species (e.g., Al-Hussaini 1947). The GL/ TL ratio is useful in classifying fishes into trophic levels. According to Al-Hussaini (1947) and Kapoor et al. (1975), carnivores, omnivores and herbivores have RGL generally ranging from 0.5–2.4, 0.8–5.0 and 2–21, respectively. Information on the ratio of GL to body length in Nigerian fishes are scarce in the literature. When taken into consideration the GL and RGL index values for the mugilids and tilapias examined in this study, it can be seen that the computed values are compatible with those reported by (Karachle and Stergiou, 2010; Al-Hussaini 1947; Kapoor et al., 1975) for ranking of the feeding relationship. For example, Crosetti (2015) reported that grey mullets are omninivores while tilapias are herbivores (Getachew and Fernado, 1989). However, Edema and Aiguobasinmwin (2007) and Edema and Ojieh (2006) found the ratio of 3.0 and 9.0, respectively Tilapia mariae. Dankwa, et al. (2005) reported relative gut length of M. cephalus in the Volta estuary to be 4.56 while in the Pra estuary the longest relative gut length of 4.33 was calculated for L. falcipinnis, concluding that the species were herbivorous. It has been observed that herbivores have longer guts needed to digest low quality fibre-rich diets than more easily digestible protein-rich foods (German and Horn 2006, Olsson et al. 2007, Wagner et al. 2009). The present study shows from the gut length that T. guineensis and O. niloticus are herbivorus while those of mugilidae also indicated either omnivory or herbivory. Gut morphologies have been shown to be plastic, varying among individuals within a species in relation to different diets (e.g., Raubenheimer and Bassil, 2007). In the same species of guppy, GL adapted to changes in environment. In the same species, Zandonà et al. (2015) found that population of origin and the environment also influenced.

Table 1: Descriptive statistics for Tilapia guineensis from New Calabar River

	TL	WT	ED	PFL	PeFL	DFL	HW	BdP	GL	RGL	HL
Min	9	11	0.5	2.1	1.2	4	2.5	3.4	60	4.63	2.5
Max	18.1	104	1.2	4.7	4.3	9.5	4.7	8.1	135	9.05	4.6
Mean	14.26	57.88	0.96	3.69	3.01	6.77	3.75	5.78	90.96	6.23	3.70
Std. error	0.54	5.85	0.04	0.15	0.17	0.31	0.13	0.27	3.41	0.28	0.12
Variance	7.35	856	0.03	0.53	0.70	2.37	0.44	1.79	290.6	1.72	0.37
Stand. Dev	2.71	29.26	0.18	0.73	0.84	1.54	0.67	1.34	17.05	1.31	0.61
Coeff. Var	19.02	50.55	18.67	19.78	27.87	22.73	17.78	23.16	18.74	21.08	16.43

Table 2: Descriptive statistics for Oreochromis niloticus from New Calabar River

	TL	WT	ED	PFL	Pel L	DFL	HW	BdP	GL	RGL	HL
Min	11.0	23.0	0.6	3	1.5	4.5	3	4	72	5.77	2.6
Max	16.5	66.0	1.2	5.2	3.9	7.2	4.5	6.3	110	8.67	4.5
Mean	13.35	39.92	0.99	4	2.61	5.78	3.64	5.06	91.1	6.86	3.69
Std. error	0.30	2.55	0.03	0.1	0.10	0.15	0.09	0.13	1.75	0.14	0.10
Variance	2.29	162.33	0.02	0.23	0.27	0.55	0.22	0.43	77	0.44	0.26
Stand. dev	1.51	12.74	0.14	0.48	0.52	0.74	0.47	0.66	8.77	0.63	0.51
Coeff. Var	11.32	31.92	13.93	12.1	19.90	12.82	12.87	12.98	9.63	9.25	13.83

Table 3: Descriptive statistics for M. cephalus from New Calabar River

	TL	WT	ED	PFL	Pel L	DFL	HW	BdP	GL	RGL	HL
Min	14	26	0.7	1.6	1.5	2.2	3	4.2	35	1.9	3
Max	23	90	1.5	3.5	2.7	4.9	4.8	6	70	3.94	4.5
Mean	18.97	59.85	1.1	2.65	2.21	3.2	3.67	4.99	52.65	2.78	3.91
Std. error	0.51	4.17	0.04	0.11	0.07	0.15	0.11	0.13	2.40	0.11	0.10
Variance	5.21	347.82	0.04	0.26	0.11	0.47	0.24	0.35	114.77	0.25	0.18
Stand. dev	2.28	18.65	0.20	0.51	0.33	0.69	0.49	0.59	10.71	0.50	0.43
Coeff. Var	12.03	31.16	17.94	19.22	14.96	21.46	13.26	11.90	20.35	17.82	11.01

Table 4: Descriptive statistics for Liza falcipinnis from New Calabar River

	TL	WT	ED	PFL	Pel L	DFL	HW	BdP	GL	RGL	HL
Min	14.5	28	1	2	1.5	1.5	1	2.5	25	1.66	3.1
Max	21	94	2.1	3.5	2.6	4.3	4.2	5.7	70	3.33	4.5
Mean	17	45.4	1.44	2.35	1.99	3.07	2.82	4.22	39.1	2.26	3.91
Std. error	0.71	6.86	0.14	0.14	0.12	0.24	0.26	0.32	4.70	0.17	0.14
Variance	5.03	471.20	0.19	0.20	0.14	0.58	0.70	1.04	220.32	0.29	0.19
Stand. Dev	2.24	21.71	0.43	0.45	0.38	0.76	0.84	1.02	14.84	0.54	0.44
Coeff. Var	13.2	47.81	30.04	19.16	19.02	24.8	29.61	24.13	37.96	24.05	11.21

Length-weight and Length-gut length relationships

The regression equation for estimating length-weight and length-gut length relationships are shown in Figs. 2-5 and Table 5. The regression coefficient (b) values of fish species were less than 3, ranging from 1.24 – 1.91. Since the value b is less than 3, growth is negatively allometric in which the rate of increase in body length of the fish species is not proportional to the rate of increase in their body weight. Regression coefficient of 3 indicates isometric growth or maintenance of dimensional equality as the organism grows (Thomas et al., 2003; Olurin and Aderibigbe, 2006). Famoofo and Abdul (2020) reported similar b values of 1.067 while Obasohan et al. (2012) and Dan-Kishiya (2013) reported a range of 1.4–1.6 for Tilapia mariae. In line with the findings of this study, several authors have reported negative allometric growths (b < 2.5) which are outside the expected range of 2.5 < b < 3.5 (Carlander, 1969; Pauly and Gayanilo, 1997) for different cichlid fish species from various water bodies, despite using a large number of specimen. For instance, Gatso et al. (2017) reported a range of values of b (0.14–0.8) for O. niloticus in their study conducted on Wudil River, Kano, Nigeria. In the study of Atama et al. (2013), wherein a total 7091 individual specimen were used, recorded b values of 0.32 for male H. fasciatus, 1.682 for female and 0.738 for the combined sexes; 0.549 in the dry season and 0.233 in wet season. This range of values (0.233–1.682) for b was far below the one (2.42) recorded in this study.

The TL-GL relationship returned a negative allometric growth pattern (Table 5 and Fig. 2-5). The values of the slope of the regression, b were 0.6866, 1.2367, 0.397 and 0.2867 for T. guineensis, O. niloticus, M. cephalus and L. falcipinnis, respectively. The coefficient of correlations were weak, being 0.010, 0.166, 0.179 and 0.364 respectively for T. guineensis, O. nilotius, M. cephalus and L. falcipinnis.

Table 5: Summary of Length-weight and Length-Gut relationship parameters of Mugil cephalus, Liza falcipinnis, Oreochromis niloticus and Tilapia guineensis from the New Calabar River, Nigeria.

FISH SPECIES	LOG TRANSFORMED LENGTH	REGRESSION EQUATION	R^2
Tilapia guineensis	Transformed total length	W = 1.6161 L^1.1676	0.4326
	Transformed gut length	W = 1.7196 GL^0.6866	0.1044
Oreochromis niloticus	Transformed total length	W = 1.5553 L^1.2811	0.5436
	Transformed gut length	W = 1.6637 GL^1.2367	0.4079
Mugil cephalus	Transformed total length	W = 1.3649 L^1.5693	0.8642
	Transformed gut length	W = 2.0075 GL^0.397	0.4236
Liza falcipinus	Transformed total length	W = 1.2872 TL^1.914	0.6810
	Transformed gut length	W = 1.9123 GL^0.2867	0.6030

Fig 2: Length-Weight and length-gut Relationship of Tilapia guineensis of New Calabar River, Nigeria

Fig. 3: Length-weight and length-gut relationship of O. niloticus from the New Calabar River, Nigeria

Fig. 4: Length-weight and length-gut relationship of Mugil cephalus from New Calabar River, Nigeria

Fig. 5: Length-weight and length-gut relationship of Liza falcipinnis from New Calabar River, Nigeria

Morphometric ratios

The ratios of each morphometric character to TL or HL are shown in Table 6.

The ratios of DFL/HL, DFL/TL and PFL/HL were significantly different between the two tilapinne species (p < 0.05) while HL/TL, BdP/HL, PFL/HL, ED/HL and ED/HL were significantly different between the mugilids (P<0.05). These ratios could be species-specific. Conventionally, morphometric ratios can be used in species-specific identification. High rate of interspecific breeding among some species, for example, cichlids may influence the ratios and hinder application. However, Solomon et al. (2015) also found significant differences (p < 0.05) in the HL/SL ratio between wild and cultured Clarias gariepinus. This appears to be supported by Gonzalez et al. (2016) who obtained mean values for the HL/SL ratio of between 0.31 and 0.45 in Cichlasoma festae. This phenotypic divergence in morphometric ratio may possibly result from change in habitat and domestication. The value of the HL/SL ratio and other relations among the morphometric measurements are closely identical to the species. Perhaps, more individuals and comparison between populations is necessary in future study to validate this result

.

Table 6: Ratio of average measurements of some morphometric characters in relation to head length and total length

Species	N	ED		PFL		DFL		BdP		HL
		HL	TL	HL	TL	HL	TL	HL	TL	TL
T. guineensis	22	0.26^a	0.067^a	0.99^a	0.26^a	1.83^a	0.48^a	1.56^a	0.41^a	0.26^a
O. niloticus	22	0.27^a	0.074^a	1.41^b	0.30^a	1.57^b	0.43^b	1.37^a	0.38^a	0.28^a
M. cephalus	20	0.28^b	0.058^b	0.68^c	0.14^c	0.82^c	0.17^c	1.28^c	0.26^c	0.21^b
L falcipinnis	20	0.37^c	0.085^c	0.60^d	0.14^c	0.79^c	0.18^c	1.08^d	0.25^c	0.23^c

Values with different superscript(s) indicated in columns (between pairs of species, that is T. guineensis vs O. niloticus and M. cephalus vs L. falcipinnis) are significantly different at 5% level.

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Cite this Article: Nwafili, SA (2022). Morphometric Characterization of Four Commercially Important Fish Species of the New Calabar River, Rivers State, Nigeria. Greener Journal of Biological Sciences, 12(1): 01-10.