Interrelationship,between,some,morphometric,parameters,and,bodyweight,of,tank-based,cultured,African,catfish,(Clarias,gariepinus,Burchell,,1822)

Ikenn Onyekwelu, Chinenye Chukwuemek Anydike,＊, Nelson Ike Ossi,Oji Achuk Nwoke, Emek Leonrd Ndulue

aDepartment of Agricultural and Bioresources Engineering, University of Nigeria, Nsukka, 410001, Enugu State, Nigeria

bDepartment of Zoology and Environmental Biology, University of Nigeria, Nsukka, 410001, Enugu State, Nigeria

ABSTRACT

Morphometrics and fish bodyweight studies have shown great importance in estimation of productivity and stock assessment for some fish species. Herein, the aim of this study was to identify the morphometric parameter(s)that has most direct correlation with bodyweight of African catfish (Clarias gariepinus). The experimental layouts were four groups of experimental units, each group was replicated twice. Morphometric parameters considered in this study were total length, standard length, head length, head width and snout length. Data collected were processed and subjected to analysis of variance (ANOVA) and correlation analyses at 5% significant level. Results revealed significantly high correlations between bodyweight and morphometric parameters, with values ranging from 0.834 to 0.977 (upper and lower limits for total and snout lengths respectively). The results further revealed that relationship between bodyweight and morphometric parameters followed third-degree polynomial, with R2 ranging from 0.700 to 0.969 (upper and lower limits for total and snout lengths respectively). Significant high correlations (>0.85) exist between morphometric parameters selected for this study. In conclusion, in sampling programs of African catfish where the aim is to select fishes with high bodyweights, emphasis should be given to fishes with highest total length.

ARTICLEINFO

Keywords:

Clarias gariepinus

Bodyweight

Morphometrics

Total length

Parameters

Clarias gariepinus, Burchell, 1822 (African catfish) has become an important fish species in Nigeria aquaculture production. In recent times, it has received extensive culture throughout Nigeria, providing employment for the rural and urban populations. African catfish belongs to Clariidae family and are air breathing fishes, naturally occurring in freshwater bodies in Africa and South-Eastern Asia where they make up a significant component of catches in rivers and lakes (Fagbuaro et al.,2015). The Clariid catfishes are of great importance as food and vital for aquaculture sustainability (Vanden Bossche & Bernacsek, 1990; Fagbuaro et al., 2015). Fagbuaro et al. (2015) reported that catfish especially Clarias gariepinus (Burchell, 1822) has suitable attributes such as:ability to withstand handling stress, disease resistance, high growth rate,yield potential, fecundity, and palatability. It is one of the most readily acceptable and palatable species of catfish in Nigeria. This is because they grow highly to large sizes and with great returns on investment to farmers (Fagbuaro et al., 2015).

Assessment of abundance of Clarias gariepinus, using morphometric analysis is important to ensure the species are not endangered (Vanden Bossche & Bernacsek, 1990; Fagbuaro et al., 2015; Iswanto et al., 2015).Morphometric analyses are important tools used to differentiate closely related species of organisms having huge similarity indices of various parameters or characters (Fagbuaro et al., 2015; Naeem & Salam, 2005).Assessment of these parameters are essential in fish studies, particularly to understand the taxonomy and differences within and among stock population. While the shapes and structures are unique to each fish species, the variations between groups of same species can be related to habitat location and genetic impurity among the stocks (Carpenter et al.,1996; Fagbuaro et al., 2015; Iswanto et al., 2015). According to Iswanto et al. (2015), Dumbo strain catfish introduced to Indonesia were phenotypically modified following improper brood-stock management practiced by fish farmers, consequently leading to changes in morphometry and genetic deterioration. Austin et al. (1999) reported that morphometric characteristics of aquatic organisms are phenotypically plastic and might be influenced seasonally by the physical environmental factors during spawning and early juvenile stages of their lives. Furthermore, morphometric assessment also gives the identification of differences in fish population and can be used effectively in stock classification and assessment of congeneric species (Carpenter et al.,1996; Gurkan & Innal, 2018; Tzeng, 2004; Buj et al., 2008). Analysis of correlations between bodyweights and morphometric parameters for some fish species has been the subject of several studies. Numerous studies have focused on the weight-length relationship for selected fish species and have reported that bodyweight correlates with total length,providing means for assessment of these species (Diodatti et al., 2008;Freato et al., 2005; Gurkan & Innal, 2018; Lawson et al., 2013).

Based on the above literature reviews, morphometric investigations help to reveal interrelations between various fish body parameters such as standard length and weight and other important functional parameters of growth. (de Souza et al., 1999; Reis Neto et al., 2012)reported that fish processing industries place less emphasis on the carcass characteristics, except for its quality. Consequently, business decisions place more emphasis on the fish bodyweight and morphometric features which readily appeal to farmers based on return on investment. This emphasizes production performance and profitability of a fish farm based on visible morphometric features at the time of assessment and production (de Souza et al., 1999; Reis Neto et al., 2012). Although,morphometric parameters of African catfish and other fish species have been studied in Nigeria (Abanikannda et al., 2019; Fagbuaro et al., 2015;Lawson et al., 2013; Okoye et al., 2018; Ola-Oladimeji et al., 2016;Owodeinde, 2012; Ugwumba, 1994). These studies have either focused on total length-weight relationship and meristic features of Clarias gariepinus or other fish species harvested from rivers and lakes. There are limited studies on comparing the bodyweight with multiple morphometric parameters of African catfish cultured under static condition, at a time when tank-based production system is increasing in Nigeria(Akinwole & Akinnuoye, 2012; Akinwole & Faturoti, 2007). Thus, this study fills the knowledge gap for this method of production in Nigeria.Therefore, the aim of this short communication is to determine which of the following morphometric parameters (total length, standard length,head length, head width and snout length) is most directly associated with bodyweight. Specific objectives are to identify relationship trends between bodyweight and morphometric parameters and to assess possible differences between experimental groups of African catfish fingerlings (C. gariepinus) cultured under static condition.

2.1.Study area and experimental procedure

The present morphometric study was carried out at Nsukka (UNN)zoological and botanical garden of the University of Nigeria, Enugu State, Nigeria. The study area is located on latitude 6.8661N and longitude 7.4113E (Fig. 1). One hundred (100) African catfish (Clarias gariepinus)fingerlings hatched from the same parent stock were procured from UNN-West Africa Agricultural Productivity Programme fish seed centre of the University of Nigeria. Fingerlings were stabilized,identified and sorted accordingly as recommended by (Adekoya, 1997;Ugwumba, 1994) in order to eliminate parasite infection and cannibalism. Four (4) plastic tanks, each with dimension 50 cm ×25 cm were used for stocking of the fingerlings. The experimental tanks were laid out in groups labeled A, B, C and D (Table 1), each group was replicated twice to checkmate morphometric variations among groups. Stocking of the fingerlings were done at nine (9)fishes per 50 cm ×25 cm following standard stocking procedures (Micha, 1975; Hecht et al., 1988).

Table 1Group label and representation.

Fig. 1.Location of study area (A) inset map of Enugu state (B). Location of Enugu state in Nigeria (C) is shown in the upper right.German coppens feeds were fed the fingerlings twice daily at 5% body weight, following (Owodeinde, 2012; Ugwumba, 1994).

2.2.Morphometric parameters and bodyweight measurements

Morphometric characterization of selected morphometric parameters and bodyweight measurements were conducted on life specimen of African catfish fingerlings. These characterizations were carried out using biometric methods as presented by (Agnese et al.,1997; Rognon et al., 1998; Teugels, 1998; Teugels et al., 1998; 1998;Turan et al., 2005; Hanssens, 2009). Selected parameters (total length(TL), standard length (SL), head length (HL), head width (HW) and snout length (SNL)) were measured point to point (Fig. 2) while bodyweights were measured using digital weighing scale (OHAUS,Switzerland) with 0.01g precision. Ictiometer (Beltec SRL, Peru) with 0.1 cm precision was used to measure total and standard lengths while other morphometric measurements were taken with a millimeter (mm)graded caliper (Mitutoyo, Japan) following (Reis Neto et al., 2012).Measurements were done for a period of six weeks.

Fig. 2.Location of measurements on C. gariepinus. Adopted from (Teugels, 1986). Note: only parameters required for this study were defined, which are TL =SL +tail fin length, SL=Standard length, HL=Head length, HW=Head width, SNL=Snout length.

2.3.Data analysis

Morphometric and bodyweight measurements were subjected to one-way ANOVA at 5% significance level using SPSS statistical package(IBM SPSS Statistics; version 18.0). Simple regression model was used to approximate relationships between bodyweights and morphometric parameters. For morphometric and bodyweight measurements, correlation analyses were performed using Pearson Product-Moment equation (equation (1)). Correlation analysis describes the strength and weakness of relationship between variables. The correlation coefficient(r)take values from −1 to+1.The sign indicates whether there’s a positive correlation (i.e. as one variable is increasing, so does the other),or a negative correlation (i.e. as one variable is increasing, the other one is decreasing). During the analysis, bodyweight of the fingerlings obtained were considered as dependent variables and the morphometric parameters as independent variables.

Note: Ris the correlation coefficient between the two variables, “x”signifies the independent variables (TL, SL, HL, HW & SNL), “y” signifies the dependent variable (bodyweight), “n” is number of observations.

3.1.Mean morphometric results

The obtained mean morphometric and bodyweight results(±standard deviation) for different groups are shown in Table 2 below.

The mean morphometric values presented in Table 2 above revealed that means for different group vary in values. This shows that sorting of fingerlings were done properly which minimized the effect of cannibalism within the experimental groups for the duration of study.

3.2.Analysis of variance (ANOVA)

Analysis of variance was performed (Table 3) to analyze the differences within and between groups.

Table 2Mean morphometric results of different groups for six weeks trials.

Table 3Analysis of variance of bodyweight and morphometric parameters within and between groups.

Results in Table 3 above revealed significant differences in bodyweight and morphometric parameters between groups, suggesting differences among the stock population. This agrees with fish sorting procedure which local fish farmers practice in order to avoid cannibalism. No significant difference (Table 3) was observed for parameters within each group, suggesting that stocks of nearly the same morphometry exist in each group.

3.3.Correlation and trend relationships

Table 4 below shows Pearson correlation coefficients for bodyweight and morphometric parameters.

The correlation coefficients were observed at

>

0.80 for all representative morphometric parameters (Table 4) against bodyweight following the order TL

>

SL

>

HW

>

HL

>

SNL. The result also showed that interrelationships exist between morphometric parameters as correlation coefficients were all positive and above 0.85 (Table 4).

Relationship between bodyweight and morphometric parameters were fitted with third degree polynomial as shown in Fig. 3(A-E) below.

It was noted that Rvalues from the trends (Fig. 3A–E) were above 0.70.

R

values of bodyweight against morphometric parameters increase in the order TL

>

SL

>

HW

>

HL

>

SNL. This entails that over 70% of changes in the bodyweight were predicted by the selected morphometric parameters selected for this study.

3.4.Discussion

The present study showed that mean morphometric parameters and bodyweights (Table 2) offish specimens varied from 5.35 cm TL (1.75 g BW) to 8.00 cm TL (4.00 g BW), 4.75 cm SL to 7.10 cm SL, 1.05 cm HL to 1.50 cm HL, 0.85 cm HW to 1.25 cm HW and 0.30 cm SNL to 0.45 cm SNL (C and A respectively). Fish assembly and experimental groups for this study were mainly to understand differences within and among groups. No significant difference was observed within groups (Table 3)of experiment units considered in this study. (Ugwumba, 1994; Adekoya et al.

,

1997) reported that fish farmers in Nigeria continue to suffer losses even at 5fishes/mstocking density particularly due to differential growth in fish population, which often result to cannibalism. In view of this, our results suggest that effective sorting (group separation)procedure was employed in this study. Although, our results may not represent an ideal scenario offish sorting assessment as this was not the main aim of the present study. In furtherance, significant difference of morphometric parameters and bodyweights (Table 3) exist between groups, suggesting size differences among fish species despite coming from the same parent stock. This result agreed with (Iswanto et al., 2015;Nurhidayat et al.

,

2017), arguing that size differences of the same fish species could be as a result of improper management of brood-stocks by farmers.It was hypothesized in the present study that working relationships exist between selected morphometric parameters and bodyweight of African catfish (

Clarias gariepinus

, Burchell, 1822). This relationship was measured following Pearson correlation coefficient (

r

) (Table 4) and coefficient of determination (

R

) (Fig. 3A–E) analyses. Result revealed highly significant positive correlations between morphometric parameters (TL, SL, HL, HW, & SNL) and bodyweight. Correlation coefficients(

r

) (Table 4) varied between 0.834 and 0.977 (upper and lower limits for TL and SNL respectively). All trend relationships between morphometric parameters and bodyweight followed third degree polynomial(Fig. 3A–E), with Rvalues ranging from 0.700 to 0.969 (upper and lower limits for TL and SNL respectively). This result therefore imply that TL has the most direct relationship with bodyweight of African catfish (

Clarias gariepinus

, Burchell, 1822), while SNL has the least correlation. An indication that increase in morphometric parameters in the order TL

>

SL

>

HW

>

HL

>

SNL will result to bodyweight increase of African catfish (

Clarias gariepinus

, Burchell, 1822). Lawson et al. (2013),reported similar range of Rvalues (0.67–0.99) in their length-weight relationship study of eleven fish species harvested from Ogudu Creek,Nigeria. Although, our result may not represent the totality of correlations that exist between bodyweight and all morphometric parameters of African catfish (

Clarias gariepinus

, Burchell, 1822). However, the present results portrayed the relevance of bodyweight estimation of African catfish following morphometric assessment. Similar results were observed by (Van Sang et al., 2009; Reis Neto et al., 2012), explaining that morphometric studies were effective in the estimation of body yield and weight of

Pangasianodon hypophthalmus.

Albeit, Reis Neto et al.(2012) reported that body height (BH) of round fish has the highest correlation coefficient of 0.83 with bodyweight. Also, Barbosa et al.(2011) explained that standard length (SL) was most correlated with liveweight of tilapia. More so, significant high positive correlations(Table 4)

>

0.85 were observed between morphometric parameters (TL,SL, HL, HW & SNL) selected for this study. It is also important to note that other factors or parameters which were not discussed in this study may affect the bodyweight of

C. gariepinus

species.

Fig. 3.(A–E): Trend relationships between bodyweight and morphometric parameters. Notes: “y” represents the bodyweight, “x” represent the selected morphometric parameter(s) (TL, SL, HL, HW, SNL).

Table 4Pearson correlation table for bodyweight and morphometric parameters.

Studies on fish morphometry as reported by Reis Neto et al. (2012)described morphometric assessment as an end to profit and business decision making in fish farming and processing industries. Buj et al.(2008), Tzeng (2004) also recommended morphometric assessment as a tool for identifying differences in fish population. Based on these reports and our findings, one could draw conclusion that morphometric assessment is a viable tool in fish stock assessment of congeneric species.

Morphometric parameters are important for characterizing fish species in order to maintain genetic purity and assess growth performance within fish population. The results obtained in this study suggest that C. gariepinus bodyweight is affected by morphometric parameters and this was evident in the high Rvalues and correlation coefficients obtained. In addition, it is important to note that bodyweight of C. gariepinus increases with increasing morphometric parameters in the order; TL >SL >HW >HL >SNL as inferred from our study. Similarities in bodyweight and morphometric parameters within groups were observed in this study which is not the same between groups. To remark,in fish sampling programs of C. gariepinus where the aim is to select fishes with high bodyweight, those with high total length can be selected, as the relationship between the total length and body weight can be used as the basis for interconversion, and understanding to a larger extent in ideal sorting, thereby avoiding cannibalism which fraught most African catfish farms in Nigeria, and improve production.

CRediT authorship contribution statement

Ikenna Onyekwelu: Methodology, Data curation, Writing - original draft. Chinenye Chukwuemeka Anyadike: Conceptualization, Supervision, Writing - review & editing. Nelson Ike Ossai: Supervision,Writing - review & editing. Oji Achuka Nwoke: Software, Writing -review & editing. Emeka Leonard Ndulue: Writing - review & editing.

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