Length-Weight Relationship, Condition Factor and Length Frequency

Asian Journal of Advances in Agricultural Research

6(1): 1-8, 2018; Article no.AJAAR.39241 ISSN: 2456-8864

Length-weight Relationship, Condition Factor and Length Frequency Distribution of the Tongue Sole Cynoglossus senegalensis from Akpa Yafe River, Bakassi, Cross River State, Nigeria

Akanse, Nsikak Nse1 and Eyo, Victor Oscar2*

1Department of Fisheries and Aquatic Environmental Management Unit, University of Uyo, P.M.B. 1017, Uyo, Akwa Ibom State, Nigeria. 2Fisheries and Aquaculture Unit, Institute of Oceanography, University of Calabar, P.M.B. 1115, Calabar, Cross River State, Nigeria.

Authors’ contributions

This work was carried out in collaboration between both authors. Author ANN managed the analyses and literature searches of the study. Author EVO designed the study, performed the statistical analysis, wrote the protocol, and wrote the first draft of the manuscript. Both authors read and approved the final manuscript.

Article Information

DOI: 10.9734/AJAAR/2018/39241 Editor(s): (1) Wuyi Liu, Professor, Department of Science & Technology Research, Fuyang Normal College (West), Anhui Province, China. Reviewers: (1) Javier E. Contreras-Reyes, Instituto de Fomento Pesquero, Chile. (2) Abdullah Ekrem Kahraman, Istanbul University, Turkey. (3) Bryan Matthias, University of Minnesota, USA. Complete Peer review History: http://prh.sdiarticle3.com/review-history/23642

Received 29th December 2017 Accepted 5th March 2018 Original Research Article th Published 15 March 2018

ABSTRACT

The length-weight parameters, condition factor and length frequency distribution of the tongue sole, Cynoglossus senegalensis (Kaup, 1858) from Akpa Yafe River, Nigeria, were estimated. A total of 292 freshly caught samples were collected between November 2014 and October 2015 from the catches of the artisanal fisheries at Ikang beach, Bakassi L.G.A., Cross River State. Results showed a negative allometric growth indicating that the fish gets slimmer as it grows larger. A significant linear relationship is given by the equation: W =.0.0413TL2.3861 and Log W = 2.3861TL - 1.3841(r2 = 0.7700, P < 0.05, n = 292, d.f. = 290). Mean monthly condition factor of C. senegalensis was highest (0.419 ± 0.01) in May and lowest (0.277 ± 0.02) in November. The ______

*Corresponding author: Email: [email protected]; Akanse and Eyo; AJAAR, 6(1): 1-8, 2018; Article no.AJAAR.39241

length frequency distribution showed that the highest length frequency was in length class 57.1- 60.0 cm (47) and the lowest (1) in 33.1- 36.0 cm, 36.1- 39.0 cm, 39.1 – 42.0 cm, 81.1 – 84.0cm, and 87.1 – 90.0 cm length class. These important findings would be useful for fishery biologists and fishery managers in evaluating the population dynamics, stock assessment and sustainable management of C. senegalensis from Akpa Yafe river and other similar water bodies.

Keywords: Length-weight relationship; condition factor; length frequency distribution; tongue sole; Cynoglossus senegalensis; Akpa Yafe River.

1. INTRODUCTION one of the most valued and important food fish for the Akpa Yafe river inhabitants due to its Length-weight relationships and condition factor taste and meat quality. This species has a flat of fishes are important tools in fisheries science. body without a pelvic fin and both eyes on the Length-weight relationship (LWR) is an important left side of the body. According to Udo et al., [12], growth index used as a sustainable management a major feature of this species is the presence of tool by fishery biologists. Length-weight a long hook on the snout over hanging relationship (LWR) is useful in fisheries science the mouth. C. senegalensis is a tropical in the following areas; estimation of average species found within the geographical range weight of fish at a given length group [1], growth (22°N 18°S and 18°W 14°E) and also in rate estimation [2], estimation of length and age subtropical oceans within the depth of 10-110 m structures [3], conversion of growth in-length [13-15]. In Akpa Yafe River, information of some equations to growth-in-weight in stock aspect of the biology of C. senegalensis which assessment models [4], estimation of biomass could be useful in the sustainable management from length frequency distributions [5]. of this species has not been documented. Information on length-weight relationship (LWR) Therefore, the aim of this study is to determine are also used in comparing morphological the length-weight relationship, condition factor aspects and life history of fish populations and length frequency distribution of inhabiting different water bodies [6]. Condition C. senegalensis from Akpa Yafe, Baksaai, factor is another important tool that is vastly used Nigeria. in fisheries science by fish biologists, fishery managers and aquaculturists. The relevance of 2. MATERIALS AND METHODS condition factor in fisheries science is widely related to health status, growth and feeding 2.1 Description of Study Area intensity in various fish species [7]. According to Contreras-Reyes [8], interpretation of condition Akpa Yafe River which is a tributary of Cross factor in fish is based on the hypothesis that River lies approximately between latitude heavier fish of a given length are in better 4.683˚N and longitude 8.517˚E. The river forms a condition. Variations in condition factor values is natural boundary between Cameroon and an indication of the degree of food source Nigeria by the Eastern flanks of Bakassi and availability, state of sexual maturity and Akpabuyo Local Government Areas of Cross suitability of a specific water body for River State, Nigeria. Its basin covers an area of healthy growth of fish [9]. Condition factor is 54,000 km3 with 40,000 km3 in Southern Nigeria useful in understanding the life cycle, and 14,000 km3 in the Cameroon. Akpa Yafe management of fish species and maintaining the River takes its rise from the Atlantic Ocean. The equilibrium in the ecosystem [10]. Length major occupation of the river inhabitant include; frequency of fishes are also very useful in fishing, farming, petty trading, boat making, palm different aspects of fisheries science. It provides wine tapping etc. The river is rich in both fin deep knowledge on the structure of natural fish fishes and shell fishes of economic value population size [2]. In gear selectivity evaluation, including, Silver catfish (Chrysichthys length frequency distribution is the first step used nigrodigitatus), African Catfish (Clarias in evaluating different gears used in the same gariepinus, Heterobranchus longifilis), Ecomog water [11]. The tonguesole fish (Cynoglossus (Heterotis niloticus), the grey mullet (Mugil senegalensis) commonly known as “Ukpek” by cephalus), the blue crab (Callinectes amnicola) the Efik and Ibibio tribes in Nigeria belongs to etc. the Cynoglossidae family. C. senegalensis is

2 Akanse and Eyo; AJAAR, 6(1): 1-8, 2018; Article no.AJAAR.39241

2.2 Collection and Identification of Departure from isometry (i.e. b = 3) for the C. senegalensis from Akpa Yafe exponents (b) of the length-weight relationship River, Nigeria was tested using a t-statistic function given in according to Pauly [20]. A total of 292 freshly caught samples of C. senegalensis were collected between t = s.d. (x) . / b - 3/ . November 2014 and October 2015 from the s.d. (y) catches of the artisanal fisheries at Ikang beach, √ − 2 Bakassi L.G.A., which is a major landing point of Where s.d. (x) is the√1 standard− deviation of the the artisanal fisheries of the Akpa Yafe River. Log L values, and s.d. (y) is the standard The fishers caught the experimental fish with a deviation of Log W values, n is the number of wide range of fishing gear such as gill net, cast samples used in the computation, b is the net, hook and line, long line and traps. Samples estimated exponent of the LWR and r2 is the collected were immediately transported in ice- correlation coefficient of the relationship. If t packed containers to the Fisheries and calculated is greater than the tabled value of t for Aquaculture laboratory, Institute of the degree of freedom, n – 2, it implies that the Oceanography, University of Calabar, for further value of b is different from 3 [21]. analysis. Identification of C. senegalensis was based on photo cards and identification key 2.5 Condition Factor (CF) of given by Fischer [16] and Schneider [17]. C. senegalensis from Akpa Yafe River, Nigeria 2.3 Measurements of Biometric Parameters of C. senegalensis from The Fulton’s condition factor (CF) was calculated Akpa Yafe River, Nigeria as follows: 3

The following biometric parameters were where CF is the= condition100 / factor, W is the total measured for each specimen: Total length (TL, body weight (TW, g), L is the total length (TL, cm) and Total weight (TW, g). Total length was cm) and 3 is a constant. measured to the nearest 0.1 cm from the tip of the mouth to the end of the caudal peduncle. 2.6 Length - Frequency Distribution of Total weight was taken to the nearest 0.1 g using Metlar-2000D electronic weighing balance [18] C. senegalensis from Akpa Yafe and [19]. River, Nigeria

2.4 Length-Weight Relationship of The data obtained for the length measurement of C. senegalensis from Akpa Yafe 292 samples of C. senegalensis from Akpa Yafe river were grouped into 20 length classes of River, Nigeria 30.1- 33.0 cm, 33.1- 36.0 cm, 36.1- 39.0 cm, 39.1 – 42.0 cm, 42.1 – 45.0 cm, 45.1 – 48.0 cm, The length- weight relationship of 48.1 -51.0 cm, 51.1 – 54.0 cm, 54.1 – 57.0 cm, C. senegalensis from Akpa Yafe River was 57.1 – 60.0 cm, 60.1 – 63.0 cm, 63.1 – 66.0 cm, estimated using the equation: given by Froese 66.1 – 69.0 cm, 69.1 – 72.0 cm, 72.1 – 75.0 cm, [20] as follows: 75.1 – 78.0 cm, 78.1 – 81.0 cm, 81.1 – 84.0cm, W = aLb 84.1 – 87.0 cm and 87.1 – 90.0 cm length classes for subsequent analysis. Where W is the total weight (TW, g), a is the intercept, L is the total length (TL, cm) and b is 3. RESULTS the slope. The parameters a (intercept) and b (slope) were estimated by linear regression 3.1 Length - Weight Relationship of based on logarithms using the linear regression C. senegalensis from Akpa Yafe routine of Microsoft Office Excel in PC windows River, Nigeria (2007) as follows: Length-weight relationship of C. senegalensis Log (W) = Log (a) + b Log (L) from Akpa Yafe river (Fig. 1) was estimated for 292 samples. The normal plot of total weight where W = total weight (TW, g) and L = total (TW, g) against total length (TL, cm) for pooled length (TL,cm)

3 Akanse and Eyo; AJAAR, 6(1): 1-8, 2018; Article no.AJAAR.39241 sex of C. senegalensis is shown in Fig. 1. A 75.0 cm (18), 75.1 – 78.0 cm (5), 78.1 – 81.0 cm significant linear relationship was established, (6), 81.1 – 84.0 cm (1), 84.1 – 87.0 cm (2) and given by the equation: W =.0.0413TL2.3861 (r2 = 87.1 – 90.0 cm (1). 0.7700, t-Test, P < 0.05, d.f. = 290), and the length-weight parameters was estimated as: a = Table 1. Mean monthly condition factor of 0.0413 and b = 2.3961. t-statistic showed that C. senegalensis from Akpa Yafe River, the value of b = 2.3961 is significantly different Nigeria from 3 and hence, the weight growth for C. senegalensis departs significantly from isometric Months No. of fish Mean ± SE condition of b=3. collected January 20 0.384 ± 0.02 3.2 Mean Monthly Condition Factor of February 22 0.311 ± 0.01 C. senegalensis from Akpa Yafe March 6 0.315 ± 0.04 River, Nigeria April 8 0.339± 0.03 Results obtained for mean monthly condition May 32 0.419 ± 0.01 factor of C. senegalensis from Akpa Yafe river June 32 0.403 ± 0.02 (Table 1) showed that the highest value (0.419 ± July 32 0.311 ± 0.02 0.01) was obtained in May, followed by 0.403 ± August 32 0.322 ± 0.01 0.02 obtained in June and least (0.277 ± 0.02) in September 32 0.358 ±0.02 November. Fig. 2 shows the monthly variation in October 35 0.352± 0.01 condition factor for C. senegalensis from Akpa November 13 0.277 ± 0.02 Yafe river. December 28 0.368 ± 0.01 Total 292 3.3 Length – frequency Distribution of C. senegalensis from Akpa Yafe 4. DISCUSSION River, Nigeria Data obtained from length-weight relationship are The length frequency distribution of C. very reliable in evaluating growth patterns and senegalensis from Akpa Yafe River (Fig. 3) relative well-being of fishes. According to Nash et showed that 30.1- 33.0 cm length class had a al. [7], values of regression coefficient from frequency of 2, 33.1- 36.0 cm (1), 36.1- 39.0 cm length-weight relationship (LWR) shows the (1), 39.1 – 42.0 cm (1), 42.1 – 45.0 cm (10), 45.1 growth pattern (isometric or allometric growth – 48.0 cm (22), 48.1 -51.0 cm (24), 51.1 – 54.0 pattern) in fish which is observed to vary cm (18), 54.1 – 57.0 cm (20), 57.1 – 60.0 cm between stocks of same species. The exponent (49), 60.1 – 63.0 cm (39), 63.1 – 66.0 cm (33), (b = 2.3961) of the length-weight relationship of 66.1 – 69.0 cm (19), 69.1 – 72.0 cm (22), 72.1 – C. senegalensis were significantly different

2500 TW = 0.0413TL2.3861 2000 R² = 0.77 n = 292 1500

1000

Total Weight Weight (TW,g) Total 500

0 0 20 40 60 80 100

Total Length (TL, cm)

Fig. 1. Total Length (TL, cm) - Weight Relationship in Pooled sex of C. senegalensis from Akpa Yafe River, Nigeria (n=292)

4 Akanse and Eyo; AJAAR, 6(1): 1-8, 2018; Article no.AJAAR.39241

0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 Mean Condition Condition Factor Mean 0.05 0.00 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months

Fig. 2. Monthly variation in condition factor of C. senegalensis from Akpa Yafe River, Nigeria

30 Frequency 20

0 30.1 - 33.0 cm 33.1 - 36.0 cm 36.1 - 39.0 cm 39.1 - 42.0 cm 42.1 - 45.0 cm 45.1 -48.0 cm 48.1 - 51.0 cm 51.1 - 54.0 cm 54.1 - 57.0 cm 57.1 - 60.0 cm 60.1 - 63.0 cm 63.1 - 66.0 cm 66.1 - 69.0 cm 69.1 - 72.0 cm 72.1 - 75.0 cm 75.1 - 78.0 cm 78.1 - 81.0 cm 81.1 - 84.0 cm 84.1 - 87.0 cm 87.1 - 90.0 cm

Length Class (cm)

Fig. 3. Length–frequency distribution of C. senegalensis from Akpa Yafe River, Nigeria

5 Akanse and Eyo; AJAAR, 6(1): 1-8, 2018; Article no.AJAAR.39241 from 3, indicating that weight growth of and 1.85 ± 0.02 reported by Ndome and C. senegalensis from Akpa Yafe river is Eteng [27] for C. browni and C. senegalensis allometric (negative). This species tend to from the East Coast of Niger Delta, Nigeria. become thinner with increasing length. Enin [22] Differences in values obtained for condition explained that results from such analyses where factor in this study compared to other studies for b-values indicate allometric growth must be used the same species may be attributed to spawning with caution bearing in mind that the assumption activities of C. senegalensis [24]. Also, Youson et of isometry in the models is violated. In most al. [29] suggested that fish condition can be aquatic organisms like fish, deviation from influenced by several extrinsic factors such as isometry is commonly observed indicating that photoperiods and changes in temperature. the fish change shape as they grow [23]. Abowei Length-frequency distribution are useful et al. [24] reported a positive allmetric growth analytical tools for managing and monitoring (b=3.508) for C. senegalensis from Nkoro River fisheries of any size. It is useful and important in in Niger Delta, Nigeria. Abowei and Hart [25] also the determination of growth and age in fish reported a positive allometric growth (b=3.5001) species [11]. The length composition of a fish for C. senegalensis from the lower Nun river, population exhibits modes among species with Niger Delta Nigeria. Sanyang et al. [26] obtained short spawning season and a uniform and rapid an isometric growth (b= 3.0000) for growth, from which the modal length of the first C. senegalensis from the Gambia. Ndome and few age groups can be easily determined [30]. In Eteng [27] gave more reasons for variation in this study, the highest length frequency of C. growth pattern to include season, gonad senegalensis was obtained in length class 57.1- maturity, habitat, diet, sex, health, stomach 60.0 cm (47), followed by 60.1- 63.0 cm length fullness, preservation methods and annual class (37) while the least frequency (1) was differences in the environmental conditions. obtained in 33.1- 36.0 cm, 36.1- 39.0 cm, 39.1 – However, findings of this study for b-value 42.0 cm, 81.1 – 84.0cm, and 87.1 – 90.0 cm (2.3961) which indicates a negative allometry length class. Length frequency distribution is agrees with that of Ndome and Eteng [27] who crucial in age and growth determination in fish reported b-values of 1.8800 and 2.0000 for C. [11]. According to Eyo and Awom [31], length browni and C. senegalensis from the East Coast composition of a fish population exhibits modes of Niger Delta, Nigeria. According to Koutrakis among species with a fast and uniform growth. and Tsikliras [28], expected values of b for fish To have a good mode characterization in length range between 2 and 4 and b-value obtained in frequency analysis, the appropriate bin-size this study (2.3960) was within this range. should be selected. Bin-size interval of 2 cm and Similarly, findings of length-weight relationships 5 cm is recommended by Anderson and in some marine flatfish species such as Citharus Neumann [32] for fish measuring up to 60 cm linguatula have also showed a negative allometry and 150 cm in length. According to Erzini [33], growth pattern [5]. This indicates that the length length bins between 1-2 cm generally gives a of C. senegalensis increases with a better mode characterization in length corresponding increase in weight. In fisheries distributions. In this study, bin size of 2.9 cm science, condition factor commonly used in helped in characterizing the mode of the length ascertaining the relative well-being of fish distribution of C. senegalensis in Akpa Yafe species. Condition factor is also used to evaluate River. Length frequency distribution of the health status of water bodies. Condition C. senegalensis in this study showed a factor could be influenced by several factors multimodal size distribution with length class such as sex, food availability, age and 57.1 – 60.0 cm exhibiting the maximum peak, environmental conditions. Low values of while smaller peaks were obtained in 48.1 – 51 condition factor in fish may be due to poor cm and 69.1-72 cm length class. environmental conditions, reduced availability of food and prey items [25]. The highest value of 5. CONCLUSION condition factor (0.419 ± 0.01) in this study was obtained in May, followed by 0.403 ± 0.02 Findings of this study has provided basic and obtained in June and least (0.277 ± 0.02) in crucial information on length-weight relationship, November. This findings is within the range of condition factor and length frequency distribution 0.28 (June) and 0.36 (October) reported by Udo of C. senegalensis from Akpa Yafe river, Nigeria. et al. [12] for the same species from the Cross These important findings would be useful for River Estuary. Values of condition factor fishery biologists and fishery managers in obtained in this study is lower than 1.52 ± 0.06 evaluating the population dynamics, stock

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