International Journal of Applied Research and Technology 215 Esxon Publishers International Journal of Applied Research and Technology ISSN 2277-0585 Publication details, including instructions for authors and subscription information: http://www.esxpublishers.com Shell Growth of Fresh Water Clam (Galatea paradoxa) in Ikebiri Creek, Bayelsa State, Nigeria Kingdom, T., Allison, M. E. and Gbenefadei, P. Niger Delta University, Wilberforce Island, Yenagoa, Bayelsa State Available online: November 10, 2012 To cite this article: Kingdom, T., Allison, M. E. and Gbenefadei, P. (2012). Shell Growth of Fresh Water Clam (Galatea paradoxa) in Ikebiri Creek, Bayelsa State, Nigeria. International Journal of Applied Research and Technology. 1(6): 215 – 219. PLEASE SCROLL DOWN FOR ARTICLE This article may be used for research, teaching and private study purposes. 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Niger Delta University, Wilberforce Island, Yenagoa, Bayelsa State (Received: 04 October 2012 / Accepted: 21 October 2012 / Published: 10 November 2012) Abstract Shell growth of Galatea paradoxa was studied in the Ikebiri Creek area of the Southern Ijaw Local Government Area of Bayelsa State. The aspects studied included the size structure, growth pattern and shell dimension - weight relationships. The shell length ranged from 6.01 to 8.75cm with a mean of 7.74±0.34cm. The shell width, height and volume had means of 4.05±0.26cm, 5.97±0.24cm and 68.54±0.50ml, respectively. The species had a mean live weight of 102.70±0.95g and a mean soft tissue weight of 23.87±0.26g. The soft tissue yield was about 24% of the live weight. The exponent ‘b’, varied from 0.302 (soft tissue weight – shell volume) to 1.439 (shell weight – shell height). The exponents were all lower than 3, indicating negative allometric function. All the shell variables showed weak correlation with live weight, soft tissue weight and shell weight (r2 values of 4 – 37 percents, P < 0.001) indicating that shell dimensions or volume are not good estimates for the biomass of G. paradoxa in the Ikebiri Creek. Keywords: Clam, Shell, Growth, Ikebiri Creek, Niger Delta. Corresponding author: E-mail: orotonbarapagha@hotmail.com ISSN 2277-0585 © 2012 Esxon Publishers. All rights reserved. International Journal of Applied Research and Technology 217 Introduction The Clam, Galatea paradoxa (Born, 1778), Egeria radiata (Larmack, 1804), Family Donacidae, is a filter – feeding bivalve mollusc that is restricted to the lower reaches of a few large rivers in West Africa such as the Volta (Ghana), Cross and Nun (Nigeria), and Sanaga (Cameroun) (Etim and Brey, 1994). King (2000) and Abowei and Hart (2008) reported the occurrence of this clam in the Nun River, a major river system in Bayelsa State. This clam has high nutritional value and constitutes an important protein source to the riparian human communities where it occurs. The soft tissue is consumed after frying, smoking, roasting, steaming or cooking. Studying bivalve’s growth and establishing allometric relationships are essential for generating useful information for managing resources and understanding changing environmental conditions and pollution (Palmer, 1990; Boulding and Hay, 1993). Often, growth is estimated by measuring shell dimensions or the volume of the animal (Rodhouse et al, 1984; Ross and Lima, 1994; Rueda and Urban, 1998; Deval, 2001), because they are simple non – destructive methods that can easily be completed in the field (Ross and Lima, 1994). Once the growth relationship is established, shell measurement is a sufficient surrogate to estimate biomass and total flesh production (Rodhouse et al, 1984; Ross and Lima, 1994; Thorarinsdottir and Johannesson, 1996; Deval, 2001). Clam fishery is an emerging fishery in Bayelsa State with little or no information (Sikoki and Otobotekere, 1999). Already, Richmond (1990) had observed that one of the main problems in the tropical region is the lack of information on the basic biology of bivalve species. This study was therefore carried out to determine the growth pattern of G. paradoxa in the Ikebiri Creek and to determine whether shell dimension (length, height, width) and shell volume can be used to monitor biomass production in population of G. paradoxa in the Ikebiri Creek. Materials and Methods The study was carried out in the Ikebiri Creek area of the Southern Ijaw Local Government Area of Bayelsa State. It is located in Longitude 60 0ʹ 32´´E and Latitude 40 44ʹ 42´´N. Samples of fresh water clam G. paradoxa were randomly collected at weekly intervals from Ikebiri Creek between April and June, 2010. A total of 420 live clams were collected from local fishermen (who dived in the creek to get the clams) and taken to the Fisheries Laboratory of the Niger Delta University, Wilberforce Island, Bayelsa State for measurement. The maximum dimension of the anterior – posterior axis was recorded as shell length (SL), maximum distance from hinge to ventral margin as shell height/breadth (SH) and maximum lateral axis as shell width/depth/thickness/degree of inflation (SWT) (i.e. maximum distance between outer edges of two halves). All measurements were made to the nearest 0.01cm using veneer callipers. Total body volume (SV) of live clam measurements (shell with soft tissue) was made to the nearest 1ml by water displacement (Quale and Newkirk, 1989; Gimin et al, 2004). Live weights (LW) were determined after drying the shell with towels. The soft tissue was removed and weighed individually (STW) after blotting. The soft tissue weight (STW) was subtracted from the Live weight (LW) to give the shell weight (SW). All weights were measured using Ohaus Scout Pro balance model SPU 402 to the nearest 0.01g. The relationships between shell dimensions (Length, height, width) and shell volume to LW, SW and STW were independently evaluated using log –transformation of the equation: Y = a Xb Where ‘Y’ is either Live weight, soft tissue weight (STW), or shell weight (SW) and ‘X’ is one of the dimension (length, height, width in centimetres) or volume (ml), ‘a’ is the intercept and ‘b’ is the slope. Routine regression analysis was completed using the SPSS version 16. The co – efficient of determination (r2) was used as an indicator of the quality of the linear regression. Results and Discussion The morphometric measurements of G. paradoxa are given in Table 1. The shell length ranged from 6.01 to 8.75cm with a mean of 7.41±0.34cm. The species had a mean live weight of 102.70±0.95g and a mean soft tissue weight of 23.87±0.26g. About 24% of the live weight of clam is made up of soft tissue (flesh) by weight. The parameters of shell dimension – weight relationship of G. paradoxa are presented as follows: LogLW = 9. 462SL1.184 (r = 0.58; r2 = 0.34; P < 0.001) 0.900 LogLW = 28.907SWT (r = 0.61; r2 = 0.37; P < 0.001) 1.378 LogLW = 8.630SH (r = 0.60; r2 = 0.35; P < 0.001) 0.430 LogLW = 16.444SV (r = 0.34; r2 = 0.12; P < 0.001) 1.163 LogSTW = 2.280SL (r = 0.52; r2 = 0.27; P < 0.001) 0.926 LogSTW = 6.442SWT (r = 0.57; r2 = 0.32; P < 0.001) 1.295 LogSTW = 2.312SH (r = 0.51; r2 = 0.25; P < 0.001) 0.302 LogSTW = 6.531SV (r = 0.22; r2 = 0.04; P < 0.001) 1.231 LogSW = 6.561SL (r = 0.49; r2 = 0.24; P < 0.001) 0.925 LogSW = 21.232SWT (r = 0.51; r2 = 0.26; P < 0.001) 1.439 LogSW = 5.888SH (r = 0.51; r2 = 0.26; P < 0.001) 0.467 LogSW = 10.799SV (r = 0.30; r2 = 0.09; P < 0.001) 2 (r = correlation of coefficient; r = coefficient of determination) International Journal of Applied Research and Technology 218 All the slopes of the regression lines were all significantly different from (3). The exponent ‘b’, varied from 0.302 (soft tissue weight – shell volume) to 1.439 (shell weight – shell height). The exponents were lower than 3, indicating negative allometric growth. All the shell variables showed week correlation with live weight, soft tissue weight and shell weight (r2 values of 4 – 37 percents, P < 0.001). The best predictor for live weight, soft tissue weight and shell weight was the shell width which accounted for 37%, 32% and 26% of the variation in the live weight, soft tissue weight and shell weight respectively. The mean shell length of G. paradoxa in this study was lower than Swan mussel, Anondota cygnea in Lake Cildir, Turkey (Bascinnar et al, 2008), but higher than that of G. paradoxa recorded in the Cross River (King, 1998). This shows that most of the clams landed from the Ikebiri Creek were dominated by adults because Moses (1990) had already recommended that in order to conserve this valuable resource and keep it at a level of sustained optimum yield in the Cross River system, there should be a regulation prohibiting the landing of young clams (< 6.0 cm shell length). By implication, juvenile clams were not landed in the clam fishery in Ikebiri Creek; whether this was deliberate will be determined in subsequent studies. However, the mean live weight in this study was higher than that of Swan mussel in Lake Cildir (Bascinar et al, 2008) and that of G. paradoxa in the Cross River (King, 1998). The difference in weight may be due to physiological conditions of the animals and variation in environmental parameters (Wilber and Owen, 1964). Soft tissue yield was close to the 24% reported for Swan mussel (Bascinar et al, 2008) in Lake Cildir, Turkey, but lower than the 37.7% observed for Unio stevenianus in Golmarmara (Cetinkaya, 1996). The exponents estimated in this study for all shell dimension – weight relationships fell short of the range of the values given by Wilber and Owen (1996) for most bivalves (2.4 – 4.5) and Park and Oh (2002) for bivalves from coastal waters of Korea. This indicates a negative allometric growth pattern (La Barbera, 1989), which was also reported for Green – lipped mussel Perna viridis from the coastal waters of Bangladesh (Khan et al, 2010). However, the ‘b’ values were closer to those estimated for live weight/volume, wet soft tissue weight/volume, dry soft tissue/volume and ash free dry weight/volume relationships of mangrove clam, Polymesoda erosa from Northern Australia (Gimin et al, 2004) and worm – like Teredo (Isham et al, 1951) in which a nearly linear relation (b = 1) was reported. The lack of strong correlations between shell dimensions and soft tissue for G. paradoxa is similar to the observation of Gimin et al,(2004) for P. erosa, but different from those reported in other bivalves, such as Mytilus edulis (Rodhouse et al, 1984), Dreissena polymorpha and G. burgensis (Ross and Lima, 1994), Artica islandica (Thorarinsdoltir and Johnannesson, 1996), Pinctada margaritifera and P. maxima (Yukihira et al, 1998) Chamelea galling (Deval, 2001), and Amiantis umbonella (Al – Khayat and Al – Mohannadi, 2006). Gimin et al (2004) had already reported that shell variables sometimes fail to estimate the flesh weight of an organism due to certain conditions. Factors such as the reproductive state of the animal (Rueda and Urban, 1998), population density (Seed 1968), and physical and biological variables of habitat (Thorarinsdittir and Johannesson, 1996) are known to affect the growth of bivalves and can change the allomentry between the shell and the flesh. Conclusion and Recommendations G. paradoxa exhibited negative allometric growth, and shell dimensions or volume were not good estimators for the biomass of G. paradoxa from the Ikebiri Creek. It is hereby recommended that more studies should to be carried out to cover other aspects such as feeding, reproductive biology as well as seasonal effects and the continued landing of adult clams should be encouraged so as to give room for the growth of the juveniles. References Abowei, J.F.N. and Hart, A.I. (2008): Artisanal fisheries characteristics of the fresh water reaches of Lower Nun River, Niger Delta, Nigeria. Journal of Applied Environmental Mangement. Vol. 12(1): 5 – 11. Al –Khayat, J.A. and Al – Mohannadi, M.S. (2006): Ecology and Biology of the Benthic Bivalve Amintis umbonella (Lamarck) in Khor Al Adaid, Qatar. Egyptian Journal of Aquatic Research Vol. 32 No. 1: 419 – 430 Bascinar, N.S., Duzgunes, E., Selim – Misir, D., Polat, H. and Zengin, B. 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(1998): Effect of body size on suspension feeding and energy budgets of the Pearl oysters Pinctada margaritifera and P. maxima. Mar. Biol. Prog. Ser. 170: 119 – 130. Table Table 1: Morphometric measurement of G. paradoxa in Ikebiri Creek, Niger Delta Parameter Minimum Maximum Mean ± Standard Error 6.01 8.75 7.41±0.03 Shell length (cm) 2.45 7.85 4.05±0.03 Shell width (cm) 58.19 188.36 102.70±0.95 Live weight (g) 5.01 6.85 5.97±0.02 Shell height (cm) 45 100 68.54±0.50 Shell volume (ml) 13.96 60.01 23.89±0.26 Soft tissue weight (g) 14.48 160.90 78.82±0.85 Shell weight (g) 12.49 80.56 23.62±0.26 Percent soft tissue (Yield %)