Age and Growth of Valamugil seheli from Sudanese Red Sea Coast

Article International Journal of Modern Plant & Animal Sciences, 2014, 2(1): 12-25 International Journal of Modern Plant & Animal Sciences Journal homepage: www.modernscientificpress.com/journals/ijplant.aspx ISSN: 2327-3364 Florida, USA Age and Growth of Valamugil seheli from Sudanese Red Sea Coast Motasim Ali Mokhtar Omer 1, *, Osman Mohammed Farah 2, Sayed Mohammed Ali 3 1 Ministry of Animal Resources and Fisheries, Fisheries Research Center, Red Sea Fisheries Research Station, Port Sudan, Sudan 2 Faculty of Marine Sciences and Fisheries, Red Sea University, Port Sudan, Sudan 3 Faculty of Science, University of Al-Neelain, Khartoum, Sudan * Author to whom correspondence should be addressed; E-Mail: motas122@yahoo.com. Article history: Received 2 January 2014, Received in revised form 3 February 2014, Accepted 6 February 2014, Published 12 February 2014. Abstract: The age and growth of the mullet fish Valamugil seheli (local name Arabi) of the family Mugilidae were estimated from the commercial catches landed at Port Sudan Fish Market in Sudanese Red Sea Coast during February 2010 to January 2011, using scales, operculum and length frequency distribution, and four age groups (+1, +2, +3 and +4 years) were found. The mean ages of the three methods were recorded. The parameters K, L and t0 of von Bertalanffy growth equation were estimated. Von Bertalanffy growth equations relating to both length and weight were established. Referring to length-weight relationship, growth followed isometric pattern. Keywords: mullet fish; Valamugil seheli; age estimation; length frequency distribution. 1. Introduction According to the Marine Fisheries Administration records Valamugil seheli constitutes high percent of the total fish landings and is available all the year round. It is the best local marine fish for preparing Fasseikh (wet-salted fishes) because of its good taste and texture (Faragalla, 2009). Methods of assessing age and growth rates are very closely related and are usually conducted

13 together. Growth is commonly considered to be a gradual increase in size or mass with time under specific environmental conditions. Food availability and temperature are the main factors that affect growth patterns (Brown, 1957) besides photoperiod and fish behavior like migration (Weatherly, 1972). There are two means of aging: (1) The direct method which depends on reading annual rings in some skeletal structures, and (2) The indirect method which represents length frequency distribution. The study of growth is basically the determination of the body size as a function of age. Therefore all stock assessment methods work essentially with age composition data. In temperate waters such data can usually be obtained through counting year rings and hard parts such as scales and operculum. These rings are formed due to strong fluctuations in environmental conditions from summer to winter and vice versa. In tropical areas such drastic changes do not occur and it is therefore very difficult, if not impossible to use this kind of seasonal rings for age determination (Ahmed, 1989). Von Bertalanffy growth model of body length as a function of age has become one of the cornerstones in fishery biology because it is used as a sub-model in more complex models describing the dynamics in fish populations. The mathematical formula of the model (Bertalanffy, 1934) is as follow: Lt = L {1- exp[-k(t-t )]} 2. Materials and Methods 2.1. Age Estimation Total length was measured to the nearest mm and total weight to the nearest 0.1 g. Aging was done using monthly random samples ranging from 25-30 Valamugil seheli fishes taken from Port Sudan Fish Market during February 2010 to January 2011. Three methods were used. 2.1.1. Age estimation from scales Scales were taken from the pectoral fin area of each fish, cleaned and the growth rings were counted under the lowest power of the optical microscope. 2.1.2. Age estimation from operculum The operculum of each fish was removed, thoroughly cleaned with boiling water and the rings were counted under the lowest power of the optical microscope. 2.1.3. Age estimation from length frequency distribution The individual total length of 600 fishes of Valamugil seheli was measured during September 2010. Length frequency distribution (Petersen s method, 1892) was used for aging.

14 2.2. Growth Von Bertalanffy equation (1938) was used to determine the growth of each species as follows: Lt = L {1- exp[-k(t- t0)]} Where Lt = is the length at time t, L = is the asymptotic length that is the length of the fish when the growth equal to zero, K = is a growth constant (curvature coefficient), t = is the age of the fish at length Lt, and t0 = is the age of the fish at length zero. The right hand side of the equation contains the age, t, L (read L-infinity), k and t0. Time t (age) is usually expressed in units of years and the lengths at the beginning of each in centimeters. Different growth curves can be created for each set of parameters; therefore it is possible to use the same basic model to describe the growth of different species simply by using special set of parameters for each species. The parameters can to some extent be interpreted. L is interpreted as the fish length when the growth equal to zero; it is also cold asymptotic length. K is a parameter which determines how fast the fish approach its L. The von Bertalanffy parameters K and L were estimated according to Ford-Walford (Sparre and Venema, 1992), and t0 was estimated according to von Bertalanffy (1934). 3. Results and Discussion 3.1. Age Estimation 3.1.1. From scales There are four age groups of Valamugil seheli (one year, two years, three years and four years). The four age groups, their corresponding average lengths and average weights are shown in Table 1. Table 1. Age estimation from scales of Valamugil seheli Age groups (years) Length (cm) Average length (cm) Average weight (g) +1 16 23 20.33 100.7 +2 23 30 27.62 207 +3 30 37 34.53 387 +4 37-44 38.7 635.7 3.1.2. From operculum The four age groups were also observed (Table 2), but there were some differences in corresponding average lengths and average weights compared to those obtained from scale readings.

15 Table 2. Age estimation from operculum of Valamugil seheli Age groups (years) Length (cm) Average length (cm) Average weight (g) +1 17 25 19.63 107.6 +2 25 32 28.67 249.27 +3 32 39 34.77 449.29 +4 39-46 41.78 727.22 3.1.3. From length frequency distribution The length frequency distribution is shown in Fig. 1. Corresponding average lengths (Table 3) also differ somewhat from those obtained from scale and operculum readings. Figure 1. The length frequency distribution of Valamugil seheli. Table 3. Age estimation from length frequency distribution of Valamugil seheli Age groups (years) Length (cm) Average length (cm) +1 17-23.5 19.28 +2 23.5-30 27.4 +3 30-35 33.78 +4 35-40.5 38.39 The age groups and corresponding lengths and weights obtained by averaging those obtained from the three methods (scale, operculum and length frequency distribution) are shown in Table 4 and were used to estimate the von Bertalanffy parameters K, L and t0.

16 Table 4. Age determination of Valamugil seheli from the three methods Age groups From scales From operculum From length frequency Mean of all length (cm) weight (g) length (cm) weight (g) length (cm) weight * (g) length (cm) weight +1 20.33 100.7 19.63 107.6 19.28 82.54 19.75 96.95 +2 27.62 207 28.67 249.27 27.4 210.01 27.9 222.09 +3 34.53 387 34.77 449.29 33.78 353.26 34.36 396.51 +4 38.7 635.7 41.78 727.22 38.39 529.76 39.39 630.89 Note: * Weight values were obtained from the established Length vs. Weight relationship: Y = 0.007X 3.114. 3.2. Growth 3.2.1. Estimation of K and L The von Bertalanffy parameters K and L were estimated according to Ford-Walford (Sparre and Venema, 1992). In Table 5 the length of fish (L(t) at age t vs. length of fish at next age (L(t+Δt)) was prepared from data in Table 4. Then the plot of L(t) vs. L(t+Δt) was made (Fig. 2) to obtain K and L. Table 5. The length of fish (L(t)) at age t vs. length of fish at next age (L(t+Δt)) Lt L(t+Δt) X Y 19.75 27.9 27.9 34.36 34.36 39.45 39.62 (g) Figure 2. The plot of L(t) vs. L(t+Δt) for Valamugil seheli.

17 y = 0.801x + 12.04, R² = 0.999, Δt = 1 year. K = -(1/Δt)ln b = (1/1) ln0.801 = 0.222. L = a/(1-b) = 12.29/(1-0.790) = 60.503 cm. 3.2.2. Estimation of t0 The von Bertalanffy parameters t0 was estimated according to von Bertalanffy (1934). First a table of t vs. ln (1-L(t)/L ) (Table 6) was prepared from data of Table 5, then a plot of t vs. ln (1- L(t)/L ) was made to obtain t0 (Fig. 3). Table 6. Estimation of the parameter t0 according to von Bertalanffy (Bertalanffy, 1934) t ln (1-L(t)/L ) 1 0.3952 2 0.6182 3 0.8391 4 1.064 Figure 3. The plot of L(t) vs. ln (1-L(t)/L ). L = 60.503 cm. t0 = - a/b = -0.172/ 0.222 = - 0.775 year 3.2.3. The established von Bertalanffy equation for Valamugil seheli K = 0.222, L = 60.503 cm, t0 = -0.775 year.

18 Lt = L (1-exp (-K (t- t0))) = 60.503 (1-exp (-0.222 (t+0.775))) 3.2.4. The growth index phi (ø) The growth index was calculated according to Pauly and Munro (1984) as follows: ø = log10 K + 2 log10 L = log10 0.222 + 2 log10 60.503 = 2.91. 3.2.5. The mathematical relationship between the length of fish and growth rates (Sparre and Venema, 1992) L/ t = K (L -L (t)) cm/year = 0.222 (60.503 - L (t)) cm/year. Table 7 below was prepared from the von Bertalanffy equation: Lt = 60.503 (1-exp (-0.222 (t+0.775))) The plot of Lt and ΔL vs. t (Fig. 4) gives the fish length (Lt) and the growth increment ( L) at different ages (t). In addition, estimated Lt and observed Lt of Valamugil seheli is given Table 8 and Fig. 5. Table 7. Fish length (Lt) and growth increment ( L) at different ages (t) t Lt ΔL 0 9.56 0 0.5 14.91 10.14 1 19.7 9.08 1.5 23.99 8.13 2 27.83 7.27 2.5 31.26 6.5 3 34.33 5.82 3.5 37.08 5.21 4 39.54 4.66 4.5 41.74 4.18 5 43.72 3.74 5.5 45.48 3.34 6 47.06 2.99 6.5 48.47 2.67 7 49.73 2.4 7.5 50.87 2.15 8 51.88 1.91 8.5 52.78 1.72 9 53.6 1.54 9.5 54.32 1.37 10 54.97 1.23

19 10.5 55.55 1.1 11 56.07 1.04 11.5 56.54 0.88 12 56.95 0.79 12.5 57.33 0.71 13 57.66 0.63 13.5 57.96 0.57 14 58.23 0.5 14.5 58.46 0.45 15 58.68 0.41 15.5 58.87 0.36 16 59.04 0.33 16.5 59.2 0.29 17 59.33 0.26 17.5 59.46 0.23 18 59.56 0.2 18.5 59.66 0.19 19 59.75 0.17 19.5 59.83 0.15 20 59.902 0.14 20.5 59.97 0.12 21 60.022 0.102 21.5 60.072 0.098 22 60.12 0.086 22.5 60.158 0.074 23 60.194 0.069 23.5 60.227 0.066 24 60.26 0.055 24.5 60.282 0.04 25 60.3 0.043 25.5 60.325 0.041 26 60.341 0.036 26.5 60.361 0.035 27 60.376 0.028 27.5 60.389 0.024 28 60.4 0.023 28.5 60.412 0.022 29 60.422 0.018 29.5 60.43 0.016 30 60.438 0.015 30.5 60.445 0.013

20 Figure 4. Fish length (Lt) and growth increment ( L) at different ages (t). Table 8. Estimated Lt and observed Lt of Valamugil seheli t Lt (Estimated) Lt (observed) -0.78 0 0 0 9.56 0.5 14.91 1 19.7 19.75 1.5 23.99 23.83 2 27.83 27.9 2.5 31.26 31.13 3 34.33 34.36 3.5 37.08 36.88 4 39.54 39.39 4.5 41.74 5 43.72 5.5 45.48 6 47.06 6.5 48.47 7 49.73 7.5 50.87 8 51.88 8.5 52.78 9 53.6 9.5 54.32

21 Figure 5. Estimated Lt and observed Lt of Valamugil seheli. 3.2.6. The weight-based von Bertalanffy growth equation Combining the von Bertalanffy growth equation Lt = L (1-exp(-K(t- t0 ))) with the length/weight relationship: W(t) = al b (t) gives the weight of a fish as a function of age. The asymptotic weight, W, corresponding to the asymptotic length is: W = a L b. Thus the weight-based von Bertalanffy equation can be written: W(t) = W (1-exp(-K(t- t0 ))) b In the present study: W(t) = al b (t) = 0.007L 3.114, L = 60.503. W = 0.007 * 60.503 3.114 = 2474.86 g. Lt = L (1-exp(-K(t- t0 ))) = 60.503 (1-exp (-0.222 (t+0.775))). Thus W(t) = W (1-exp(-K(t- t0 ))) b = 2474.86(1- exp (-0.222 (t+0.775))) 3.114, and the results are given in Table 9 and Fig. 6.

22 Table 9. Fish weight (Wt) in gram at different ages (t) in years t Wt 0 7.92 0.5 31.606 1 75.228 2 220.375 3 423.91 4 658.192 5 899.563 6 1131.525 7 1344.263 8 1533.063 9 1696.668 10 1835.95 11 1952.948 12 2050.226 13 2130.47 14 2196.226 15 2249.929 16 2293.553 17 2328.904 18 2357.483 19 2380.543 20 2399.122 21 2414.073 22 2426.093 23 2435.749 24 2443.502 25 2449.723 26 2454.714 27 2458.716 28 2461.924 29 2464.496 30 2466.557 31 2468.208 32 2469.532 33 2470.592 34 2471.441

23 Figure 6. Growth (in grams total weight) of Valamugil seheli. 4. Discussion The three methods employed in age determination of V. seheli indicated that there were four age groups: +1, +2, +3, and +4. Lengths at age group obtained from scales, operculum and length frequency distribution were close to each other, but weights at age group differ. Weights at age group obtained from scales and operculum were close to each other, but were smaller than those obtained from the length frequency distribution. Similar results were found by Khalifa and Munro (2007) for V. seheli and V. buchanani from Abu Hashish area. Moorthy et al. (2003) estimated the age of V. seheli from Mangalore, India, using scales, and found four groups: first year 15-24 cm, second year 24.1-31 cm, third year 31.1-36 cm and fourth year more than 36 cm. The length-weight relationship of V. seheli showed isometric growth; that is, the values of the constant (b) from the power equation were 3.09 for males and 3.10 for females i.e. close to 3. The von Bertalanffy growth function by length was found to be: Lt = 60.503(1- e -0.222(t+0.775 )). Moorthy et al. (2003) from Mangalore region-india reported that studies on age and growth of V. seheli revealed that males grow faster than females and the von Bertalanffy equation was: Lt= 60.176(1- e -0.2309(t+0.6934) )) for males and, Lt= 53.453(1- e -0.2853(t+0.5632 )) for females. Borafy and Soliman (1988) observed five age groups in females and four age groups in males of V. seheli in UAE waters. They also observed a faster growth rate in females. The differences in growth rates between these two studies and the present study could be attributed to ecological factors affecting biological activities of the fish in different environments. They obtained L as 56.47 cm for V. seheli. Baburaj (1987) obtained L as 49.32 cm for V. sperigleri in Mangalore waters. Wijayaratne

24 and Costa (1987) reported L for V. buchanani and V. cunnesius from Negombo lagoon, Sri Lanka, as 58.6 and 30 cm, respectively. 5. Conclusions (1) Using more than one method in age estimation obtain accurate results of age determination, (2) Reading growth rings from scales is easier than from operculum, and (3) Von Bertalanaffy equations describing growth of Valamugil seheli were formulated. References Ahmed, A. A. (1989). On some environmental and physiological factors affecting growth and development of some viable Nile fishes. Ph.D. Thesis, Department of Zoology, University of Khartoum, p. 2. Baburaj, D. (1987). Some aspects of biology of the mullet, Valamugil speigleri (Bleeker) from Mangalore region. M. F. Sc. Thesis, University of Agricultural Sciences, Bangalore, p. 155. Bertalanffy, L. V. (1934). Untersuchungen über die Gesetzlichkeit des Wachstums. I. Allgemeine Grundlagen der Theorie; mathematische und physiologische Gesetzlichkeiten des Wachstums bei Wassertieren. Arch. Entwicklungsmech., 131: 613-652. Bertalanffy, L. V. (1938). A quantitative theory of organic growth (Inquiries on growth laws. II). Human Biol., 10: 181-213. Borafy, F. A., and Soliman, F. M. (1988). Biology of Valamugil seheli Forskal from inshore waters of United Arab Emirates I. Age and growth. J. Mar. Biol. Ass. India, 30: 164-170. Brown, M. E. (1957). Experimental studies on growth. In: The Physiology of Fishes, Vol. 1. Metabolism. Academic Press, New York. pp. 361-400. Faragalla, A. M. (2009). Biochemical studies of three marine fishes, "Fasseikh". Ph.D. Thesis, Faculty of Science, University of Khartoum, 104 pp. Khalifa, A. (2007). Some environmental and biological aspects of Valamugilseheli and Valamugilbuchanani from Abu Hashish Area, Port Sudan. Msc. Thesis, Department of Zoology, University of Khartoum, 117 pp. Moorthy, K. S. V., Reddy, H. R. V., and Annappaswamy, T. S. (2003). Age and growth of blue spot mullet, Valamugil seheli (Forskal) from Mangalore. Indian J. Fish., 50: 73-79. Pauly, D., and Munro, J. L. (1984). Once more on the comparison of growth in fish and invertebrates. ICLARM, Fish byte, 2: 21. Petersen, C. G. J. (1892). Fiskens biologiske for hold: Holboek Fjord, 1890-91. Beretning frade Danske Biologiske station for 1890 (91), 1: 121-183.

25 Sparre, P., and Venema, S. C. (1992). Introduction to Tropical Fish Stock Assessment, Part 1-Manual. FAO Fisheries Technical Paper 306-1 rev. 1, 376 pp. Weatherly, A. H. (1972). Growth and Ecology of Fish Populations. London, Academic Press Ltd, p. 293. Wijayaratne, M. J. S., and Costa, H. H. (1987). The food and feeding and reproduction of the Borneo mullet, Liza macrolips (Smith) in a coastal estuary in Sri Lanka. Indian J. Fish., 34: 283-291.