Age, Growth, Mortality and Exploitation Rates of Round Sardinella, Sardinella Aurita from the East Mediterranean Sea (North Sinai Coast)

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Age, Growth, Mortality and Exploitation Rates of Round Sardinella, Sardinella aurita from the East Mediterranean Sea (North Sinai Coast)

1Salem, M., 2El_Aiatt, A.A. and 3Ameran, M.

1Suez Canal University, 2GAFRD

Abstract: Age, growth, Mortality and exploitation rates of Sardinella auritawere estimated from 6591specimens ranging from 7 to 22.9 cm as Lt, while the mean total weight ranged from 4.3 to 75 gm. The relationship between length and weight was described by the power relationship: W = 0.0267 L2.524. Growth in length and growth in weight at the end of each year was calculated. Age was determined by scales and age groups 0 to 4 years. Obtained von Bertalanffy growth parametres (L4 = 25.83 cm, !1 ! k = 0.299 year and t0 = 0.878 year). The growth performance index was calculated (ö = 2.29). Total (Z: 1.49 yr!1 ), natural (M: 0.73 yr!1 ) and fishing mortality (F: 0.76yr!1 ) were obtained. The maximum

allowable limit of exploitation (E max) was 0.87 and maximum economic yield was 0.71. The estimated values for the total mortality and the exploitation rate (E = 0.51), show that the round sardinella stock in the east Mediterranean Sea, North Sinai coast is balanced position.

Key words: Sardinella aurita; growth; mortality;east Mediterranean Sea; Egypt.

INTRODUCTION boat with mesh size 8 mm. The measurements as total length to the nearest millimeter and total weight to the Sardine fisheries was highly important before the nearest one gram of the fish were recorded for each construction of Aswan High Dam. Before 1966, the specimen. For age determination, the scales samples Sardine accounted for about 40% of the total landed were removed from the left side of each fish behind catch of the Egyptian Mediterranean waters. By that the tip of the pectoral fin for 3131 specimens[21]. time, fisheries of Sardine was mainly operated during autumn[7] . The sardine is a major catch which are 2.1. Length-weight Relationship: The relationship average 90% of the total catch in the Mediterranean between length and weight was described by the coast of Sinai fishery during 1989 to 2009. Sardine is potential equation (W = aLb,[24]), where W is the total the first in its importance to the Mediterranean coast of weight (g), and L is the total length (Cm), a and b the Egypt however during the last 39 years a drastic constant. The coefficient of determination (r2) was used decline in sardine landing along the Egyptian as an indicator of the quality of the linear regression[25]. Mediterranean coast has been observed[33]. The round sardinella, Sardinella aurita is commercially exploited 2.2. Scales Preparation and Age Determination: In in several southern Mediterranean countries such as the laboratory, the scales were cleaned and stored dry Egypt[35]; Algeria[3] and Tunisia[10]. In spite of the round in envelopes for the subsequent study. Later on, scales sardinella, S. aurita is the most important (about 85% were soaked overnight in 10% ammonia solution. 5-7 of total catch) in Mediterranean coast of Sinai fishery, scales were placed between two glass slides, and there is little information on fishery biology of this examined by a projector with 33 x magnifications. On species. The main objectives of this work (1) estimate the clearest scale from each batch, the total scales the age and growth from scales (2) estimate the radius as well as of each annulus were measured to the mortality rates and (3) estimate the exploitation rates. nearest 0.01. The relationship between total length and total scales radius was calculated for all fishes. MATERIALS AND METHODS According to Whitney and Calendar, 1956, the best regression to use the fish length and average scale The study was carried out in North Sinai in the radius using liner regression: major landing site of Mediterranean coast (EL-Arish

Port). 6591 both sexes combined of Sardinella aurita Lt = a + b R were collected monthly From January to December,

2007. Samples were collected from the purse - seine Where: Lt is total length of fish in cm; R is magnified

Corresponding Author: Mohamed Salem, Faculty of Environmental Agricultural Sciences, EL-arish, University of Suez Canal.

32 Res. J. Fish. & Hydrobiol., 5(1): 32-38, 2010 scale radius in cm; a & b the constant representing the M is the natural mortality, K is the body growth intercept and the slope of the straight line respectively. coefficient and E is the exploitation rate. The relative biomass per recruit (B`/R) = (Y`/R)/F where,(Y`/R) is 2.3. The back-calculated: The back-calculated total the relative yield-per-recruit and F is the fishing length were determined from scale measurements using mortality.The optimum exploitation rate which produces

Lea’s equation, 1910 as L x = L p(S x/S P) Where: L x maximum yield was found from the yield-per-recruit equals length of fish at age (x), L p equals the fish and biomass-per-recruit model (E m ax). The exploitation length at capture S x equals the scale length at check (x) rate at which the marginal increase of Y /R is 0.1 and Sp equals present scale length. The back- (E0.1), the reduced to 50% of its unexploited biomass calculated weight at the end of each year was (E0.5) and zero exploitation (E = 0) were estimated. estimated by length-weight equation. 3. Results: 2.4. Growth Parameters: The von Bertalanffy models, 3.1. Length – Weight Relationship: The observed -k(t – t ) 1934 and 1949, (L t = L4 (1- e 0 )) was used to total length of 6591 Sardinella aurita caught from the describe growth in size, where Lt is the length at age Mediterranean coast (Sinai) from January to December, t, L4 the asymptotic length, K the body growth 2007 ranged from 7 to 22.9 cm (fig. 1) and the coefficient and defines the growth rate towards L4 and observed total weight from 4.3 to 75 g. The length – t0 the hypothetical age at which a fish would have zero weight relationship (fig. 2) was described by the power 2.526 2 length. The values of L 4, K and t0 were estimated by equation as: W= 0.026 L (r = 0.93), the negative [8] [34] plotting L t vs L t+ 1 using the Ford, , Walford allometry was established. procedure[14]. The growth performance index was calculated by using the phi prime test (ö') = 3.2. Body Length – Scale Radius Relationship: 3131 logk+2logL4 (Munro and Pauly, 1983) which can be specimen were collected for ageing and growth used to compare growth rates among species and to analysis. Age estimated ranged between 0 – 4 years, evaluate growth performance under environmental age - length keys were calculated (Table. 1). The mean [22] stresses . The maximum length (L max) was obtained fish length and the average scale radius per each length from extreme value theory[9]. group are given with the ratio of fish length to scale size in fig. 3. Data for S. aurita between fish length 2.5. Mortality Rates: Total mortality (Z) was and scale radius show a linear trend on their scatter estimated by a method of Beverton and Holt[2], as diagram where described by this equation: L =- 0.484 +2.089 R. – – Z = K*(L4 – L ) / (L – L') 3.3. The Back – Calculations: The average back – where, K is the body growth coefficient (year-1),L4 is calculation lengths and annual increment of the the asymptotic length, L' is the length for which all combined sexes (Table. 2) are 11.1, 14.7, 18 and 19.8 fish under full exploitation and L– is the mean length cm for ages 1, 2, 3 and 4 respectively. The highest of fish at and above L'. Natural mortality coefficient annual increment occurred during the first year of life, was estimated by using the equations of Pauly,[20]. while a noticeable decrease is observed in the second log M = [ - 0.0066 – 0.279 log L 4 + 0.6543 log K + year, reaching its minimal value during the fourth year 0.4634 log T ] of life. Fishing mortality coefficient (F) was estimated Back–calculation weights at the end of each year directly by subtracting the value of the natural of life for S. aurita were estimated by applying the mortality from the value of the mean total mortality as length – weight relationship and the results are given F= Z-M. in Table (3). The results in the table show that the maximum 2.6. The Relative Yield and Biomass per Recruit: value of annual weight increases successively and The model of Beverton and Holt, 1966 as modified by reaches its maximum at the end of third group of life. Pauly and Soriano,[23] incorporated in FiSAT program[11] was used to predict the relative yield-per-recruitment 3.4. Growth Parameters: The parameters of von and the relative biomass per recruit as Bertalanffy growth were calculated as L 4 = 25.83, K = -1 0.299 yr and t 0 = -.878 and the obtained equation was M /K 2 -0.298(t – (-0.878)) Y`/R = EU [1- (3U/1+m) + (3U /1+2m) – (Lt = 25.83 (1- e )). The asymptotic length (U3/1+3m)] is higher the maximum observed length. The growth where, U = 1- (Lc / L4), m = (1-E)/ (M/K) = (K/Z):

33 Res. J. Fish. & Hydrobiol., 5(1): 32-38, 2010

Fig. 1: Length frequency distribution of S. aurita sampled off the Mediterranean coast, Sinai

Fig. 2: Length weight relationship for S. aurita of the Mediterranean coast, Sinai

Fig. 3: Relationship between the total length and scale radius for S. aurita of the Mediterranean coast, Sinai

34 Res. J. Fish. & Hydrobiol., 5(1): 32-38, 2010

Table 1: age - length keys for S. aurita of the Mediterranean coast, Sinai Age classes (years) TL (cm) ------0 I II III IV 7 – 7.9 50 ------8 – 8.9 147 ------9 – 9.9 293 10 ------10 – 10.9 69 182 ------11 – 11.9 62 439 3 ------12 – 12.9 34 183 9 ------13 – 13.9 123 106 ------14 – 14.9 10 130 ------15 – 15.9 555 3 ------16 – 16.9 225 20 ------17 – 17.9 28 86 3 ------18 – 18.9 8 125 17 ------19 – 19.9 42 25 ------20 – 20.9 49 45 ------21 – 21.9 10 22 ------22 – 22.9 18 n 655 947 1064 335 130 ------mean 9.46 11.7 15.3 18.5 20.3

Table 2: Back – calculation length (TL, cm) at the end of life different years of S. aurita Age group No. of fish Observed length Average calculated lengths at the end of each year (cm) ------I II III IV I 947 11.7 11.2 ------II 1064 15.3 11 14.7 ------III 335 18.5 10.8 14.7 18 ------IV 130 20.3 11.1 14.5 17.9 19.8 Average 11.1 14.7 18 19.8 ------Increment 11 3.6 3.29 1.83

Table 3: Back – calculation weight at the end of life different years of S. aurita Age group No. fish Average calculated weight at the end of each year (g) ------I II III IV I 947 11.9 ------II 1064 11.3 23.6 ------III 335 10.8 23.6 39.3 ------130 11.6 22.8 38.8 50.0 Average 11.5 23.5 39.2 50.0 ------Increment 11.5 12.0 15.7 10.8

35 Res. J. Fish. & Hydrobiol., 5(1): 32-38, 2010

performance index for S aurita was about 2.29. In This study, the maximum length (L max =

Observed and predicted extreme lengths (L max) were 22 22.52 cm) and the asymptotic length (L 4 = 25.83) is and 22.52 cm, respectively (Fig 4). lower than and the body growth coefficient (K = 0.299 yr-1 ) is higher than most Mediterranean stocks which

3.5. Mortality and Exploitation Rates: Total mortality obtained by Buaziz et al., 2001 (L max = 25.5; L 4 = coefficient (Z), defined as the total loss by natural and 34.96; K = 0.236 yr-1 ) in Algeria coast and Gaamour -1 [10] -1 fishing death of individuals (Z = 1.49 yr ). The natural et al., (L max = 27.35; L 4 = 31.32; K = 0.240 yr ) in mortality (0.73 yr!1 at 20.7c°) versus fishing mortality Tunisia coast, the hypothetical age at which a fish !1 (0.0.76 yr ) observed for S aurita indicates the would have zero length (t0 = -.878) similar which [4] balanced position of the stock. The current established obtained by Buaziz et al., (t0 = -0.717) for the same exploitation rate was 0.51 (E = 51 %). The current species. Differences in growth parameters may be due exploitation rate is optimally exploited stock (50 %) to genetic structure; temperature; food availability and according to Gulland[12]. diseases[22,37]. The index of growth performance (ö) is considered 3.6. The Relative Yield and Biomass per Recruit: a useful tool for comparing the growth curves of Figure (5) shows the results of the relative yield(Y' different populations of the same species and/or of 'R) and biomass (B' 'R) per recruit analysis against different species belonging to the same family[27,11]. In exploitation rate (E) using the knife-edge selection. The our study, the value of growth performance (ö = 2.29). ' [10] maximum (Y' R) was obtained as: 0.87 at E max. Both This result is agreed with Gaamour et al., (ö = 2.27)

(E 0.1) and (E 0.5) were estimated as 0.71 and 0.37 in Tunisia coast, but lower compared with Chesheva, respectively. 1998 (ö = 2.66) in Mauretania coast. In the Mediterranean sea, The mean index of growth 4- Discussion: In the present study the power “ b “ performance is lower than for the another regions[30]. was 2.526 indicated acute negative allometric growth Maximum length (L max) to the asymptotic length for S aurita. The previous results for the same species (L4) is an important parameter of the life history as a showed the 'b' value ranged from 2.4 to 3.179 recorded by Stergiou,[28], where founded the mean value according to EL Aiatt, 2004 (Mediterranean coast, El of L m ax /L4 for marine fish ranged between 0.56 and [1] Arish) and Abdalla and El–haweet, (Mediterranean 1.34 with a mean value is 0.90. Maximum length (L max coast, Alex.) respectively. Also, Moutopoulos and = 22.52 cm) and the value of L m ax /L 4 (0.87) very Stergion,[17] and Sinovcic et al.,[26] mentioned that the closed to the mean value which reported by Stergiou et [29] . power “ b “ for S aurita was 2.804 and 3.12 al, for 383 Mediterranean marine fish (L m ax /L 4 respectively. The relationship between body length and 0.89). weight can also be change with many condition factor In present work, the results estimation of annual as season, sex, food, maturity stage and techniques of total mortality coefficient (Z), defined as the total loss sampling[16]. The slightly negative allometric growth in by natural and fishing death of individuals as 1.49 yr!1. El- Arish, Mediterranean coast, may be related to Similar results was obtained by Hashem and Faltas,[13] unavailable of food and unsuitable of environment. and Faltas,[7] where Hashem and Faltas,1982 estimated the total mortality for S. aurita in Alexandria region The body length and scale radius relationship show (1.377) and EL Aiatt, 2004 estimated an average value a linear on their scatter diagram L = - 0.4847+2.0893 of total mortality (Z) for S. aurita in EL-Arish region R. This results agree with EL Aiatt et al.,[6] (L = - (1.262 and 1.519 in seasons 2000 and 2001 0.7994 +2.1604 S, 2000) and (L = - 0.7670 +2.1356 S, respectively). The natural mortality (0.73 yr!1) versus 2001). The total length at the end of each year was fishing mortality (0.76 yr!1) observed for S. aurita 11.1,14.7,18.0,19.8 cm. The obtained results of the indicates the balanced position of the stock. Gulland,[12] back calculation length at the end of each year showed suggested that, fishing mortality should be about equal the highest increment in length occurred at the first to natural mortality, resulting in an exploitation rate of year 11.1 cm of S. aurita, after which the annual 0.5 year!1 . However, exploitation rates should be very increment in length decreases with further increase in conservative for relatively long lived species[19] . The age. The length at the end of each year in this study is current established exploitation rate was 0.51 (E = 51 a lower than that obtained by Faltas, 1983 where he %). The current exploitation rate is optimally exploited found the length at the end of the first fourth years for stock (50 %) according to Gulland,[12]. Fig. (5) gavethe S aurita 12.7,15.9,18.7,and 21cm respectively. Also EL optimum exploitation rate which produces maximum

Aiatt, 2004 where found the length at the end of the and economic sustenable yield (E max = 0.87 and E 0.1 = fir s t fo u r th years fo r th e s a m e s p e c ie s 0.71). The current exploitation rate is less than the

12.38,15.91,18.77,20.54 in season 2000 and predicted (Emax) and (E0.1), where this means that the 12.18,15.23,18.56 20.02 in season 2001 respectively. stock is not overexploited.

36 Res. J. Fish. & Hydrobiol., 5(1): 32-38, 2010

Fig. 4: Observed and predicted extreme lengths (L max) for S. aurita of the Mediterranean coast, Sinai

Fig. 5: The relative yield and biomass per recruit for S. aurita of the Mediterranean coast, Sinai

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