Egyptian Journal of Aquatic Research 43 (2017) 219–227 Contents lists available at ScienceDirect Egyptian Journal of Aquatic Research journal homepage: www.sciencedirect.com/locate/ejar Full length article Age and growth of the fish, Gerres filamentosus (Cuvier, 1829) from Hurghada Red Sea, Egypt Taher Mohamed Ahmed Abu El-Nasr Department of Zoology, Faculty of Science, Zagazig University, Egypt article info abstract Article history: A total of 669, Gerres filamentosus (Cuvier, 1829) were collected from Hurghada area in the Egyptian Red Received 3 May 2017 Sea coast (January – December 2010). The author investigated the age and growth by two different meth- Revised 24 July 2017 ods through scale-annuli reading (Direct method) and Length-frequency distribution (Indirect method) Accepted 26 July 2017 which showed new record of lengths for the species. The equations of the length-weight relationship Available online 8 November 2017 was W = 0.0143⁄ L2.9564 (Males), W = 0.0146⁄ L2.9543 (Females) and W = 0.0144⁄ L2.9597 (combined sexes). The von Bertalanffy growth equation was calculated by three different mathematical methods. It was Keywords: concluded that it would be economical to protect this species from capture until at least their 5th year, Mojarra after the fish has reached about 32.71 cm in total length and about 439.15 grams in weight. Whipfin Ó Silver-biddy 2017 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access Length-weight article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Age groups Frequency distribution Introduction studied the same species from Fort Kochi, Kerala, India, by using dif- ferent types of fishing gears like gill nets, seines and cast nets. More- Age and growth studies on fishes are very essential in planning over, Sivashanthini (2008) reported that, the silver-biddy, Gerres and managing of fish culture and fishery researches. Not only filamentosus (Cuvier, 1829) males reach maturity at 143.8 mm and retardation of metabolism but also disturbances in conditions such that of the females at 136.6 mm total length in Parangipetti water as feeding, temperature or unfavorable changes of many factors as (South East coast of India). According to Dickie (1978) a number pollution and diseases affected on growth of fishes (Nikolsky, of mathematical growth curves have been published together with 1963). The distribution and Landings of Gerreids in the Red Sea methods of fitting them statistically. On the other hand, by the were given by Bayoumi (1972) and were common in sandy bottom, appropriate otolith preparation methods, deep-water snappers sea grass and muddy areas (Kerschner et al., 1985). In the main were estimated age precisely in acceptable level (Williams et al., Egyptian fishing areas of the north western part of the Red Sea, 2015). In spite of its importance, the present study is an attempt which are Al-Ghardaqa and Safaga Bay, the representatives of Ger- to age of G.filamentosus (Cuv.) using scale circuli and analyze growth res filamentosus (Cuv.,) offers some of the most economic species from length-frequency data in the Red Sea coast of Hurghada, Egypt (Boraey, 1980a). Unfortunately, although the favorable taste of this to evaluate its growth rate and productivity. species for Egyptian peoples, no studies and lack of knowledge about the biology hinder its proper management. However, the scale method is widely used in age and growth Materials and methods studies (Lagler, 1956). The reduction in growth leads to checks’ for- mation on the hard parts of the fish and the growth ring marked dur- Random mid-monthly commercial-trawler samples of G.fila- ing the months of summer due to nourishment of food. (Bilton, mentosus from freshly caught catches off Egyptian Hurghada Red 1974). Among the valuable works adopted the scale after being val- Sea, during from January to December 2010. A total of 669 fish idated, in calculating growth are those of Boraey (1980b); Boraey (12–39 cm in total length) were taken. Of each fish sex, total and Soliman (1985a,b), El-Agamy (1988); Da Costa et al. (2012) weight (to the nearest 0.01 g) and the total length (to the nearest and Espino-Bar et al. (2014). Divakaran and Kuttyamma (2014) 0.1 cm) were measured. The length data were classified into length groups at 0.9 cm interval. The relationship of length–weight was estimated from the power-equation: Peer review under responsibility of National Institute of Oceanography and b Fisheries. W=aL (Hile, 1936) and (Le Cren, 1951) .The values for ‘‘a” and E-mail addresses: [email protected], [email protected] ‘‘b” estimated by least squares method (Lagler, 1956). https://doi.org/10.1016/j.ejar.2017.07.003 1687-4285/Ó 2017 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 220 T.M.A. Abu El-Nasr / Egyptian Journal of Aquatic Research 43 (2017) 219–227 Direct method for age determination (Scale reading) Ln ðL1 À LtÞ¼Ln L1 þ Kt0 À Kt The plots of time ‘‘t” against Ln (L1 À L ) gives the values of ‘‘a” A number of scales (about 6–10) were removed with a stout for- t and ‘‘b”. ceps from the flank region behind the left pectoral fin of each indi- vidual fish-specimen and kept in paper envelops. The scales were then soaked in 10% ammonia solution, cleaned, washed in distilled water and pressed dry in between two glass slide for further inves- tigation. The scales representing rings or annuli formation (growth checks) were measured from its anterior margin along a line to the focus, according to the method recommended by Lee (1920) and Bagenal and Tesch (1978). The examination and measurement of the fish scales were made by a zoom-microscope at a micrometer eye-piece with magnifica- tion of (X16), placing the zero graduation of the micrometer eye- piece on the focus of the scales. The total radius of each scale ‘‘S” (The distance from the focus to the nth annulus) were measured to nearest 0.01 mm. The scale edge in the anterior field was also measured for the marginal increment analysis and for back- calculating fish length at the time of annulus ring-formation. The fish were classified into age groups based on the number of com- pleted years of life. Then, the relation was represented as follows: Rn = ST-Sn/ST X 100 Where: Rn = Ratio of marginal growth. ST = Total scale radius in millimeter. Sn = Distance from the focus to the last annulus in millimeter. The fish were classified into age-groups based on the numbers of true-rings of year-life. The Fig. 1. The L-W relationship (Males) G. filamentosus. relationship of fish body-length to scale-radius was based on the assumption that scale growth is proportional to fish growth according to Lee (1920): L=a+bSWhere: L = fish length in cen- timeters, S = scale radius in centimeters, b = slope value, a = the ini- tial fish length before scale formation. The fish length-scale radius relationship was back-calculated as follows: Ln = (L-a) (Sn/S) + a... (Lee, 1920) Where: Ln = calculated length at ‘‘n” years. L = total fish capture-length in centimeters, Sn = radius of scale at annulus ‘‘n”. S = total scale-radius, a = intercept at Y-axis. The von Bertalanffy Growth Formula (von Bertalanffy, 1934, 1938), was then used to )ÀK(tÀt relate fish length to age as follows: Lt = L1 [1-e0 ] To deter- mine the asymptotic length (L1) graphically, the graphical method of Ford-Walford plot (Ricker, 1958) was adopted. The point at which the straight line relationship between Lt+1 and LtÀ cuts the 450 diagonal from the origin yielded L1 value. The calculated weights at every year of life were estimated by applying the corre- sponding L-W equations to the back-calculated lengths. W=cLn The constant of the von Bertalanffy model (L1, K and t0) were esti- mated by the following three methods: ÀK ÀK i) Lt+1 = L1(1Àe )+(e )Lt according to Ford (1933) – Fig. 2. The L-W relationship (Females) of G. filamentosus. Walford (1946) where, Lt and Lt+1 are the size of the fish at age t and t+1, respectively. From the least-squares linear regression relationship described by Walford line: Ltþ1 ¼ a þ bLt This shows the mathematical validity of linearity of Ford- Walford plot for fishes obeying von Bertalanffy’s growth curve, where, ÀK ÀK a ¼ L1ð1 À e Þ; and b ¼ e L1 ¼ intercept=1 À slope; K ¼Ln slope The intercept value of this regression was then used to solve for t0 estimation. From von Bertalanffy’s growth curve rearrangement (age = t), was estimated as: Fig. 3. The L-W relationship (combined sexes) of G. filamentosus. T.M.A. Abu El-Nasr / Egyptian Journal of Aquatic Research 43 (2017) 219–227 221 a ¼ LnL1 þ Kt0; b ¼Kt a ¼ KL1; t0 ¼ Intercept À Ln L1=K b ¼KorK¼b ii) Lt+1 À Lt=KL1 À K(Lt+1 + Lt/2) (Gulland and Holt, 1959) L1 ¼ a=KorL1 ¼ a= À b; where, ÀK ÀK iii) Lt+1 À Lt=L1 (1 À e ) À (1 À e )Lt (Chapmann, 1960) where, ÀK a ¼ L1ð1 À e Þ b ¼ð1 À eÀKÞ ÀK L1 ¼ a=ð1 À e Þ or L1 ¼ a= À b Lnð1 þ bÞ¼KorK¼Lnð1 þ bÞ For calculating ‘‘t0” Gulland (1969) equation was used as fol- lows:t0=t + 1/K Ln {(L1 À Lt)/L1} The value of t0 can be computed as the mean of all ages.