Journal of Aquaculture & Fisheries Category: Aquaculture Type: Research Article
Age, Growth and Mortality of Terapon puta (Cuvier, 1829) in the Lake Timsah, Egypt
- Mohamed El-Drawany^{1*}
- ^{1} Department Of Zoology, Zagazig University, Zagazig, Egypt
^{*}Corresponding Author:
Mohamed El-DrawanyDepartment Of Zoology, Zagazig University, Zagazig, Egypt
Email:samy_drawany@yahoo.com
Received Date: Jul 27, 2017 Accepted Date: Sep 04, 2017 Published Date: Sep 18, 2017
Abstract
In the present study Age, Growth and Mortality of Terapon puta was estimated for 335 specimens collected by monthly sampling. This study was carried out from June 2012 to May 2013 in the Lake Timsah, Egypt. The age of Terapon puta was estimated by examining scales and it was found out that the maximum age was three years. The main total length and total weight values were calculated as 10.73±1.04 cm to 28.9±1.73 g and the calculated length-weight relationships were W = 0.023425 L^{2.88}. The von Bertalanffy growth parameters were L_{∞} = 17.18 cm, K = 0.2632 year^{-1} and t_{o} = -1.9363 year. The instantaneous rate of total mortality (Z) was 1.49882, the natural Mortality (M) was 0.4322 and the Fishing mortality (F) was estimated to be 1.06662. The exploitation rate (E) was calculated as 0.71 using value of M and F. Therefore, the population of Terapon puta off Lake Timsah was under the threat of over fishing.
Keywords
INTRODUCTION
Terapon puta is a medium size fish which inhabits the sea in Egyptian coasts. This fish has been popular as excellent sea food with a sensible market price. Though they are not commercially important, they constitute a regular fishery throughout the year. No information available regarding the growth studies of Terapon puta with the view of supplementing this, the present study was undertaken in the Lake Timsah, Egypt.
In this study, it is expected to determine the age, growth rate, length- weight relationship and age composition of Terapon puta with von Bertalanffy growth models. Additionally, the natural and fishing mortality and the level of exploitation of this fish species off Lake Timsah were also estimated. The main aim of the present study was to shed light on some biological and dynamic features of the Terapon puta. Using such information is essential for the management and the good precision of the fishing in the lake Timsah.
MATERIALS AND METHODS
Age was determined by counting the annual rings on the scales using micrometer eye piece. In order study the time of ring formation to establish its annular nature, the scales representing rings under formation (growth checks) at the outer margin in different months were examined. To clarify further, the time of annulus formation, the distance from the last annulus to the margin of the scales were measured. A plot of monthly frequency of such scales which have marginal rings indicated the seasonal and established the annual nature.
Length-weight relationship was obtained since the total weight of each fish specimen was given with a digital balance to an accuracy of 0.01 g and total length was measured with a precision of 0.01 cm. This relationship was determined according to the allometric equation given by Sparre et al., [3] as:
W = a L^{b}
Where (W) is the total body weight in g, (L) is total length in cm; a and b are regression constants (Figures 1 and 2).
Figure 1: Showing Terapon puta (12.5 cm).
Lt = L_{∞} (1 - e^{- k(t - to)} )
Whereas (L) is the asymptotic total length, (Lt) is the total length at age (t), (k) is the growth curvature parameter and (to) is the theoretical age when fish is at zero total length. These growth parameters were estimated by means of von Bertalanffy plot Sparre and Venema [4].
Total mortality rate (Z) was estimated based on the length at first capture methods evaluated by Beverton and Holt [5].
L_{∞} - L_{m}
Z = K * (--------------)
Lm - LC
Where: Lm = The average total length of the entire catch.
LC = The length at which 50% of the fish entering the gear are retained Sparre et al., [3].
Instantaneous natural mortality rates (M) were estimated using the equation derived by Ursin [6] based on the mean total length where:
M = W–(1/b)
W = Mean total length.
b = Constant of length weight relationship.
Fishing mortality rates (F) were calculated as the difference between Z and M (Z = F + M). The value of the average annual exploitation rate (E) was obtained by E = F/Z.
RESULTS
Figure 3: Length frequency distribution for Terapon puta off Lake Timsah in Egypt.
The time of the annulus formation
The mean marginal growth was calculated from scales for each month in order to establish the time of annulus formation which is shown in table 2 and represented graphically in figure 4 for Terapon puta. From table and figure it is indicated that the annulus formation occur in the month of Apr. and this means that the annual rings were formed in the period of spring.
Figure 4: Monthly record of marginal growth for the scales of Terapon puta of Lake Timsah in Egypt.
Month | Jan | Feb | Mar | Apr | May | June | July | Aug | Sept | Oct | Nov | Dec |
No. of Fishes | 10 | 12 | 9 | 10 | 9 | 10 | 7 | 9 | 11 | 13 | 10 | 10 |
MarginalIncrement(mm) | 0.036 | 0.030 | 0.032 | 0.015 | 0.020 | 0.037 | 0.043 | 0.056 | 0.050 | 0.046 | 0.040 | 0.036 |
The age composition and growth
The growth of the studied fish was described by the von Bertalanffy model Von Bertalanffy [7] based on the back-calculated length at age data (Figure 5). The estimated growth function was:
L_{t} = 17.18 cm (1 - e^{-0.3632 (t +1.9363)})
The growth constant (K) was estimated at 0.3632. However, the maximum theoretical length (L_{∞}) and t0 describes the theoretical age where L_{t} is zero were 17.18 cm and -1.9363, respectively.
Growth in length
Body length-scale radius relationship:
L = 3.19644 +1.48960 S (r = 0.996)
Where L is the total length in cm and S is the scale radius in mm.
Back-calculations
LN = (L – 3.19644) Sn / S+3.19644
Where: LN is the length at the end of n^{th} year, SN is the radius of the scale to n^{th} annulus, S is the total radius of the scale and L is the total length at capture. From the data given in table 3, it is obvious that, Terapon puta attains its highest growth rate in the first year of life, after which a gradual decrease in growth increments was noticed with further increase in age.
Age Group | MeanNumber | ObservedLength (cm) | Back Calculated Lengths | ||
1 | 2 | 3 | |||
0^{+} | 119 | 7.5 | 8.2 | ||
I^{+} | 124 | 11.8 | 8.4 | 11.46 | |
II^{+} | 93 | 14.3 | 7.4 | 11.18 | 13.8 |
Average total | 335 | 8.0 | 11.63 | 13.8 | |
Increment of length | 8.0 | 3.63 | 2.17 |
Length-weight relationship:
Figure 6: Length- weight relationship of Terapon puta off Lake Timsah in Egypt.
Growth in weight
Age Group | MeanNumber | Mean ObservationWeight (gm) | Back Calculated Weights | ||
1 | 2 | 3 | |||
0 | 119 | 10.13 | 8.71 | ||
I | 124 | 31.69 | 11.27 | 28.47 | |
II | 93 | 45.15 | 10.70 | 29.63 | 42.69 |
Average total | 335 | 10.22 | 29.05 | 42.69 | |
Increment of length | 10.22 | 14.17 | 17.96 |
The obtained results indicated that the growth rate in weight was slow during the first year of life. Then the annual growth increment in weight increased with further increase in age until it reached its maximum value at the end of the third year of life.
Mortality rates
Figure 7: Cumulative curve from which length at first capture was determined.
Exploitation rate (E)
Length at first Capture (LC)
DISCUSSION
Age and back-calculated growth were determined from annual rings in the scales. Increase in length is rapid during the first year and slow thereafter. This study showed that the mean annual growth rate for 0+-II+ year's old fish ranged between 2.17 and 3.3 6 cm (Table 3).
The result of the growth rate in the first year of the small scaled Terapon puta reported in the present study is 8.0 cm. The same result may be obtained by Sabrah et al., [10]. The largest individual caught in the Lake Timsah were 14.6 cm Similar observation was made by Sabrah et al., [10] concluded that based on the number of rings on the otoliths, the oldest fish were 2 years old (14.2 cm) recorded in Lake Timsah. While Allen and Swainston [11] in Australia reported 16.0 cm as a maximum total length of Terapon puta.
The present study on the length-weight relationship of Terapon puta from the Lake Timsah coast has been studied. It is known that the relationship between length and weight has been studied in different fish species all over the world. The (b) values in fish is species specific and varies with sex, age, seasons, physiological conditions, growth increment and nutritional status of fish Bagenal and Tesch [12]. The relationship between total length and total body weight of Terapon puta was revealed highly correlation (r2 0.98) and the relationship was computed as w = 0.023425 L^{2.88}. It is clear that the growth in weight of Terapon puta in lake Timsah was characterized by negative allometric growth (b < 3).The same result was obtained by Karna and Panda [13] who concluded that the value of exponent (b) of Terapon puta in Chilika Lagoon, Odisha (India) equal 2.76 as well Sabrah et al., [9] prove that the value of (b) of Terapon puta in Lake Timsah, Egypt equal 2.72. Also Nandikeswari and Sambasivam [14] finished to the exponent (b) equal to 2.0246 for males and 2.2074 for females. It is clear that, if b < 3, then large specimens have changed the body shape to become more elongated or small specimens were in better nutritional condition at the time of sampling Froese [15].
The von Bertalanffy growth parameters were estimated using scales of Terapon puta in Lake Timsah, Egypt (L_{∞}: 17.18 cm, K: 0.3632 year^{-1} and t_{0}: -1.9363 year). While the value of parameters reported by Sabrah et al., [10] was as L_{∞}: 15.5 cm, K: 0.7 year^{-1} for Terapon puta in Lake Timsah, Egypt. The estimated parameters may vary as a function of a variety of factors such as region, year and methodology Goncalves et al. [16].
The exploitation rate of Terapon puta in the present study (E = 0.71) is higher than 0.50 of Gulland suggested that as a rule of thumb a fish stock is optimally exploited at a level of fishing mortality that generates E = 0.50 where optimum fishing mortality equal the natural mortality (F = M). Therefore, the stock of small scaled fish (Terapon puta) from the lake Timsah is being acutely over-exploited such observation noted also from the lake Timsah by Sabrah et al. [10]. The estimating total and fishing mortality rates in the lake Timsah with the exploitation rates were very high.
CONCLUSION
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Citation:El-Drawany M (2017) Age, Growth and Mortality of Terapon puta (Cuvier, 1829) in the Lake Timsah, Egypt. J Aquac Fisheries 1: 002.
Copyright: © 2017 Mohamed El-Drawany, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.