The growth characteristics of Liza ( Mugil ) abu ( Heckel , 1843 ) in Atatürk Dam Lake

In this study, the population features of Liza abu in the Atatürk Dam Lake were examined. During the month of March 2004 and February 2005 period, 821 fish samples were collected by gillnets with mesh sizes of 18, 22, 26, 30, 34 and 38 mm. The total length differed between 11.10 and 22.20 cm. The total weights were 16.20 to 136.60 g, and the age distribution was between 1 and 5. 50.99% of the caught samples were female and 49.01% were male. The average condition values were K = 1.18 for males and K = 1.15 for females. The length-weight relationship was calculated as Log W = -0.87 + 2.08*Log L for males and Log W = -1.79 + 2.88*Log L for females. The Von Bertalanfy growth parameters were L∞ = 24.63 cm, K = 0.28, Lt = 24.63(1-e -0.28(t-(-1.36) ), to = -1.36 years, W∞ = 362.95 g, K = 0.07 and Wt = 362.95 (1-e -

Several studies have been done about the fish inhabiting in the Euphrates and Tigris rivers and their branches (Beckman, 1962;Bozkurt, 1994;Şevik and Bozkurt, 1997).The presence of Liza abu in the Euphrates and Tigris river system of Turkey was mentioned for the first time by Kuru (1979).There are many studies showing Mugil species except L. abu living Mediterranean connected waters of Turkey (Balik et al., 1992).There are also other researches carried out in other regional countries showing L. abu inhabits in Euphrates and Tigris river systems (Mahdi, 1967;Değer et. al., 2013).The feeding ecology of Liza ramada in the south-west of Portugal, Almeida (2003) and the age estimation and scales of Liza aurata in Greece's Ksilova (Messolonghi) lagoon were studied (Hotos, 2003).Akın et al. (2005) showed that, there were 7 species except L. abu belonging to the Mugilidae living in the Köyceğiz lagoon in Turkey.However, the first noteworthy study about L. abu inhabiting in other waters out of the Mediterranean was performed by Ünlü et al. (2000).
Many data exists on the growth characteristics of freshwater fishes in regarding the effects of different water conditions.After construction of Atatürk Dam in 1990, L. abu population could not find an opportunity to migrate to the sea.So, these conditions might affect some characteristics of this population.
The aim of this study was to determine some growth characteristics such as total length and weights, sex, age composition and the findings may reflect the effects of the newly constructed dams on the L. abu.

Working area
The Atatürk Dam Lake has a surface area of 81700 ha (Karadede et al., 2004).This feature makes it the biggest dam and the second biggest inland water of Turkey.It has been built for irrigation and energy purposes, but it is also important for the fishery points (Figure 1).

Data analysis
The total of 821 L. abu caught during the period of March 2004 to February 2005 constituted the fish material.The samples were caught by gill nets, and they were brought immediately to the laboratory where their lengths were measured in centimeters.Then, their total weights were weighed by using a scale with 0.01 g sensitivity.
The evaluation of data and statistical calculations were done on MS Excel program.The significance between different checked parameters was controlled by using χ² test.The length-weight relationship was calculated by the logarithmic explanation of the equation W = a*L b (Le Cren, 1951).In this equation, the values W = total weight, L = total length, a = the weight of the unit fish length, b = relative growth index between length and weight.The condition factor was calculated with the formula K = W/L³*100.Since the age estimation from hard tissues of boned fishes is reliable (Hoşsucu, 2000), the ages estimation of L. abu were determined from otoliths that photos were taken with a stereo-microscope and an inverted photo-microscope (Nikon SMZ 2 T stereo).The Von Bertalanffy equation was calculated by the regression method.
For the length L∞ = a/(1-b), for the weight W∞ = a/(1-b), for hypothetical zero age t0 = (Ln (L∞)-a2)/b2 and for any t age the length Lt = L∞ (1-e Kt-t 0) ) and for the weight Wt = W∞ (1-e Kt-t 0 ) ) equation have been used (Avşar, 1998).In these equations, L∞ and W∞ show the infinite length and weight of the fish, K = Body growth coefficient (year -1 ), t0 = the hypothetical age (in years) of the fish before coming out of the egg and Lt and Wt shows the length and weight at the t age.

RESULTS
The smallest female specimen of L. abu population was determined as 13.70 cm, and this value also showed the lowest fishing length.Out of the 821 specimens caught, 65 of them (7.92%) were smaller than 13.70 cm in total length.As the sampling was made with nets used in commercial fishing, approximately 8% of L. abu were caught before the female reached the stage of sexual maturity.As this is an indicator of early fishing, this character has been found to be statistically significant by the χ² -test (χ²-= 582.29,P > 0.05).

Sex and age composition
Out of the 821 caught specimens, the sexuality determination was done on the 810 specimens, and it was found that, the male: female ratio was 1.04 (49.01:50.99%)and the χ² test was (χ² = 0.32, P < 0.05).These results showed that, the difference between the male: female ratio is not statistically significant.The sexuality composition, length distribution and the standard deviation are given in Table 1.
The total lengths of the sexualities changed between 11.10 to 22.20 cm.Out of these specimens 306 were in   The age groups of the collected specimens showed a distribution of 1 to 5 years.As there were no specimens caught in the 0+, there were also any specimens in the 6 years age group.The examples (where the age areas have been shown) of every age group of otoliths of L. abu are in Figure 2.

The condition, length-weight relationship and growth features
Monthly condition change values have shown similarity in the two sexualities.In both sexualities, the condition values were found to be the lowest in July (male = 1.07 and female = 0.99), however the highest values were determined in August (male = 1.37 and female = 1.30).The conditional values of male and female sexualities according to the months have been given in Figure 3.
When the length-weight relationship considered, the data belonging to the 397 male specimens have been calculated with log a = -0.87 and b = 2.08 and the data belonging to 413 female specimens have been calculated with log a = -1.79 and b = -2.87.The length-weight relationship for the male and female specimens can be seen in Figure 4. Also, the regression equations were given on the graph of same figure.
For the Von Bertalanffy, the formula of the average lengths and weights of the age groups have been given in Table 3.The values in Table 4 have been calculated from the data in Table 3.

DISCUSSION
The age distribution of the total of 821 specimen of L. abu population caught from the Atatürk Dam Lake was varied from the ages of 1 to 5, and their total length varied from 11.10 to 22.20 cm.Age groups of L. abu living in the Tigris River were varied between ages of 1 and 5, and their fork lengths were determined as between 11.50 and 19.20 mm (Ünlü et al., 2000).Our findings in the Atatürk Dam were similar to Tigris River.
Out of the 1048 specimens of L. aurata, living in the Messolonghi lagoon in the west of Greece, the age groups were varied from 0+ and 8+, (only female specimens were found in 7+ and 8+ ages) and the total lengths were determined as 9.00 to 59.00 cm (Hotos, 2003).In the same article, the researcher emphasized that, the total lengths of the L. aurata in some other studies were varied between 20.00 and 42.00, 8.10 to 41.40, 7.30 to 30.00, 2.00 to 29.00 cm.The reason for
In our study, the caught specimens constituted of 49.01%male and 50.99% female (1:1.0403).Similarly, in the Mugil cephalus population in Greece this ratio was 51: 49 (Katselis et al., 2005).As a result of the study, it was determined that, both of the sexualities belong to the L. abu specimen were in their lowest condition in July (male = 1.07 and female = 0.99) and were in their highest condition in August (male = 1.37 and female = 1.30).The highest L. abu condition for both sexuality living in the Tigris River were determined in August, however, any values could not have been recorded in July (Ünlü et al., 2000).These highest values determined in August were in harmony in both studies.The condition values being the lowest in Atatürk Dam in July showed that, reproduction activity of L. abu was completed before July.Graphics and equations belong to the 810 specimen for both sexualities can be seen in Figure 4. Logarithms taken for the same equation data were determined as simple linear regression form in Morocco's Zerga, Tunisia's Ichkeul, and Egypt's Edku lakes as y = 3.15 × -2.25 and R² = 0.97; y = 2.82 × -1.74 and R² = 0.83; y = 3.13 × -2.22 and R² = 0.84, respectively (Kraïem et al., 2001).The calculations by taking the fork length as the base made on the females of L. abu living in the Tigris river were determined as log W = -5.85+ 3.44 log FL (R² = 0.96) and W = -5.37 + 3.22 log FL (R² = 0.95) for males (Ünlü et al., 2000).
The L∞, K and t 0 values in Table 4 were found to be higher than the values L∞ = 195.77mm, K = 0.38 and t 0 = -1.96found for the same species in the Tigris river.Once again, the value W∞ = 362.95g obtained at the Atatürk Dam was higher than that of the Tigris river and K = 0.07 value was lower than that of the Tigris river (Ünlü et al., 2000).The same values were found for L. ramada in Morocco's Zerga, Tunisia's Ichkeul and Egypt's Edku lakes to be for L∞ 50.70, 53.00, 54.60, for the value K 0.21, 0.22, 0.23 and for t 0 -0.31, -0.19, -0.08 (Kraïem et al., 2001).In the same study, L∞ for L. ramada in France were determined as 31.60 cm for males and 47.00 cm for females; in Greece 31.60 cm for males and 45.90 cm for females.The L∞ values determined for L. abu were smaller than the L∞ values established for L. ramada.
The smallest female specimen of L. abu population was determined as 13.70 cm, and this value also showed the lowest fishing length.Out of the 821 specimens caught, 65 of them (7.92%) were smaller than 13.70 cm in total length.As the sampling was made with nets used in commercial fishing, approximately 8.00% of L. abu were caught before the female was reached the sexual maturity.
As this is an indicator of early fishing, this character has been found to be statistically significant by the χ²-test (χ²-= 582.29,P > 0.05).
As seen in Table 1, it is excited that, there are no male specimens bigger than 17.90 cm.Our results is similarity to that of Ünlü et al. (2000) study, they determined the fork length 18.70 mm for male and 19.20 mm for female.In a research at L. aurata carried out in Greece, it was determined that, males live until the age of 6 and 48.80 cm length, females live until the age of 8 and 52.80 cm length (Hotos, 2003).Our results showed the similarity with male not living as much as female.
L. abu is a species of the Mugilidae that goes to the sea for the completion of their reproduction cycle.The research population could not migrate from the river to the sea as of 1990, since after this date the water was started to keep in Atatürk Dam.This situation could have affected some of the features of the research species.Some Mugil species could adapt to 100.00% fresh and 100.00% salty (S = 39%) water (Chervinski, 1977).However, it can be expected that, Mugil species in fresh water, which had been cut off from the sea may expose the growth and reproduction problems.In normal situation, it can be expected that, there would be a strong relationship between the length and weight gain.Building of Atatürk Dam highly affected living story of the L. abu species.In our study, low R² values showed that, some characteristics such as length-weight relationship (R² = 0.58 for the male and R² = 0.79 for the female) were affected by the cut off from the sea.Some studies related to this subject stated that, the lowest R² value was found to be 0.83 in Mugilidae (Kraïem et al., 2001).
According to these results, Atatürk Dam Lake may have affected some growth characteristics of L. abu by changing water conditions and also feeding conditions.Further studies are needed to search the effects of Atatürk Dam on L. abu species in the near future.

KFigure 3 .
Figure3.The conditions of male and female sexualities according to the months.

Figure 4 .
Figure 4. Length-weight relationship of male and female sexualities.

Table 1 .
The length groups of L. abu in Atatürk Dam according to the sexualities and the specimen numbers with their standard deviations.

Table 2 .
The average length and weight with their standard deviations and minimum and maximum limits according to the age groups.

Table 3 .
The average length of the age groups and the Von Bertalanffy equation data.