Length-Weight Relationship and Condition Factor of Spotted Flounder Citharus linguatula (Linnaeus, 1758) in Iskenderun Bay, North-eastern Mediterranean, Turkey

A total of 252 spotted flounder, Citharus linguatula (Linnaeus, 1758) were caught in the Iskenderun Bay from October 2012 to September 2013 using a commercial bottom trawler. Length-weight relationships (LWRs), sex ratio and condition factor of the fish specimens were investigated. Within collected C. linguatula samples, most of the individuals ranged from 10.0 to 15.0 cm (80.15%), the minimum and maximum total lengths of the specimens were 7.0 and 18.5 cm, respectively. Negative allometric growth were observed for male, female and both sexes. The sex ratio (females: males) was 1:1.04. Length-weight relationships for females, males and both sexes, were calculated as W= 0.0099 TL, W= 0.0086TL and W= 0.0092TL, respectively Fulton’s condition factor (KF) values for female (0.7228) and male (0.7095) specimens also showed significant variations (P<0.01).


Introduction
The spotted flounder, Citharus linguatula (Linnaeus, 1758), is commercially important species in the east Atlantic and Mediterranean waters (Nielsen, 1986).C. linguatula is a flat and demersal fish that belongs to the family Citharidae.C. linguatula is most likely to be found at 10 to 100 m depth although it may be seen in shallow waters to 200 m depth (Froese & Pauly, 2016).
Length-weight relationship is an important component in fish and fisheries biology and very useful for fish population dynamics and fisheries management (Froese et al., 2011).The aim of this study is to determine length and weight parameters and condition factor of C. linguatula in the Iskenderun Bay, in order to compare the population characteristics of this species in the other regions.The data on length and weight parameters are expected to be helpful in fisheries management in the North-eastern Mediterranean part of Turkey.

Material and Methods
C. linguatula samples were obtained from the Iskenderun Bay (Figure 1) between October 2012 to September 2013 with commercial trawler, at depths ranging from 24 m to 55 m.Length and sex-ratio distributions were constructed separately for the specimens of species.Specimens were measured to the nearest 0.1 cm total length and weighted to the nearest 0.1 g.The isometric (b = 3) or allometric growth relationship between total length (TL, cm) and total body weight (W, g) was described for these fishes growing with their bodies becoming heavier using a plotted power function; W = axTL b in which a is the power function coefficient (the regression intercept) and b the exponent (the regression slope), (Ricker, 1975).The relationships were estimated by linear regression analyses based on natural logarithms: ln (W) = ln (a)+b ln (TL).
Prior to the analyses, ln-ln plots of length and weight values were performed for visual inspection of outliers in accordance to Froese (2006).Growths' were considered positively allometric if the estimate of b was approximately equal or greater than 3 and negative if less than 3. Fulton's condition factor (KF) (Cone, 1989) was calculated using the equation: KF = 100×(W/L -3 ).Where: W = Total body weight (W, g), L = Total length (TL, cm).The scaling factor of 100 was used to bring the KF close to unit.

Results
A total of 252 specimens of C. linguatula were examined with 48.8% (n=123) female and 51.2% (n=129) male.The ratio of female to male was 1:1.04.Total length values of overall, female and male specimens ranged from 7.0-18.5 cm, 7.6-18.4cm and 7.0-18.5 cm, respectively.Total weight values of overall were 2.88-46.86g; of females, 3.46-45.89g; and males 2.88-46.86g.The estimated parameters of the length-weight relationships are given in Table 1.There was not significant difference between length of male and female individuals.Females were larger than males (P>0.05).Negative allometric growth was observed for male, female and both sexes.Length-weight relationships for females, males and both sexes were calculated as W= 0.0099TL 2.874 , W= 0.0086TL 2.920 and W= 0.0092TL 2.896 , respectively (Figure 2, Figure 3 and Figure 4).Fulton's condition (KF) factor values also showed significant variations (P<0.01) with the best and worst performers being female (0.7228) and male (0.7095) for C. linguatula specimens, respectively.A comparison concerning the lengthweight relationship for the species was also made using the results achieved by previous studies (Table 2).

Discussion
There has been several data on the population length structure of C. linguatula in the Mediterranean Sea (Abdallah, 2002;Vassilopoulou & Papaconstantinou 1994;Moutopoulos & Stergiou 2002;Cicek et al., 2006;Karakulak et al., 2006;Sangun et. al, 2007).In the present study, females grow slight quicker and to a larger size (18.50 cm) than males (18.40 cm) in the Iskenderun Bay, Turkey (North-eastern Mediterranean).Vassilopoulou & Papaconstantinou (1994) reported that maximum length of C. linguatula for males and for females were 18.50 cm and 23.90 cm respectively from the Aegean Sea (Greece).
The equations of the length-weight relationship revealed no differences between sexes, with the coefficient b different from 3, indicating negative allometric growth.In this study, the values found for C. linguatula (b=2.896)showed a negative allometric growth.The allometric parameter estimate in the present study closely matches to the estimations given by Santos et al. (2002) and Borges et al. (2003)  by Campillo (1992) from the Eastern Atlantic (Italy), and by Petrakis and Stergiou (1995) from Aegen Sea (Greece) and also by Sangun et al. (2007) from the North-eastern Mediterranean (Turkey).However, Abdallah (2002) and Cicek et al. (2006) reported b values closer to isometric growth in Egypt coast and in Babadilli Bight (NE Mediterraenan Sea, Turkey), for C. linguatula.
In addition, the value of b in the present study differs from the estimations made by Merella et al. (1997), Mendes et al. (2004) and Torres et al. (2012) where they found positive allometric growths estimated as b=3.300, 3.207 and 3.084.Several factors are known to influence the length-weight relationships in fish, including gonad maturity, stomach fullness, season, health and preservation techniques (Bagenal & Tesch, 1978), all of which were not observed in the present study.
In conclusion, the present study provides some basic essential biological information on the native spotted flounder species, C. linguatula for fishery management from the Iskenderun Bay.

Figure 2 .
Figure 2. Length-weight relationships females of Citharus linguatula from the Iskenderun Bay, North-eastern Mediterranean coast of Turkey

Figure 4 .
Figure 4. Length-weight relationships of both sexes of Citharus linguatula from the Iskenderun Bay, North-eastern Mediterranean coast of Turkey

Table 1 .
Length-weight relationships of C. linguatula from the Iskenderun Bay (the Northestern Mediterranean, Turkey)

Table 2 .
Biogeographic comparison of LWRs parameters for C. linguatula from the Algarve coast (southern Portugal), and