Abstract: In this research, population structure of the species Aphanius danfordii found in Sirakaraağaçlar stream has been studied. During the research, sex, age, weight and length composition of 452 fishes has been examined and lenght-weight relationship and Von Bertalanffy growth function has been calculated. Female-male sex proportion has been calculated as 1.06:1.00, lenght-weight relationship and Von Bertalanffy growth function has been calculated as W = 0.0139 L^3.1641, L_t = 5.149 (1-e^{-5.945 (t-0.502)}) and W_t = 2.483 (1-e^{-5.945 (t-0.502)}).

INTRODUCTION

Turkey has created an environment with its zoogeographic location that many sub-cultures are found by enabling environments to be formed, the ecological factors of which differ from each other. When the first evolution periods of the world are considered, all the living things were evaluated within specific classes and the fishes moving from sea to fresh waters were examined under the name secondary fresh-water fishes. The oldest secondary fresh-water fish species known in Anatolia are the species which belong to type Aphanius.

In the latest taxonomic studies carried out on Aphanius sp. which are defined 14 species that belong to 6 species and 4 subspecies occur in Anatolia, Aphanius asquamatus, A. mento, A. anatoliae, A. fasciatus, A. danfordii, A. villwocki and sub-species are A. anatoliae anatoliae, A. anatoliae splendens, A. anatoliae sureyanus, A. anatoliae transgrediens (Wildekamp et al., 1999; Hrbek et al., 2002; Hrbek and Wildekamp, 2003).

Aphanius danfordii is endemic in Turkey that widely known as Killifish. In several studies, this species has been defined as A. danfordii however, it has been synonymized as A. chantrei by Wildekamp et al. (1999). A. danfordii could live in freshwater to lightly brackish water with exception of some algae, these habitats lack submerged vegatation and feed on crustaceans, insect larvae and some plankton species (Aksiray, 1987; Frenkel and Goren, 2000; Demirsoy, 1999; Hrbek and Meyer, 2003).

In the several studies carried out on Aphanius sp. (Homski et al., 1994; Frenkel and Goren, 2000) it has been indicated that these fishes may have bio-indicator features due to high tolerance they have for organic and inorganic pollutions and low amount of O₂. Moreover, research of the bio-ecologic characteristics of the species belonging to Aphanius type which has a prominent place in respect of biological diversity in Anatolia is important for living resources to be protected.

For this reason, various biological characteristics of the species Aphanius danfordii living in Sirakaraagaclar stream found in Sinop-Akliman area has been examined.

MATERIALS AND METHODS

Study area: Sirakaraagaclar stream is located in Sinop-Akliman zone of occupation in the north of Turkey (42°21' 24"N-35°1'5"E) (Fig. 1). Total length of the stream with two is 3.2 km. Its average depth is 1.5 m and maximum depth is 2.5 m. While its bottom part is of muddy structure, the part of the stream which opens to sea is of sandy structure. In periods of heavy raining, the areas around the stream used for agriculture turn into marsh due to large amount of water flow. Water heat change is between 5-26.1°C and salinity is between 0-4 ppt for a year. Apart from A. danfordii, fish species of the stream are Pleuronectes sp., Gobius minutus, Gobius niger, Neogobius melanostomus, Cyprinus carpio, Gasterosteus aculeatus.

Fish samples have been collected from Sirakaraagaclar stream through the landing-net of 30 cm diameter and 2.5 m length with a 1 mm mesh size. A. danfordii samples caught have been first divided into two groups as female and male in the sampling area according to their morphological structures and have been carried to the laboratory for examination.

Physical and chemical parameters of the study area were measured at average depth of 75 cm. The age was determined from scales taken from the part between dorsal fin and pectoral fin close to dorsal.

Fig. 1:	Study area (Siraykaraagaclar stream)

Total Lengths (TL) of fishes were measured by scale and total weights were recorded with a digital scale to the nearest 0.001 g.

The relation between weight and total length was established by the exponential regression equation W = a x L^b where W is the weight in g, L is length in cm, a and b is the parameters to be established. Age-length relationship was calculated through the Von Bertalanffy growth function L_t = L_∞ (1-e^{-K (t-to)}) and age-weight relationship was calculated through Von Bertalanffy growth function W_t = W_∞(1-e^{-K (t-to)})^b (Erkoyuncu, 1995).

Statistical importance controls were made with t-test. p<0.05 confidence limit was taken as a basis. (Duzgunes et al., 1995; Uyanik and Bat, 2004).

RESULTS AND DISCUSSION

Age and sex composition: It has been determined that 66.37% of 452 A. danfordii species caught between the dates 2005 June-May 2006 from Sirakaraagaclar stream in Sinop-Akliman zone of occupation belong to 0⁺ age group, 31.86% of them belong to 1⁺ and 1.77% of them belong to 2⁺ age group.

About 51.55% of the total A. danfordii population represents female fishes while 48.45% of them represent male fishes. Female-male proportion of the fishes within the population was found out to be 1.064:1.00 (p>0.05). Composition of the age groups within the population and their sex proportions are shown in the Table 1.

Table 1:	Age and sex composition of A. danfordii population

Table 2:	Sirakaraagaclar stream age-total length (cm) composition in A. danfordii population

Length composition: Total Lengths (TL) of the fishes were which belong to the species Aphanius danfordii taken from Sirakaraagaclar stream range from 1.8-5 cm. It has been found out that this length composition changes between 1.9-5 cm for female while it was changes between 1.8-4.8 cm for male (Table 2). Approximately 80% of the samples are comprised of individuals within 2-4 cm length group (Table 3).

Weight composition: Weights of the fishes were which belong to the species Aphanius danfordii taken from the study area changes between 0.09 and 2.6 g. It has been found out that this weight composition changes between 0.2 and 2.6 g for female fishes and it changes between 0.09 and 1.8 g for male fishes according to ages (Table 4). Approximately, 72% of the samples are comprised of individuals within 0.2-1 g weight group (Table 5).

Length-weight relationship: In the population made up of 452 Aphanius danfordii individuals caught from the study area, length-weight relationship of individuals was exponentially and logarithmically examined and the coefficients and equations obtained were shown in Fig. 2-4. According to Von Bertalanffy growth functions, age-length relationship was calculated to be L_t = 5.149 (1-e^{-5.945 (t-0.502)}) and when the obtained data was generally examined, the difference between measured length and length values calculated through growth functions was found to be not significant (p>0.05).

According to Von Bertalanffy growth functions, age-weight relationship was calculated to be W_t = 2.483 (1-e^{-5.945 (t-0.502)})^3.1641 and the difference between measured weight and the weight calculated through growth functions was found to be not significant (p>0.05).

Table 3:	Sirakaraagaclar stream length composition in A. danfordii population

Table 4:	Sirakaraagaclar stream age-weight (g) composition in A. danfordii population

Table 5:	Sirakaraagaclar stream weight composition (g) in A. danfordii population

In this study the species A. danfordii that found in Sirakaraagaclar stream were investigated and the female:male proportion was found to be 1.064:1.00 (p>0.05). This value is close to the proportion of 1.00:1.00 desired to exist in nature. Moreover this proportion is similar with A. mento and A. iberus (Delgado et al., 1988) but differs from female-male proportion (0.64:1.00) in the study made by Guclu et al. (2007) in the lake of Burdur on the species A. anatoliae sureyanus and the female-male proportion (2.44:1) in the study made by Leonardos and Sinis (1999) in Mesolongi and Etoligon lagoon (Greece) on the species A. fasciatus. And also, it has been stated that proportion of female individuals in A. fasciatus population increase from the end of spring until the beginning of summer and the survival rates of female individuals are more than that of male individuals (Leonardas and Sinis, 1998). Length, weight and age relationships of A. danfordii individuals found in Sirakaraagaclar stream show that the lengths of these fishes are small and the populations is comprised of young individuals.

Fig. 2:	The total lenght-weight relationships of A. danfordii from the Sirakaraagaclar stream (female)

Leonardos and Sinis (1999) determined A. fasciatus, in Mesolongi and Etoligon lagoon (Greece), that the longest female fish is of 70.65 mm and the longest male fish is of 68.12 mm. In the study made by Keivany and Soofiani (2004) on the species A. vladykovi, maximum value recorded for female is 76 mm and for male is 58 mm.

Fig. 3:	The total lenght-weight relationship of A. danfordii from the Sirkarragaclar stream (male)

Fig. 4:	The total lenght-weight relationship of A. Danfordii from the Sirakaraagaclar stream (female-male)

In the study made in Kirkgoz spring (Turkey) on the population of A. mento, it has been found out that the longest female fish is of 87.8 mm and the longest male fish is of 74.4 mm.

Body weights determined in A. danfordii individuals change between 0.09 and 2.6 g. Body weights of the fish samples obtained in the study made by Guclu on the species A. mento changes between 0.09 and 17.56 g. Weights in A. fasciatus individuals change between 65.0-4598.9 mg (Leonardos and Sinis, 1999).

Keivany and Soofiani (2004) determined maximum weight as 7.10 g for female fishes and 3.70 g for male fishes in the individuals which belong to the species A. vladykovi. The differences between the lengths and weights of fishes are owing to they belong to different species and they live in different environments. The age of A. danfordii from Sirakaraagaclar stream ranged from 0-2 and the individuals in age group 0 contain 66.37% of population. The age of A. iberus from Guadalquiver stream (Delgado et al., 1988) and from La Rubina lagoon (Berthou and Amich, 1992) ranged from 0-2 and the age of A. vladykovi from Modar-Dokhtar spring (inland of Iran) (Keivany and Soofiani, 2004) ranged from 0-2. However, in the study made by Guclu et al. (2007) in the lake of Burdur on the species A. anatoliae sureyanus, it has been stated that there are individuals within the age group 0-4 and ages within the A. fasciatus population from Mesolongi and Etolikon lagoon in the west of Greece ranged from 0-6 age group (Leonardos and Sinis, 1999).

As a result of the examination of A. mento population spreading in Kirkgoz Spring, individuals between the age group 0-7 has been found out. According to Nikolsky (1980), age composition in a population is of wide range as the indication of adequate level of nutrient status of that water system.

In the study, b value within the total length-weight relationship of A. danfordii individuals were determined 3.1641. This result shows that A. danfordii individuals in Sirakaraagaclar stream have an isometric growth. The relationship total length-weight of A. danfordii species correlation coefficient r = 0.987. In this study relationship (r = 0.987) is similar to A. fasciatus (r = 0.976) (Koutrakis and Tsikliras, 2003), A. iberus (r = 0.987) (Andreu-Soler et al., 2006), A. iberus (r = 0.992) (Verdiell-Cubedo et al., 2006), A. fasciatus (r = 0.990) (Gaygusuz et al., 2006). But it differs from A. vladykovi (Keivany and Sofiani, 2004), A. mento (r = 0.865) (Guclu and Kucuk, 2008).

CONCLUSION

As a result, Sirakaraagaclar stream is one of the most suitable habitats for the species A. danfordii to reproduce and survive. Although, owing to it is among the endemic fish species and has a prominent place for biological diversity is very important with regard to living resources.

ACKNOWLEDGEMENTS

The researchers are grateful to the Sinop University for supporting this research. The researchers also like to thanks for research assistant Dilek Sahin for technical treatment during the experimental phase and preparation of manuscript.