The First Data on the Biology of Anatolichthys meridionalis (Actinopterygii, Aphaniidae): an Endemic and Endangered Fish of Turkey (Dalaman River Basin)

Abstract

Species belonging to the Aphaniidae, extant as well as fossil, are widel distributed along the late-period Tethys Sea coast lines. Among the mentioned genera, Anatolichthys is the genus that includes the 13 species. Anatolia has been a center in the diversity of Anatolichthys. The study is one of the first studies on the growth of the species. On this occasion, in study, it was aimed to examine the growth parameters of the Anatolichthys meridionalis Akşiray, 1948 population, which is an endemic and endangered species in Anatolia. The population structure of endemic species Anatolichthys meridionalis in Gökpınar Spring (Dalaman River basin-Turkey) (37.34° N, 29.44° E) was studied, using 108 fish in October 2019 and September 2020. The growth and reproductive characteristics of A. meridionalis were examined in the study. Males made up 42.59%, females 57.41% of the population. The length-weight relationship and Von Bertalanffy growth equation were W = 0.0112L^3.4638, R² = 0.9793, L_t = 22.97 (1 – e^{–0.0304 (t+2.834)}), respectively. Average growth performance and condition factor are calculated as 1.21 and 1.84, respectively. The gonadosomatic index was found in a maximum value (12.742%) in July and a minimum value (0.545%) in January. Reproduction time was found to be in between of July and September. The mean fecundity and mean egg diameter were found as 147.94 ± 28.03 number/individual/year and 1.35 ± 0.04 mm, respectively. The first maturation was found to be at age I. First maturity length (L_m) was estimated at 23.95 mm for females and 22.04 mm for males. Although the study shows that the species has no problem in finding food and is a population with a wide age range, the presence of invasive species in the habitat, the habitat is directly affected by pollution from agricultural activities, water is drawn by pumps for agricultural activities, and it is narrowly distributed and endangered species, A. meridionalis and its habitat Gökpınar Spring should be protected.

INTRODUCTION

Species belonging to the Aphaniidae, extant as well as fossil, are widely distributed along the late-period Tethys Sea coast lines. Today, species belonging to the Aphaniidae family are found in North Africa, South-Western Asia and Europe (Wildekamp et al., 1999; Freyhof and Yoğurtçuoğlu, 2020). 19 species belonging to 4 genera (Anatolichthys, Aphanius, Kosswigichthys, Paraphanius) of Aphaniidae family spread in Anatolia (Freyhof and Yoğurtçuoğlu, 2020). Among the mentioned genera, Anatolichthys is the genus that includes the most species; Anatolichthys villwocki, A. transgrediens, A. iconii, A. anatoliae, A. fontinalis, A. sureyanus, A. splendens, A. saldae, A. marassantensis, A. maeandricus, A. irregularis, A. danfordii and A. meridionalis. In this context, Anatolia has been a center in the diversity of Anatolichthys (Freyhof and Yoğurtçuoğlu, 2020).

Many studies have been conducted to determine the molecular taxonomic and population characteristics of Anatolichthys species. However, most of the studies aimed at determining the ecological characteristics did not go beyond the studies of the length-weight relationships (Birecikligil et al., 2016; Yoğurtçuoğlu and Ekmekçi, 2015; Kırankaya et al., 2014; İnnal et al., 2019). There are 2–3 studies that reveal all bio-ecological characteristics of species belonging to the genus (Güçlü et al., 2007; Güçlü, 2012; Yoğurtçuoğlu and Ekmekçi, 2013; Yoğurtçuoğlu et al., 2020).

A. meridionalis Akşiray, 1948 is an endemic cyprinodontid restricted to a few populations found in a few springs in the Dalaman River basin (Burdur-Denizli province), Lake Gölhisar, Yeşilova (Burdur), Kocapınar and Kırpınar springs (Antalya) (Freyhof et al., 2017; Freyhof and Yoğurtçuoğlu, 2020). The species is of great importance in determining the zoogeographic distribution of other species in Anatolia and understanding the status of tetis remains (Hrbek et al., 2002; Hrbek and Meyer, 2003). However, there are no studies on the biology of the species so far. Especially for endemic species, before determining the conservation status and management, it is necessary to reveal their biology, particularly life history characteristics. For this purpose, in this study, the first data about the biology of A. meridionalis has been tried to be revealed.

MATERIALS AND METHODS

The study was carried out in Gökpınar Spring (Dalaman River basin-Turkey) (37.34° N, 29.44° E). Montly samples were carried out in October 2019 and September 2020 with drift nets of tulle of 2 mm mesh size and 108 individuals were caught from Gökpınar Spring. Sampling could not be done only in April 2020 due to covid-19 epidemic restrictions. Fish species found in the same locality are Gasterosteus aculeatus, Gambusia holbrooki and Oncorhynchus mykiss. Specimens were measured to the nearest 0.01 cm total length (TL) and weighted to the nearest 0.01 g total weight (W). The age was determined from scales taken from the left side of the body, between the end of the pectoral fin and the beginning of the dorsal fin. Observations were made using a stereoscope with transmitted light.

Female and male distributions were determined according to age. The overall ratio of males to females was evaluated with χ² test (0.05) (Düzgüneş et al., 1995). Total length and weight in cm frequency distributions for all specimens were calculated. The relation of weight to total length was established using the exponential regression equation

1

where W was the body weight in g, TL the total length in cm, “a” is intercept and “b” is regression coefficient. The coefficient of determination (R²) was also estimated (Ricker, 1975). The growth of the A. meridionalis population was estimated with the following Von Bertalanffy growth equations:

2

where L_t is the total length in cm at age “t”, L_∞ the average asymptotic length in mm, k the body growth coefficient, “t_o” the hypothetical age and “a” and “b” constants (Le Cren, 1951). The statistical significance level of the coefficient of determination (R²) and 95% confidence intervals (95% CI) of b were also estimated (Zar, 1999). Comparison of the difference of slope value from b = 3 (isometric growth) for all species, Pauly’s t-test was performed (Pauly, 1984).

Pauly’s t-test was calculated as:

3

where is the standard deviation of the values, is the standard deviation of the values, n is the number of fish species used in the computation. The value of b is different from 3 if t value is greater than the tabled t values for n – 2 degrees of freedom (Pauly, 1984). Measured total length and calculated total length in Von Bertalanffy growth equation were evaluated with t test (0.05). Average growth performance (Ø', phi prime) was calculated with the formula (4) (Gayanilo et al., 1988):

Ø' = log k + 2 log L_∞ (4)

Fulton’s coefficient of condition factor was calculated by Cf = (W/TL3) × 100 (Sparre and Venema, 1992). The gonadosomatic index (GSI) was calculated as:

5

where GW was the gonad weight and W, the total body weight of the fish (Gibson and Ezzi, 1980). Spawning period was determined from monthly evaluation of GSI. Fecundity was estimated by gravimetrically from the number of mature oocytes in 31 ripe females (spawning stage). The diameters of eggs were measured by means of a microscobic micrometer (Nikolsky, 1980). The method used to estimate the maturity level of mature females was based on fitting of the sigmoid, logistic curve. Estimation of the length at first sexual maturity is as follows (De Martini et al., 2000): Firstly, it was plotted L against ln[(1 – P_x)/P_x] using simple linear regression to estimate values for “a” and “b”, where P_x is the observed proportion of mature at length x. Secondly, the mean lengths at 50% maturity was calculated by Lm = –a/b. Thereafter, the estimated proportions of mature at length L were calculated using the equation (6) and give of first sexual maturity was drawn.

6

where PL is the estimated proportion of mature at length L (De Martini et al., 2000).

RESULTS

The age of the fish ranged from I to IV years. The dominant age groups are I and II age groups (Table 1–3). Of the total fish examined, 46 (42.59%) were male and 62 (57.41%) female. The overall ratio of males to females was 0.74 : 1.00 and χ² analysis showed this to be significant (p < 0.05) (Table 1). The age distribution shows for age classes (Tables 2, 3), total length and weight in frequency distributions (Fig. 1). The total length and weight range were from 1.91–4.28 cm, 0.09–1.93 g respectively (Fig. 1; Table 2, 3).

Table 1.  .

Age and sex distribution of females (F), males (M) and all A. meridionalis specimens

Age group	F		M		F + M		M : F
	N	%N	N	%N	N	%N
I	28	25.93	17	15.74	45	41.67	0.61 : 1.00 (p < 0.05)
II	23	21.30	15	13.89	38	35.19	0.65 : 1.00 (p < 0.05)
III	8	7.41	12	11.11	20	18.52	1.50 : 1.00 (p < 0.05)
IV	3	2.77	2	1.85	5	4.62	0.66 : 1.00 (p < 0.05)
Σ	62	57.41	46	42.59	108	100	0.74 : 1.00 (p < 0.05)

N—number of samples, N%—percent of samples.

Table 2.  .

Total length (min–max) and age composition of females and males of A. meridionalis

Total length, cm	Age class								Total
	I		II		III		IV
	♀	♂	♀	♂	♀	♂	♀	♂
1.91–2.21	10	7							17
2.22–2.52	3	4							7
2.53–2.83	12	6		8					26
2.84–3.14	3		5	7		7			22
3.15–3.45			12			3			15
3.46–3.76			6		5	1			12
3.77–4.07					3	1			4
4.08–4.38							3	2	5
∑	28	17	23	15	8	12	3	2	108
M ± SD (min–max)
♀	2.46 ± 0.06		3.28 ± 0.03		3.73 ± 0.04		4.21 ± 0.05		3.40 ± 0.05
	(1.97–2.89)		(2.96–3.61)		(3.58–3.92)		(4.11–4.28)		(1.97–4.28)
♂	2.31 ± 0.07		2.81 ± 0.01		3.20 ± 0.09		4.18 ± 0.004		3.11 ± 0.04
	(1.91–2.69)		(2.73–2.89)		(2.90–3.96)		(4.18–4.19)		(1.91–4.19)

M ± SD—avarage length + standard deviation.

Fig. 1.

Total length (a) and weight (b) in frequency distributions for A. meridionalis. F—female, M—male, F + M—all specimens.

The following Von Bertalaffy growth equation was obtained for all L_t = 22.97 (1 – e^{–0.0304 (t+2.834)}) (Fig. 2). The differences between observed and expected total lengths were statistically not significant in all age groups (t-test, p > 0.05) (Table 4). Average growth performance (Ø', phi prime) is calculated as 1.21.

Fig. 2.

L_∞ value according to Von Bertalanffy growth equation of A. meridionalis.

Table 4.  .

Measured avarage total length and calculated avarage total length values by ages groups in Von Bertalanffy growth equation of A. meridionalis

Age group	Observed avarage length, cm	Expected avarage length, cm	t-test
I	2.40	2.52	p > 0.05
II	3.10	3.13	p > 0.05
III	3.41	3.73	p > 0.05
IV	4.20	4.30	p > 0.05

Monthly changes in GSI are plotted in Fig. 3. Spawning occurred between July and September. The GSI values reached a maximum in July (12.742%) and declined rapidly thereafter, reaching a minimum in January (0.545%) (Fig. 3). The first maturation was found to be at age I. First maturity length (L_m) was estimated at 23.95 mm for females and 22.04 mm for males (Fig. 4). Average fecundity per individual was found to be 147.94 ± 28.03 number/individual/year (minimum 18 number/individual/year, maximum 355.78 number/individual/year) (Fig. 5, Table 5). Average egg diameter was measured 1.35 ± 0.04 mm.

Fig. 3.

GSI values by months of A. meridionalis population in Gökpınar (Sampling could not be done in April 2020 due to covid-19 epidemic restrictions).

Fig. 4.

Length at first maturity of male and female A. meridionalis population in Gökpınar Spring. Vertical black arrows indicate first maturity (L_m).

Fig. 5.

Fecundity values by months of female individuals with eggs of A. meridionalis population in Gökpınar Spring (Sampling could not be done in April 2020 due to covid-19 epidemic restrictions).

Table 5.  .

Average total length, weight and gonad weight and fecundity values of female individuals with eggs according to age of A. meridionalis

Age group	n	TL± SH	W ± SH	GW± SH	F ± SH
I	14	2.25 ± 0.09	0.97 ± 0.14	0.11 ± 0.02	135.36 ± 21.47
II	11	3.32 ± 0.05	0.79 ± 0.04	0.08 ± 0.01	117.18 ± 27.51
III	3	3.78 ± 0.09	1.18 ± 0.14	0.13 ± 0.03	139.01 ± 36.92
IV	3	4.20 ± 0.03	1.60 ± 0.10	0.12 ± 0.02	200.22 ± 26.25
Σ	31	3.38 ± 0.07	1.14 ± 0.11	0.11 ± 0.02	147.94 ± 28.03

W—weight, g; GW—gonad weight, g; TL—total length, cm; SE—standart error; n—number of samples; F—number/individual/year.

The total length-weight relationships were calculated for female, male and all of the A. meridionalis samples. The length-weight relationships are visually represented (Fig. 6, Table 6). The estimates of parameter b in the length-weight relationships are 3.5064 (males), 3.4568 (females) and 3.4638 (all specimens). The determination coefficient (R²) values were close to for all specimens (Fig. 6, Table 6). The mean value of the condition factor are 1.85 (females), 1.83 (males) and 1.84 (all specimens) (Table 6).

Fig. 6.

The total length–weight relationships female (a), male (b) and all specimens (c) of A. meridionalis.

Table 6.  .

The total length–weight relationships parameters and condition factor (female, male and all specimens) of A. meridionalis

Sex	a	b	R 2	95% Confidence interval b (±SE)	Pauly’s t-test	P	Cf	Growth type
Female	0.0112	3.456	0.9817	3.333–3.577 (±0.061)	7.523	<0.001	1.85	+ Allometry
Male	0.0109	3.506	0.9749	3.334–3.675 (±0.085)	5.938	<0.001	1.83	+ Allometry
All	0.0112	3.463	0.9738	3.365–3.559 (±0.049)	9.426	<0.001	1.84	+ Allometry

Cf—fulton’s coefficient, SE—standart error.

DISCUSSION

Many studies have been conducted to determine the molecular taxonomic and population characteristics of Anatolichthys species. However, most of the studies aimed at determining the ecological characteristics did not go beyond the studies of the length-weight relationships. There are 2–3 studies that reveal all bio-ecological characteristics of species belonging to the genus (Table 7).

Table 7.  .

Comparison of growth parameters of Anatolichthys species reported by different studies in Turkey

Species	Locality	Ref.	N	Age range	TL (range)	M : F	L ∞	k	t 0	Ø'	a	b	R 2	Cf
A. iconii	Lake Eğirdir	1	522	I–IV	16.70–50.28	1.07 : 1.00	54.51	0.279	–1.345	–	0.0136	3.1894	0.6864	–
A. transgrediens	Lake Acıgöl	2	160	–	2.30–3.40	0.11 : 1.00	–	–	–	–	0.0237	2.732	0.936	–
A. marassantensis	Kızılırmak River	3	45	–	1.70–4.60	–	–	–	–	–	0.019	2.987	0.96	1.92
A. danfordii	Hirfanlı Reservoir, Kızılırmak River basin	4	758	–	1.47–6.68	–	–	–	–	–	–2.1538	3.668	0.95	1.72
A.fontinalis	Lake Karaevli, Burdur	5	107	–	2.00–5.30	–	–	–	–	–	0.0094	3.256	0.961	1.07
A. danfordii	Sırakaraağaçlar Stream, Sinop	6	452	0–II	1.80–5.00	1.02 : 1.00	5.149	5.945	0.502	–	0.0139	3.1641	0.987	–
A. sureyanus	Lake Burdur	7	460	0–IV	0.95–4.95	1.54 : 1.00	7.52	0.16	–1.69	–	0.0078♂	3.4903♂	0.9669♂	0.93
											0.0076♀	3.4675♀	0.9787♀
A. danfordii	Hirfanlı Reservoir, Kızılırmak River basin	8	2234	0–II	1.29–6.86	0.83 : 1.00	6.12♂	–0.19♂	2.76♂	–	0.000004	3.44	0.977	–
							12.66♀	–0.09♀	2.35♀
A. iconii	Lake Eğirdir	9	166	–	2.30–5.57	–	–	–	–	–	00.0091	3.28	0.973	–
A. marassantensis	Hirfanlı Reservoir, Kızılırmak River basin	9	385	–	2.39–6.60	–	–	–	–	–	0.0111	3.40	0.965	–
A. saldae	Lake Salda	9	76	–	3.87–6.01	–	–	–	–	–	0.0121	2.86	0.953	–
A. sureyanus	Lake Burdur	9	53	–	2.37–4.67	–	–	–	–	–	0.0090	3.11	0.954	–
A. transgrediens	Lake Acıgöl	9	113	–	1.78–5.41	–	–	–	–	–	0.0095	3.30	0.983	–
A. villwocki	Özyurt Creek–Ankara	9	180	–	1.60–7.04	–	–	–	–	–	0.0117	3.26	0.982	–
A. asquamatus	Lake Hazar– Elazığ	9	87	–	2.24–3.83	–	–	–	–	–	0.0061	3.44	0.973	–
A. fontinalis	Lake Salda	9	50	–	2.13–5.62	–	–	–	–	–	0.0094	3.36	0.982	–
A. iconii	Lake Eğirdir	10	206	I–IV	2.1–4.2	1.31 : 1.00	–	–	–	–	0.0152	2.7132	0.92	–
A. saldae	Lake Salda	10	525	I–IV	2.80–5.20	5.56 : 1.00	–	–	–	–	0.0133	2.5869	0.91	–
A. sureyanus	Lake Burdur	10	350	0–IV	1.2–4.5	0.41 : 1.00	–	–	–	–	0.0077	3.2207	0,.96	–
A. transgrediens	Lake Acıgöl	10	165	I–V	2.0–6.1	1.54 : 1.00	–	–	–	–	0.0118	3.0274	0.97	–
A.meridionalis	Gökpınar Spring, Dalaman River basin	This study	108	I–IV	1.91–4.28	0.74 : 1.00	22.97	0.0304	–2.834	1.21	0.0112	3.4638	0.9793	1.84

Ref—References: 1—(Güçlü, 2012); 2—(Sarı et al., 2017); 3—(Birecikligil et al., 2016); 4—(Kırankaya et al., 2014); 5—(İnnal et al., 2016); 6—(Karslı and Oral, 2010); 7—(Güçlü et al., 2007); 8—(Yoğurtçuoğlu and Ekmekçi, 2013); 9—(Yoğurtçuoğlu and Ekmekçi, 2015); 10—(İnnal et al., 2019).

In this study, the age of A. meridionalis ranged from I to IV. The age range of small fish species is limited (Nikolsky, 1980). Despite this, the age range of the population is wide.

Nikolsky (1980) suggested that the situation in wide range of age distribution in a population is to be accepted as an indication of enough level in the food of water system. The decrease of individuals in old age groups in the population will cause increase of individuals in young age groups, decreasing the food competition. And it is also an indication of the addition of new individuals to the population, due to success in the breed’s ability to reproduce. The individuals in age group I consist 41.67% almost half of the population. 46.29% of the population consists of fish in the 1.91–2.83 cm length groups. These length groups also include I and II age groups. Age ranges are similar to other Anatolichthys species studies (Table 7).

The sex ratio of females to males of A. meridionalis is 0.74 : 1.00 (χ², p < 0.05). This ratio found in the research is unlike the 1.00 : 1.00 ratio which gives it to a range of species (Nikolsy, 1980). According to Nikolsky (1980), sex ratio varies considerably from species to species; but in the majority of species, it is close to one. The sex differences might be due to the shorter life and earlier maturation of the males, sexual differences in growth, mortality rates, or reproductive energy costs. Also, it is suggested that dominance of one sex relative to the other could be due to different behaviors leading to an easier catch of one sex and differences in mortality of sexes (Ghafouri et al., 2019). The fact that the M : F ratio was out of the expected ratio in our study is probably due to the sampling method. The M : F ratio in our study was found to be compatible with some of the studies of other Anatolichthys species, and it was found to be inconsistent with some of them (Table 7). These differences can be shaped by the fishing gear, sample size and species. As in most of the studies, the number of females in our study is dominant. Especially during the spawning period (between May and September), it has been observed that males mate with more than one female. This will provide a very important advantage for the breeding success of the species in the habitat and will be a determining factor for a developing population. In addition, it is seen that female individuals have greater total length than male individuals at all ages (Table 2). As a result, their weight is dominant at all ages (Table 3).

Table 3.  .

Weight and age composition of females and males of A. meridionalis

Weight (class range), g	Age class								Total
	I		II		III		IV
	♀	♂	♀	♂	♀	♂	♀	♂
0.094–0.294	141	11							25
0.295–0.495	14	6	1	13		1			35
0.496–0.696			10	2		9			21
0.697–0.897			10		2	1			13
0.898–1.098			2		5				7
1.099–1.299					1				1
1.300–1.500						1	1	1	3
1.501–1.701							1	1	2
1.702–1.902									–
1.903–2.103							1		1
Σ	28	17	23	15	8	12	3	2	108
M ± SD (min–max)
♀	0.27 ± 0.02		0.70 ± 0.03		1.02 ± 0.04		1.65 ± 0.14		0.91 ± 0.06
	(0.10–0.45)		(0.44–0.91)		(0.85–1.26)		(1.44–1.93)		(0.10–1.93)
♂	0.22 ± 0.02		0.43 ± 0.01		0.64 ± 0.07		1.51 ± 0.18		0.70 ± 0.07
	(0.09–0.36)		(0.35–0.51)		(0.49–1.46)		(1.32–1.70)		(0.09–1.70)

M ± SD—avarage weight + standard deviation.

Differences in growth parameters may be due to ecological differences between research regions, water temperature, water quality and the amount of nutrients in the environment (Atar and Mete, 2009). The differences between the observed and expected total lengths were statistically not significant (t test, p > 0.05) of A. meridionalis (Table 4). It is seen that the population reaches 22.97 cm, which is L_∞, at the age of approximately 140 years. Differences about L_∞; it is thought that it may change depending on the species difference, water temperature, environment and nutrition (Table 7). Other studies have been related to Anatolichthys that distribution in natural lakes and dams. In large lentic systems, water temperatures change according to the seasons and can reach high temperatures in the summer months. However, our study was conducted in a spring water whose water temperature is 15–16 degrees throughout the year. Therefore, the water temperature of the A. meridionalis habitat is lower than other habitats. It is stated that the value of L_∞ increases inversely with the decrease in temperature (Nikolsky, 1980).

Length-weight relationship parameters are important parameters for the management and proper utilization of fish populations. The exponent b in the length-weight relationship in the present study varies between 2 and 4, but often is a value close to 3; a value of 3 indicates isometric growth and values other than 3 indicate allometric growth (Tesch, 1971). According to Le Cren (1951), the b value in the length-weight relationship also changes according to the seasons depending on the gonad development of the fish. The exponents of the total length-weight relationship of A. meridionalis show positive allometry (Table 6). Usually a reduced length range and the abundance of smaller fish can result in a higher b value because small and juvenile fish usually have a more “pumpkin’’-shaped body and become more fusiform with age (Froese, 2006). In studies performed with other Anatolichthys species, generally positive allometric growth was observed (Table 6). The relationship of total length-weight of samples regression coefficient R² = 0.9793 for all specimens. This situation exhibits unimportant deviation expected regulation increase in relationships of total length-weight. The regression coefficient R² value is genarally similar to other studies (Table 7).

Spawning occurred between July and September (Fig. 3). The first maturation was found to be at age I. First maturity length (L_m) was estimated at 23.95 mm for females and 22.04 mm for males (Fig. 4). This situation is similar to the GSI values (May-September) and hence breeding times of the andemic Anatolichthys danfordii species that spread in the Kızılırmak River basin (Yoğurtçuoğlu and Ekmekçi, 2013). Spawning in batches allows relatively large eggs to be laid, which have a higher possibility of survival (Wootton, 1990). Also, repeated spawning with a prolonged reproduction period can be expressed as an adaptation to prevent food competition between juveniles and adult individuals (Nikolsky, 1980). Early sexual maturation, short life cycle, repeated spawning and laying of eggs having rich yolk content is a common reproductive strategy exhibited by fish living under labile systems (Yoğurtçuoğlu and Ekmekçi, 2013). Yoğurtçuoğlu et al., 2020, said that, the gonado-somatic index and the duration of hydratedeggs of Anatolichthys transgrediens in the Acıgöl (Turkey) showed that reproduction continued from February to May in both habitats; nonetheless, a second spawning event occurred during July and August in the unstable habitat. In stable and unstable habitats in Acıgöl, A. transgrediens determined their first maturity length (L_m) as for females was 24.5 and 23.0 mm and for males 21.6 and 20.1 mm, respectively (Yoğurtçuoğlu et al., 2020).

Several factors, such as the size and age of the females, life history strategy, food supply, water temperature and other environmental factors affect the fecundity (Thrope et al., 1984). The mean absolute fecundity of this fish (147.94 number/individual/year) is higher than that given for some other species of Anatolichthys; 45 and 39, stable habitat, unstable habitat in A. transgrediens (Yoğurtçuoğlu et al., 2020).

CONCLUSIONS

Therefore, the A. meridionalis species and its habitat in a narrow special area Gökpınar Spring should be protected. It is seen that O. mykiss, which shares the same habitat in the environment and escapes from the near trout aquaculture farms or is deliberately released to the environment, may soon start to put pressure on the species. As a result, A. meridionalis, with its growth rates and reproductive characteristics, appears as a species that has a highly competitive ability to survive in the Gökpınar Spring with two other species, G. aculeatus and invasive O. mykiss and G. holbrooki.

COMPLIANCE WITH ETHICAL STANDARDS

Conflict of interest. The author declares no conflicts of interest.

Statement on the welfare of animals. The care of experimental animals was consistent with the Republic of Turkey animal welfare laws, guidelines and policies approved by Isparta University of Applied Sciences Local Ethics Committee for Animal Experiments (permit reference number 2020/001).