This study aimed to provide the length–weight relations and condition factors of 34 Oxynoemacheilus species from the inland waters of Turkey: Oxynoemacheilus anatolicus Erk’akan, Özeren et Nalbant, 2008; Oxynoemacheilus angorae (Steindachner, 1897); Oxynoemacheilus argyrogramma (Heckel, 1847); Oxynoemacheilus arsaniasus Freyhof, Kaya, Turan et Geiger, 2019; Oxynoemacheilus atili Erk’akan, 2012; Oxynoemacheilus banarescui (Delmastro, 1982); Oxynoemacheilus bergianus (Derjavin, 1934); Oxynoemacheilus cf. bureschi (Drensky, 1928); Oxynoemacheilus ceyhanensis (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus ciceki Sungur, Jalili et Eagderi, 2017; Oxynoemacheilus cilicicus Kaya, Turan, Bayçelebi, Kalayci et Freyhof, 2020; Oxynoemacheilus cyri (Berg, 1910); Oxynoemacheilus ercisianus (Erk’akan et Kuru, 1986); Oxynoemacheilus eregliensis (Bănărescu et Nalbant, 1978); Oxynoemacheilus euphraticus (Bănărescu et Nalbant, 1964); Oxynoemacheilus evreni (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus frenatus (Heckel, 1843); Oxynoemacheilus germencicus (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus hamwii (Krupp et Schneider, 1991); Oxynoemacheilus hazarensis Freyhof et Özuluğ, 2017; Oxynoemacheilus insignis (Heckel, 1843); Oxynoemacheilus kaynaki Erk’akan, Özeren et Nalbant, 2008; Oxynoemacheilus mediterraneus (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus namiri (Krupp et Schneider, 1991); Oxynoemacheilus nasreddini Yoğurtçuoğlu, Kaya et Freyhof, 2021; Oxynoemacheilus paucilepis (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus samanticus (Bănărescu et Nalbant, 1978); Oxynoemacheilus seyhanensis (Bănărescu, 1968); Oxynoemacheilus seyhanicola (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus simavicus (Balik et Bănărescu, 1978); Oxynoemacheilus theophilii Stoumboudi, Kottelat et Barbieri, 2006; Oxynoemacheilus tigris (Heckel, 1843); Oxynoemacheilus veyselorum Çiçek, Eagderi et Sungur, 2018. Based on the results, the growth coefficient values (b) ranged from 2.770 (O. argyrogramma) to 3.285 (O. theophilii) with an R² estimate greater than 0.91. Fulton’s condition factor (K_F) of the studied fishes ranged from 0.598 (O. insignis) to 1.07 (O. nasreddini) . Relative conditions (K_R) were found to have a narrow distribution range (0.856–1.014 with a mean of 1.005). The form factors of these species were calculated between 0.006 and 0.14, with a mean and median value of 0.01. This study represents the first reports of LWRs parameters for 22 species, new maximum total length data were bigger than given in FishBase for 21 species, and first species listing for maximum total length for seven species. The findings of this study provide useful information for further fisheries management and fish population dynamic studies.

condition factor, form factor, length–weight relation, loach, Nemacheilidae

The Nemacheilidae are small fishes inhabiting the freshwaters of Asia, Europe, and northeastern Africa (Nelson et al. 2016; Sungur et al. 2017). This family has great diversity in Turkish inland waters with 48 species, of which 28 are endemics (Çiçek et al. 2015, 2018, 2020). They do not have commercial value but are important components for aquatic ecosystems (Kottelat 2012; Çiçek et al. 2015, 2018).

The study of the length–weight relation (LWR) of any fish species is a prerequisite for assessing its population characteristics (Le Cren 1951). As a result, LWRs provide fundamental knowledge in fisheries biology, which is required for management and conservation. Few Turkish nemacheilids have LWR data available (Gaygusuz et al. 2012; Erk’akan et al. 2013, 2014; Birecikligil et al. 2016; Özcan and Altun 2016; Yazıcıoğlu and Yazıcı 2016; İnnal 2019; Özdemir et al. 2019); hence, providing such data for these taxa is crucial for their management and conservation (Tabatabaei et al. 2015; Keivany et al. 2016; Jafari-Patcan et al. 2018).

Condition factor is computed using the weight and length of fish species to describe the condition or well-being of fish individuals in a particular water body (Froese 2006). It is assumed that the growth of fish in ideal conditions maintains equilibrium in length and weight and is a useful index for monitoring feeding intensity, age and growth rate, and assessing the status of the aquatic ecosystem where fish live (Radkhah and Eagderi 2015; Zamani-Faradonbe et al. 2015). Based on the above-mentioned background, the presently reported study was conducted to determine the LWRs parameters, condition factors, and form factors of 34 species of the genus Oxynoemacheilus inhabiting inland waters of Turkey. The following species were studied: Oxynoemacheilus anatolicus Erk’akan, Özeren et Nalbant, 2008; Oxynoemacheilus angorae (Steindachner, 1897); Oxynoemacheilus argyrogramma (Heckel, 1847); Oxynoemacheilus arsaniasus Freyhof, Kaya, Turan et Geiger, 2019; Oxynoemacheilus atili Erk’akan, 2012; Oxynoemacheilus banarescui (Delmastro, 1982); Oxynoemacheilus bergianus (Derjavin, 1934); Oxynoemacheilus cf. bureschi (Drensky, 1928); Oxynoemacheilus ceyhanensis (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus ciceki Sungur, Jalili et Eagderi, 2017; Oxynoemacheilus cilicicus Kaya, Turan, Bayçelebi, Kalayci et Freyhof, 2020; Oxynoemacheilus cyri (Berg, 1910); Oxynoemacheilus ercisianus (Erk’akan et Kuru, 1986); Oxynoemacheilus eregliensis (Bănărescu et Nalbant, 1978); Oxynoemacheilus euphraticus (Bănărescu et Nalbant, 1964); Oxynoemacheilus evreni (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus frenatus (Heckel, 1843); Oxynoemacheilus germencicus (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus hamwii (Krupp et Schneider, 1991); Oxynoemacheilus hazarensis Freyhof et Özuluğ, 2017; Oxynoemacheilus insignis (Heckel, 1843); Oxynoemacheilus kaynaki Erk’akan, Özeren et Nalbant, 2008; Oxynoemacheilus mediterraneus (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus namiri (Krupp et Schneider, 1991); Oxynoemacheilus nasreddini Yoğurtçuoğlu, Kaya et Freyhof, 2021; Oxynoemacheilus paucilepis (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus samanticus (Bănărescu et Nalbant, 1978); Oxynoemacheilus seyhanensis (Bănărescu, 1968); Oxynoemacheilus seyhanicola (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus simavicus (Balik et Bănărescu, 1978); Oxynoemacheilus theophilii Stoumboudi, Kottelat et Barbieri, 2006; Oxynoemacheilus tigris (Heckel, 1843); Oxynoemacheilus veyselorum Çiçek, Eagderi et Sungur, 2018.

A total of 1801 specimens of Oxynoemacheilus species were collected between May 2009 and September 2019 from Turkish inland water using an electrofishing device (SAMUS MP750). The sampling year of the species is given in Table 1. After anesthesia, the specimens were preserved in 4% buffered formalin and transported to the laboratory.

In the laboratory, the total length (L) and total weight (W) of each individual were determined using a digital caliper to the nearest 0.1 cm and 0.01 g, respectively. The LWRs were calculated by the method of least squares using the equation

W = aL^b

and logarithmically transformed (Froese 2006) into

LogW = loga + b log L

where W is the whole-body weight [g], L is the total length [cm], a is the intercept, and b is the slope. Prior to regression analyses, log–log plots of the length–weight pairs were performed to identify outliers (Froese et al. 2011). Outliers perceived in the log–log plots of all species were evacuated from the regression. Fulton’s condition factor (K_F) was estimated using the following formula (Ricker 1975; Froese 2006)

K _F = 100WL^–3

The relative condition factor (K_R) was calculated using the equation of Froese (2006)

K _R = W (aL^b)^–1

The mean condition factor (K_M) for a given length is derived from the respective WLR using the formula (Froese 2006)

K _M = 100aL^{b – 3}

The form factor (a3:0) can be used to determine whether the body shape of a population or species differs significantly from that of others. It was calculated using the formula (Froese 2006)

a3:0 = 10^{loga – S (b – 3)}

where S is the slope of the loga vs. b regression, the mean slope S = a – 1.358 proxy for estimating the form factor (Froese 2006).

The degree of dependence between the variables was computed by the determination coefficient R². The significance level of R² was estimated by ANOVA. The Student’s t-test was used to determine whether parameter b is significantly different from the expected or theoretical value of 3 (i.e., b = 3, P < 0.05). All statistical analyses were performed in MS Excel 2016 and Past 3.26.

The presently reported study provides the LWRs and condition factors of 34 Oxynoemacheilus species. The descriptive statistics of length and weight with the parameters of the LWR; regression parameters a and b, the 95% confidence limits of b; the 95% confidence limits of a; correlation coefficient (R²) and type of growth for the studied species are given in Tables 1 and 2. Based on our collected specimens, new maximum total lengths were recorded for 23 species.

The parameter b of the studied species ranged from 2.770 (O. argyrogramma) to 3.285 (O. theophilii) with the median value of 3.071 (Table 2 and Fig. 1). The value of b generally lies between 2.5 and 3.5 (Froese 2006) though the ideal value of b is 3.0 (Hile 1936). In LWRs, b-values that are higher and lower than 3 indicate positive and negative allometric growth, respectively. According to the b-value, 27 species are isometric; two are negative allometry and five are positive allometry (Table 2). The coefficient of determination (R²) between length and weight varied from 0.91 for O. ciceki to 0.99 for O. cf. bureschi.

Figure 1. 

Box plot of (A) allometric co-efficient b values, (B) Fulton’s condition factor (K_F), (C) form factor for 34 Oxynoemacheilus species from Turkey.

The values of K_F varied from 0.598 (O. insignis) to 1.070 (O. nasreddini). Clark (1928) showed the relation between K_F and the parameters of the respective WLR (Table 2 and Fig. 1). The K_M for a given length is derived from the respective WLR (Froese 2006) which ranged from 0.856 to 1.014 with a mean of 1.005. Clark (1928) also demonstrates that if b is not significantly different from 3, K_F can be compared directly. Le Cren (1951) proposed the relative condition factor (K_R), which accounts for changes in form or condition as length increases and therefore assesses an individual’s divergence from the sample’s mean weight for length. To facilitate such comparisons, Le Cren (1951) introduced the relative condition factor, which compensates for changes in form or condition with an increase in length and thus measures the K_R. The values of K_R varied from 0.985 (O. hamwii) to 1.041 (O. veyselorum) (Table 2).

The condition factor is an index reflecting interactions between biotic and abiotic factors on the physiological condition of the fishes. Therefore, it can be used as an index to assess the status of the aquatic ecosystem in which fish live (Anene 2005). The results of the K_R value indicated good health and better environmental conditions for all the studied species.

The form factor a3:0 can be used to determine whether the body shape of a given population or species is significantly different from others (Froese 2006). The form factor varied from 0.006 to 0.014 for 34 species showing the fishes in the range of the elongated body shape (Table 2 and Fig. 1).

The LWRs of 22 species, provided in this paper, have not hitherto been available in FishBase (Froese and Pauly 2021). The results of this study provide useful information for fisheries management, fish population dynamic studies, and comparisons in future studies.

This work was financially supported by the Scientific Research Foundation of the Nevşehir Hacı Bektaş Veli University (Grant No. BAP-16).