A NEW LOCALITY FOR THE ENDEMIC Gobio sakaryaensis TURAN , EKMEKÇİ , LUSKOVA & MENDEL , 2012 IN THE MARMARA REGION ( TURKEY ) AND THE LENGTH-WEIGHT RELATIONSHIP OF THE SPECIES

One of the endemic freshwater fish species of Turkey, Gobio sakaryaensis Turan, Ekmekci, Luskova & Mendel, 2012 is reported for the first time from the Lake Sapanca Basin. A total of 18 G. sakaryaensis specimens was captured using electroshocker on October 18, 2008 and February 5, 2009 from the Masukiye Stream (western Lake Sapanca). This finding has increased the number of the fish species living in the basin. The value of parameter b in the LWR equation was calculated 3.176.


Introduction
The last comprehensive checklist of the freshwater fishes of Turkey has reported that a total of 409 fish species inhabit in the freshwater systems and 194 of them is endemic to Anatolia (Çiçek et al., 2018).The genus, Gobio is known to be one of the richest genera because of its adaptations to different habitats (Turan et al., 2016).Recently, a total of 14 species belonging to the genus Gobio was recognised from Turkish inland waters, and except Gobio bulgaricus and Gobio kovatschevi all of these species are the Anatolian endemics (Naseka et al., 2006;Kottelat and Freyhof, 2007;Turan et al., 2012;Turan et al., 2016;Turan et al., 2017;Turan et al., 2018).Gobio sakaryaensis is one of the endemic gudgeons and it was described from the Tozman and Porsuk streams in the Sakarya River drainage (northwestern Anatolia, Black Sea basin) (Turan et al., 2012).
One of the most important lakes in the Marmara region of northwest Turkey, the Lake Sapanca is used for fisheries, recreation and potable water resource (Albay et al., 2003).The lake is fed by numerous streams (e.g.Maşukiye, Yanık, Mahmudiye, Kurtköy, İstanbul, Liman, Sarp, Arifiye, Maden) and it has one outflowing river (Çark Stream) connected to Sakarya River (Ercan et al., 2013).The Lake Sapanca and its streams have a rich fish diversity and a total of 27 fish species has been reported from the lake basin (Özuluğ et al., 2007;Tarkan et al., 2007;Tarkan et al., 2008;Okgerman and Altuğ, 2008).This study aims to report the unrecorded fish species, G. sakaryaensis for the Lake Sapanca Basin and provide its length-weight relationship.

Material and Methods
The routine ichthyological surveys of the Lake Sapanca Basin between 2008 and 2009 were conducted using a portable SAMUS 750-MP electroshocker.The Maşukiye Stream where G. sakaryaensis specimens were collected is flowing from the westward of the lake (Figure 1).The fish samples were killed immediately upon capture with an overdose clove oil and they fixed in 5% formaldehyde solution.
Measurements were made point-to-point with calipers and recorded to 0.1 mm.Meristic counts were made under a binocular microscope.Methods for counts and measurements follow Kottelat and Freyhof (2007).Standard length (SL) was measured from anteriormost point of the head to the end of the hypural complex.The length of the caudal peduncle is measured from behind the base of the last anal-fin ray to the end of the hypural complex, at mid-height of the caudalfin base.Lateral line scales are counted from the anteriormost scale (the first one to touch the shoulder girdle) to the last scale at the end of the hypural complex.The last two branched rays articulating on a single pterygiophore in the dorsal and anal fins are noted as "1½".Scales on the caudal fin itself are indicated by "+".Gill rakers were counted on the anterior gill arch.Valid species name was attributed according to Eschmeyer et al. 2018.Fish specimens were deposited as museum material in the Collection of İstanbul University, Faculty of Aquatic Sciences in 70% ethanol.
The samples were measured for standard length (SL) to the nearest 0.1 cm and weighed for total body weight (W) on a digital balance with a 0.01 g accuracy.The LWR was calculated using the equation: W=aL b , where W is the total weight (g), L is the standard length (cm), a and b are regression parameters (Le Cren, 1951;Froese, 2006).The equation (W=aL b ) was converted into the natural logarithmic form (lnW=lna+blnSL)) and parameters a (regression intercept) and b (slope) were calculated by the regression analysis (King, 2007).A total of 18 G. sakaryaensis specimens was caught from the Maşukiye Stream.Morphometric data of the species was given in Table 1.
Gobio sakaryaensis reported in this study has not previously been recorded from the Lake Sapanca Basin, and this finding has increased the number of the fish species living in the basin.It is thought that G. sakaryaensis, known to live in the Sakarya River Basin, may had come to the Sapanca Lake Basin with Çark Creek, which connects the Sakarya River to the lake.The occurrence of this species in the Lake Sapanca Basin shows that its distribution range has extended.
Not unexpected, there is a small difference in the morphometric of our materials (Table 1) and the data given by Turan et al. ( 2012 2012)).This difference is likely to be the result of differences in measuring fish, larger variations in fish sizes/numbers or seasonal variations.
The value of b in the LWRs is expected to be ranged between 2.5 and 3.5 (Froese, 2006).In present study, the value of b for G. sakaryaensis was within this range and, therefore the results can be used as valid.According to İnnal and Erk'akan (2015), the b value of G. sakaryaensis in Çamkoru Pond (Ankara, Turkey) was calculated 3.217.The differences in the b values of the same species are possible affected by temporal and spatial variations due to different habitats, size range, sex, and season, gonad maturity, feeding habit and diseases, although these two estimated values of b (3.217 for Çamkoru Pond population and 3.176 for Maşukiye Stream population) were similar.