New Record of the Big-Scale Sand Smelt Atherina boyeri Risso , 1810 ( Atherinidae ) in the Seyhan Dam Reservoir ( Seyhan River basin , Turkey )

Fifteen specimens of the big-scale sand smelt, Atherina boyeri were caught by a single trawl haul with a net mesh size of 3 mm on February 2017 from the Seyhan Dam Reservoir (South Anatolia, Adana/Turkey). In this study the big-scale sand smelt, A. boyeri, was recorded for the first time in the Seyhan Dam Reservoir. In addition, some morphometric and meristic measurements of A. boyeri were given and these values were compared to populations in two different lakes. Furthermore, the possible ecological effects of A. boyeri on Seyhan Dam Reservoir were briefly discussed.


Introduction
Atherina boyeri is one of the 165 Atherinid species present in the seas around the world that is naturally found in the coastal areas of seas and oceans and river mouths.A. boyeri is euryhaline fish species.This fish species is often found in coastal lagoons, in brackish water with different salt levels, in entirely fresh water and highly salty water (pers.comm., Bardawil Lagoon, Israel that has 110 ppt maximum salt level (Gon & Ben Tuvia 1983;Henderson & Bamber, 1987;Kottelat & Freyhof, 2007).A. boyeri is prevalent in the Mediterranean and connected seas, and it is also found in northeastern Atlantic, from Azores to the south, to the southern and northwestern shores of Scotland and the southern parts of the North Sea.In addition, it is also present in Lake Aral and the Caspian Sea (Gon & Ben Tuvia, 1983;Quignard & Pras, 1986;Henderson & Bamber, 1987).Atherina boyeri is reported in Europe as a translocated species in landlocked lakes Lake Trasimeno Lake (Italy), Trichonis (Greece), Almyros Lake (Crete), and Kourna Lake (Crete) (Gon & Ben Tuvia, 1983;Freyhof & Kottelat, 2012;Barbieri et al., 2005).A. boyeri has become one of the most important economic species in lakes it is found especially in Greece (Boudinar et al., 2016) and Turkey.
In the latest studies, A. boyeri was also reported in Tigris drainage (Devegeçidi Dam Lake), Aslantaş Dam Reservoir on River Ceyhan, Obruk Dam Reservoir on Kızılırmak River, and in Kılıçkaya, Süreyya Bey and Babaoğlu Dam Reservoirs in the Yeşilırmak River (Kırankaya et al., 2016).While it is not known how A. boyeri was transported to landlocked reservoirs, it is thought that it was introduced by accident or intentionally (by commercial fishermen) to these lakes (Innal & Erk'akan, 2006;Küçük et al., 2009;Gençoğlu & Ekmekci, 2016).In the Seyhan River basin, A. boyeri is naturally present in the estuarine area, and in Akyatan and Tuzla lagoons (Saç et al., 2015), but it has not yet been reported in the upper parts of the river and in the Seyhan Dam Lake (Erk'akan & Özdemir, 2011;Ergüden & Göksu, 2012).
This study is reporting the presence of A. boyeri in Seyhan Dam Reservoir for the first time.Some meristic and morphometric measurement information for the population is given.Also, possible ecological effect A. boyeri might cause in the Seyhan Dam Reservoir was briefly discussed.

Materials and Methods
The study was performed in February 2017 in Seyhan Dam Reservoir on the Seyhan River (37° 05' 04.18'' N, 35° 16' 28.36'' E) (Figure 1).The temperature of the sampling area was measured as 16.75 °C, salt level as 0.34, pH as 8.54, dissolved oxygen as 9.17 mg/L and conductivity as 0691 mS/cm (measurements were taken using a YSI probe).Sampling was performed using a single trawl haul with a net mesh size of 3 mm.15 specimens caught were brought to the lab in Çukurova University Aquaculture Department Faculty of Fisheries and here they were confirmed as A. boyeri by following Palmer et al. (1979), Akşiray (1987), Kottelat & Freyhof (2007) and Geldiay & Balık (2002).
Morphometric measurements given in Table 1 were taken from the individuals caught.The overall appearance of the species was given in Figure 2. Measurements were taken using a digital caliper with a sensitivity of 0.1mm according to Palmer (1979) and Altun (1999).In addition, the number of scales on the lateral line, the number of rays on the dorsal, ventral, pelvic and anal fins and weight were measured.Also, to determine the number of vertebrae, radiography image was taken according to Lowe & Lewbart (1997) using Siemens Heliodent 56 KVP X-ray with equipped Agfa CR 30-X printer.

Results
As seen in measurements given for 15 individuals on Table 1.Some metrics and meristic characters measured and counted in the Seyhan Dam Reservoir population were compared to the values taken from other populations (Devegeçidi Dam Lake and İznik Lake), (Table 1).Total length (TL), fork length (FL), standard length (SL), total weight (W), head length (HL), head depth (HD), eye diameter (ED), interorbital distance (IO), postorbital length (POL), pre-orbital length (PRL), pre-dorsal length from first dorsal fin (LD1), pre-dorsal length from second dorsal fin (LD2), distance between two dorsal fins (D1-D2) caudal peduncle length (CPL), caudal peduncle depth (CPD), distance between pectoral and ventral fins (P-V), distance between ventral and anal fins (V-A),SQ: Squame lateral, Vert: Number of vertebrae, GR: Gill rakers, D1: First dorsal fin rays, D2: Second dorsal fin rays, A: Anal fin, P: Pelvic fin Minimum total weight was measured as 2.1 gr, maximum total weight as 5.9 gr, and average total weight was calculated as 3.6 gr (Table 1).Head length varied between 20.1 mm -31.1 mm, head depth was in the range of 4.1 mm -7.1 mm (Table 1).The number of rays was 6-7 in the first dorsal fin, 10-12 in the second dorsal fin, 12 -14 in the anal fin, 13 -16 in the pectoral fin and 7 -8 in the pelvic fin (Table 1).The number of barbs on the gills were determined as 25 -28 (Table 1).The number of scales on the squame lateral was determined as 44 -48 (Table 1).In the radiographical image taken, the number of vertebrae was counted as 42 -45 (Figure 3).

Discussion
In this study, meristic counts of A. boyeri were determined to be similar to the population in Devegeçidi Dam Reservoir (Ünlü et al., 2016) and Iznik Lake (Altun, 1999).Concerning gill rakes, the population in the Seyhan Reservoir was determined to be similar to the Devegeçidi population.However, it was found that the number of gill rakes in the Lake Iznik population is higher than both of the other dam lakes (Table 1).
Ratios regarding some metrics of A. boyeri from different populations compared to the measurements in this study.The values found in this study were determined to be different from those in Altun (1999) andÜnlü et al. (2016).It is known that these differences are caused by the differences of environmental conditions in the areas the populations are found, and errors in the measurements.For this reason, it was considered that our findings and the findings of other researchers are different.
Atherina boyeri, a native-translocated fish for Turkey, is one of the target fish species in landlocked inland waters.According to TUIK data, 3680-6677 tons of A. boyeri was caught between 2006-2015(TUIK 2016).Being an economical species, easily adapting to inland waters, fast growth and school forming behavior suggests that this species is deliberately introduced to lakes and rivers by those who have a commercial interest in fish (Gençoğlu, 2010).Previous studies in Seyhan Dam Reservoir didn't encounter A. boyeri (Balık, 1985;Bostancı, 2006;Erk'akan & Ozdemir, 2011;Ergüden & Göksu, 2012).A. boyeri found in this study is thought to be introduced by those with a commercial interest in fish, like the other lakes in Turkey.After determining that the species was A. boyeri, dives performed in the lake encountered A. boyeri schools of various sizes, suggesting that A. boyeri has adapted to the lake.
After its appearance in the inland waters in Turkey in the 1970s, A. boyeri has spread rapidly, became a dominant species in the habitats it is found and started affecting negatively, quickly becoming an invasive species.For example, in the Hirfanlı Dam Reservoir, in the 1970s, the dominant and most caught species was the local/endemic Alburnus escherichii, but in stock determination studies in 2005, the dominant species is found to be A. boyeri, previously not known to be present in the lake (DSI 2005).Until then, A. boyeri maintains its status as the most caught species, while latest studies report that no Alburnus escherichii is found (Innal, & Erk'akan, 2006;Ekmekçi et al., 2013;Gençoğlu & Ekmekci, 2016;Kırankaya et al., 2016).
Obviously, if A. boyeri becomes the dominant species in the Seyhan Dam Reservoir, it will affect the native species it shares same niche with, Alburnus orontis, and our local/endemic species A. adanensis.Because both species share the pelagic zone close to the surface with A. boyeri and feed on zooplankton.On the other hand, A. boyeri is an opportunistic carnivore, feeding on zooplankton and depending on the abundance of food, benthic invertebrates (mostly Crustacea), insect nymphs and adult fish and fish eggs (Bartulovic et al., 2004).In the Seyhan Dam Reservoir, if A. boyeri feeds in the benthic zone, other fish present in the lake and feeding from the benthic zone might be effected negatively.
In conclusion, monitoring the A. boyeri population in the Seyhan Dam Reservoir and researching its biological and ecological characteristics would be advisable for the future of the lake ecosystem.

Figure 1 .
Figure 1.The overall appearance of Seyhan Dam Reservoir and the sampling area

Figure 2 .
Figure 2. The overall appearance of A. boyeri caught in Seyhan Dam Reservoir

Table 1 .
Morphometric and meristic measurements of A. boyeri caught in Seyhan Dam Reservoir *