Turkish Journal of Zoology Turk J Zool (2020) 44: 542-547 http://journals.tubitak.gov.tr/zoology/ © TÜBİTAK Case Report doi:10.3906/zoo-2008-20

An alien species or another perspective to the freshwater gobies puzzle: a new finding in Lake Prespa

1, 2 2 1 Blagoja TRAJCHEVSKI *, Zoran SPIRKOVSKI , Dushica ILIKJ-BOEVA , Trajce TALEVSKI  1 Department of Cyprinid Fauna, Hydrobiological Institute - Ohrid, Ohrid, R.N., Macedonia 2 Department of Applied Fishery and Aquaculture, Hydrobiological Institute - Ohrid, Ohrid, R.N., Macedonia

Received: 24.08.2020 Accepted/Published Online: 30.10.2020 Final Version: 20.11.2020

Abstract: Here we present a discovery of a new fish from the family Gobiidae in Lake Prespa, which is known as a European hotspot for biodiversity and endemism. This is the first detection of a fish species from this family, not only regarding this lake but also in the territory of the Republic of North Macedonia in general. The close examination of the recorded specimens revealed the presence of perianal organ surrounding the anus. This unique organ and various other observed morphometric and phenotypic characteristics point out to the genus Economidichthys. The two known fish species from this genus are currently considered endemic only to the rivers and lakes of western Greece. This new finding could be an evidence of alien species introduced in this lake, or an evidence of native species that are not recorded yet because of their characteristic life habits. Either way, this is a very important finding for the taxonomy and biogeographical distribution of the freshwater gobies in the Balkans.

Key words: Lake Prespa, Gobiidae, Economidichthys, first record

The Gobiidae family (gobies) is a large family with Lake Trichonis (Figure 1a). E. pygmaeus is originally mostly marine and brackish water species, and a smaller described by Holly (1929) as Gobius pygmaeus (Holly, number of freshwater species1. The European gobiid fauna 1929). Bianco et al. (1987) set this taxon as a type species comprises mostly Atlantic-Mediterranean marine and of the new genus Economydichthys, along with the euryhaline species, as well as Ponto-Caspian endemics, other species E. trichonis. The most important trait that inhabiting fresh and mostly hyposaline waters from Eastern distinguishes these two species from other Gobiide species Europe to the Caspian Sea. Outside the Black Sea drainage is the presence of a dermal perianal organ that surrounds system, and the Caspian Sea, freshwater gobies have been the anus, which is unique among teleosts (Bianco et al., reported from the freshwaters of the Mediterranean region 1987; Economidis and Miller, 1990; Miller, 1990). The (Economidis and Miller, 1990; Kottelat and Freyhof, 2007). Economydichthys species have a small body size, short The taxonomy of all groups of European gobies is far from life span, early onset of maturity, and high reproductive resolved. The eastern Mediterranean, in particular the effort concentrated early in life (Gkenas and Leonardos, Balkans and the Black Sea and Caspian Sea basins, hosts 2012). Spawning of the two Economidichthys species takes the highest diversity of gobies in Europe, including many place between late February and the middle of May in the endemic species dominated in freshwater by the so called cavities of broken reeds (Phragmites australis), in nests with ‘sand gobies’ (Kottelat and Freyhof, 2007). the males guarding them (Daoulas et al. 1993). The species One of the most notable endemic representatives of inhabit both flowing and stagnant shallow waters with freshwater gobies is the genus Economidichthys. This genus abundant vegetation and detrital substrate (Miller, 1990), is considered endemic to the rivers and lakes of western and their diet is specialized zooplanktivorous (especially Greece and is composed of two species (Economidis and copepods) in all size classes and seasons (Gkenas et al., Miller, 1990): Economidichthys pygmaeus (Holly, 1929) 2012). that is widespread in the freshwater bodies in western Lake Prespa is a mesotrophic water body, located on Greece (Miller, 1990), and Economidichthys trichonis the Balkan peninsula, and is shared by three countries: (Economidis and Miller, 1990), that was found only in North Macedonia, Albania, and Greece. This lake belongs 1 Froese R, Pauly D (editors) (2020). FishBase [online]. Website www.fishbase.se [accessed 15 October 2020] * Correspondence: [email protected] 542

This work is licensed under a Creative Commons Attribution 4.0 International License. TRAJCHEVSKI et al. / Turk J Zool to the watershed of the river Crn Drim that flows into the E), two specimens at SS2 (40°56’25’’ N, 20°54’47’’ E), Adriatic Sea (Popovska and Bonacci, 2007). The three major four specimens at SS3 (40°54’34’’ N, 20°59’10’’ E), and contributors to water input in the lake are river runoff from one specimen at SS4 (40°58’14’’ N, 20°03’38’’ E ) (Figure numerous small streams, direct precipitation onto the lake 1b). They were in a muddy or sandy bottom, with dense surface, and inflow from Small Prespa Lake (Matzinger et vegetation and reed belt. After sampling, fish were al., 2006). Lake Prespa has a very high percentage of fish preserved in 4% formaldehyde for further investigation. endemism (Oikonomou et al., 2014). There are a total of 25 The meristic and morphometric measurements were fish species identified in Lake Prespa, out of which 13 are performed on 9 of the 10 sampled specimens, because one native and 12 are introduced at different times in history fish caught at the sampling site SS4 was damaged in the (Ilik-Boeva et al., 2017). Out of the 13 native species, 8 process and not all of the measurements could be taken. are endemic and found only in this lake or the watershed For the measurements, we used most of the meristic and of the lake (Spirkovski et al., 2012). Talevski et al. (2009) morphometric parameters used by Economidis and Miller reported 11 native and 12 introduced fish species in this (1990) for measuring the freshwater gobies in Greece. The lake. Nevertheless, none of the recorded fish species from abbreviations are as follow: Lake Prespa is a member of the Gobiidae family. Meristics: A (anal fin), C (caudal fin), D1 (first dorsal A total of 10 specimens was caught during a sampling fin), D2 (second dorsal fin), P (pectoral fin), V (pelvic campaign in Lake Prespa carried out from 25 to 31 July disc), and LL (lateral line scales). The last bifid ray of D2 2017. The sampling was conducted using electrofishing and A is counted as one. gear in the shallow littoral area of the lake. The Morphometrics: Ab (anal fin base), Ad (body depth specimens were caught in four different locations: three at anal fin origin), Aw (body width at anal fin origin), specimens were caught at SS1 (40°59’14’’ N, 20°55’28’’ Cl (caudal fin length), CHd (cheek depth), CP (caudal

Figure 1. Distribution of Economidichthys sp. in western Greece (a) the location of Lake Prespa, and the sampling sites (b).

543 TRAJCHEVSKI et al. / Turk J Zool peduncle length), CPd (caudal peduncle depth), D1b (1990), we assigned the specimens from Lake Prespa (first dorsal fin base), D2b (second dorsal fin base), E (eye to the genus Economidichthys. The main and most diameter), H (head length), Hw (head width), I (interorbital important indicator was the perianal organ that surrounds width), Pl (pectoral fin length), PO (postorbital length), SL the anus (Figure 2b), which is unique for the members (standard length), SN (snout length), SN/A (distance from of this genus (Bianco et al., 1987) and is absent in all of snout to vertical of anal fin origin), SN/AN (distance from the other Gobiide species from freshwater, marine, or snout to vertical of the anus), SN/D1 (distance from snout brackish water. This perianal organ was present in all of to origin of the first dorsal fin), SN/D2 (distance from snout our specimens. Also, the two other distinct features of this to orgin of the second dorsal fin), SN/V (distance from genus, the transverse interorbital rows of papillae and the snout to vertical of pelvic spinous ray), V/AN (distance absence of head canals (Bianco et al., 1987) were observed. from the origin of the pelvic spinous ray to opposite anus), Because of the main characteristics of the specimens Vd (body depth at the origin of pelvic spinous ray), and Vl from Lake Prespa, like body coloration, meristic counts, (distance from the origin of the pelvic spinous ray to the morphometric measurements, and most importantly, size tip of longest pevic ray). of the perianal organ, these specimens are identified as E. The meristic parameters were counted, while the pygmaeus. The perianal organ in all of the specimens is morphometric parameters were measured using stereo half or more of the length of the pelvic disc (Table), which microscope ZEISS Stemi 305 (Carl Zeiss GmbH, is one of the main distinguishing features between the Oberkochen, Germany), and the ZEISS Zen software. two Economidichthys species. Also, the presence of three The collected specimens (Figure 2a) had a total transverse rows of the interorbital papillae are noted, which, length of the body that ranged from 18.25 to 31.98 mm. in the case of E. trichonis, are two rows. The maximum They had an elongated body with a dark yellow to pale total length in our measurements was 31.98 mm, which yellow coloration, and a rounded caudal fin. The smaller is lower than the reported maximum length between 47 specimens had black bars on the sides of the body, located mm (Kottelat and Freyhof, 2007) and 54 mm (Economidis around the midline of the body, not extending to the and Miller, 1990). However, taking into consideration that dorsal or ventral ends. In the larger specimens, the black this is a fish with a short life span and life cycle (one year) bars were less or absent. The abdomen was naked with the (Gkenas and Leonardos, 2012), it is not surprising to have presence of a heart-shaped perianal organ surrounding the different size spectrums in the specimens collected in anus (Figure 2b). The perianal organ was half or more of different seasons of the life cycle. Also, we could not dismiss the length of the pelvic disk. The fins were as follows: D1 the possibility of a local growth variation, similar to the V-VI; D2 I/8-9; A I/7-9; C 14-16; P 16-18 V I/5+I/5, and the examples from Lefkas island presented by Economidis and lateral line scales ranged from 30 to 32. The morphometric Miller (1990), with a maximum length reaching 34 mm. measurements are expressed as a percent of SL, CP, H, E, There are some meristic and morphometric differences V/AN, and Vl and can be found in Table. between the specimens from Lake Prespa versus the ones Using the species determination key for gobies described by Economidis and Miller (1990). The Prespa provided by Kottelat and Freyhof (2007), and the one for specimens have a bigger head width and caudal peduncle freshwater gobies in Greece by Economidis and Miller depth, and a smaller body and cheek depth (Table), as

Figure 2. Economidichthys pygmaeus from Lake Prespa (a), and the perianal organ of one of the specimens (b).

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Table. Morphometric measurements of Economidichthys Leonardos, 2012). There are numerous occurrences of pygmaeus from Lake Prespa presented as percentages of SL, CP, freshwater gobies colonizations and invasions in Europe, H, E, V/AN, and Vl. but this is usually the case in hydrosystems that are connected (Tletchea and Baisel, 2018). We can exclude the Parameters Range Mean ± St.dev. possible intentional introduction to Lake Prespa because these species are not of any commercial or recreational H 27.50 – 30.27 29.17 ± 0.97 interest for the fisheries and the fishermen (Ilik-Boeva Hw 18.88 – 23.06 20.42 ± 1.45 et al., 2017; Castadorakis et al., 2018). An accidental SN/D1 38.20 – 46.64 41.87 ± 3.03 introduction is a possibility, but the most common way, SN/D2 54.82 – 62.13 59.26 ± 2.60 through fish stocking, is regulated by the authorities. SN/AN 57.04 – 67.88 60.54 ± 3.89 Stocking on Lake Prespa has been performed annually, SN/A 61.98 – 72.21 65.20 ± 3.42 only with autochthonous carp fry and fingerlings (Ilik- SN/V 31.64 – 40.32 34.88 ± 3.14 Boeva et al., 2017). Because of the characteristic life cycle (short life span), feeding habits and reproduction (Gkenas CP 15.34 – 23.44 19.27 ± 2.58 and Leonardos, 2012; Gkenas et al., 2012), which restricts D1b 8.06 – 14.67 11.05 ± 2.00 them to shallow waters with dense vegetation, and of D2b 13.80 – 23.70 18.64 ± 3.14 %SL course their small size, they are not reported or noticed in Ab 11.72 – 17.17 14.29 ± 1.71 the catch of the fishermen from Lake Prespa region, both Cl 17.37 – 22.87 20.65 ± 2.24 commercially and recreationally. This is also the case in Pl 14.56 – 20.49 18.16 ± 1.70 recent scientific studies (Ilik-Boeva et al., 2017; Shumka Vl 16.84 – 20.17 18.52 ± 1.32 and Apostolou, 2018). In personal communication with Spase Shumka from the Agricultural University in Tirana, Vd 13.06 – 16.90 15.48 ± 1.34 we were informed that very recently, in August 2020, one Ad 18.18 – 20.67 19.29 ± 0.87 specimen of Economidichthys, identified asE. pygmaeus, Aw 9.64 – 13.95 11.38 ± 1.46 was sampled in the Albanian part of Lake Prespa, but was CPd 10.10 – 12.08 11.16 ± 0.65 not recorded in earlier studies (Shumka and Apostolou, V/AN 25.44 – 31.07 27.62 ± 2.03 2018). With all said above and the fact that the collected pal 8.21 – 12.63 10.14 ± 1.62 specimens are of different sizes, we can assume that there has been a continuous population of Economidichthys in %CP CPd 49.73 – 71.79 58.99 ± 9.57 Lake Prespa, at least in recent years. SN 17.51 – 23.62 21.09 ± 1.89 The origin of this genus is placed in the late Miocene E 22.46 – 28.07 26.01 ± 1.69 (10 Mya (million years ago)) and it is the earliest %H PO 50.63 – 57.82 54.59 ± 2.24 freshwater goby to diversify (Thacker and Gkenas, 2019). CHd 14.21 – 25.60 18.79 ± 3.90 There are known exceptions to the generally very low Hw 62.38 – 83.84 70.17 ± 6.88 genetic diversity within E. pygmaeus, with the specimens %E I 53.85 – 80.93 66.89 ± 10.13 from Chiliadou springs, off the Mornos River, that differ from the other population of this species by 1.5%–1.7%, %V/AN Vl 58.10 – 76.03 67.24 ± 5.26 and that a split from the general population had occurred %Vl pal 48.75 – 64.36 54.54 ± 6.08 0.8–2.3 Mya (Vanhove et al., 2012). The lakes of the southern Balkans are often believed to derive from a giant Neogene palaeolake system, before ponding out in the well as a slightly higher number of caudal fin rays (14-16), Pleistocene. This resulted in a high degree of lake basin- but these differences are not enough to differentiate the based endemicity (Frogley et al., 2001). Lakes Prespa specimens as a distinct species. and Lake Pamvotis share the same tectonic origin and Lake Prespa is isolated and does not have any are thought to have formed at the same time in the late connections with the water bodies containing this Tertiary (2–3 Mya or more) (Reed et al., 2004). So the species. The only inflow from the Greek side is from paleogeological studies suggest that, in a certain period of Small Lake Prespa (Matzinger et al., 2006) and the river the geological history of the Balkans, the freshwater lakes Agios Germanos. The locations in Lake Prespa, where of the southern parts were interconnected, so there is a the samples were collected are distant from one another, probability that Economidichthys in Lake Prespa can be a but all of them resemble their natural habitat, western remnant of that time. Greece, where these gobies can be found: sandy or muddy Regarding the various phenotypic and morphometric areas overgrown with aquatic vegetation (Gkenas and traits, and most importantly the presence of the perianal

545 TRAJCHEVSKI et al. / Turk J Zool organ, we identified the specimens collected in Lake biodiversity and endemism, regarding the ichthyofauna Prespa, as members of the genus Economidichthys, more in Lake Prespa, and gives another point of view on the precisely belonging to the species E. pygmaeus. The possible biogeographical distribution and the spatial patterns of this intentional introduction in the lake is highly unlikely and endemic species, and the distribution of freshwater gobies the only plausible natural translocation is from Small Prespa in general. Lake. The most common way of accidental introduction, fish stocking, is regulated by the authorities. However, Acknowledgments taking into consideration that the specimens were sampled The sampling was conducted as part of the larval fishing in distant areas, and are of different sizes, we can assume campaigns 2017 for Lake Prespa Fish and Fisheries the possibility that there has been a continuous population monitoring, within the Project: Conservation and of Economidichthys in Lake Prespa. Nevertheless, more sustainable use of biodiversity at Lakes Prespa, Ohrid, ecological, molecular and genetic investigations are needed and Skadar II (CSBL II), financed by the German Federal to determine the exact spot of the Lake Prespa specimens Ministry for Economic Cooperation and Development, in this genus, whether this is an alien species colonizing the BMZ and implemented by the Deutsche Gesellschaft fur lake, or relict native species waiting to be recorded. This is a Internationale Zusammenarbeit, GIZ, and realized by PSI very important discovery, because it complements the high Hydrobiological Institute - Ohrid.

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