Status and distribution of the pumpkinseed sunfish ( Lepomis gibbosus ) in Bulgarian water bodies. A historical

1. Status and distribution of the pumpkinseed sunfish (Lepomis gibbosus) in Bulgarian water bodies. A historical overview of his spread and recent status of the populations. Boris Velkov*, Apostolos Apostolou* * Department of Hydrobiology Institute of Zoology Bulgarian Academy of Sciences

2. AIMS OF THE INVESTIGATION • BASED ON LITERATURE DATA, PUMPKINSEED ECOLOGY AND INVASION THEORY TO REVEAL THE HISTORICAL TRENDS AND GENERAL ASPECTS OF SPREAD AND DISTRIBUTION OF THE PUMPKINSEED • TO DESCRIBE AND SUMMARIZE BASIC FEATURES OF THE POPULATIONS, INHABITING DIFFERENT TYPES OF WATER BASINS IN BULGARIA.

3. FOREWORD ABOUT THE • PUMPKINSEED SUNFISH • Native to east and central parts of North America • Dominant fish species in the significant proportion of standing waters on the North-American continent • Introduced to Europe approximately 140 years ago (France) • Inhabits lakes, reservoirs, ponds, river pools. Mainly in vegetated areas. • Very common in Southern and Eastern parts of Europe

4. The spread of pumpkinseed in Bulgaria Year of establishment 1920 1955 - 1960 1965 - 1970 1970 - 1975 1975 - 1980 1980 - 1985 1985 - 1990 1990 - 2000 2000 -

5. The first observation of the pumpkinseed the Svishtov marsh around 1920 (Drensky, 1920) Danube River – the invasion highway Since that time (and probably earlier) the pumpkinseed is present in Danube (Borcea I., 1933-1934, Drensky,1951; Marinov,1966). About 30 – 40 years later new locations started to appear. All of them are Danube’s on-line marshes (Drensky,1951; Bulgurkov, 1958), tributaries (Karapetkova , 1972;Karapetkova and Unjian, 1988) and a reservoire (Karapetkova , 1972) . Danube tributaries located further upstream were later found to contain pumpkinseed approximately simultaneously (Karapetkova and Dikov, 1986; Karapetkova, 1994). After the western and the central part of northern Bulgaria were invaded by the species, came probably the first record from the Southern Bulgaria – Ovcharitsa Reservoir (Zivkov and Grupcheva, 1987). The spread south from the Balkan/Haemus Mountain Proceeded in constantly increasing rates and many vectors. Struma/Strimon R. (Vassilev and Pehlivanov, 2002), Mesta/Nestos R. (Apostolou, 2005; pers. comm.), Arda/Ardas R. (Pehlivanov, 2000; Steffanov and Trichkova, 2004). The first observation of the pumpkinseed in Maritsa/Evros R. and Tundja R. in the literature in unclear, according to many personal communications with colleagues and fisherman however the period is the same (in 80s and 90s).

6. Probably the area, which was most recently included in the areal is North-Eastern part of Bulgaria (pers. observ., pers. comm.). Although close in Geographic terms it is very isolated hydrologically, with low density of river network, low number of standing water bodies and rivers, running dry in summer. The latest Bulgarian watershed invaded by the pumpkinseed was Black Sea watershed, except Kamchiya River probably (Vassilev, M. 1999). Here also Isolation between the watersheds played role. There are no published materials, concerning pumpkinseed in Black Sea rivers and Lakes, except Kamchia R.. Personal communications revealed that the pumpkinseed recently invaded many of the Black Sea lakes, Shabla, Durankulak (Stefanov, pers. comm.), Varna and Bourgas lakes, Mouths of almost all of the Black sea rivers for example. Probably the last rivers, where the fish is not present yet are the southernmost Veleka and Rezovska.

7. Recent distribution of pumpkinseed sunfish in Bulgaria: All plane- and middle-mountain reservoirs Mountain lakes (Smolyan Lakes) Black Sea coastal lakes Huge majority of the microdams (approx. 1500 in Bulgaria). The majority of Danube tributaries, Aegean and Black sea rivers (middle and lower stretches). Mouths of larger Black sea Rivers, Black Sea coastal lakes Not present in: The majority of high altitude reservoirs and Lakes (Smolyan lakes) exceptional Upper and usually middle stretches of the rivers Standing water bodies which run dry periodically Some controlled water bodies used for aquaculture

8. Spread summary • In Danube watershed much slower dispersal (upstream, less anthropogenic influence at that moment, less fish stocking activities). • In the Aegean watershed very intensive dispersal (downstream, high levels of habitat modifications and other human induced factors, intensive and uncontrolled stockings). • Landscape obstacles, watershed factors and patch density important to the intensity and direction of spread. • Anthropogenic influence extremely important

9. Main types of Water bodies, where pumpkinseed populations occur: Marshes and microdams : • Small sized. • Usually high variation of basic environmental parameters • Usually highly vegetated • Comparatively poor community, crucian carp and eurasian perch are the most common . • Mosquito fish, roach, false harlequin, carp also often found

10. Large and medium sized reservoirs: • More stable conditions in terms of temperature, oxygen concentrations. • High variation of the water levels, hence less developed emergent vegetation • Larger variety of fish species: Eurasian perch, crucian carp, bleak, chub often co occur • with the pumpkinseed.

11. Role of the reservoirs and micro dams in dispersal of pumpkinseed • “CONTAINERS”, which support abundant populations and provide propagules for further spread. • Their locations in the landscape schedule and patchiness are important for the intensity of the invasion processes. • They are objects of fish stockings, which so far are the most important way for the spread.

12. Rivers: Riverine habitats are not typical for the pumpkinseed. Lower and middle stretches of larger rivers however can provide suitable conditions and were found to contain pumpkinseeds. The accomplishment of the entire life cycle of this species in rivers is doubtful, because of spawning and incubation requirements and the vulnerability of larvae and young-of-the-year. Although ripe fish were found in riverine habitats, actual breeding was not confirmed so far in rivers. High mortality rates among young-of- The-year sunfishes were found as result of floods, during years with low and moderate discharge (Jennings and Phillip1994). Furthermore in rivers pumpkinseeds are found more often in locations below or next to standing waters, connected to the river.

13. Pumpkinseed and bluegill sunfish (close congener of the pumpkinseed) were found to be rather sedentary in lotic Environments(< 100m relocation in three month) (Gatz et al. 1994) On rare occasion however they can move up- and downstream at distances as long as 17 km. True Riverine populations (breeding successfully in rivers) actually have not been confirmed so far. The fish originate from the adjacent standing waters Rivers however are extremely important as a corridors for movement and transportation especially when floods or high waters occur. PUMPKINSEED SPREAD RESERVOIRS MICRODAMS RIVERS CONTAINERS MULTIPLIERS HOTSPOTS HIGHWAYS VEINS

14. Mesta / Nestos River Before 1994 no pumpkinseed was present in the River of Mesta / Nestos (Apostolou, pers.comm.) In 1997 and 2005 fish samples were collected near the city of Gotse Delthev. During both of the samplings abundant pumpkinseed populations were found. BALKAN PENINSULA MESTA / NESTOS RIVER

15. Locations of the other Investigated pumpkinseed populations Yasen 1 and 2 serbia Samoranovo microdam stojkovci res. St. kladenets res. Kardjali res.

16. The samples from Mesta/Nestos were collected from the on-line micro dam, next to the river and in the river below the micro dam.

17. Species composition of the catch from Mesta/Nestos River near the city of Gotse Delchev, South-western Bulgaria Both samples had the pumpkinseed dominating. Other numerous species were perch, which is translocated to the river, false harlequin– another alien species, roach and chub. Below 500 m downstream the micro dam we did not find pumpkinseed sunfish.

18. Size structure of the pumpkinseed population in Mesta/Nestos River Mean size of the fish was larger in 2005, than in 1997 (93.7 vs. 73.6 mm) A highly probable explanation is the “youth” of the population in 1997, therefore composed by younger and respectively smaller fish.

19. SIZE STRUCTURE OF THE INVESTIGATED POPULATIONS MESTA/NESTOS RESERVOIRS MICRODAMS SIZE GROUP, mm SIZE GROUP, mm

20. Size at age of pumkinseed populations from Mesta/Nestos R. and other locations in Bulgaria ST. KLADENETS RES. MESTA/NESTOS1997 2005 KARDJALI RES. STANDARD LENGTH, mm STOJKOVCI RES. YASEN MARSH MICRO AGE, years

21. Growth summary • The growth of the pumpkinseed from Mesta/Nestos population is among the fastest of known Bulgarian populations. • Up to age two the fish grow largest, compared to other water bodies, included in this study. • The growth is similar to the populations of large reservoirs • The investigated micro-dams and marshes had lower growth parameters

22. Age structure of populations from different types of water bodies Percent composition Age group • Marshes/microdams: • Lower number of age groups • The youngest and the oldest age groups • poorly represented • Mortality low after 1+ • Large and middle-sized reservoirs • Relatively many age groups • Consistent mortality among age groups • Abundant and stable recruitment • Rivers (Mesta / Nestos R.) • Poor young of the year • Older fish well represented • Relatively consistent mortality

23. Trans-boundary issues • The Mesta / Nestos pumpkinsed population, as well as other Aegean rivers is fully capable of producing “fish spores”, ready to be carried downstream and to gain new waters. There is nothing new. The pumpkinseed, the false harlequin, the bighead carp, the grass carp already inhabit Greek waters (Economidis et al., 2000). • It is a fact, that the pumpkinseed sunfish have already been established and naturalized in Bulgarian waters. We must learn however the ecological lessons and to cooperate in the name of our Environment.

25. References Bulgurkov, К. 1958Hydrological peculiarities of the Lake srebarna Reserve and its fish composition. Proceedings of the Institute of Zoology. , 7: 251 - 263. Vasssilev, M., L. Pehlivanov 2002 The ichthyofauna of the Bulgarian part of the Struma River (In Bulgarian, English summary)Historia Naturalis Bulgarica 14: 103-108 Zivkov, M. 1987 Ichthyofauna and fishery of the Dospat Reservoir. Hydrobiology30:15-22 Zivkov, M., G. Grupcheva 1987. Hydrochemical condition, the ichthyofauma formation and fishery of the Ovcharitsa cooling reservoir.Hydrobiology 30: 23-36 Karapetkova, M.., 1972Ichthyofauna of the Yantra River Proceedings of the Institute of Zoology36: 149-182 Karapetkova, M. and C. Dikov 1986, On the composition, distribution, density and biomass of the Vit River Ichthyofauna. Hydrobiology 28: 14-34. Karapetkova, M. E.H. Undjian 1988. Ichthyofauna of the Roussenski Lom Hydrobiology, 32: 44-49. Apostolou Apostolos, 2005. The ichthyofauna from the Bulgarian Sector of the Mesta River. Acta Zoologica Bulgarica, 57(2): 191-196. Borcea I., 1933-1934 Sur la presence du Poisson soleil americain (Eup. Gibbosus) dans le bas DanubeAnnales Sciens. Nat. de Jassi, 19: 232-235 Drenski, P. 1920. A new fish species from the Svishtov marsh. Agricultural Reports. 5: 11. Drenski P.1951. The fishes in Bulgaria. Bulgarian Academy of Science. Economidis PS, Dımıtrıou E, Pagoni R, Michaloudi E, Natsis L (2000) Introduced and translocated fish species in the inland waters of Greece. Fish Manage Ecol 7:239–250 Schaefer, Jacob F., William I. Lutterschmidt, Loren G. Hill, 1999 Physiological performance and stream microhabitat use by the centrarchidsLepomis megalotis and Lepomis macrochirus. Environmental Biology of Fishes 54: 303–312 Stefanov, T., T. Trichkova 2004, Fish species diversity in the Eastern Rhodopes (Bulgaria). Beron, P. and A. Popov (Eds.) Biodiversity of Bulgaria 2. Biodiversity of Eastern Rhodopes (Bulgaria and Greece) Pensoft & Nat Mus. Nat. Hist., Sofia Gatz, A. J.Jr. and Adams, S. M.: 1994,Patterns of Movement of Centrarchids in Two Warmwater Streams in Eastern Tennessee, Ecology of Freshwater Fish 3, 35–48.

26. Jennings, M.J. & D.P. Philip. 1994. Biotic and abiotic factorsaffecting survival of early life history intervals of a streamdwellingsunfish. Env. Biol. Fish. 39: 153–159 Karapetkova, M., 1994. Vertebrate animals. In: Russev, B. (Ed.), Limnology of the Bulgarian Danube tributaries. Book tiger, Sofia: 175-186. Marinov, B., 1966 On the ichthyofauna of the Bulgarian stretch of the Danube River.Proceedings of the Institute of Zoology and Museum. 20: 139-155. Pehlivanov, L. 2000. Ichthyofauna of the East Rhodopes (South Bulgaria): Composition and Distribution. Acta Zoologica Bulgarica, 52(3): 45-53. Vassilev, M. 1999 Changes of ichthyofauna in the Lesenski and the Mazen Marshes (Kamchia Reserve, Bulgaria),Acta Zoologica Bulgarica, 51(1): 57-60.