Status and distribution of the pumpkinseed sunfish

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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
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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.

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• 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

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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 -
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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 Danubes 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).
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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.
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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
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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

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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

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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.

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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.

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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 Phillip 1994).
Furthermore in rivers pumpkinseeds are found
more often in locations below or next to standing
waters, connected to the river.
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Pumpkinseed and bluegill sunfish (close congener
of the pumpkinseed) were found to be rather
sedentary in lotic Environments (lt 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
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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
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Locations of the other Investigated pumpkinseed
populations
Yasen 1 and 2
serbia
Samoranovo microdam
stojkovci res.
St. kladenets res.
Kardjali res.
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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.
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Species composition of the catch from
Mesta/Nestos River near the city of Gotse
Delchev, South-western Bulgaria
Species Number of fish Number of fish
  1997 2005
Rotilus rutilus 21 32
Leuciscus cephalus 15 24
Scardinius erythrophthalmus 1  
Chondrostoma vardarense 12 17
Tinca tinca   1
Rhodeus amarus 5 13
Barbus cyclolepis 8  
Carassius auratus gibelio 7 14
Pseudorasbora parva 14 23
Perca fluviatilis 27 19
Lepomis gibbosus 97 80
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.
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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.
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SIZE STRUCTURE OF THE INVESTIGATED POPULATIONS
MESTA/NESTOS
RESERVOIRS
MICRODAMS
SIZE GROUP, mm
SIZE GROUP, mm
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Size at age of pumkinseed populations from
Mesta/Nestos R. and other locations in Bulgaria
ST. KLADENETS RES.
MESTA/NESTOS 1997
2005
KARDJALI RES.
STANDARD LENGTH, mm
STOJKOVCI RES.
YASEN MARSH
MICRO
AGE, years
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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

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Age structure of populations from different types
of water bodies

• 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

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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.

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