(Neogobius melanostomus) and Chinese sleeper

Saulius Stakėnas, Tomas Virbickas, Vytautas
Rakauskas, Andrius Steponėnas, Artūras Skabeikis
Dispersion, impact and abundance
mitigation study of round goby (Neogobius
melanostomus) and Chinese sleeper
(Perccottus glenii) in Lithuania
Institute of Ecology, Nature Research Centre
Chinese (Amur) sleeper (Perccottus glenii)
First record in Lithuania – year 1985.
Most likely source: intentional release as unwanted
aquarium fish.
Current distribution - up to date found and confirmed in 77
water bodies. Unconfirmed sites – plus 11.
83 % of sites are in urbanized areas, 71 % within two biggest
cities in Lithuania.
Eradication (unintentional !!!) – up to date in 7 water bodies.
Fish communities structure with chinese sleeper
Fish population structure with chinese sleeper
Very slow growth,
Most abundant age group:
Chinese sleeper – 7;
Prussian carp – 7.
Moderate growth,
Most abundant age group:
Chinese sleeper – 3;
Prussian carp – 7;
European perch – 7.
Fish population stucture with CS and northern pike
Moderate-fast growth,
Most abundant age groups:
Chinese sleeper – 3;
Prussian carp - 3;
European perch - 1.
Completely vanished in 7 water bodies, after restocking with pike.
… but still present in 3 after restocking with pike.
Very dense aquatic vegetation and bad-moderate water
transparency seems to allow CS to survive, or CS territorial
behavior adapted to be less vulnerable in presence of pike.
Chinese sleeper diet
Cannibalism were recorded in all
samples and tadpoles were
virtually absent in all sites.
The δ15N signatures of CS
became increasingly enriched
with larger body size.
However, the δ13C signatures of
CS little changed with fish size.
Trend of δ15N values suggests
CS shift to a more predatory diet,
with ontogenetically increasing
proportion of other fish in the
diet.
Chinese sleeper eradication programm
Northern pike stocking.
Problem: CS extremely tolerant to lack of DO.
DO concentrations in 7 out of 10 surveyed water bodies
were bellow 0,5 mg/L since end of January (minimum
0,12 mg/L – saturation 1,1 % !).
Artificial aeration of water bodies during winter needed.
Public awareness projects to tackle further intentional or
unintentional release.
Most vulnerable water bodies:
lentic waters, lakes, ponds, backwaters and marshes
with dense underwater vegetation, poorly oxygenated
water and low abundance of predatory fishes.
Round goby (Neogobius melanostomus)
First record in Lithuania – year 2002.
Most likely invasion sources: ballast waters and/or natural
dispersion from the gulf of Gdańsk.
Current distribution within Lithuania territory– territorial
Baltic sea, northern part of Curonian lagoon.
No records about dispersion upstream from
Curonian lagoon to rivers.
Multiple spawning first time recorded in 2011.
Recent explosion of abundance I Baltic sea coastal zone.
Initial rapid dispersion stopped.
2004
2005
2007
2007
2007
2008
During 2012 season surveys
round goby was found only in
northern part of Curonian lagoon.
Meanwhile in Baltic sea coastal
zone population exploded, mean
CPUE raised 5 times over last
three years.
Density driven dispersion?
Round goby - drastic diet change in lagoon
Stomach analysis - 2 years age group.
3 years and older main diet component still zebra mussels.
2007 - 46% mean share by number, abundance up to 25 ind/100m2
2010 - 27% mean share by number, abundance up to 11 ind/100m2
Round goby trophic niche in lagoon:
Isotopic bi-plot showing mean (± SD) δ13C and δ15N values for
different fish and bird species of the Curonian lagoon in 2010.
Round goby trophic niche in lagoon:
Our initial hypothesis that the trophic niche of the round goby in
the lagoon would overlap with that of other molluscivorous fish
species such as roach or bream was not proved.
Surprisingly, there was not any overlap in the isotopic niches of
the round goby and large roach which has been reported to have
zebra mussels as the main diet component. In contrast, the
closest isotopic niches were those of the round goby and the
Eurasian ruffe suggesting the largest dietary or habitat overlap.
Round goby become important component of predatory fish diet.
26 % of European perch and 18 % of pikeperch diet .
Unknown role of burbot (Lota lota) in round goby abundance
decline, but RG decline coincided with stricter fishing rules on
burbot, … but proper assessment complicated.
Round goby in Baltic sea coastal zone
Pilot studies in 2011 revealed bay mussel (Mytilus trossulus)
decline up to 80 % since RG invasion.
RG important prey item in cod (Gadus morhua), turbot (Psetta
maxima) diet.
Thanks for attention ☺
Questions???
This study were funded by the
Research Council of Lithuania.