Lesutiene, J.

Siaulys, A.

Skabeikis, A.

OceanRep

 Seasonal and ontogenetic dietary changes of round goby (Neogobius melanostomus) in the exposed coastal waters of SE Baltic Sea  Jūratė Lesutienė1, Artūras Skabeikis2 and Andrius Šiaulys1  1Coastal Research and Planning Institute, Marine Science and Technology Center, Klaipėda University, Manto 84, LT-92294, Klaipėda, Lithuania 2Lithuanian Sea Museum, Smiltynės 3, LT-93100, Klaipėda, Lithuania    September 4th-5th 2014, Charlottenlund Castle, Denmark Effects of round goby in the coastal ecosystem  © V. Gasiūnaitė Round goby changes invaded ecosystem by reducing abundances of its feeding objects – predominantly molluscs, competing for food resources with native demersal fish and bird species or becoming an important component in the diet of piscivorous fish, birds and mammals.   0500100015002000250030003500400045002003 2006 2008 2011 2012 1013Blue mussel biomass, g m-2 Stupelytė, 2014. Distribution and biomass dynamics of blue mussel (Mytilus edulis trossulus, (Gould, 1850)) in the Lithuanian coastal waters of the Baltic Sea. Bachelor‘s thesis    In Lithuanian coastal areas Mytilus abundance at 0-15 m depth decreased ~95% during a decade after invasion of roundgoby 1) Monitoring data of wintering waterfowl; 2) L. Šniaukšta Results of wintering waterfowl counts 2014. BIRDS The magazine of Lithuanian Ornithological Society 2014/1  020004000600080001000012000140001600018000200002001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014Long tailed Duck, indv Mytilus decline coinsided with the decreased abundanced of wintering Long tailed Duck (Clangula hyamalis) and complete  010020030040050060070080090020012002200320042005200620072008200920102011201220132014Steller's eider, indv Diet composition of Long-tailed Duck  By Žydelis (2002)                       Recent study Rasa Morkūnė, Jūratė Lesutienė, Julius Morkūnas FOOD SOURCES OF WINTERING VELVET SCOTER AND LONG-TAILED DUCK ON THE SE BALTIC SEA: TRIPLE STABLE ISOTOPE AND GUT CONTENT ANALYSIS  Diet composition of Velvet Scoter   By Žydelis (2002)                   Recent study © J. Fedotova The main objective of the study was to determine seasonal and ontogenetic dietary changes of round goby in the soft bottom area adjacent to artificial substrate i.e. harbour mole   During May - October 2012, guts of 282 individuals were analysed  Skabeikis A., Morkūnė  R. Barisevičiūtė and Lesutienė J. Seasonal and ontogenetic changes in the diet of round goby (Neogobius melanostomus) in the coastal waters of SE Baltic Sea (submited manuscript)    Sampling area Juveniles were collected using a trap at 2-3m depth, larger gobies using gill nets at 6-11m depth 01020304050607080903 6 16Biomass, g m-2 Depth, m Other invert.Other molluscsCerastodermaMacomaAmphipodaPygospioHedisteMarenzelleriaSAMPLING    Seabed at the sampling site is dominated by soft and sandy sediments, strongly affected by wave action  Soft bottom fauna is dominated by polychaetes at 2-3m depth and Macoma balthica at 6-11m.   MDS ordination plot of biomasses of prey items, determined in the the guts of differently sized round gobies  Size group Pseudo - F P <5 cm 1.169 0.317 5 - 9.9 cm 1.148 0.29 10-14.9 cm 2.652 0.013 14.9-19.9 cm  2.216 0.049 ≥20 cm 1.743 0.118 PERMANOVA results of season effect  010203040506070809010010 - 14.9 15 - 19.9 ≥20 Size groups, cmIRI, %Other preyPiscesAmphipodaCrangon crangonPolychaetaBalanus improvisusMytilus trossulusMacoma balthicaSpring 0102030405060708090100<5 5 - 9.9 10 - 14.9 15 - 19.9 ≥20 Size groups, cmIRI, %Other preyCopepodaCladoceraOstracodaPiscesSaduria entomonAmphipodaCrangon crangonPolychaetaBalanus improvisusMytilus trossulusMacoma balthicaSummer 0102030405060708090100<5 5 - 9.9 10 - 14.9 15 - 19.9 ≥20 Size groups, cmIRI, %Other preyCopepodaCladoceraOstracodaPiscesSaduria entomonAmphipodaCrangon crangonPolychaetaBalanus improvisusMytilus trossulusMacoma balthica0102030405060708090100<5 5 - 9.9 10 - 14.9 15 - 19.9 ≥20 Size groups, cmIRI, %Other preyCopepodaCladoceraOstracodaPiscesSaduria entomonAmphipodaCrangon crangonPolychaetaBalanus improvisusMytilus trossulusMacoma balthicaAutumn Patinai0123456Gegužė Birželis Liepa Rugpjūtis Rugsėjis SpalisMėnesiaiSkrandžio užpildymo indeksas10 - 14,9 cm15 - 19,9 cm>20 cmPatelės0123456Gegužė Birželis Liepa Rugpjūtis Rugsėjis SpalisMėnesiaiSkrandžio užpildymo indeksas10 - 14,9 cm15 - 19,9 cm>20 cmDynamic of gut fullnes of female and male individuals FEMALE MALE May       June      July     August    Sept     October  May       June      July     August    Sept     October  Conclusions Juvenile round gobies forage on zooplankton, meiobenthic organisms and amphipods. Importance of mollusks in the diet increases significantly at the size of ≥10 cm.  The share of mollusks increases with a fish size. Largest specimens >20cm have relatively consistent diet composition with highest amounts of Macoma, while individuals of intermediate 10-20cm size switch to polychaetes during the summer, fish and other mollusks (Mytilus?) during the fall.    These findings indicate size specific partitioning of spawning-foraging grounds within the population of round goby. It seems that largest individuals occupy areas with the highest abundance of Macoma, while smaller individuals are pushed towards shallower waters with polychaete dominated benthic community.   Population size structure and spatial (depth specific) distribution of round goby should be investigated during the autumn to evaluate the mollusk prey loss in the bird diving areas.        

Seasonal and ontogenetic dietary changes of round goby (Neogobius melanostomus) in the exposed coastal waters of SE Baltic Sea

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