Vieraslajin Cercopagis pengoi seuranta ja esiintyminen Suomenlahdella Hangon edustalla asemalla Längden UUS-23 vuosina 1995-2005

Vieraslaji Cercopagis pengoi havaittiin Riianlahdella vuonna 1992 ja Suomenlahdella 1995. Koukkuvesikirppu on plank-tonäyriäinen ja kotoisin Kaspianmeren alueelta. Tämän petovesikirppulajin esiintymistä seurattiin vuosina 1998-2005 Hankoniemen edustalla asemalla Längden, UUS-23. Lajia ei havaittu vuoden 1998 näytteissä. Se esiintyi kaikkina muina seurantavuosina, mutta runsaana vain vuonna 2002. Koukkuvesikirpun aikuisvaihe on planktinen, mutta munat vajoavat meren pohjalle ja voivat siellä kärsiä pohjanlähei-sestä happivajeesta. YksilömääränDen invasive arten rovvattenloppan Cercopagis pengoi är ett pelagiskt kräftdjur som påträffades för första gången i Rigabuk-ten år 1992 och i Finska viken år 1995. Rovvattenloppan härstammar från den Ponto-Kaspiska regionen. Under åren 1998-2005 togs planktonprover utanför Hangöudd på stationen Längden UUS-23. I proven från 1998 saknas rovvattenloppan, men den förekom alla andra uppföljningsår. Endast år 2002 anses den ha förekommit i riklig mängd. C. pengoi är en planktisk art, vars ägg ligger i bottensedimentet under en stor del av året och kan där dö till följd av syrebrist. Syrebrist var troligtvis orsak till den markanta nedgången i individantalet från 215 ind.m-3 år 2002 till endast 1 ind.m-3 år 2003.The alien predatory planktonic crustacean Cercopagis pengoi appeared in the Gulf of Riga in 1992 and in the Gulf of Finland in 1995. By origin C. pengoi is Ponto-Caspian species. During 1998-2005 plankton samples were taken at the entrance to the Gulf of Finland, at station Längden, UUS-23. C. pengoi was not found in samples taken 1998, but occurred after that every sampling year. Only in 2002 its abundance can be estimated as high. C. pengoi is a planktonic organism, but its resting eggs spend bigger part of the year in the bottom sediment, where they can die off anoxic condition. Evidently anoxia in Hanko area might be a reason of the enormous declining of C. pengoi abundance from 215 ind.m-3 in 2002 to only 1 ind.m-3 in 2003. Julkaisun saavutettavuus on tarkistettu

<i>Ptychogena lactea</i> A. Agassiz, 1865 (Hydrozoa; Laodiceidae): What We Know on Taxonomy, Life-Cycle and Distribution

The hydromedusa Ptychogena lactea A. Agassiz, 1865 is a large and remarkable jellyfish; it has been found in many Arctic and even boreal localities and at various depths, from the mesopelagial to the surface. However, it is still regarded in the literature as a rare deep-water species, with an unknown polyp stage. The hydroid was reared from the medusa P. lactea in the Franz-Josef Land archipelago field laboratory. The hydroid was identified as Cuspidella procumbens Kramp, 1911: a poorly known Campanulinoidea, “Cuspidella-like” Arctic hydroid whose medusa stage was hitherto unknown. Both stages are here proposed to link taxonomically into a one nominal species. Co-distribution of the well-known medusa and the little-known hydroid is studied and mapped. Data on the distribution and ecology of both stages is added. Some data has already been published in Russian literature, but remains unknown to English-speaking scientists. New observations show that P. lactea is neither a deep-water species nor rare, and establish the continuity between medusae and polyp stages of the life cycle

Herring and sprat: dynamics, status, and catches

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