miðvikudagur 2. maí 2012

Ógnar flundran afkomu laxfiska?

Fimmtudaginn 3. maí mun Danny O‘Farrell meistaranemi í haf- og strandsvæðastjórnun kynna lokaritgerð sína um áhrif flundru á laxfiska á Vestfjörðum. Ritgerðin ber titilinn Range expansion of European Flounder Platichthys flesus to Icelandic waters. A threat to native salmonids? Fyrirlesturinn, sem fer fram á ensku, hefst kl. 16:00 í stofu 1-2 í Háskólasetrinu og eru allir velkomnir.

Leiðbeinandi verkefnisins er dr. Scott Heppell, lektor við Oregon State University í Bandaríkjunum og prófdómari er prófessor Vincent Gallucci, gestafræðimaður við Háskólasetur Vestfjarða og prófessor við Háskólann í Washington í Bandaríkjunum.

Rannsókn Danny O‘Farrell gekk út á að kanna áhrif tilkomu flundru í vistkerfið á Vestfjörðum á laxfiska (lax, silung og sjóbirting) sem fyrir voru á svæðinu. Þessi áhrif eru greind með ýmsum hætti: Dreifing og magn flundrunnar var kannað; fæða hennar og hugsanlega fæðusamkeppni við laxfiska, m.a. með tilliti til magainnihalds tegundanna og skörun flundrunnar og laxfiska í tíma og rúm. Einnig var aldursdreifing flundra sem veiddust í Önundarfirði og Hornvík frá júní til september 2011 könnuð sérstaklega.

Ágrip á ensku:
Warming ocean temperatures have influenced the distribution and abundance of many new species to Icelandic waters. The purpose of this study was to identify the potential impacts of emergence of Plactichthys flesus on Icelandic salmonids (Salmo salar, Salmo trutta, salvenlinus alpinus) by identifying: (1) the distributional range of P. flesus in the Westfjords region, Iceland; (2) the relative abundance of P. flesus in that area; (3) the diet of P. flesus and potential for diet overlap for salmonids; (4) the spatial and temporal overlap between P. flesus and salmonids; and (5) prey specific abundance of prey items found in the stomach contents between P. flesus and salmonids in estuaries. I also examined the age distribution of P. flesus from fish caught in Önundarfjörður and Hornvík through the months of June-September 2011. P. flesus was found throughout the areas of Önundarfjörður, Hornvík, Skálmarfjörður and Norðurfjörður, Iceland. The highest abundance of P. flesus was found in the month of August (CPUE = 4.5833) in Önundarfjörður, where Gammarus spp. was the most important prey item of both P. flesus and salmonids. In the Hornvík estuary, Chironomidea, had the highest numerical index, while Idotea emarginata had the highest occurrence and gravimetrical indices in the relative abundance importance of prey items found in the diet of P. flesus. In salmonids, Gammarus spp. was the most important prey item for salmonids for all calculated prey indices. The spatial overlap between P. Flesus and salmonids was 94% of the time in Önundarfjörður the two groups co-occured, while in Hornvík the two groups co-occurred 45% of the time. The temporal niche overlap results between P. Flesus and salmonids in Önundarfjörður showed significant overlap in three methods, while in Hornvík, the temporal niche overlap results also showed a significant overlap in one method. Prey specific abundance of diet items of P. flesus and salmonids in Önundarfjörður showed specialized feeding strategies and narrow niche widths. In Hornvík, both species had generalist feeding strategies and broad niche widths. The age of P. flesus ranged in Önundarfjörður from 1 to 6 years and in Hornvík between1 and 5 years). P. flesus will likely continue to spread in Icelandic waters, with the potential to compete both spatially and temporally with salmonids.

Danny O'Farrell við rannsóknir í Hornvík sumarið 2011. Ljósmynd: Danny O'Farrell.
Danny O'Farrell við rannsóknir í Hornvík sumarið 2011. Ljósmynd: Danny O'Farrell.