Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/12312
Range expansion of European flounder Platichthys flesus to Icelandic waters : a threat to native salmonids?
Warming ocean temperatures have influenced the distribution and abundance of 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. Including examination on the age distribution of P. flesus from fish caught in Önundarförður and Horvik through the months of June-September 2011. P. flesus was found throughout the areas of Önundarfjörður, Hornvik, Skálmarfjöður and Norðurföður, 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 Hornvik 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 niche overlap between P. Flesus and salmonids was 94% in Önundarfjorður where the two groups co-occured, while in Hornvik the two groups co-occurred 45%. The temporal niche overlap results between P. Flesus and salmonids in Önundarfjörður showed significant overlap in three methods, while in Hornvik, 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 Hornvik, both species had generalist feeding strategies and broad niche widths. The age of P. flesus ranged in Önundarfjörðdur from 1 to 6 years and in Hornvik between 1 and 5 years. P. flesus will likely continue to spread in Icelandic waters, with the potential to compete both spatially and temporally with salmonids.