Using commercial catch data to investigate effects of air-guns on fish catch rates
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Poster presented at International Conference on the Effects of Noise on Aquatic Life, Cork, Ireland, August 15-20 2010. Summary: IMR, Bergen, has analysed data from official databases of landed catches from the period in which seismic data collection was carried out by the Norwegian Petroleum Directorate in the Lofoten/Vesterålen area summer 2008. Except for in the gillnet fisheries for saithe (Pollachius virens) and haddock (Melanogrammus aeglefinus), no significant negative effects could be documented. The catch rates of cod (Gadus morhua), ling (Molva molva), tusk (Brosme brosme) and Atlantic halibut (Hippoglossus hippoglossus) were not significantly changed during seismic activity, while those of red-fish (Sebastes marinus) and monkfish (Lophius piscatorius) seemed to increase. The catch rates of saithe and haddock caught by gillnets decreased, while similar negative effects could not be documented in the fisheries using other fishing gears (long line, hook-and-line or Danish seine). In the total investigation area there was a 45 % decrease in total amount of saithe delivered summer 2008 relative to in 2006 and 2007, but not less than in the period 2003 to 2005. However, the databases used are not constructed for this type of analyses, and has a structure that makes it difficult to trace minor changes in catch rates due to external effects. Also, the majority of the seismic data collection summer 2008 was 2D shooting scattered in time and space, which cannot be expected to have major influences on the fisheries.