Institute of Marine Research
North Sea Skagerrak Northern Shrimp Bottom Trawl Index
Recommended citation:
Guldborg Søvik
(2020)
North Sea Skagerrak Northern Shrimp Bottom Trawl Index
https://doi.org/10.21335/NMDC-1417601993
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Abstract
This is a parent site of all data sets for North Sea Skagerrak Northern Shrimp Bottom Trawl Index over several years. It contains the latest data set and links to previous versions. The survey indices by carapace length group (mm) for bottom trawl for northern shrimp from the Shrimp survey in the Norwegian Deep and Skagerrak are calculated. Updated data series are provided in annual survey reports (e.g. Søvik et al. 2019). The survey data consist of: 1) a time series from 1984-2002 (October/November) using R/V Michael Sars; 2) a point estimate for 2003 (October) with R/V Håkon Mosby; 3) a time series from 2004-2005 (May/June) with R/V Håkon Mosby; and 4) a time series from 2006 until present (January/February), using R/V Håkon Mosby (2006-2016) and R/V Kristine Bonnevie (from 2017). The survey gear used is the Campelen trawl except on the 2003 survey when the Shrimp trawl 1420 was used, as winches on Håkon Mosby at that time were not powerful enough for the Campelen-trawl. There is therefore no StoX-estimate from 2003. The Campelen trawl is rigged with extra floats (“North Sea rigging”) to prevent mud hauls on soft bottom, as well as a small meshed inner net. This rigging is now standardized, but in former years the number of floats may have varied. The inner net was not used on the surveys in 2012-2014. In 2016, there were technical problems with the survey trawl (unequal wire lengths of the trawl gear). The StoX-estimate from 2016 is probably an underestimate and should not be used. The survey area is divided into nine strata and has a fixed station design. In 2006, it was decided that the 100 stations trawled during the 2000 survey should be considered fixed stations for future surveys. The station list has since been slightly changed (described in Søvik et al. 2019), resulting in a list of 111 fixed stations. Due to time restrictions, mainly due to bad weather, the survey area was not fully covered in some years and the number of stations trawled have varied between 61 and 111. For the first time series, this pertains to 1984, 1986, and 2002. For the most recent time series, this happened in 2006, 2007, 2008, 2012, 2014, and 2015. It is mainly parts of the Norwegian Deep west of Lindesnes that has not been covered, except in 1984 when two strata in Skagerrak were not covered. The StoX-estimates have not been corrected for this lack of coverage.
Scientific keywords:
EARTH SCIENCE> BIOLOGICAL CLASSIFICATION> ANIMALS/INVERTEBRATES> ARTHROPODS> CRUSTACEANS> DECAPODS
Key words:
Northern shrimp