Barents Sea 0-group fish (6-8 months old) data 1980-2023

A joint Norwegian-Russian survey of 0-group fish (here defined as fish hatched earlier in the same calendar year) in the Barents Sea was started in September 1965 with the motivation to provide initial information on year class strength of commercially important fish stocks (ICES 1965, Eriksen and Prozorkevich 2011). The results from the survey have been calculated and expressed as a set of 0-group fish abundance indices of the main commercial species of fish found in the Barents Sea (Dingsør 2005, Eriksen et al. 2009, Eriksen and Prozorkevich 2011).
The procedures for sampling, analysis and calculation of results and the discussion of associated sources of error are described in detail in the report (Eriksen et al. 2024, link to report). The report also provides information on the historical development of the survey, the survey period, the vessels involved, the estimation methods and distribution maps for 0-group cod, haddock, polar cod, herring, capelin and redfish.
Trawling procedure: The “Harstad” trawl is designed to capture small fish and has been the standard equipment since around 1980 for the 0-group fish survey, the capelin survey, and later the ecosystem survey (Anon. 1980, Eriksen and Gjøsæter 2013). Since 1980 the the standard trawling procedure where the trawl is operated in steps with the headline at 0 m, 20 m and 40 m. With a nominal trawl opening of 20x20 m, this provides an integrated sample from the upper 60 m of the water column. The trawling procedure prescribes a towing speed of 3 knots and a tow distance of 0.5 nm for each depth interval . Additional tows with the headline at 60 and 80 m, and with distance of 0.5 nm, were made when dense concentration was recorded deeper than 60 m on the echo-sounder.

The data set include Norwegian data only for the period 1980-2023. The row catch data is standardised for trawling distance, covered vertical layer and corrected for low capture efficiency for small fish to avoid misunderstandings of sampling and estimation methodology (described by Dingsør 2005, Eriksen et al. 2009) and thus the representativeness of the data. The standardised data are now expressed as the density of 0-group fish (kg) per nautical mile and are comparable between stations, areas and years.