Aug 05
The end of the beginning

​"You can have data without information, but you cannot have information without data." Daniel Keys Moran.DSC_0113.JPGSimilar to how landed fish go on to feed society and the economy, the story of the data collected on the Johan Hjort during the IBTS cruise doesn't end at the port. In fact, in many ways it is just the beginning.

The scientists on board have done their bit: the trawl net has been systematically deployed and catches sorted; various species have had samples, lengths, weights and ages taken; valuable data has been stored. All carried out with efficiency and admirable character, especially given the nature of their shift work.

It's now time for the next stage of the data's life-cycle as it is processed and cleaned to remove any inaccurate or duplicate records, before being submitted to ICES DATRAS database by IMR in September along with that from the other countries in the survey. DATRAS is a hub of facts and figures from all the trawl surveys hosted by ICES, containing fish sampling data (fisheries independent data: that gathered outside the realm of commercial fisheries) in a standardized format. It includes North Sea IBTS data harking back to 1965.

This DATRAS data can be downloaded from the ICES website as various products by ICES scientists, stock assessors, working groups, and just about anyone else (the data is open access after all) for use in research and stock assessments. Some of the downloadables include the catch per unit of effort (CPUE). In the case of IBTS, that's adjusted in DATRAS to indicate catch of fish of the same species per hour of trawling; these help produce indices of relative abundance. Also available are age-length keys, used to estimate the age structure of a fish population by extrapolating the known data taken at sea.​ ​Then there's the CTD data. ​

species sample data.JPGData stored on board the Johan Hjort, arranged by species, weight and count amongst other parametres

But this only tells part of the story. To explain the next chapter, Fishing for Data will be back in September with a post describing how some of the data collected on the North Sea during the cruise is stored, downloaded and transformed into the building blocks that go on to build the stock assessments which underpin ICES advice.​ This then goes on to guide the fishing, completing the cycle. be continued....


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