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GSL-south #5
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@AquaAuma , can you please clarify the issue a bit more for me? It's possible I can answer. |
This survey I think is broken down into three sub-surveys by DFO and we should not merge them because they use different designs, which was the main concern |
I think it may be the same issue for the northern survey |
the GSL northern survey has used four vessels with slightly different gear types, documented here: #10 (comment) |
Fishglob currently has data from 1970-2019 for GSL-S. From https://waves-vagues.dfo-mpo.gc.ca/Library/115732.pdf, we know:
The dataset we import from OceanAdapt only includes the Western IIA (1985&1987-2019) and the Yankee 36 (1970-1986). In the cleaning code (get.gsl-s.R), I adjust the area_swept based on the gear type. These two gear types overlap in 1985. For my taxonomic homogenization work, I only used 1992-2019 because of an additional gear/vessel change in 1992. See https://github.com/AquaAuma/fishglob/issues/72. |
My notes from talking to Hugues Benoît (DFO) n 2009:
He also recommended these for people who want more details:
|
so based on all this, what do you think is the best to ensure more accurate usage of the dataset in fishglob? |
Explain what we know and encourage users to consult the original sources to understand other specifics relevant to their analysis. |
I agree! I'll add some content to the metadata.
I wonder if we should include a similar disclaimer to this on our home
page for the repository? (From DATRAS)
"*You need to accept the following before you can submit.*
*Data policy*
The trawl survey database can be accessed depending on your permission
level (see data access policy)
<https://datras.ices.dk/Data_products/Download/Download_Data_public.aspx#>
*'Healthy' warning*
Whilst the data have been extensively checked by both the supplying
institutes and ICES there are inherent flaws in gathering the information.
For example:
* In spite of the fact that now all bottom trawl surveys are in the same
database and often at least partially overlap in time period or area
covered, there are differences between the surveys that may not allow the
combination of data from different surveys in one analysis unless this
point is specifically addressed.
* There is no guarantee that the ground gear types deployed adequately
sample all species (e.g. catchability of flatfish in beam trawls is
markedly higher than that of GOV). It should be realized that each survey
gear catches a gear-dependent subset of the fish community. Also, for the
same gear, catchability can be largely modified by rigging, ticklers, or
other elements as those described under Gear Exceptions field (for instance
bobbins, rockhopper etc.)
* A common property of all surveys is that over time species determination
skills improve. As a result new taxa will emerge in the dataset that were
previously reported as part of another closely-related taxon.
* Over time the sampling procedures, gear characteristics, timing of the
survey or the area covered may have changed thereby influencing the
catches. Expert advice recommendations are given in order to prevent bias
in the analyses using DATRAS catch data, caused by such factors.
Thus users are urged to treat the data with caution. If the user has any
queries on the validity of the data or the conclusions to be drawn they
should contact either the ICES Secretariat or the Chairs of the relevant
Working Group (IBTS, BITS or BEAM)
To guide the users of the trawl data the relevant working groups have
provided the users with an expert advise. Please read these before using
the data: Expert advice <http://datras.ices.dk/ExpertAdvice.aspx>
This is an informative note. For further details on the current data
policy, please read carefully the disclaimer included in the download
package.
I accept the documents and their associated restrictions and agree to
acknowledge the data source."
…On Thu, Sep 7, 2023 at 6:29 AM Malin Pinsky ***@***.***> wrote:
Explain what we know and encourage users to consult the original sources
to understand other specifics relevant to their analysis.
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|
I agree. A version of this disclaimer would be very appropriate for FISHGLOB as well. |
I like that idea! Would any of you volunteer to draft one? Otherwise will do at the end of this month. I'm trying to wrap things up quickly, and I have a lot to do on the dataset itself |
I could do it the last week of September, but unfortunately not before then! |
that will work, since there were too many tasks on the revision, I've delayed the resubmission deadline again |
Just double checked we have this in the metadata docs So we should be fine? I'll just resolve |
I think we better document in the data GSL Case properly, and consider each as a survey_unit, what do you think @zoe?
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