Report of the workshop on taxonomic quality issues in the DATRAS database (WKTQD)

Abstract

Quality control of data collections is

an issue of primary importance in

conducting science and this is no

different for surveys intended to

monitor changes in fish abundance.

Essentially, quality control is the responsibility of

the national institutes conducting the

surveys. However, if the national data

are combined in a common international

data base, as is the case with DATRAS, the consistency of the data

submitted engages an international

dimension, because the reliability of

any comprehensive analysis of changes in

the fish community at large that could serve as the basis for ICES advice

depends on the reliability of the

species identifications in all national

subsets. Many of the surveys that are

routinely carried out jointly under the

auspices of ICES have a long history during which the primary

objectives have changed. Thus, the IBTS

started as a Young Herring Survey, was

then transformed in a Young Fish Survey

to obtain recruitment estimates of commercial species, and

became only a general monitoring survey

of the entire fish community at a later

stage. Despite these changes in general

objectives, the emphasis in data use is still largely focused on the

commercial species that are relatively

easy to identify. Although measurement

errors and punching errors for this

group may have entered the data base, as evident from unrealistically

small or large individuals reported in

some cases, it seems generally safe to

conclude that, in view of the large

amount of detailed data collected for

these species, these could lead only to minor

and negligible distortions in the

analyses. However, when it comes to the

less common species, studies of the IBTS

component in the past have proven major inconsistencies in species

identification in the data set that has

been entered in DATRAS. This problem is

not restricted to a single or a few

countries, but affects all countries, although the species involved

may differ. This suggests that it is a

direct consequence of the large number

of people involved in data collection on

board and of a generic lack of good

taxonomic knowledge among the scientific

staff at large that inhibits the

maintenance of enough quality control. The problems identified in the past have

been the direct reason for holding this

one-off workshop to discuss the various

aspects of identifying inconsistencies

and correcting species identifications in historic data sets

and of ensuring correct species

identification in future data

collections. Taxonomic quality control

is a complex issue, because the problems

vary by region depending on the species that may

be encountered and therefore may require

specific approaches regionally.

Moreover, the ultimate responsibility

for introducing specific protocols for quality control rests with the

survey working groups responsible for

data collection rather than that the

appropriate procedures can be prescribed

by others. Therefore, the aim of the workshop has been to provide generic

guidelines for development of suitable

protocols by the survey working groups

rather than to come up with a final

answer. It must be emphasized that so far

progress in identifying inconsistencies

in reporting of various taxa has been

restricted to the IBTS component of

DATRAS, which covers the North Sea, Skagerak and Kattegat. For all

other surveys, similar analyses have not

yet been conducted, but there is no

reason to assume that the situation

would be any different. Following the Terms of Reference, the

report is split in four sections that

deal with each of these respectively.

Section 3 deals with ToR a): “Identify

and correct taxonomic

mis-identifications and input errors in DATRAS”. Obviously, this

ultimate goal was beyond reach during a

three-day workshop, and a lot more work

needs to be done. This section lists

dubious species, inconsistent information provided

regarding taxonomic level reported,

maximum attainable size and area of

distribution, and examples of

inconsistent information reported for

some problematic taxa. The information given

is restricted to the IBTS component of

DATRAS, but should not be interpreted as

a comprehensive analysis of all

inconsistencies that may be 2 | ICES WKTQD Report 2007 present in

this data set. Rather, it highlights

methodical aspects as to how

inconsistencies may be elucidated. Section 4 deals with ToR

b): ”Development of protocols for

ensuring the appropriate treatment of

data reported at higher taxonomic

levels”. Historically, different

countries have reported variously species at different

taxonomic levels (genus or families).

Also, uncertain species records may have

to be adjusted by using a higher

taxonomic level. As a consequence, subsequent community analyses may

require that these higher taxa are split

into its constituting species based on

identifications considered reliable.

Because there are various ways to do such computations depending

on the assumptions made, different

analyses could give different answers.

From an ICES perspective, some

consistency in the approaches used by different working groups would seem

appropriate. This section provides the

essentials of an appropriate algorithm

based on using length frequencies, area

of distribution and year of catch, that could serve as a first

guideline for comprehensive community

analyses as well as for trend analysis

of individual species. Section 5 deals with ToR c): “Develop

improved protocols to ensure that

species identification in trawl surveys

is appropriate for fish community

studies, including the development of photo-ID keys for nations participating

in surveys”. Various initiatives have

been taken by individual countries to

develop appropriate tools for species

identification, including training courses. This section lists a number of

ways by which future data collections

may be improved or by which species

identification can be ascertained at a

later stage in the process. Finally, section 6 deals with ToR d).

“Develop protocols for (i) improving

quality control during the submission of

data to DATRAS and (ii) the future

checking and quality assurance of DATRAS data. This ToR relates to the

important aspect of the responsibility

of ICES for ensuring that all taxonomic

data in DATRAS are correct or, if they

are dubious but cannot be corrected, that the information provided

to external users is properly identified

as being of a dubious nature. The

section describes a warning system that

should be developed at the submission stage of new data so as to

inform each country that the data

submitted contain information that is

inconsistent with what is known about

the biology of the species and therefore should be carefully checked.

It is also stressed that historic data

that cannot be corrected but remain

dubious are properly flagged internally

and potentially adjusted when made

available to external users. Proper

taxonomic quality control will remain an

issue of all monitoring programmes that needs continuous attention and

adjustments. We can only hope that this

comprehensive description of its many

aspects helps the survey working groups

to make real progress in achieving an urgently required revision

of the historic information provided as

well as in improving future data

submission.