Bottom Trawl Surveys - Proceedings of a Workshop Held at Ottawa ...

professional fisherman. No matter how
commendable this individuality may be, it is not
conducive to consistent fishery resource
surveys. So far, we have been satisfied to
insist that surveys be conducted on research
vessels rather than on commercial vessels, we
have tried to maintain consistent command of
these research vessels, and we have drawn up
"standard" plans, usually arbitrarily, for the
survey trawls. However, there is still
considerable latitude in the rigging and
operation of the gear, and inspection of the
gear to assure it is to specification is
generally quite lax. Much more can be done to
tighten up technical procedures, even though
operations staff may object, and this should
reduce the variations in catch results which
originate in variations in gear catchability
{that fraction of the fish in the path of the
trawl which is retained in the catch).
Various national and international
standards are available whose recognition would
reduce ambiguities and misunderstandings in
communication and which provide uniform
procedures for describing and defining fishing
gear in an unambiguous way.
In 1960, the International Standards
Organization (ISO) established a subcommittee
(SC9) on fishing gear materials (netting and
twines) under its technical committee on
textiles (TC38). This subcommittee was quite
active for about a decade and developed several
standards which have been accepted
internationally (ISO 1969-1976) with the more
recent revisions of the standards resulting
primarily from subsequent metric conversion.
This list also includes ISO standards developed
by other subcommittees but which have relevance
to fishing gear. The only outstanding work on
ISO/TC38/SC9 books is a draft standard on the
method for measuring mesh size. This is in
abeyance at present pending further advice from
ICES on the effect of mesh load during
measurement on the results of selectivity
experiments.
In 1958, the Canadian Government
Specifications Board (now the Canadian General
Standards Board) published a standard on netting
for fishing gear. This originated primarily in
problems with mesh size stability in the
regulation of drift gillnet fisheries in the
Great Lakes. It is limited in scope and is now
very much out of date. However, metric
conversion has provided the opportunity to
revise this Canadian Standard and expand it also
to include the essential features of the ISO
Standards, as required to give legal force to
these latter. A draft of this revised Canadian
Standard is being prepared by CGSB and DFO for
consideration by the re-constituted CGSB
Committee on Specifications for Fishing Gear.
Representatives of the federal and provincial
governments, the fishing industry and fishing
gear suppliers have been invited to sit on this
committee.
The scope of the draft standard is:
1. Terms and definitions with
cross-reference to other recognized
glossaries.
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2. Unambiguous and definitive designation
of twines and netting, including fibre
type, construction and size.
3. Methods and conditions for test of:
Twine thickness;
Mesh size:
Dimensional stability to wetting,
loading, dyeing, etc.;
Load-elongation characteristics:
Strength and elasticity (resistance
to tearing).
4. Specification of fishing gear
construction and components.
As an example, Figures 5 and 6 give the
trawl plan and rigging of the Maritimes Region,
Atlantic Western IIA, groundfish survey trawl
drawn according to the procedures laid down in
ISO Standard 3169-1975 and used in the FAD
fishing gear catalogues {FAD 1972, 1975). All
mesh counts and cutting rates are shown, as are
the methods of joining and hanging. There are
no ambiguous proprietary twine numbers; instead
the twine designation given in ISO Standards
858-1973 and 1144-1969 is used. All materials
and dimensions are specified. There is very
little scope for "poetic licence" in the
construction of the gear without violating the
specifications.
The use of standard definitions of
technical terms as given in ISO Standards
1107-1974, 1530-1973, 1531-1973 and in other
international and Canadian standards should be
used in all communications relating to research
and regulation in the fisheries, to minimize
confusion and to avoid ambiguity.
. It is hoped that the eventual revised
version of Canadian Standard 55-GP will contain
all the relevant technical information from
pertinent ISO Standards in one or, at the most,
two documents for ready reference and that, with
the legal force of a Canadian Standard in the
purchase of fishing gear and gear materials, it
will be useful in developing and maintaining
more consistent trawl survey gear.
It is suggested that the trend to
standardization which is seen with respect to
the specification of fishing gear be extended to
the procedures used in resource inventory
fishing. The intention, at least at first,
should be simply to "tighten" survey procedures
in order to reduce catch variability now
generated by relatively uncontrolled trawl
behaviour, without substantially altering the
inherent biases in gear catchability. New catch
data should then still be comparable, and more
precisely so, with historical data. Substantial
changes in procedures to improve catchability
should be approached with more caution. It is