Final Report on the Nova Scotia Gear Selectivity
Training Programme, 1997
- Presented by
David Tait, sr. and William Tait, Nordsea Limited
for
- Nova Scotia
Fisheries (R.I.T.C.)
- The Nova
Scotia Department of Fisheries
- Human
Resources Development Canada (H.R.D.
C.)
- The
Federation of Gulf Nova Scotia Ground Fishers (Fixed,
Mobile, Less Than 45 Competitive)
-
EXECUTIVE
SUMMARY
The purpose of these
experiments was to complement a comprehensive fisheries
training program involving Nova Scotian inshore mobile
fishers. The program was designed to demonstrate to the
trainees the effectiveness of selectivity gear developments
in Canadian and global fisheries, and illuminate their
importance in establishing a responsible and sustainable
fishery.
One segment of the agenda
was to examine the selectivity characteristics of codend
mesh sizes and configuations. This experiment was conducted
on board two vessels selected from the inshore mobile gear
fleet in Nova Scotia.
The program was intended
for mobile ground fishers fishing with vessels 45 feet and
under. Larger and more powerful vessels may experience
different results from similar experiments. In the past the
majority of mobile gear selectivity experiments have been
conducted on more powerful offshore vessels.
The plan was to conduct
the program in four phases, the major components
concentrated on training the fishers in selectivity
procedures, and involved them in the entire selectivity
experimental process from conception to
completion.
Phase One commenced with
a series of seminars on selectivity methods and procedures
held in Nova Scotia at Cheticamp, Bay St. Lawrence, Pictou,
Antigonish, and Port Hood. The Seminars were very well
received and coments positive. Addendum 1 and 2 contain the
seminars schedule and a summary of attendees'
comments.
Phase Two consisted of
training fishers on site at the trawl manufacturer and
having them assist in the design and construction of
experimental fishing gears.
Phase Three involved
instruction at sea on how to monitor, analyse, and collate
data from a selectivity experiment.
Phase Four was a
presentation of the methodology and experiment results to
industry.
The experiments were
conducted in NAAFO area 4Tg (figure 1), in depths of 15 to
25 fathoms. Strict project protocol was introduced by
Nordsea Limited to ensure that the final results of phase
three would withstand rigid scientific scrutiny. The
trawling gear was continuously monitored using Scanmar
equipment. Codend mesh size was frequently checked using an
ICES gauge and a standard flat gauge.
The experimental codends
(figure 2) constructed for both vessel projects were
four-seamed with no covers or chafing gear fitted, a lifting
strap was placed on each codend, the netting was braided
green double polyethylene. No selvedge ropes or
strengthening ropes were fitted. The control codend was
two-seamed and constructed of braided green 2.5mm single
polyethylene. All codends were similar in circumference and
length.
The four codend
configurations tested were:
140mm diamond mesh on top
and bottom with square mesh side panels. Material. Double
4mm polyethylene.
140mm square mesh on top
and bottom with diamond mesh side panels. Material. Double
4mm polyethylene.
140mm all square mesh.
Material. Double 4mm polyethylene.
130mm square mesh on top
and bottom with diamond side panels. Material. Double 4mm
polyethylene.
Control
Codend:
55mm diamond mesh control
codend. Material. Single 2.5mm polyethylene.
All catches were measured
and weighed according the the predetermined protocol and a
small mesh control codend sampled the totalfish population.
Frequency graphs and selectivity curves are
presented.
Prior to starting each
experiment five tows were made with identical codends to
check the validity of the experimental split
nets.
Results for the validity
tests on the trawler show that the number of fish caught on
each side was 50.26%/49.74%. This is not statistically
different from a 50/50 split.
Results for the validity
tests on the Scottish seiner show that the number of fish
caught on each side was 49.59%/50.41%. This is also not
statistically different from a 50/50 split. Also the
distribution lengths in both cases were not significantly.
See figures 26 and 27.
Retention curve
parameters for the trawler "Amy Marie" for each
gear:
Gear
|
130 DS
|
140 DS
|
140 SD
|
140 SS
|
50% retention length
|
29.5
|
33.7
|
32.5
|
28.7
|
Selectivity range (cm)
|
4.5
|
6.0
|
5.0
|
4.0
|
Proportion in experimental
gear
|
0.51
|
0.54
|
0.50
|
0.52
|
Retention curve
parameters for the trawler "Celtic Pride" for each
gear:
Gear
|
130 DS
|
140 DS
|
140 SD
|
140 SS
|
50% retention length
|
28.0
|
30.1
|
33.2
|
31.4
|
Selectivity range (cm)
|
4.7
|
8.3
|
8.0
|
8.2
|
Proportion in experimental
gear
|
0.40
|
0.56
|
0.72
|
0.52
|
The following is a
summary of the comments from the attendees at the
seminar:
Thirty one of the
attendees responded to the questionnaire. Almost all thought
the timing of the seminar was good and the subjects were
covered adequately. When asked what there should be more on,
the replies, highest number of votes first, are as
follows:
a) Scottish
seining
b) selective methods for
the under 45 foot fishery
c) selective
gears
d) experimental
trawls
e) doors and net
design
When asked which aspects
of the seminar were most interesting, the majority chose the
videos and verbal presentation. Many liked all aspects,
including the overheads and scale models.
To summarize, the
attendees were very positive in their reaction. They felt
that the presentation was excellent, they had learned a
great deal and would like the opportunity to attend more
seminars on selectivity in the under 45 foot sector. One
very telling comment was that information of this nature was
a great help to fishers planning in their future.
|