The newly developed 25m high opening trawl possesses the properties of a high rising bottom trawl and a semi-pelagic trawl. The new gear is effective for the capture of demersal and semi-pelagic fishes. The net offered more horizontal opening and less resistance with significantly high catch of ribbon fish when compared with bulged belly trawl

Boopendranath, M.R.

Gopalakrishnan, K.

Kunjipalu, K.K.

Kuttappan, A.C.

Aquatic Commons

A New High Opening Trawl Veraval Waters 
K. K. KUNJIPALU, M. R. BOOPENDRANATH, K. GOPALAKRISHNAN* and 
A. C. KUTTAPPAN** 
Veraval Research Centre of Central Institute of Fisheries Technology, Veraval- 362 265 
The newly developed 25m high opening trawl possesses the properties of a high rising 
bottom trawl and a semi-pelagic trawl. The new gear is effective for the 
capture of demersal and semi-pelagic fishes. The net offered more horizontal opening 
and less resistance with significantly high catch of ribbon fish when compared with 
bulged belly trawl. 
Emphasis on more head-line height is for cat-
ching off bottom :fishes also by a ground trawl. 
This is effected by using a kite (Takayama & 
Koyama, 1959; Nakamura, 1971) or by mul-· 
tiplication in the number of panels/seams of 
the net as in six-seam, eight-seam, or in the 
body of the gear as in the vertical twin body 
trawl (Nakamura, 1971; Kodera, 1971). 
The high opening ground trawls (Garner, 
1967, 1978) and multi-purpose semi-pelagic 
trawls (Brandt, 1971) have been so designed 
to give more head line height while keeping 
contact with the sea-bed. Suitability of a 
six-seam trawl along the north west-coast 
has been reported by Deshpande eta!. (1970) 
and a dual purpose trawl 011 the south-west 
coast by Kartha & Sadanandan (1973). 
Kunjipalu (1980) observed a good percen-
. tage of ribbon fishes in the trawl catches off 
Veraval. A net to catch these semi-pelagic 
species is therefore designed on the lines of 
an eight panelled multi-purpose and semi-
pelagic type trawl net and the results of 
investigations are detailed in this communi-
cation. 
Materials and Methods 
The 25m high opening trawl was operated 
from the Central Institute of Fishery Tech-
nology vessel Fishtech viii (15.2 m 
OAL fitted with 165 hp engine) 
during 1978-80. The gear was operated 
*Present address: Goa Base of Fishery Survey of 
India, Panaji, Goa 
**Central Institute of Fisheries Technology, Cochin-
682029 
Vol. 21, 1984 
along with 25 m bulged belly trawl described 
by Kunjipalu et al. (1979), in combination 
with .flat rectangular otter boards of 
1524 mm x }62 mm size and 100 kg weight 
each (Kuriyan et a!., 1964) and double 
~L'~ 
R 
120 
12 
100 
' 120 
Fig. 1. 25 m high opening trawl 
87 K.K. KUNJIPALU M. R.BOOPENDRANATH, K. GOPALAKRISHNAN AND 
' A. C. KUTTAPPAN 
Table la. Detaifs of lines and ropes 
a b c d e I 
Material High density polyethelene ................................... . 
Diameter, mm 
Breaking strength, kg 
Length, m 
18 ........................................................ ······· ..... . 
3460 ................................................................. . 
4.0 
25 
32.25 
2.25 8.2 2.8 11.0 3.0 
Head rope, m 
Foot rope, m 
Rib lines 30m x 4 Nos 6 mm HDPE (Breaking strength 425 kg) 
Table lb. Details of floats, sinkers and otter boards 
Floats 
Number 19 (13+6) 
Material Hard plastic 
Shape Spherical 
Diameter, rnm 150 
Length, mm 
Breadth, mm 
Static buoyancy, kg ·1.550 each 
Weight in air, kg .0.300 each 
sweep line each of 5 m long in between the 
net leg and otter board .. Towing warp 
tension and horizontal opening between 
otter boards were measured as described by 
Benyami (1959), Deshpande (1960) and 
Satyanarayana & Nair (1965). The catch 
and composition of each haul were recorded 
separately for the. two gears. B6th the nets 
were operated on the same d~y keeping 
depth, ground, length of warp; >'trawling 
speed, duration of each haul and course 
constant. 
Details of 25 m high opening trawl are 
shown in Fig. 1 and Tables 1 (a) and (b). 
Attachment of floats in the two nets is shown 
in Fig.2. Fifty seven comparative hauls each of 
one hour duration, were made. The nets 
landed 8672.256 kg fish. · 
Results and Discussion 
The results of comparative fishing opera-
tions are presented in Table 2 and the com-
position of catch in Table 3. For the pur-
pose of statistical analysis, the data on 
horizontal opening was taken as such but 
Sinkers Otter boards 
2 
Iron Iron and wood 
Link chain Rectangular flat 
6 
1524 
762 
30.00 100.00 each 
Fig. 2. Distribution of floats in traditional (A) 
and high opening bottom trawls (B). 
data on tension and catch were con-. 
verted to log values. The variance ratio 
test (F) was employed for comparing the 
variability and paired 't' for testing "no 
FISHERY TECHNOLOGY 
STUDIES ON HIGH OPENING TRAWLS 88 
Table 2. Results of comparative .fishing operations with 25 m bulged belly trawl and 25 m high 
opening trawl 
25m bulged 25m high 
belly trawl opening trawl 
Number of hau1s 57 57 
Fishing effort, h 57 57 
Depth range, m 26-50 26-50 
Range ofwarp, m 130-250 130-250 
Trawling speed, knots 2.5 2.5 
Horizontal opening, m 
Average 13.93 16.11 
Range 12.00-20.00 13.84-22.00 
Warp Tension, kg 
Average 604.160 596.560 
Range 530-684 506-658 
Catch, kg 
Total 3881.400 4790.850 
CPUE, kg/h 68.095 84.050 
Range, kg/h 7.1-159.3 9.0-305.0 
Table 3. Composition of catch in 25 m bulged belly trawl and 25 m high opening trawl 
25m bulged belly trawl 25m high opening trawl 
weight 
kg 
Quality fish 69.8 
Ribbon fish 813.0 
Lactarius 458.0 
Elasmo branchs 49.0 
Cephalopods 160.0 
Prawns 7.1 
Sciaenids 196.0 
Miscellaneous fish 2128.5 
Total 3881.4 
differences" in the mean horizontal 
opening, tension and catch. The 
variance of the two nets, the variance ratio 
(F), degree of freedom, the modulus of the 
mean difference d, unbiased estimate of 
the population, standard deviation (S) and 
the paired 't' values are given in Table 4. 
The variance ratios (F) were not significant 
at 5% level in all the cases except in the 
quality fish, indicating equal variance of 
the experimental data at 5% level for both 
the nets. The paired 't' values for testing 
the difference in mean horizontal opening 
of the two nets were significant at 0.1% level. 
Vol. 21, 1984 
% weight % 
kg 
34.0 135.4 66.0 
34.5 1543.0 65.5 
48.0 493.0 52.0 
83.0 10.0 17.0 
52.3 146.0 47.7 
56.3 5.5 43.7 
50.0 196.0 50.0 
48.5 2262.0 51.5 
44.8 4790.9 55.2 
High opening trawl has given significantly 
high horizontal opening compared to bul-
ged belly trawl. But for the mean catch of 
ribbon fishes, there were no significant differe-
nce in total catch, catch of quality and mis-
cellaneous fish and tension at 5% level, 
between the two nets. Though statistically 
not significant, data (Tables 2 and 3) indicate 
more of total catch, quality fishes and ribbon 
fishes in high opening trawl. Generally 
ribbon fish and quality fish swim away 
from bottom but the other fishes generally 
tend to be on the bottom or near the bottom. 
As the catch of ribbon fish and quality fish 
alone are more in the high opening trawl, it 
:::1 
tZl 
::r: 
~ 
>-<: 
tri () 
2 
0 
t'"' 
0 
Q 
>-<: 
Table 4. Statistical comparison of high opening trawl and bulged belly trawl 
Horizon- Tension Total Quality Ribbon Lactar-
tal catch fish fish lUS 
opening 
Variance (Bulged belly) 2.5427 0.0008 0.0880 0.0938 0.4164 0.4069 
Variance (high opening) 2.6161 0.008 0.1275 0.1591 0.4678 0.4175 
F 1.03 1.00 1.45 1.70* 1.12 1.03 
Degrees of freedom (56,56) (56,56) (56,56) (56,56) (56, 56) (56,56) 
/d/ 2.1743 0.0054 0.0652 0.0682 0.1639 0.0115 
s 1.2086 0.0208 0.2911 0.2980 0.5378 0.1819 
•t' 13.585*** 1.946 1.691 1.727 2.301* 0.477 
Degrees of freedom 56 56 56 56 56 56 
* = p < 0.05; ** = p < 0.01; *** = p < 0.001 
Cepha- Prawns 
lopods 
0.1725 0.0072 
0.1583 0.0058 
1.09 1.25 
(56; 56) (56,56) 
0.0256 0.0095 
0.2387 0.0614 
0.809 1.168 
56 56 
Sciaenids Miscel-
laneous 
0.2358 0.2806 
0.2386 0.2299 
1.01 1.22 
(56, 56) (56,56) 
0.0059 0.0358 
0.2494 0.3277 
0.178 0.826 
56 56 
00 
\0 
0 
~ 
~ 
c 
~ 
..... 
'"ti 
> r 
~c 
~ 
~ 
t:i:l 
0 
~ 
td 
z 
u 
~ 
~ 
J-3 
~::r1 
0 
a 
0 
'"ti 
> r 
> ?>?'i 
(')~ 
...... 
?'i!Zl 
c::r1 ~~ 
>Z 
::g> 
>Z 
zo 
STUDIES ON HIGH OPENING TRAWLS 
can be presumed that the new gear would have 
developed better vertical mouth opening 
and is suitable and efficient for the capture 
of semi-pelagic species. The extra panels, 
rib lines and floats in the high opening trawl 
might have offered a better vertical opening. 
High opening trawl also offered a better 
horizontal opening and lesser (Tables 3 and 
4) warp tension compared to bulged belly 
net. It was not necessary to enhance the 
engine r. p. m to tow the high opening trawl 
at the required towing speed of 2.5 knots. 
The high opening trawl can be employed 
as a multi-purpose trawl for exploiting both 
bottom and semi-pelagic fishes without any 
additional requirements like increased r. p. m 
and fuel consumption of the engine, the two 
pre-requisites for mid-water and pelagic 
trawling. 
The high opening trawl with its many 
sections and joints has 2,47,000 meshes 
when compared with 3,30,000 meshes of 
the bulged belly trawl. Additional rib lines 
offer a distribution of resistance at the mouth 
of . the net and the triangular panels offer 
enough slack to offer better opening of the 
mouth. The net is so designed 
to develop a round mouth to give better 
flow through the water. Additional floats 
can be attached to the high opening trawl 
at the upper rib lines (Fig. 2) when com-
pared with the traditional nets. The lower 
rib lines enhance the stability of the foot 
rope holding it to the bottom at all times, 
when the head line tends to lift up. The 
net is capable of giving greater spread, 
much better lift, while still firmly in contact 
with the sea-bed. 
Authors express their thanks to Dr. C. C. Pandu-
ranga Rao, Director for permitting to publish this 
paper. Thanks are also due to Shri H. Krishna 
Iyer for the statistical analysis of the data and to 
Shri M.S. Fernando, Skipper and his crew for their 
co-operation. 
References 
Benyami, M. (1959) Modern Fishing Gear 
of the World. (Kristjonsson, H., Ed.) 
p. 213, Fishing News (Books) Ltd., 
London 
Vol. 21, 1984 
90 
Brandt, A. V. (1971) in Modern Fishing Gear 
of the World 3 (Kristjonsson, H., Ed.) 
p. 455, Fishing News (Books) Ltd., 
London 
Deshpande, S. D. (1960) Indian J. Fish. 
7, 458 
Deshpande, S. D., Rama Rao, S.V.S. & 
Vijayan, V. (1970) Fish. Techno!. 7, 
186 
Garner, John (1967) in Modern Deep Sea 
Trawling Gear. Fishing News (Books) 
Ltd., Surrey England 
Garner, John (1978) Pelagic and Semi-
Pelagic Trawling Gear, Fishing News 
(Books) Ltd., Surrey, England 
Kartha, K. N. & Sadanandan, K. A. (1973) 
Fish. Techno!. 10, 79 
.Kodera, K. (1971) in Modern Fishing Gear 
of the World 3 (Kristjonsson, H. Ed.) 
p. 413, Fishing News (Books) Ltd., 
London 
Kuriyan, G. K., Satyanarayana, A. V. V. & 
Nair, R. S. (1964) Proc. Indo-Pacific 
Fish. Coun. 11, 204 
Kunjipalu, K. K., George Mathai, P. & 
Kuttappan, A. C. (1979) Fish. Tech-
no!. 16, 55 
Kunjipalu, K. K. (1980) Ribbon Fishes-
A New Trawl Resource off Veraval. 
Paper presented at the seminar on 
"Recent Trends in Teaching and Resea-
rch in Aquatic Biology" Bhavanagar, 
26-28 September 
Nakamura, M. (1971) in Modern Fishing 
Gear of the World 3 (Kristjonsson, H., 
Ed.) p. 461, Fishing News (Books) Ltd., 
London 
Satyanarayana, A.V.V. & Nair, R. S. (1965) 
Res. Ind. 10, 229 
Takayama, S. & Koyama, T. (1959) in 
Modern Fishing Gear of the World (Krist-
jonsson, H., Ed.) p. 185 Fishing 
News (Books) Ltd., London 


A new high opening trawl for Veraval waters

http://aquaticcommons.org/18445/1/FT21.2_086.pdf

A new high opening trawl for Veraval waters

Abstract

Similar works

Full text

Available Versions

Aquatic Commons